TY  - THES
A1  - Saatchi, Mersa
T1  - Study on manufacturing of multifunctional bilayer systems
N2  - Layered structures are ubiquitous in nature and industrial products, in which individual layers could have different mechanical/thermal properties and functions independently contributing to the performance of the whole layered structure for their relevant application. Tuning each layer affects the performance of the whole layered system.
Pores are utilized in various disciplines, where low density, but large surfaces are demanded. Besides, open and interconnected pores would act as a transferring channel for guest chemical molecules. The shape of pores influences compression behavior of the material. Moreover, introducing pores decreases the density and subsequently the mechanical strength. To maintain defined mechanical strength under various stress, porous structure can be reinforced by adding reinforcement agent such as fiber, filler or layered structure to bear the mechanical stress on demanded application.
In this context, this thesis aimed to generate new functions in bilayer systems by combining layers having different moduli and/or porosity, and to develop suitable processing techniques to access these structures.
Manufacturing processes of layered structures employ often organic solvents mostly causing environmental pollution. In this regard, the studied bilayer structures here were manufactured by processes free of organic solvents.
In this thesis, three bilayer systems were studied to answer the individual questions.
First, while various methods of introducing pores in melt-phase are reported for one-layer constructs with simple geometry, can such methods be applied to a bilayer structure, giving two porous layers?
This was addressed with Bilayer System 1. Two porous layers were obtained from melt-blending of two different polyurethanes (PU) and polyvinyl alcohol (PVA) in a co-continuous phase followed by sequential injection molding and leaching the PVA phase in deionized water. A porosity of 50 ± 5% with a high interconnectivity was obtained, in which the pore sizes in both layers ranged from 1 µm to 100 µm with an average of 22 µm in both layers. The obtained pores were tailored by applying an annealing treatment at relevant high temperatures of 110 °C and 130 °C, which allowed the porosity to be kept constant. The disadvantage of this system is that a maximum of 50% porosity could be reached and removal of leaching material in the weld line section of both layers is not guaranteed. Such a construct serves as a model for bilayer porous structure for determining structure-property relationships with respect to the pore size, porosity and mechanical properties of each layer. This fabrication method is also applicable to complex geometries by designing a relevant mold for injection molding.
Secondly, utilizing scCO2 foaming process at elevated temperature and pressure is considered as a green manufacturing process. Employing this method as a post-treatment can alter the history orientation of polymer chains created by previous fabrication methods. Can a bilayer structure be fabricated by a combination of sequential injection molding and scCO2 foaming process, in which a porous layer is supported by a compact layer? 
Such a construct (Bilayer System 2) was generated by sequential injection molding of a PCL (Tm ≈ 58 °C) layer and a PLLA (Tg ≈ 58 °C) layer. Soaking this structure in the autoclave with scCO2 at T = 45 °C and P = 100 bar led to the selective foaming of PCL with a porosity of 80%, while the PLA layer was kept compact. The scCO2 autoclave led to the formation of a porous core and skin layer of the PCL, however, the degree of crystallinity of PLLA layer increased from 0 to 50% at the defined temperature and pressure. The microcellular structure of PCL as well as the degree of crystallinity of PLLA were controlled by increasing soaking time.
Thirdly, wrinkles on surfaces in micro/nano scale alter the properties, which are surface-related. Wrinkles are formed on a surface of a bilayer structure having a compliant substrate and a stiff thin film. However, the reported wrinkles were not reversible. Moreover, dynamic wrinkles in nano and micro scale have numerous examples in nature such as gecko foot hair offering reversible adhesion and an ability of lotus leaves for self-cleaning altering hydrophobicity of the surface. It was envisioned to imitate this biomimetic function on the bilayer structure, where self-assembly on/off patterns would be realized on the surface of this construct. 
In summary, developing layered constructs having different properties/functions in the individual layer or exhibiting a new function as the consequence of layered structure can give novel insight for designing layered constructs in various disciplines such as packaging and transport industry, aerospace industry and health technology.
N2  - Schichtstrukturen sind in der Natur und in Industrieprodukten allgegenwärtig, wobei die einzelnen Schichten unterschiedliche mechanische/thermische Eigenschaften und Funktionen haben können, die unabhängig voneinander zur Leistungsfähigkeit der gesamten Schichtstruktur für die jeweilige Anwendung beitragen. Die individuelle Abstimmung jeder einzelnen Schicht wirkt sich auf die Leistungsfähigkeit des gesamten Schichtsystems aus. 
Poren werden in verschiedenen Bereichen eingesetzt, in denen eine geringe Dichte, aber eine große Oberfläche erforderlich ist. Außerdem können offene und miteinander verbundene Poren als Übertragungskanal für chemische Gast-Moleküle dienen. Die Form der Poren beeinflusst das Kompressionsverhalten des Materials. 
In diesem Zusammenhang zielte diese Arbeit darauf ab, neue Funktionen in zweischichtigen Systemen durch die Kombination von Schichten mit unterschiedlichen Modulen und/oder Porosität zu erzeugen und geeignete Verarbeitungstechniken zu entwickeln, um diese Strukturen zu erreichen. 
Bei der Herstellung von Schichtstrukturen werden häufig organische Lösungsmittel verwendet, die meist eine Umweltbelastung darstellen. Daher wurden die hier untersuchten Doppelschichtstrukturen mit Verfahren hergestellt, die frei von organischen Lösungsmitteln sind. 
In dieser Arbeit wurden drei Doppelschichtsysteme untersucht, um die einzelnen Fragen zu beantworten. 
Erstens: Während verschiedene Methoden zur Einführung von Poren in der Schmelzphase für einschichtige Konstruktionen mit einfacher Geometrie bekannt sind, stellt sich die Frage, ob solche Methoden sich auf eine zweischichtige Struktur anwenden lassen und somit zwei unterschiedlich poröse Schichten ergibt? 
Dies wurde mit dem Zweischichtsystem 1 untersucht. Zwei poröse Schichten wurden durch das Mischen in der Schmelze von zwei verschiedenen Polyurethanen (PU) und Polyvinylalkohol (PVA) in einer co-kontinuierlichen Phase erhalten. Es folgte sequentielles Spritzgießen und das Entfernen der PVA-Phase durch „Leaching“ in entionisiertem Wasser. Es wurde eine Porosität von 50 ± 5 % mit einer hohen Interkonnektivität erzielt, wobei die Porengrößen in beiden Schichten zwischen 1 µm und 100 µm lagen, mit einem Durchschnittswert von 22 µm in beiden Schichten. Diese Herstellungsmethode ist auch auf komplexe Geometrien anwendbar, es muss lediglich eine entsprechende Form für das Spritzgießen entworfen werden. 
Zweitens: die Verwendung des scCO2-Schäumungsverfahrens bei erhöhter Temperatur und erhöhtem Druck wird als umweltfreundlicher Herstellungsprozess betrachtet. Durch den Einsatz dieser Methode als Nachbehandlung kann die Historie der Ausrichtung der Polymerketten, die durch frühere Herstellungsmethoden entstanden ist, verändert werden. Kann eine zweischichtige Struktur durch eine Kombination aus sequentiellem Spritzgießen und scCO2-Schäumverfahren hergestellt werden, bei der eine poröse Schicht von einer kompakten Schicht getragen wird? 
Ein solches Konstrukt (Bilayer System 2) wurde durch sequentielles Spritzgießen einer PCL-Schicht (Tm ≈ 58 °C) und einer PLLA-Schicht (Tg ≈ 58  °C) erzeugt. Das Einweichen dieser Struktur in scCO2 im Autoklaven bei T = 45 °C und P = 100 bar führte zum selektiven Aufschäumen von PCL mit einer Porosität von 80%, während die PLA-Schicht unverschäumt blieb. Die Behandlung im scCO2-Autoklav führte zur Bildung einer porösen Kern- und Hautschicht des PCL, während der Kristallinitätsgrad der PLLA-Schicht bei der definierten Temperatur und dem definierten Druck von 0 auf 50 % anstieg. Die mikrozelluläre Struktur von PCL sowie der Kristallinitätsgrad von PLLA wurden durch die Erhöhung der Einweichzeit gesteuert. 
Drittens verändern Falten auf Oberflächen im Mikro-/Nanomaßstab die Eigenschaften, die mit der Oberfläche zusammenhängen. Falten bilden sich auf der Oberfläche einer zweischichtigen Struktur mit einem nachgiebigen Substrat und einem steifen dünnen Film. Die Falten waren jedoch nicht reversibel. Darüber hinaus gibt es in der Natur zahlreiche Beispiele für dynamische Falten im Nano- und Mikromaßstab, wie z. B. Gecko-Fußhaare, die eine reversible Adhäsion ermöglichen, und die Fähigkeit von Lotusblättern, sich selbst zu reinigen, indem sie die Hydrophobizität der Oberfläche verändern. Diese biomimetische Funktion sollte auf der Doppelschichtstruktur nachgeahmt werden, wobei auf der Oberfläche dieses Konstrukts selbstorganisierende On/Off-Muster realisiert werden sollten.
Zusammenfassend kann gesagt werden, dass die Entwicklung geschichteter Konstrukte mit unterschiedlichen Eigenschaften/Funktionen in den einzelnen Schichten oder mit einer neuen Funktion als Folge der geschichteten Struktur neue Erkenntnisse für den Entwurf geschichteter Konstrukte in verschiedenen Disziplinen wie der Verpackungs- und Transportindustrie, der Luft- und Raumfahrtindustrie und der Gesundheitstechnologie liefern kann.
T2  - Studie zur Herstellung multifunktionaler Doppelschichtsysteme
KW  - bilayer system
KW  - biomaterials
KW  - wrinkles
KW  - polymer
KW  - injection molding
KW  - Doppelschichtstruktur
KW  - Biomaterialien
KW  - poröse Struktur
KW  - Falten
KW  - Spritzgießen
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-601968
ER  - 
TY  - THES
A1  - Bouakline, Foudhil
T1  - Manifestations of Quantum-Mechanical Effects in Molecular Reaction Dynamics
N2  - This habilitation thesis summarises the research work performed by the author during the last quindecennial period. The dissertation reflects his main research interests, which revolve around quantum dynamics of small-sized molecular systems, including their interactions with electromagnetic radiation or dissipative environments. This covers various dynamical processes that involve bound-bound, bound-free, and free-free molecular transitions. The latter encompass light-triggered rovibrational or rovibronic dynamics in bound molecules, molecular photodissociation induced by weak or strong laser fields, state-to-state reactive and/or inelastic molecular collisions, and phonon-driven vibrational relaxation of adsorbates at solid surfaces. Although the dissertation covers different topics of molecular reaction dynamics, most of these studies focus on nuclear quantum effects and their manifestations in experimental measures. The latter are assessed through comparison between quantum and classical predictions, and/or direct confrontation of theory and experiment. Most well known quantum concepts and effects will be encountered in this work. Yet, almost all these quantum notions find their roots in the central pillar of quantum theory, namely, the quantum superposition principle. Indeed, quantum coherence is the main source of most quantum effects, including interference, entanglement, and even tunneling. Thus, the common and predominant theme of all the investigations of this thesis is quantum coherence, and the survival or quenching of subsequent interference effects in various molecular processes. The lion's share of the dissertation is devoted to two associated quantum concepts, which are usually overlooked in computational molecular dynamics, viz. the Berry phase and identical nuclei symmetry. The importance of the latter in dynamical molecular processes and their direct fingerprints in experimental observables also rely very much on quantum coherence and entanglement. All these quantum phenomena are thoroughly discussed within the four main topics that form the core of this thesis. Each topic is described in a separate chapter, where it is briefly summarised and then illustrated with three peer-reviewed publications. The first topic deals with the relevance of quantum coherence/interference in molecular collisions, with a focus on the hydrogen-exchange reaction, H+H2 --> H2+H, and its isotopologues. For these collision processes, the significance of interference of probability amplitudes arises because of the existence of two main scattering pathways. The latter could be inelastic and reactive scattering, direct and time-delayed scattering, or two encircling reaction paths that loop in opposite senses around a conical intersection (CI) of the H3 molecular system. Our joint theoretical-experimental investigations of these processes reveal strong interference and geometric phase (GP) effects in state-to-state reaction probabilities and differential cross sections. However, these coherent effects completely cancel in integral cross sections and reaction rate constants, due to efficient dephasing of interference between the different scattering amplitudes. As byproducts of these studies, we highlight the discovery of two novel scattering mechanisms, which contradict conventional textbook pictures of molecular reaction dynamics. The second topic concerns the effect of the Berry phase on molecular photodynamics at conical intersections. To understand this effect, we developed a topological approach that separates the total molecular wavefunction of an unbound molecular system into two components, which wind in opposite senses around the conical intersection. This separation reveals that the only effect of the geometric phase is to change the sign of the relative phase of these two components. This in turn leads to a shift in the interference pattern of the molecular system---a phase shift that is reminiscient of the celebrated Aharonov-Bohm effect. This procedure is numerically illustrated with photodynamics at model standard CIs, as well as strong-field dissociation of diatomics at light-induced conical intersections (LICIs). Besides the fundamental aspect of these studies, their findings allow to interpret and predict the effect of the GP on the state-resolved or angle-resolved spectra of pump-probe experimental schemes, particularly the distributions of photofragments in molecular photodissociation experiments. The third topic pertains to the role of the indistinguishability of identical nuclei in molecular reaction dynamics, with an emphasis on dynamical localization in highly symmetric molecules. The main object of these studies is whether nuclear-spin statistics allow dynamical localization of the electronic, vibrational, or even rotational density on a specific molecular substructure or configuration rather than on another one which is identical (indistinguishable). Group-theoretic analysis of the symmetrized molecular wavefunctions of these systems shows that nuclear permutation symmetry engenders quantum entanglement between the eigenstates of the different molecular degrees of freedom. This subsequently leads to complete quenching of dynamical localization over indistinguishable molecular substructures---an observation that is in sharp contradiction with well known textbook views of iconic molecular processes. This is illustrated with various examples of quantum dynamics in symmetric double-well achiral molecules, such as the prototypical umbrella inversion motion of ammonia, electronic Kekulé dynamics in the benzene molecule, and coupled electron-nuclear dynamics in laser-induced indirect photodissociation of the dihydrogen molecular cation. The last part of the thesis is devoted to the development of approximate wavefunction approaches for phonon-induced vibrational relaxation of adsorbates (system) at surfaces (bath). Due to the so-called 'curse of dimensionality', these system-bath complexes cannot be handled with standard wavefunction methods. To alleviate the exponential scaling of the latter, we developed approximate yet quite accurate numerical schemes that have a polynomial scaling with respect to the bath dimensionality. The corresponding algorithms combine symmetry-based reductions of the full vibrational Hilbert space and iterative Krylov techniques. These approximate wavefunction approaches resemble the 'Bixon-Jortner model' and the more general 'quantum tier model'. This is illustrated with the decay of H-Si (D-Si) vibrations on a fully H(D)-covered silicon surface, which is modelled with a phonon-bath of more than two thousand oscillators. These approximate methods allow reliable estimation of the adsorbate vibrational lifetimes, and provide some insight into vibration-phonon couplings at solid surfaces. Although this topic is mainly computational, the developed wavefunction approaches permit to describe quantum entanglement between the system and bath states, and to embody some coherent effects in the time-evolution of the (sub-)system, which cannot be accounted for with the widely used 'reduced density matrix formalism'.
N2  - Diese Habilitationsschrift fasst die Forschungsarbeiten des Autors während der letzten 15 Jahre zusammen. Die wissenschaftliche Abhandlung spiegelt seine hauptsächlichen Forschungsinteressen wider, die sich um die Quantendynamik kleiner molekularer Systeme drehen, einschließlich ihrer Wechselwirkung mit elektromagnetischer Strahlung oder dissipativer Umgebungen. Dies umfasst verschiedene dynamische Prozesse, die Übergänge zwischen molekulare Zuständen (gebunden-gebunden, gebunden-frei und frei-frei) beinhalten. Dazu zählen lichtgesteuerte rovibronische Dynamik in gebundenen Molekülen, molekulare Photodissoziation durch schwache oder starke Laserfelder, reaktive und/oder inelastische molekulare Kollisionen und phononengesteuerte Schwingungsrelaxation von Adsorbaten auf Festkörperoberflächen. Obwohl die Habilitationsschrift verschiedene Themengebiete molekularer Reaktionsdynamik abdeckt, konzentrieren sich die meisten Arbeiten auf nukleare Quanteneffekte und wie sich diese in experimentellen Messgrößen äußern.. Dies wird durch den Vergleich von quantenphysikalischen und klassischen Vorhersagen und/oder eine direkte Gegenüberstellung von Theorie und Experiment beurteilt. Die meisten wohlbekannten quantenphysikalischen Konzepte und Effekte kommen in dieser Arbeit vor. Fast alle davon beruhen auf der zentralen Säule der Quantentheorie, dem Quanten-Superpositionsprinzip. Tatsächlich ist Quantenkohärenz die Hauptquelle der meisten Quanteneffekte, einschließlich Interferenz, Verschränkung und sogar Tunneln. Daher ist das gemeinsame und vorherrschende Thema aller Untersuchungen in dieser Arbeit die Quantenkoheränz und das Fortbestehen oder die Auslöschung der daraus folgenden Interferenzauswirkungen in verschiedenen molekularen Prozessen. Der Hauptanteil dieser Habilitationsschrift behandelt zwei verwandte Quantenkonzepte, die in Molekulardynamik-Rechnungen meist keine Beachtung finden, nämlich der Berry-Phase und der Symmetrie identischer Kerne. Deren Bedeutung in dynamischen molekularen Prozessen und ihre Anzeichen in experimentellen Messgrößen beruhen auch zu großen Teilen auf Quantenkohärenz und Verschränkung. Alle diese Quantenphänomene werden in den vier Hauptthemen, die den Kern dieser Arbeit bilden, umfassend behandelt. Jedes Themengebiet wird in einem separaten Kapitel beschrieben, in dem es kurz zusammengefasst und durch drei extern begutachtete Veröffentlichungen dargestellt wird. Das erste Themengebiet behandelt die Relevanz von Interferenz bei molekularen Kollisionen, wobei der Fokus auf der Wasserstoff-Austauschreaktion, H+H2 --> H2+H, und ihren Isotopologen liegt. Die Bedeutsamkeit der Interferenz der Wahrscheinlichkeits-Amplituden für solche Kollisionsprozesse erwächst aus der Existenz zweier Haupt-Streupfade. Dabei kann es sich um inelastische und reaktive Streuung, direkte und zeitverzögerte Streuung oder zwei gegenläufige Reaktionspfade um eine konische Durchschneidung (conical intersection, CI) im H3-Molekülsystem handeln. Unsere gemeinsamen theoretische und experimentelle Untersuchungen dieser Prozesse offenbaren einen starken Einfluss von Interferenz und der geometrischen Phase (GP) auf “state-to-state” Reaktionswahrscheinlichkeiten und differentielle Querschnitte. Allerdings heben sich diese kohärenten Effekte bei integralen Querschnitten und Reaktionsgeschwindigkeitskonstanten durch effiziente Dephasierung der Interferenz zwischen verschiedenen Streuamplituden komplett auf. Als Nebenprodukte dieser Studien heben wir die Entdeckung zweier neuartiger Streumechanismen hervor, die herkömmlichen Lehrbuchmeinungen widersprechen. Das zweite Thema dreht sich um die Auswirkungen der Berry-Phase auf molekulare Photodynamik an konischen Durchschneidungen. Um diesen Effekt zu verstehen, haben wir einen topologischen Ansatz entwickelt, der die gesamte molekulare Wellenfunktion eines ungebundenen molekularen Systems in zwei Komponenten trennt, die sich in unterschiedlichen Richtungen um die CI winden. Diese Unterteilung zeigt, dass die einzige Auswirkung der geometrischen Phase ein Vorzeichenwechsel der relativen Phase der beiden Komponenten ist. Dieser führt seinerseits zu einer Verschiebung im Interferenzmuster des molekularen Systems---eine Phasenverschiebung, die an den berühmten Aharonov–Bohm-Effekt erinnert. Dieses Verfahren wird numerisch anhand der Photodynamik von üblichen CI-Modellen sowie der Dissoziation von zweiatomigen Molekülen an lichtinduzierten konischen Durchschneidungen (light-induced conical intersections, LICIs) in starken Feldern dargestellt. Neben den fundamentellen Aspekten dieser Arbeiten erlauben die Ergebnisse auch, den Einfluss der geometrischen Phase auf zustandsaufgelöste oder winkelaufgelöste Spektren in “Pump-Probe”-Experimenten zu interpretieren und vorherzusagen, insbesondere die Verteilungen von Photofragmenten in Photodissoziationsexperimenten. Das dritte Themengebiet betrifft die Rolle der Ununterscheidbarkeit identischer Kerne in der molekularen Reaktionsdynamik, wobei der Schwerpunkt auf der dynamischen Lokalisierung hochsymmetrischer Moleküle liegt. Zentraler Gegenstand dieser Arbeiten ist die Frage, ob Kernspin-Statistiken eine dynamische Lokalisierung der Elektronen-, Vibrations- oder sogar Rotations-Dichte auf eine spezifische molekulare Unterstruktur oder Konfiguration anstelle einer anderen identischen (ununterscheidbaren) Teilstruktur erlauben. Gruppentheoretische Betrachtungen der symmetrisierten molekularen Wellenfunktionen dieser Systeme zeigen, dass die nukleare Permutationssymmetrie eine Quantenverschränkung zwischen den Eigenzuständen der verschiedenen molekularen Freiheitsgrade verursacht. Dies führt zu einer kompletten Löschung der dynamischen Lokalisierung auf ununterscheidbare molekulare Teilstrukturen---ein Ergebnis, das in krassem Widerspruch zu weitverbreiteten Lehrbuchansichten ikonischer molekularer Prozesse steht. Dies wird anhand verschiedener Beispiele für die Quantendynamik in achiralen Molekülen mit symmetrischem Doppelminimumspotential illustriert, wie etwa der prototypische pyramidale Inversion von Ammoniak, der elektronischen Kekulé-Dynamik im Benzol-Molekül und der gekoppelte Elektron-Kern-Dynamik bei der laser-induzierten indirekten Photodissoziation des Diwasserstoff-Kations. Der letzte Teil der Habilitationsschrift widmet sich der Entwicklung genäherter Wellenfunktions-Ansätze für die phononengesteuerte Schwingungsrelaxation von Adsorbaten (System) auf Oberflächen (Bad). Aufgrund des sogenannten “Fluchs der Dimensionalität” können diese System-Bad-Komplexe nicht mit üblichen Wellenfunktionsmethoden behandelt werden. Um deren exponentielle Skalierung zu vermindern, haben wir genäherte, aber recht genaue, numerische Verfahren mit polynomialer Skalierung in Bezug auf die Bad-Dimensionen entwickelt.. Die entsprechenden Algorithmen vereinen eine symmetriebasierte Verringerung des vollen Vibrations-Hilbertraums und iterative Krylov-Verfahren. Diese genäherten Wellenfunktionsansätze ähneln dem “Bixon-Jortner Modell” und dem allgemeineren “Quanten-Stufenmodell”. Sie werden auf den Zerfall der H(D)-Si-Schwingungen auf einer komplett mit H (D) bedeckten Siliziumoberfläche angewandt, die durch ein Phononenbad mit mehr als zweitausend Oszillatoren dargestellt wird. Diese Näherungsverfahren erlauben eine zuverlässige Abschätzung der Schwingungslebensdauern der Adsorbate und gewähren Einsicht in die Vibrations-Phonon-Kopplungen an Festkörperoberflächen. Obwohl dieses Thema hauptsächlich rechenbetont ist, ermöglichen die entwickelten Wellenfunktionsmethoden eine Beschreibung der Quantenverschränkung zwischen System- und Bad-Zuständen und die Illustration einiger kohärenter Effekte in der zeitlichen Entwicklung des (Teil-)Systems, die nicht mit dem häufig verwendeten reduzierten Dichtematrix-Formalismus erfasst werden können.
KW  - Molecular Collisions
KW  - Conical Intersections
KW  - Berry Phase
KW  - Nuclear-Spin-Statistics
KW  - Dissipation-Decoherence
KW  - Molekulare Kollisionen
KW  - Konischen Durchschneidungen
KW  - Berry-Phase
KW  - Kernspin-Statistiken
KW  - Dissipation-Dekohärenz
Y1  - 2023
ER  - 
TY  - JOUR
A1  - Gonzalez-Chavarria, Ivan
A1  - Duprat, Felix
A1  - Roa, Francisco J.
A1  - Jara, Nery
A1  - Toledo, Jorge R.
A1  - Miranda, Felipe
A1  - Becerra, Jose
A1  - Inostroza, Alejandro
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Heydenreich, Matthias
A1  - Paz, Cristian
T1  - Maytenus disticha extract and an isolated β-Dihydroagarofuran induce mitochondrial depolarization and apoptosis in human cancer cells by increasing mitochondrial reactive oxygen species
JF  - Biomolecules
N2  - Maytenus disticha (Hook F.), belonging to the Celastraceae family, is an evergreen shrub, native of the central southern mountains of Chile. Previous studies demonstrated that the total extract of M. disticha (MD) has an acetylcholinesterase inhibitory activity along with growth regulatory and insecticidal activities. beta-Dihydroagarofurans sesquiterpenes are the most active components in the plant. However, its activity in cancer has not been analyzed yet. Here, we demonstrate that MD has a cytotoxic activity on breast (MCF-7), lung (PC9), and prostate (C4-2B) human cancer cells with an IC50 (mu g/mL) of 40, 4.7, and 5 mu g/mL, respectively, an increasing Bax/Bcl2 ratio, and inducing a mitochondrial membrane depolarization. The beta-dihydroagarofuran-type sesquiterpene (MD-6), dihydromyricetin (MD-9), and dihydromyricetin-3-O-beta-glucoside (MD-10) were isolated as the major compounds from MD extracts. From these compounds, only MD-6 showed cytotoxic activity on MCF-7, PC9, and C4-2B with an IC50 of 31.02, 17.58, and 42.19 mu M, respectively. Furthermore, the MD-6 increases cell ROS generation, and MD and MD-6 induce a mitochondrial superoxide generation and apoptosis on MCF-7, PC9, and C4-2B, which suggests that the cytotoxic effect of MD is mediated in part by the beta-dihydroagarofuran-type that induces apoptosis by a mitochondrial dysfunction.
KW  - Maytenus disticha
KW  - beta-dihydroagarofuran-type sesquiterpene
KW  - dihydromyricetin
KW  - dihydromyricetin-3-O-beta-glucoside
KW  - cytotoxic
KW  - activity
KW  - Mitochondrial ROS
Y1  - 2020
U6  - https://doi.org/10.3390/biom10030377
SN  - 2218-273X
VL  - 10
IS  - 3
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Keckeis, Philipp
A1  - Zeller, Enriko
A1  - Jung, Carina
A1  - Besirske, Patricia
A1  - Kirner, Felizitas
A1  - Ruiz-Agudo, Cristina
A1  - Schlaad, Helmut
A1  - Cölfen, Helmut
T1  - Modular toolkit of multifunctional block copoly(2-oxazoline)s for the synthesis of nanoparticles
JF  - Chemistry - a European journal
N2  - Post-polymerization modification provides an elegant way to introduce chemical functionalities onto macromolecules to produce tailor-made materials with superior properties. This concept was adapted to well-defined block copolymers of the poly(2-oxazoline) family and demonstrated the large potential of these macromolecules as universal toolkit for numerous applications. Triblock copolymers with separated water-soluble, alkyne- and alkene-containing segments were synthesized and orthogonally modified with various low-molecular weight functional molecules by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) and thiol-ene (TE) click reactions, respectively. Representative toolkit polymers were used for the synthesis of gold, iron oxide and silica nanoparticles.
KW  - block copolymers
KW  - click chemistry
KW  - nanoparticles
KW  - ring-opening
KW  - polymerization
KW  - surfactants
Y1  - 2021
U6  - https://doi.org/10.1002/chem.202101327
SN  - 0947-6539
SN  - 1521-3765
VL  - 27
IS  - 32
SP  - 8283
EP  - 8287
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Chen, Lu
A1  - Yan, Runyu
A1  - Oschatz, Martin
A1  - Jiang, Lei
A1  - Antonietti, Markus
A1  - Xiao, Kai
T1  - Ultrathin 2D graphitic carbon nitride on metal films
BT  - underpotential sodium deposition in adlayers for sodium-ion batteries
JF  - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition
N2  - Efficient and low-cost anode materials for the sodium-ion battery are highly desired to enable more economic energy storage. Effects on an ultrathin carbon nitride film deposited on a copper metal electrode are presented. The combination of effects show an unusually high capacity to store sodium metal. The g-C3N4 film is as thin as 10 nm and can be fabricated by an efficient, facile, and general chemical-vapor deposition method. A high reversible capacity of formally up to 51 Ah g(-1) indicates that the Na is not only stored in the carbon nitride as such, but that carbon nitride activates also the metal for reversible Na-deposition, while forming at the same time an solid electrolyte interface layer avoiding direct contact of the metallic phase with the liquid electrolyte.
KW  - 2D films
KW  - carbon nitride
KW  - chemical vapor deposition
KW  - sodium-ion
KW  - batteries
KW  - underpotential deposition
Y1  - 2020
U6  - https://doi.org/10.1002/anie.202000314
SN  - 1433-7851
SN  - 1521-3773
VL  - 59
IS  - 23
SP  - 9067
EP  - 9073
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Witzorky, Christoph
A1  - Paramonov, Guennaddi
A1  - Bouakline, Foudhil
A1  - Jaquet, Ralph
A1  - Saalfrank, Peter
A1  - Klamroth, Tillmann
T1  - Gaussian-type orbital calculations for high harmonic generation in vibrating molecules
BT  - Benchmarks for H-2(+)
JF  - Journal of chemical theory and computation
N2  - The response of the hydrogen molecular ion, H-2(+), to few-cycle laser pulses of different intensities is simulated. To treat the coupled electron-nuclear motion, we use adiabatic potentials computed with Gaussian-type basis sets together with a heuristic ionization model for the electron and a grid representation for the nuclei. Using this mixed-basis approach, the time-dependent Schrodinger equation is solved, either within the Born-Oppenheimer approximation or with nonadiabatic couplings included. The dipole response spectra are compared to all-grid-based solutions for the three-body problem, which we take as a reference to benchmark the Gaussian-type basis set approaches. Also, calculations employing the fixed-nuclei approximation are performed, to quantify effects due to nuclear motion. For low intensities and small ionization probabilities, we get excellent agreement of the dynamics using Gaussian-type basis sets with the all-grid solutions. Our investigations suggest that high harmonic generation (HHG) and high-frequency response, in general, can be reliably modeled using Gaussian-type basis sets for the electrons for not too high harmonics. Further, nuclear motion destroys electronic coherences in the response spectra even on the time scale of about 30 fs and affects HHG intensities, which reflect the electron dynamics occurring on the attosecond time scale. For the present system, non-Born-Oppenheimer effects are small. The Gaussian-based, nonadiabatically coupled, time-dependent multisurface approach to treat quantum electron-nuclear motion beyond the non-Born-Oppenheimer approximation can be easily extended to approximate wavefunction methods, such as time-dependent configuration interaction singles (TD-CIS), for systems where no benchmarks are available.
KW  - Basis sets
KW  - Chemical calculations
KW  - Ionization
KW  - Lasers
KW  - Quantum mechanics
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jctc.1c00837
SN  - 1549-9618
SN  - 1549-9626
VL  - 17
IS  - 12
SP  - 7353
EP  - 7365
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Hechenbichler, Michelle
A1  - Laschewsky, Andre
A1  - Gradzielski, Michael
T1  - Poly(N,N-bis(2-methoxyethyl)acrylamide), a thermoresponsive non-ionic polymer combining the amide and the ethyleneglycolether motifs
JF  - Colloid and polymer science
N2  - Poly(N,N-bis(2-methoxyethyl)acrylamide) (PbMOEAm) featuring two classical chemical motifs from non-ionic water-soluble polymers, namely, the amide and ethyleneglycolether moieties, was synthesized by reversible addition fragmentation transfer (RAFT) polymerization. This tertiary polyacrylamide is thermoresponsive exhibiting a lower critical solution temperature (LCST)-type phase transition. A series of homo- and block copolymers with varying molar masses but low dispersities and different end groups were prepared. Their thermoresponsive behavior in aqueous solution was analyzed via turbidimetry and dynamic light scattering (DLS). The cloud points (CP) increased with increasing molar masses, converging to 46 degrees C for 1 wt% solutions. This rise is attributed to the polymers' hydrophobic end groups incorporated via the RAFT agents. When a surfactant-like strongly hydrophobic end group was attached using a functional RAFT agent, CP was lowered to 42 degrees C, i.e., closer to human body temperature. Also, the effect of added salts, in particular, the role of the Hofmeister series, on the phase transition of PbMOEAm was investigated, exemplified for the kosmotropic fluoride, intermediate chloride, and chaotropic thiocyanate anions. A pronounced shift of the cloud point of about 10 degrees C to lower or higher temperatures was observed for 0.2 M fluoride and thiocyanate, respectively. When PbMOEAm was attached to a long hydrophilic block of poly(N,N-dimethylacrylamide) (PDMAm), the cloud points of these block copolymers were strongly shifted towards higher temperatures. While no phase transition was observed for PDMAm-b-pbMOEAm with short thermoresponsive blocks, block copolymers with about equally sized PbMOEAm and PDMAm blocks underwent the coil-to-globule transition around 60 degrees C.
KW  - polyacrylamide
KW  - water-soluble polymers
KW  - responsive systems
KW  - lower
KW  - critical solution temperature
KW  - polymer amphiphile
Y1  - 2020
U6  - https://doi.org/10.1007/s00396-020-04701-9
SN  - 0303-402X
SN  - 1435-1536
VL  - 299
IS  - 2
SP  - 205
EP  - 219
PB  - Springer
CY  - Berlin; Heidelberg
ER  - 
TY  - JOUR
A1  - Mehr, Fatemeh Naderi
A1  - Grigoriev, Dmitry
A1  - Heaton, Rebecca
A1  - Baptiste, Joshua
A1  - Stace, Anthony J.
A1  - Puretskiy, Nikolay
A1  - Besley, Elena
A1  - Böker, Alexander
T1  - Self-assembly behavior of oppositely charged inverse bipatchy microcolloids
JF  - Small : nano micro
N2  - A directed attractive interaction between predefined "patchy" sites on the surfaces of anisotropic microcolloids can provide them with the ability to self-assemble in a controlled manner to build target structures of increased complexity. An important step toward the controlled formation of a desired superstructure is to identify reversible electrostatic interactions between patches which allow them to align with one another. The formation of bipatchy particles with two oppositely charged patches fabricated using sandwich microcontact printing is reported. These particles spontaneously self-aggregate in solution, where a diversity of short and long chains of bipatchy particles with different shapes, such as branched, bent, and linear, are formed. Calculations show that chain formation is driven by a combination of attractive electrostatic interactions between oppositely charged patches and the charge-induced polarization of interacting particles.
KW  - electrostatic interactions
KW  - patchy particles
KW  - polyelectrolyte inks
KW  - sandwich microcontact printing
KW  - self-assembly
Y1  - 2020
U6  - https://doi.org/10.1002/smll.202000442
SN  - 1613-6810
SN  - 1613-6829
VL  - 16
IS  - 14
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Lendlein, Andreas
A1  - Heuchel, Matthias
T1  - Shape-memory polymers designed in view of thermomechanical energy storage and conversion systems
BT  - Effective temporary shape fixation by strain-induced formation of supramolecular nanostructures enables high energy density one-way shape-memory polymers
JF  - ACS central science
KW  - Actuators
KW  - Deformation
KW  - Energy
KW  - Energy storage
KW  - Polymers
Y1  - 2021
U6  - https://doi.org/10.1021/acscentsci.1c01032
SN  - 2374-7951
VL  - 7
IS  - 10
SP  - 1599
EP  - 1601
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Hartlieb, Matthias
T1  - Photo-iniferter RAFT polymerization
JF  - Macromolecular rapid communications : publishing the newsletters of the European Polymer Federation
N2  - Light-mediated polymerization techniques offer distinct advantages over polymerization reactions fueled by thermal energy, such as high spatial and temporal control as well as the possibility to work under mild reaction conditions. Reversible addition-fragmentation chain-transfer (RAFT) polymerization is a highly versatile radical polymerization method that can be utilized to control a variety of monomers and produce a vast number of complex macromolecular structures. The use of light to drive a RAFT-polymerization is possible via multiple routes. Besides the use of photo-initiators, or photo-catalysts, the direct activation of the chain transfer agent controlling the RAFT process in a photo-iniferter (PI) process is an elegant way to initiate and control polymerization reactions. Within this review, PI-RAFT polymerization and its advantages over the conventional RAFT process are discussed in detail.
KW  - light
KW  - photo-iniferter reversible addition-fragmentation chain-transfer
KW  - photo-mediated polymerization
KW  - radical polymerization
KW  - reversible
KW  - addition-fragmentation chain-transfer polymerization
Y1  - 2021
U6  - https://doi.org/10.1002/marc.202100514
SN  - 1521-3927
VL  - 43
IS  - 1
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Gaebel, Tina
A1  - Bein, Daniel
A1  - Mathauer, Daniel
A1  - Utecht, Manuel
A1  - Palmer, Richard E.
A1  - Klamroth, Tillmann
T1  - Nonlocal STM manipulation of chlorobenzene on Si(111)-7 x 7
BT  - Potentials, kinetics, and first-principles molecular dynamics calculations for open systems
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - We use quantum chemical cluster models together with constrained density STM Ph CI functional theory (DFT) and ab initio molecular dynamics (AIMD) for open system to simulate tip and rationalize nonlocal scanning tunneling microscope (STM) manipulation experiments for Philh ci chlorobenzene (PhCl) on a Si(111)-7 X 7 surface. We consider three different processes, namely, the electron-induced dissociation of the carbon-chlorine bond for physisorbed PhCl molecules at low temperatures and the electron- or hole-induced desorption of chemisorbed PhCl at 300 K. All processes can be induced nonlocally, i.e., up to several nanometers (nm) away from the injection site, in STM experiments. We rationalize and explain the experimental findings regarding the STM-induced dissociation using constrained DFT. The coupling of STM-induced ion resonances to nuclear degrees of freedom is simulated with AIMD using the Gadzuk averaging approach for open systems. From this data, we predict a 4 fs lifetime for the cationic resonance. For the anion model, desorption could not be observed. In addition, the same cluster models are used for transition-state theory calculations, which are compared to and validated against time-lapse STM experiments.
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jpcc.1c02612
SN  - 1932-7447
SN  - 1932-7455
VL  - 125
IS  - 22
SP  - 12175
EP  - 12184
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Wojnarowska, Zaneta
A1  - Lange, Alyna
A1  - Taubert, Andreas
A1  - Paluch, Marian
T1  - Ion and proton transport in aqueous/nonaqueous acidic tonic liquids for fuel-cell applications-insight from high-pressure dielectric studies
JF  - ACS applied materials & interfaces / American Chemical Society
N2  - The use of acidic ionic liquids and solids as electrolytes in fuel cells is an emerging field due to their efficient proton conductivity and good thermal stability. Despite multiple reports describing conducting properties of acidic ILs, little is known on the charge-transport mechanism in the vicinity of liquid-glass transition and the structural factors governing the proton hopping. To address these issues, we studied two acidic imidazolium-based ILs with the same cation, however, different anions-bulk tosylate vs small methanesulfonate. High-pressure dielectric studies of anhydrous and water-saturated materials performed in the close vicinity of T-g have revealed significant differences in the charge-transport mechanism in these two systems being undetectable at ambient conditions. Thereby, we demonstrated the effect of molecular architecture on proton hopping, being crucial in the potential electrochemical applications of acidic ILs.
KW  - proton hopping
KW  - dielectric spectroscopy
KW  - high pressure
KW  - ion transport
KW  - acidic ionic liquids
Y1  - 2021
U6  - https://doi.org/10.1021/acsami.1c06260
SN  - 1944-8244
SN  - 1944-8252
VL  - 13
IS  - 26
SP  - 30614
EP  - 30624
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - THES
A1  - Strauß, Volker
T1  - Laser-induced carbonization - from fundamentals to applications
N2  - Fabricating electronic devices from natural, renewable resources has been a common goal in engineering and materials science for many years. In this regard, carbon is of special significance due to its biological compatibility. In the laboratory, carbonized materials and their composites have been proven as promising solutions for a range of future applications in electronics, optoelectronics, or catalytic systems. On the industrial scale, however, their application is inhibited by tedious and expensive preparation processes and a lack of control over the processing and material parameters. Therefore, we are exploring new concepts for the direct utilization of functional carbonized materials in electronic applications. In particular, laser-induced carbonization (carbon laser-patterning (CLaP)) is emerging as a new tool for the precise and selective synthesis of functional carbon-based materials for flexible on-chip applications. 
We developed an integrated approach for on-the-spot laser-induced synthesis of flexible, carbonized films with specific functionalities. To this end, we design versatile precursor inks made from naturally abundant starting compounds and reactants to cast films which are carbonized with an infrared laser to obtain functional patterns of conductive porous carbon networks. In our studies we obtained deep mechanistic insights into the formation process and the microstructure of laser-patterned carbons (LP-C). We shed light on the kinetic reaction mechanism based on the interplay between the precursor properties and the reaction conditions. Furthermore, we investigated the use of porogens, additives, and reactants to provide a toolbox for the chemical and physical fine-tuning of the electronic and surface properties and the targeted integration of functional sites into the carbon network. Based on this knowledge, we developed prototype resistive chemical and mechanical sensors. In further studies, we show the applicability of LP-C as electrode materials in electrocatalytic and charge-storage applications.
To put our findings into a common perspective, our results are embedded into the context of general carbonization strategies, fundamentals of laser-induced materials processing, and a broad literature review on state-of-the-art laser-carbonization, in the general part.
N2  - Die Herstellung elektronischer Geräte aus natürlichen, erneuerbaren Ressourcen ist seit vielen Jahren ein gemeinsames Ziel in den Ingenieurs- und Materialwissenschaften. Kohlenstoff kommt dabei aufgrund seiner biologischen Verträglichkeit eine besondere Bedeutung zu. Im Labor haben sich karbonisierte Materialien und ihre Verbundwerkstoffe als vielversprechende Lösungen für eine Reihe zukünftiger Anwendungen in der Elektronik, Optoelektronik oder katalytischen Systemen erwiesen. Im industriellen Maßstab wird ihre Anwendung jedoch durch langwierige und teure Herstellungsverfahren und mangelnde Kontrolle über die Verarbeitungs- und Materialparameter gehemmt. Daher erforschen wir neue Konzepte für die direkte Nutzung funktionaler karbonisierter Materialien in elektronischen Anwendungen. Insbesondere die laserinduzierte Karbonisierung / Kohlenstoff-Laserstrukturierung (KoLaSt) entwickelt sich zu einem neuen Werkzeug für die präzise und selektive Synthese von funktionellen Materialien auf Kohlenstoffbasis für flexible On-Chip-Anwendungen.
Wir haben einen integrierten Ansatz für die direkte laserinduzierte Synthese von flexiblen, karbonisierten Filmen mit spezifischen Funktionalitäten entwickelt. Zu diesem Zweck haben wir vielseitige Vorläufertinten aus natürlich vorkommenden organischen Ausgangsstoffen und Reaktanten entwickelt, um Filme aufzutragen, die mit einem Infrarotlaser karbonisiert werden um dadurch funktionelle Muster aus leitfähigen porösen Kohlenstoffnetzwerken zu erhalten. In unseren Studien haben wir tiefe mechanistische Einblicke in den Bildungsprozess und die Mikrostruktur von laserstrukturierten Kohlenstoffen (LP-C) erhalten. Wir beleuchten den kinetischen Reaktionsmechanismus basierend auf dem Zusammenspiel zwischen den Vorläufereigenschaften und den Reaktionsbedingungen. Darüber hinaus untersuchen wir die Verwendung von Porogenen, Additiven und Reaktanten, um eine Toolbox für die chemische und physikalische Feineinstellung der elektronischen und Oberflächeneigenschaften und die gezielte Integration von funktionellen Einheiten in das Kohlenstoffnetzwerk bereitzustellen. Basierend auf diesem Wissen haben wir Prototypen resistiver chemischer und mechanischer Sensoren entwickelt. In weiteren Studien zeigen wir die Anwendbarkeit von LP-C als Elektrodenmaterialien in elektrokatalytischen und Ladungsspeicheranwendungen.
Um unsere Erkenntnisse in eine allgemeine Perspektive zu bringen, betten wir unsere Ergebnisse im allgemeinen Teil in den Kontext bekannter Karbonisierungsstrategien, Grundlagen der laserinduzierten Materialbearbeitung und einer breiten Literaturübersicht zum Stand der Technik der Laserkarbonisierung ein.
KW  - Laser-Carbonization
KW  - Carbonization
KW  - Chemical Sensors
KW  - Electronic materials
KW  - Laserkarbonisierung
KW  - Karbonisierung
KW  - chemische Sensoren
KW  - elektronische Materialien
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-591995
ER  - 
TY  - JOUR
A1  - Balk, Maria
A1  - Behl, Marc
A1  - Lendlein, Andreas
T1  - Actuators based on oligo[(epsilon-caprolactone)-co-glycolide] with accelerated hydrolytic degradation
JF  - MRS advances : a journal of the Materials Research Society (MRS)
N2  - Polyester-based shape-memory polymer actuators are multifunctional materials providing reversible macroscopic shape shifts as well as hydrolytic degradability. Here, the function-function interdependencies (between shape shifts and degradation behaviour) will determine actuation performance and its life time. In this work, glycolide units were incorporated in poly(epsilon-caprolactone) based actuator materials in order to achieve an accelerated hydrolytic degradation and to explore the function-function relationship. Three different oligo[(epsilon-caprolactone)-co-glycolide] copolymers (OCGs) with similar molecular weights (10.5 +/- 0.5 kg center dot mol(-1)) including a glycolide content of 8, 16, and 26 mol% (ratio 1:1:1 wt%) terminated with methacrylated moieties were crosslinked. The obtained actuators provided a broad melting transition in the range from 27 to 44 degrees C. The hydrolytic degradation of programmed OCG actuators (200% of elongation) resulted in a reduction of sample mass to 51 wt% within 21 days at pH = 7.4 and 40 degrees C. Degradation results in a decrease of T-m associated to the actuating units and increasing T-m associated to the skeleton forming units. The actuation capability decreased almost linear as function of time. After 11 days of hydrolytic degradation the shape-memory functionality was lost. Accordingly, a fast degradation behaviour as required, e.g., for actuator materials intended as implant material can be realized.
KW  - actuation
KW  - shape memory
KW  - polymer
KW  - crystalline
Y1  - 2020
U6  - https://doi.org/10.1557/adv.2019.447
SN  - 2059-8521
VL  - 5
IS  - 12-13
SP  - 655
EP  - 666
PB  - Cambridge University Press
CY  - New York, NY
ER  - 
TY  - JOUR
A1  - Liang, Xiao
A1  - Behl, Marc
A1  - Lützow, Karola
A1  - Lendlein, Andreas
T1  - Cooligomers from morpholine-2,5-dione and para-dioxanone and catalyst complex SnOct(2)/2-hydroxyethyl sulfide
JF  - MRS advances : a journal of the Materials Research Society (MRS)
N2  - Complexes from catalysts and initiator can be used to insert a specific number of additional chemical functional groups in (co)polymers prepared by ring-opening polymerization (ROP) of lactones. We report on the synthesis of cooligomers from sec-butyl-morpholine-2,5-dione (SBMD) and para-dioxanone (PDX) by ROP with varied feed ratios in the bulk using the catalyst complex SnOct(2)/2-hydroxyethyl sulfide. M-n of the cooligomers (determined by GPC) decreased with decreasing SBMD feed ratio from 4200 +/- 420 to 800 +/- 80 g mol(-1). When the feed ratio was reduced from 80 to 50 mol% the molar ratio of SBMD of the cooligomers (determined by H-1-NMR) remained nearly unchanged between 81 and 86 mol% and was attributed to a higher reactivity of SBMD. This assumption was confirmed by fractionation of GPC, in which an increase of SBMD with increasing molecular weight was observed. The catalyst/initiator system provides a high potential to create orthogonal building blocks by cleavage of the sulfide bond.
Y1  - 2021
U6  - https://doi.org/10.1557/s43580-021-00082-5
SN  - 2059-8521
VL  - 6
IS  - 32
SP  - 764
EP  - 768
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - López-Salas, Nieves
A1  - Albero, Josep
T1  - CxNy
BT  - new carbon nitride organic photocatalysts
JF  - Frontiers in Materials
N2  - The search for metal-free and visible light-responsive materials for photocatalytic applications has attracted the interest of not only academics but also the industry in the last decades. Since graphitic carbon nitride (g-C3N4) was first reported as a metal-free photocatalyst, this has been widely investigated in different light-driven reactions. However, the high recombination rate, low electrical conductivity, and lack of photoresponse in most of the visible range have elicited the search for alternatives. In this regard, a broad family of carbon nitride (CxNy) materials was anticipated several decades ago. However, the attention of the researchers in these materials has just been awakened in the last years due to the recent success in the syntheses of some of these materials (i.e., C3N3, C2N, C3N, and C3N5, among others), together with theoretical simulations pointing at the excellent physico-chemical properties (i.e., crystalline structure and chemical morphology, electronic configuration and semiconducting nature, or high refractive index and hardness, among others) and optoelectronic applications of these materials. The performance of CxNy, beyond C3N4, has been barely evaluated in real applications, including energy conversion, storage, and adsorption technologies, and further work must be carried out, especially experimentally, in order to confirm the high expectations raised by simulations and theoretical calculations. Herein, we have summarized the scarce literature related to recent results reporting the synthetic routes, structures, and performance of these materials as photocatalysts. Moreover, the challenges and perspectives at the forefront of this field using CxNy materials are disclosed. We aim to stimulate the research of this new generation of CxNy-based photocatalysts, beyond C3N4, with improved photocatalytic efficiencies by harnessing the striking structural, electronic, and optical properties of this new family of materials.
KW  - CXNY
KW  - carbon nitrides
KW  - C2N
KW  - C3N
KW  - C1N1
KW  - C3N5
KW  - photocatalysis
Y1  - 2021
U6  - https://doi.org/10.3389/fmats.2021.772200
SN  - 2296-8016
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Izraylit, Victor
A1  - Hommes-Schattmann, Paul J.
A1  - Neffe, Axel T.
A1  - Gould, Oliver E. C.
A1  - Lendlein, Andreas
T1  - Polyester urethane functionalizable through maleimide side-chains and cross-linkable by polylactide stereocomplexes
JF  - European polymer journal
N2  - Sustainable multifunctional alternatives to fossil-derived materials, which can be functionalized and are degradable, can be envisioned by combining naturally derived starting materials with an established polymer design concept. Modularity and chemical flexibility of polyester urethanes (PEU) enable the combination of segments bearing functionalizable moieties and the tailoring of the mechanical and thermal properties. In this work, a PEU multiblock structure was synthesized from naturally derived L-lysine diisocyanate ethyl ester (LDI), poly(L-lactide) diol (PLLA) and N-(2,3-dihydroxypropyl)-maleimide (MID) in a one-step reaction. A maleimide side-chain (MID) provided a reactive site for the catalyst-free coupling of thiols shown for L-cysteine with a yield of 94%. Physical cross-links were generated by blending the PEU with poly(D-lactide) (PDLA), upon which the PLLA segments of the PEU and the PDLA formed stereocomplexes. Stereocomplexation occurred spontaneously during solution casting and was investigated with WAXS and DSC. Stereocomplex crystallites were observed in the blends, while isotactic PLA crystallization was not observed. The presented material platform with tailorable mechanical properties by blending is of specific interest for engineering biointerfaces of implants or carrier systems for bioactive molecules.
KW  - Functionalization
KW  - Polylactide stereocomplex
KW  - Biomolecules coupling
Y1  - 2020
U6  - https://doi.org/10.1016/j.eurpolymj.2020.109916
SN  - 0014-3057
SN  - 1873-1945
VL  - 137
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Izraylit, Victor
A1  - Hommes-Schattmann, Paul Jacob
A1  - Neffe, Axel T.
A1  - Gould, Oliver E. C.
A1  - Lendlein, Andreas
T1  - Alkynyl-functionalized chain-extended PCL for coupling to biological molecules
JF  - European polymer journal
N2  - Chemical functionalization of poly(epsilon-caprolactone) (PCL) enables a molecular integration of additional function. Here, we report an approach to incorporate reactive alkynyl side-groups by synthesizing a chain-extended PCL, where the reactive site is introduced through the covalently functionalizable chain extender 3 (prop-2-yn-1-yloxy)propane-1,2-diol (YPD). Chain-extended PCL with M-w of 101 to 385 kg.mol(-1) were successfully synthesized in a one-pot reaction from PCL-diols with various molar masses, L-lysine ethyl ester diisocyanate (LDI) or trimethyl(hexamethylene)diisocyanate (TMDI), and YPD, in which the density of functionalizable groups and spacing between them can be controlled by the composition of the polymer. The employed diisocyanate compounds and YPD possess an asymmetric structure and form a non-crystallizable segment leaving the PCL crystallites to dominate the material's mechanical properties. The mixed glass transition temperature T-g = - 60 to - 46 degrees C of the PCL/polyurethane amorphous phase maintains the synthesized materials in a highly elastic state at ambient and physiological conditions. Reaction conditions for covalent attachment in copper(I)-catalyzed azide-alkyne-cycloaddition reactions (CuAAC) in solution were optimized in a series of model reactions between the alkyne moieties of the chain-extended PCL and benzyl azide, reaching conversions over 95% of the alkyne moieties and with yields of up to 94% for the purified functionalized PCL. This methodology was applied for reaction with the azide-functionalized cell adhesion peptide GRGDS. The required modification of the peptide provides selectivity in the coupling reactions. The obtained results suggest that YPD could potentially be employed as versatile molecular unit for the creation of a variety of functionalizable polyesters as well as polyurethanes and polycarbonates offering efficient and selective click-reactions.
KW  - copper-catalyzed alkyne-azide cycloaddition
KW  - chain-extended
KW  - polycaprolactone
KW  - RGD-peptide
KW  - side-chains functionalization
Y1  - 2020
U6  - https://doi.org/10.1016/j.eurpolymj.2020.109908
SN  - 0014-3057
SN  - 1873-1945
VL  - 136
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Liu, Yue
A1  - Gould, Oliver E. C.
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - On demand sequential release of (sub)micron particles controlled by size and temperature
JF  - Small : nano micro
N2  - Polymeric devices capable of releasing submicron particles (subMP) on demand are highly desirable for controlled release systems, sensors, and smart surfaces. Here, a temperature-memory polymer sheet with a programmable smooth surface served as matrix to embed and release polystyrene subMP controlled by particle size and temperature. subMPs embedding at 80 degrees C can be released sequentially according to their size (diameter D of 200 nm, 500 nm, 1 mu m) when heated. The differences in their embedding extent are determined by the various subMPs sizes and result in their distinct release temperatures. Microparticles of the same size (D approximate to 1 mu m) incorporated in films at different programming temperatures T-p (50, 65, and 80 degrees C) lead to a sequential release based on the temperature-memory effect. The change of apparent height over the film surface is quantified using atomic force microscopy and the realization of sequential release is proven by confocal laser scanning microscopy. The demonstration and quantification of on demand subMP release are of technological impact for assembly, particle sorting, and release technologies in microtechnology, catalysis, and controlled release.
KW  - on demand particle release
KW  - temperature-memory effect
KW  - thermosensitive
KW  - polymer surface
Y1  - 2022
U6  - https://doi.org/10.1002/smll.202104621
SN  - 1613-6810
SN  - 1613-6829
VL  - 18
IS  - 5
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Moradian, Hanieh
A1  - Gossen, Manfred
A1  - Lendlein, Andreas
T1  - Co-delivery of genes can be confounded by bicistronic vector design
JF  - MRS Communications
N2  - Maximizing the efficiency of nanocarrier-mediated co-delivery of genes for co-expression in the same cell is critical for many applications. Strategies to maximize co-delivery of nucleic acids (NA) focused largely on carrier systems, with little attention towards payload composition itself. Here, we investigated the effects of different payload designs: co-delivery of two individual "monocistronic" NAs versus a single bicistronic NA comprising two genes separated by a 2A self-cleavage site. Unexpectedly, co-delivery via the monocistronic design resulted in a higher percentage of co-expressing cells, while predictive co-expression via the bicistronic design remained elusive. Our results will aid the application-dependent selection of the optimal methodology for co-delivery of genes.
KW  - Molecular
KW  - Packaging
KW  - Protein
Y1  - 2022
U6  - https://doi.org/10.1557/s43579-021-00128-7
SN  - 2159-6859
SN  - 2159-6867
VL  - 12
IS  - 2
SP  - 145
EP  - 153
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Lindic, Tilen
A1  - Sinha, Shreya
A1  - Mattsson, Stefan
A1  - Paulus, Beate
T1  - Prediction of a model crystal structure for Ni2F5 by first-principles calculations
JF  - Zeitschrift für Naturforschung : B, Chemical sciences
N2  - Electrochemical fluorination in anhydrous HF, also known as the Simons process, is a widely used industrial method for fluorination of organic compounds. Its mechanism, being not so well understood, has long been debated and is believed to involve higher valent nickel fluorides formed on the nickel-plated anode during the process. One of these is speculated to be Ni2F5, which was previously reported in the literature and assigned via infrared spectroscopy, but its crystal structure is not yet known. We have identified known crystal structures of compounds with similar stoichiometries as Ni2F5 and utilized them as a starting point for our periodic DFT investigations, applying the PBE+U method. Ni2F5 as the most stable polymorph was found to be of the same crystal structure as another mixed valent fluoride, Cr2F5. The calculated lattice parameters are a = 7.24 angstrom, b = 7.40 angstrom, c = 7.08 angstrom and beta = 118.9 degrees with an antiferromagnetic ordering of the nickel magnetic moments.
KW  - crystal structure prediction
KW  - DFT
KW  - Ni2F5
Y1  - 2022
U6  - https://doi.org/10.1515/znb-2022-0072
SN  - 0932-0776
SN  - 1865-7117
VL  - 77
IS  - 6
SP  - 469
EP  - 473
PB  - De Gruyter
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Laroque, Sophie
A1  - Reifarth, Martin
A1  - Sperling, Marcel
A1  - Kersting, Sebastian
A1  - Kloepzig, Stefanie
A1  - Budach, Patrick
A1  - Hartlieb, Matthias
A1  - Storsberg, Joachim
T1  - Impact of multivalence and self-assembly in the design of polymeric antimicrobial peptide mimics
JF  - ACS applied materials & interfaces
N2  - Antimicrobial resistance is an increasingly serious challenge for public health and could result in dramatic negative consequences for the health care sector during the next decades. To solve this problem, antibacterial materials that are unsusceptible toward the development of bacterial resistance are a promising branch of research. In this work, a new type of polymeric antimicrobial peptide mimic featuring a bottlebrush architecture is developed, using a combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and ring-opening metathesis polymerization (ROMP). This approach enables multivalent presentation of antimicrobial subunits resulting in improved bioactivity and an increased hemocompatibility, boosting the selectivity of these materials for bacterial cells. Direct probing of membrane integrity of treated bacteria revealed highly potent membrane disruption caused by bottlebrush copolymers. Multivalent bottlebrush copolymers clearly outperformed their linear equivalents regarding bioactivity and selectivity. The effect of segmentation of cationic and hydrophobic subunits within bottle brushes was probed using heterograft copolymers. These materials were found to self-assemble under physiological conditions, which reduced their antibacterial activity, highlighting the importance of precise structural control for such applications. To the best of our knowledge, this is the first example to demonstrate the positive impact of multivalence, generated by a bottlebrush topology in polymeric antimicrobial peptide mimics, making these polymers a highly promising material platform for the design of new bactericidal systems.
KW  - RAFT polymerization
KW  - ROMP
KW  - antimicrobial polymers
KW  - antimicrobial peptide
KW  - mimics
KW  - bottlebrush copolymers
Y1  - 2020
U6  - https://doi.org/10.1021/acsami.0c05944
SN  - 1944-8244
SN  - 1944-8252
VL  - 12
IS  - 27
SP  - 30052
EP  - 30065
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Bouakline, Foudhil
A1  - Tremblay, Jean Christophe
T1  - Is it really possible to control aromaticity of benzene with light?
JF  - Physical chemistry, chemical physics : PCCP
N2  - Recent theoretical investigations claim that tailored laser pulses may selectively steer benzene's aromatic ground state to localized non-aromatic excited states. For instance, it has been shown that electronic wavepackets, involving the two lowest electronic eigenstates, exhibit subfemtosecond charge oscillation between equivalent Kekule resonance structures. In this contribution, we show that such dynamical electron-localization in the molecule-fixed frame contravenes the principle of the indistinguishability of identical particles. This breach stems from a total omission of the nuclear degrees of freedom, giving rise to nonsymmetric electronic wavepackets under nuclear permutations. Enforcement of the latter leads to entanglement between the electronic and nuclear states. To obey quantum statistics, the entangled molecular states should involve compensating nuclear-permutation symmetries. This in turn engenders complete quenching of dynamical electron-localization in the molecule-fixed frame. Indeed, for the (six-fold) equilibrium geometry of benzene, group-theoretic analysis reveals that any electronic wavepacket exhibits a (D-6h) totally symmetric electronic density, at all times. Thus, our results clearly show that the six carbon atoms, and the six C-C bonds, always have equal Mulliken charges, and equal bond orders, respectively. However, electronic wavepackets may display dynamical localization of the electronic density in the space-fixed frame, whenever they involve both even and odd space-inversion (parity) or permutation-inversion symmetry. Dynamical spatial-localization can be probed experimentally in the laboratory frame, but it should not be deemed equivalent to charge oscillation between benzene's identical electronic substructures, such as Kekule resonance structures.
Y1  - 2020
U6  - https://doi.org/10.1039/c9cp06794a
SN  - 1463-9076
SN  - 1463-9084
VL  - 22
IS  - 27
SP  - 15401
EP  - 15412
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Behl, Marc
A1  - Razzaq, Muhammad Yasar
A1  - Mazurek-Budzynska, Magdalena
A1  - Lendlein, Andreas
T1  - Polyetheresterurethane based porous scaffolds with tailorable architectures by supercritical CO2 foaming
JF  - MRS advances
N2  - Porous three-dimensional (3D) scaffolds are promising treatment options in regenerative medicine. Supercritical and dense-phase fluid technologies provide an attractive alternative to solvent-based scaffold fabrication methods. In this work, we report on the fabrication of poly-etheresterurethane (PPDO-PCL) based porous scaffolds with tailorable pore size, porosity, and pore interconnectivity by using supercritical CO2(scCO(2)) fluid-foaming. The influence of the processing parameters such as soaking time, soaking temperature and depressurization on porosity, pore size, and interconnectivity of the foams were investigated. The average pore diameter could be varied between 100-800 mu m along with a porosity in the range from (19 +/- 3 to 61 +/- 6)% and interconnectivity of up to 82%. To demonstrate their applicability as scaffold materials, selected foams were sterilized via ethylene oxide sterilization. They showed negligible cytotoxicity in tests according to DIN EN ISO 10993-5 and 10993-12 using L929 cells. The study demonstrated that the pore size, porosity and the interconnectivity of this multi-phase semicrystalline polymer could be tailored by careful control of the processing parameters during the scCO(2)foaming process. In this way, PPDO-PCL scaffolds with high porosity and interconnectivity are potential candidate materials for regenerative treatment options.
Y1  - 2020
U6  - https://doi.org/10.1557/adv.2020.345
SN  - 2059-8521
VL  - 5
IS  - 45
SP  - 2317
EP  - 2330
PB  - Cambridge University Press
CY  - New York, NY
ER  - 
TY  - THES
A1  - Hwang, Jinyeon
T1  - Influence of the pore structure and chemical properties of all-carbon composites on their electrochemical properties in lithium-ion capacitors
T1  - Einfluss der Porenstruktur und chemischen Eigenschaften von All-Carbon-Kompositen auf ihre elektrochemischen Eigenschaften in Lithium-Ionen-Kondensatoren
N2  - Lithium-ion capacitors (LICs) are promising energy storage devices by asymmetrically combining anode with a high energy density close to lithium-ion batteries and cathode with a high power density and long-term stability close to supercapacitors. For the further improvement of LICs, the development of electrode materials with hierarchical porosity, nitrogen-rich lithiophilic sites, and good electrical conductivity is essential. Nitrogen-rich all-carbon composite hybrids are suitable for these conditions along with high stability and tunability, resulting in a breakthrough to achieve the high performance of LICs. In this thesis, two different all-carbon composites are suggested to unveil how the pore structure of lithiophilic composites influences the properties of LICs. Firstly, the composite with 0-dimensional zinc-templated carbon (ZTC) and hexaazatriphenylene-hexacarbonitrile (HAT) is examined how the pore structure is connected to Li-ion storage property as LIC electrode. As the pore structure of HAT/ZTC composite is easily tunable depending on the synthetic factor and ratio of each component, the results will allow deeper insights into Li-ion dynamics in different porosity, and low-cost synthesis by optimization of the HAT:ZTC ratio. Secondly, the composite with 1-dimensional nanoporous carbon fiber (ACF) and cost-effective melamine is proposed as a promising all-carbon hybrid for large-scale application. Since ACF has ultra-micropores, the numerical structure-property relationships will be calculated out not only from total pore volume but more specifically from ultra-micropore volume. From these results above, it would be possible to understand how hybrid all-carbon composites interact with lithium ions in nanoscale as well as how structural properties affect the energy storage performance. Based on this understanding derived from the simple materials modeling, it will provide a clue to design the practical hybrid materials for efficient electrodes in LICs.
N2  - Lithium-Ionen-Kondensatoren (LICs) sind vielversprechende Energiespeicher, indem sie eine Anode mit einer vergleichsweise hohen Energiedichte wie die von Lithium-Ionen-Batterien und eine Kathode mit hoher Leistungsdichte und Langzeitstabilität wie die Superkondensatoren asymmetrisch kombinieren. Für die weitere Verbesserung von LICs ist die Entwicklung von Elektrodenmaterialien mit hierarchischer Porosität, stickstoffreichen lithiophilen Zentren und guter elektrischer Leitfähigkeit unerlässlich. Stickstoffreiche Vollcarbon-Verbundwerkstoffe sind für diese Bedingungen zusammen mit hoher Stabilität geeignet, was zu einem Durchbruch bei der Erzielung der hohen Leistung von LICs führt. In dieser Dissertation werden zwei verschiedene All-Carbon-Komposite vorgeschlagen, um aufzudecken, wie die Porenstruktur von lithiophilen Kompositen die Eigenschaften von LICs beeinflusst. Zunächst wird der Verbund mit 0-dimensionalem Zink-Templat-Kohlenstoff (ZTC) und Hexaazatriphenylen-Hexacarbonitril (HAT) untersucht, wie die Porenstruktur mit der Li-Ionen-Speichereigenschaft als LIC-Elektrode verbunden ist. Da die Porenstruktur von HAT/ZTC-Kompositen je nach Synthesefaktor und Verhältnis jeder Komponente leicht einstellbar ist, werden die Ergebnisse tiefere Einblicke in die Li-Ionen-Dynamik verschiedener Porositäten und eine kostengünstige Synthese durch Optimierung des Verhältnisses ermöglichen. Zweitens wird der Verbund mit 1-dimensionaler nanoporöser Kohlefaser (ACF) und kostengünstigem Melamin als vielversprechender All-Carbon-Hybrid für die großtechnische Anwendung vorgeschlagen. Da ACF Ultra-Mikroporen aufweist, werden die Struktur-Eigenschafts-Beziehungen nicht nur aus der Gesamtporen, sondern insbesondere aus Ultra-Mikroporen berechnet. Aus den obigen Ergebnissen wäre es möglich zu verstehen, wie hybride All-Carbon-Komposite mit Lithiumionen im Nanomaßstab interagieren und wie sich strukturelle Eigenschaften auf die Energiespeicherleistung auswirken. Basierend auf diesem aus der einfachen Materialmodellierung abgeleiteten Verständnis wird es einen Anhaltspunkt für das Design praktischer Hybridmaterialien für effiziente Elektroden in LICs liefern.
KW  - lithium ion capacitors
KW  - hierarchical pore structure
KW  - lithiophilicity
KW  - all-carbon composites
KW  - All-Carbon-Kompositen
KW  - hierarchische Porenstruktur
KW  - Lithiophilizität
KW  - Lithium-Ionen-Kondensatoren
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-591683
ER  - 
TY  - JOUR
A1  - Liu, Yue
A1  - Gould, Oliver E. C.
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Shape-memory actuation of individual micro-/nanofibers
JF  - MRS Advances
N2  - Advances in the fabrication and characterization of polymeric nanomaterials has greatly advanced the miniaturization of soft actuators, creating materials capable of replicating the functional physical behavior previously limited to the macroscale. Here, we demonstrate how a reversible shape-memory polymer actuation can be generated in a single micro/nano object, where the shape change during actuation of an individual fiber can be dictated by programming using an AFM-based method. Electrospinning was used to prepare poly(epsilon-caprolactone) micro-/nanofibers, which were fixed and crosslinked on a structured silicon wafer. The programming as well as the observation of recovery and reversible displacement of the fiber were performed by vertical three point bending, using an AFM testing platform introduced here. A plateau tip was utilized to improve the stability of the fiber contact and working distance, enabling larger deformations and greater rbSMPA performance. Values for the reversible elongation of epsilon(rev)= 3.4 +/- 0.1% and 10.5 +/- 0.1% were obtained for a single micro (d = 1.0 +/- 0.2 mu m) and nanofiber (d = 300 +/- 100 nm) in cyclic testing between the temperatures 10 and 60 degrees C. The reversible actuation of the nanofiber was successfully characterized for 10 cycles. The demonstration and characterization of individual shape-memory nano and microfiber actuators represents an important step in the creation of miniaturized robotic devices capable of performing complex physical functions at the length scale of cells and structural component of the extracellular matrix.
Y1  - 2020
U6  - https://doi.org/10.1557/adv.2020.276
SN  - 2059-8521
VL  - 5
IS  - 46-47
SP  - 2391
EP  - 2399
PB  - Cambridge Univ. Press
CY  - New York
ER  - 
TY  - JOUR
A1  - Henning, Ricky
A1  - Liebig, Ferenc
A1  - Prietzel, Claudia Christina
A1  - Klemke, Bastian
A1  - Koetz, Joachim
T1  - Gold nanotriangles with magnetite satellites
JF  - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects
N2  - This work describes the synthesis of hybrid particles of gold nanotriangles (AuNTs) with magnetite nanoparticles (MNPs) by using 1-mercaptopropyl-3-trimethoxysilan (MPTMS) and L-cysteine as linker molecules. Due to the combination of superparamagnetic properties of MNPs with optical properties of the AuNTs, nanoplatelet-satellite hybrid nanostructures with combined features become available. By using MPTMS with silan groups as linker molecule a magnetic "cloud" with embedded AuNTs can be separated. In presence of L-cysteine as linker molecule at pH > pH(iso) a more unordered aggregate structure of MNPs is obtained due to the dimerization of the L-cysteine. At pH < pH(iso) water soluble positively charged AuNTs with satellite MNPs can be synthesized. The time-dependent loading with MNP satellites under release of the extinction and magnetization offer a hybrid material, which is of special relevance for biomedical applications and plasmonic catalysis.
KW  - nanotriangles
KW  - Superparamagnetic magnetite
KW  - Satellite hybrid
KW  - nanostructures
KW  - L-Cysteine
KW  - UV-Vis-NIR
KW  - HRTEM
Y1  - 2020
U6  - https://doi.org/10.1016/j.colsurfa.2020.124913
SN  - 0927-7757
SN  - 1873-4359
VL  - 600
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Bastian, Philipp U.
A1  - Nacak, Selma
A1  - Roddatis, Vladimir
A1  - Kumke, Michael Uwe
T1  - Tracking the motion of lanthanide ions within core-shell-shell NaYF4 nanocrystals via resonance energy transfer
JF  - The journal of physical chemistry : C
N2  - Lanthanide resonance energy transfer (LRET) was used to investigate the motion of dopant ions during the synthesis of core-shell-shell-nanocrystals (NCs) that are frequently used as frequency upconversion materials. Reaction conditions (temperature, solvent) as well as lattice composition and precursors were adapted from a typical hydrothermal synthesis approach used to obtain upconversion nanoparticles (UCNPs). Instead of adding the lanthanide ions Yb3+/Er3+ as the sensitizer/activator couple, Eu3+/Nd3+ as the donor/acceptor were added as the LRET pair to the outer shell (Eu-3) and the core (Nd-3). By tailoring the thickness of the insulation shell ("middle shell"), the expected distance between the donor and the acceptor was increased beyond 2 R-0, a distance for which no LRET is expected. The successful synthesis of core- shell-shell NCs with different thicknesses of the insulation layer was demonstrated by high-resolution transmission electron microscopy measurement. The incorporation of the Eu3+ ions into the NaYF4 lattice was investigated by high-resolution time-resolved luminescence measurements. Two major Eu3+ species (bulk and surface) were found. This was supported by steady-state as well as time-resolved luminescence data. Based on the luminescence decay kinetics, the intermixing of lanthanides during synthesis of core- shell UCNPs was evaluated. The energy transfer between Eu3+ (donor) and Nd3+ (acceptor) ions was exploited to quantify the motion of the dopant ions. This investigation reveals the migration of Ln(3+) ions between different compatiments in core-shell NCs and affects the concept of using core-shell architectures to increase the efficiency of UCNPs. In order to obtain well-separated core and shell structures with different dopants, alternative concepts are needed.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jpcc.0c02588
SN  - 1932-7447
SN  - 1932-7455
VL  - 124
IS  - 20
SP  - 11229
EP  - 11238
PB  - American Chemical Society
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Neffe, Axel T.
A1  - Izraylit, Victor
A1  - Hommes-Schattmann, Paul J.
A1  - Lendlein, Andreas
T1  - Soft, formstable (Co)polyester blend elastomers
JF  - Nanomaterials : open access journal
N2  - High crystallization rate and thermomechanical stability make polylactide stereocomplexes effective nanosized physical netpoints. Here, we address the need for soft, form-stable degradable elastomers for medical applications by designing such blends from (co)polyesters, whose mechanical properties are ruled by their nanodimensional architecture and which are applied as single components in implants. By careful controlling of the copolymer composition and sequence structure of poly[(L-lactide)-co-(epsilon-caprolactone)], it is possible to prepare hyperelastic polymer blends formed through stereocomplexation by adding poly(D-lactide) (PDLA). Low glass transition temperature T-g <= 0 degrees C of the mixed amorphous phase contributes to the low Young's modulus E. The formation of stereocomplexes is shown in DSC by melting transitions T-m > 190 degrees C and in WAXS by distinct scattering maxima at 2 theta = 12 degrees and 21 degrees. Tensile testing demonstrated that the blends are soft (E = 12-80 MPa) and show an excellent hyperelastic recovery R-rec = 66-85% while having high elongation at break epsilon(b) up to >1000%. These properties of the blends are attained only when the copolymer has 56-62 wt% lactide content, a weight average molar mass >140 kg center dot mol(-1), and number average lactide sequence length >= 4.8, while the blend is formed with a content of 5-10 wt% of PDLA. The devised strategy to identify a suitable copolymer for stereocomplexation and blend formation is transferable to further polymer systems and will support the development of thermoplastic elastomers suitable for medical applications.
KW  - thermoplastic elastomer
KW  - biomaterial
KW  - stereocomplexes
KW  - mechanical
KW  - properties
KW  - form stability
KW  - crystallinity
Y1  - 2021
U6  - https://doi.org/10.3390/nano11061472
SN  - 2079-4991
VL  - 11
IS  - 6
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Bäckemo, Johan Dag Valentin
A1  - Liu, Yue
A1  - Lendlein, Andreas
T1  - Bio-inspired and computer-supported design of modulated shape changes in polymer materials
JF  - MRS communications / a publication of the Materials Research Society
N2  - The Venus flytrap is a fascinating plant with a finely tuned mechanical bi-stable system, which can switch between mono- and bi-stability. Here, we combine geometrical design of compliant mechanics and the function of shape-memory polymers to enable switching between bi- and mono-stable states. Digital design and modelling using the Chained Beam Constraint Model forecasted two geometries, which were experimentally realized as structured films of cross-linked poly[ethylene-co-(vinyl acetate)] supported by digital manufacturing. Mechanical evaluation confirmed our predicted features. We demonstrated that a shape-memory effect could switch between bi- and mono-stability for the same construct, effectively imitating the Venus flytrap.
KW  - Additive manufacturing
KW  - Biomimetic
KW  - Shape memory
KW  - Modelling
KW  - Polymer
Y1  - 2021
U6  - https://doi.org/10.1557/s43579-021-00056-6
SN  - 2159-6867
VL  - 11
IS  - 4
SP  - 462
EP  - 469
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Das, Abhijna
A1  - Noack, Sebastian
A1  - Schlaad, Helmut
A1  - Reiter, Günter
A1  - Reiter, Renate
T1  - Exploring pathways to equilibrate Langmuir polymer films
JF  - Langmuir
N2  - Focusing on the phase-coexistence region in Langmuir films of poly(L-lactide), we investigated changes in nonequilibrated morphologies and the corresponding features of the isotherms induced by different experimental pathways of lateral compression and expansion. In this coexistence region, the surface pressure II was larger than the expected equilibrium value and was found to increase upon compression, i.e., exhibited a nonhorizontal plateau. As shown earlier by using microscopic techniques [Langmuir 2019, 35, 6129-6136], in this plateau region, well-ordered mesoscopic clusters coexisted with a surrounding matrix phase. We succeeded in reducing Pi either by slowing down the rate of compression or through increasing the waiting time after stopping the movement of the barriers, which allowed for relaxations in the coexistence region. Intriguingly, the most significant pressure reduction was observed when recompressing a film that had already been compressed and expanded, if the recompression was started from an area value smaller than the one anticipated for the onset of the coexistence region. This observation suggests a "self-seeding" behavior, i.e., pre-existing nuclei allowed to circumvent the nucleation step. The decrease in Pi was accompanied by a transformation of the initially formed metastable mesoscopic clusters into a thermodynamically favored filamentary morphology. Our results demonstrate that it is practically impossible to obtain fully equilibrated coexisting phases in a Langmuir polymer film, neither under conditions of extremely slow continuous compression nor for long waiting times at a constant area in the coexistence region which allow for reorganization.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.langmuir.0c01268
SN  - 0743-7463
VL  - 36
IS  - 28
SP  - 8184
EP  - 8192
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Belasri, Khadija
A1  - Topal, Leila
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
A1  - Fulop, Ferenc
A1  - Szatmari, Istvan
T1  - Synthesis and conformational analysis of naphthoxazine-fused phenanthrene derivatives
JF  - Molecules
N2  - The synthesis of new phenanthr[9,10-e][1,3]oxazines was achieved by the direct coupling of 9-phenanthrol with cyclic imines in the modified aza-Friedel-Crafts reaction followed by the ring closure of the resulting bifunctional aminophenanthrols with formaldehyde. Aminophenanthrol-type Mannich bases were synthesised and transformed to phenanthr[9,10-e][1,3]oxazines via [4 + 2] cycloaddition. Detailed NMR structural analyses of the new polyheterocycles as well as conformational studies including Density Functional Theory (DFT) modelling were performed. The relative stability of ortho-quinone methides (o-QMs) was calculated, the geometries obtained were compared with the experimentally determined NMR structures, and thereby, the regioselectivity of the reactions has been assigned.
KW  - modified Mannich reaction
KW  - cyclic imines
KW  - [4+2] cycloaddition
KW  - NMR
KW  - spectroscopy
KW  - conformational analysis
KW  - DFT calculations
Y1  - 2020
U6  - https://doi.org/10.3390/molecules25112524
SN  - 1420-3049
VL  - 25
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Farhan, Muhammad
A1  - Behl, Marc
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Origami hand for soft robotics driven by thermally controlled polymeric fiber actuators
JF  - MRS communications / a publication of the Materials Research Society
N2  - Active fibers can serve as artificial muscles in robotics or components of smart textiles. Here, we present an origami hand robot, where single fibers control the reversible movement of the fingers. A recovery/contracting force of 0.2 N with a work capacity of 0.175 kJ kg(-1) was observed in crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, which could enable the bending movement of the fingers by contraction upon heating. The reversible opening of the fingers was attributed to a combination of elastic recovery force of the origami structure and crystallization-induced elongation of the fibers upon cooling.
KW  - Robotics
KW  - Polymer
KW  - Fiber
KW  - Actuation
KW  - Shape-memory
Y1  - 2021
U6  - https://doi.org/10.1557/s43579-021-00058-4
SN  - 2159-6859
SN  - 2159-6867
VL  - 11
IS  - 4
SP  - 476
EP  - 482
PB  - Springer
CY  - Berlin
ER  - 
TY  - THES
A1  - Frank, Bradley D.
T1  - Complex and adaptive soft colloids
BT  - templated from reconfigurable jamus emulsions
Y1  - 2023
ER  - 
TY  - JOUR
A1  - Kossmann, Janina
A1  - Sanchez-Manjavacas, Maria Luz Ortiz
A1  - Brandt, Jessica
A1  - Heil, Tobias
A1  - López-Salas, Nieves
A1  - Albero, Josep
T1  - Mn(ii) sub-nanometric site stabilization in noble, N-doped carbonaceous materials for electrochemical CO2 reduction
JF  - Chemical communications : ChemComm / The Royal Society of Chemistry
N2  - The preparation of stable and efficient electrocatalysts comprising abundant and non-critical row-materials is of paramount importance for their industrial implementation. Herein, we present a simple synthetic route to prepare Mn(ii) sub-nanometric active sites over a highly N-doped noble carbonaceous support. This support not only promotes a strong stabilization of the Mn(ii) sites, improving its stability against oxidation, but also provides a convenient coordination environment in the Mn(ii) sites able to produce CO, HCOOH and CH3COOH from electrochemical CO2 reduction.
Y1  - 2022
U6  - https://doi.org/10.1039/d2cc00585a
SN  - 1359-7345
SN  - 1364-548X
VL  - 58
IS  - 31
SP  - 4841
EP  - 4844
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Dettmann, Sophie
A1  - Huittinen, Nina Maria
A1  - Jahn, Nicolas
A1  - Kretzschmar, Jerome
A1  - Kumke, Michael
A1  - Kutyma, Tamara
A1  - Lohmann, Janik
A1  - Reich, Tobias
A1  - Schmeide, Katja
A1  - Azzam, Salim Shams Aldin
A1  - Spittler, Leon
A1  - Stietz, Janina
T1  - Influence of gluconate on the retention of Eu(III), Am(III), Th(IV), Pu(IV), and U(VI) by C-S-H (C/S = 0.8)
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The retention of actinides in different oxidation states (An(X), X = III, IV, VI) by a calcium-silicate-hydrate (C-S-H) phase with a Ca/Si (C/S) ratio of 0.8 was investigated in the presence of gluconate (GLU). The actinides considered were Am(III), Th(IV), Pu(IV), and U(VI). Eu(III) was investigated as chemical analogue for Am(III) and Cm(III). In addition to the ternary systems An(X)/GLU/C-S-H, also binary systems An(X)/C-S-H, GLU/C-S-H, and An(X)/GLU were studied. Complementary analytical techniques were applied to address the different specific aspects of the binary and ternary systems. Time-resolved laser-induced luminescence spectroscopy (TRLFS) was applied in combination with parallel factor analysis (PARAFAC) to identify retained species and to monitor species-selective sorption kinetics. ¹³C and ²⁹Si magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to determine the bulk structure and the composition of the C-S-H surface, respectively, in the absence and presence of GLU. The interaction of Th(IV) with GLU in different electrolytes was studied by capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS). The influence of GLU on An(X) retention was investigated for a large concentration range up to 10⁻² M. The results showed that GLU had little to no effect on the overall An(X) retention by C-S-H with C/S of 0.8, regardless of the oxidation state of the actinides. For Eu(III), the TRLFS investigations additionally implied the formation of a Eu(III)-bearing precipitate with dissolved constituents of the C-S-H phase, which becomes structurally altered by the presence of GLU. For U(VI) sorption on the C-S-H phase, only a small influence of GLU could be established in the luminescence spectroscopic investigations, and no precipitation of U(VI)-containing secondary phases could be identified.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1318 
KW  - actinide, organic ligand, sorption, cementitious material, concrete, luminescence
KW  - organic ligand
KW  - sorption
KW  - cementitious material
KW  - concrete
KW  - luminescence
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-588455
SN  - 1866-8372
IS  - 1318
ER  - 
TY  - JOUR
A1  - Dettmann, Sophie
A1  - Huittinen, Nina Maria
A1  - Nicolas, Jahn
A1  - Kretzschmar, Jerome
A1  - Kumke, Michael
A1  - Kutyma, Tamara
A1  - Lohmann, Janik
A1  - Reich, Tobias
A1  - Schmeide, Katja
A1  - Azzam, Salim Shams Aldin
A1  - Spittler, Leon
A1  - Stietz, Janina
T1  - Influence of gluconate on the retention of Eu(III), Am(III), Th(IV), Pu(IV), and U(VI) by C-S-H (C/S = 0.8)
JF  - Frontiers in Nuclear Engineering
N2  - The retention of actinides in different oxidation states (An(X), X = III, IV, VI) by a calcium-silicate-hydrate (C-S-H) phase with a Ca/Si (C/S) ratio of 0.8 was investigated in the presence of gluconate (GLU). The actinides considered were Am(III), Th(IV), Pu(IV), and U(VI). Eu(III) was investigated as chemical analogue for Am(III) and Cm(III). In addition to the ternary systems An(X)/GLU/C-S-H, also binary systems An(X)/C-S-H, GLU/C-S-H, and An(X)/GLU were studied. Complementary analytical techniques were applied to address the different specific aspects of the binary and ternary systems. Time-resolved laser-induced luminescence spectroscopy (TRLFS) was applied in combination with parallel factor analysis (PARAFAC) to identify retained species and to monitor species-selective sorption kinetics. ¹³C and ²⁹Si magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to determine the bulk structure and the composition of the C-S-H surface, respectively, in the absence and presence of GLU. The interaction of Th(IV) with GLU in different electrolytes was studied by capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS). The influence of GLU on An(X) retention was investigated for a large concentration range up to 10⁻² M. The results showed that GLU had little to no effect on the overall An(X) retention by C-S-H with C/S of 0.8, regardless of the oxidation state of the actinides. For Eu(III), the TRLFS investigations additionally implied the formation of a Eu(III)-bearing precipitate with dissolved constituents of the C-S-H phase, which becomes structurally altered by the presence of GLU. For U(VI) sorption on the C-S-H phase, only a small influence of GLU could be established in the luminescence spectroscopic investigations, and no precipitation of U(VI)-containing secondary phases could be identified.
KW  - actinide
KW  - organic ligand
KW  - sorption
KW  - cementitious material
KW  - concrete
KW  - luminescence
Y1  - 2023
U6  - https://doi.org/10.3389/fnuen.2023.1124856
SN  - 2813-3412
VL  - 2
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Liu, Yue
A1  - Gould, Oliver E. C.
A1  - Rudolph, Tobias
A1  - Fang, Liang
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Polymeric microcuboids programmable for temperature-memory
JF  - Macromolecular materials and engineering
N2  - Microobjects with programmable mechanical functionality are highly desirable for the creation of flexible electronics, sensors, and microfluidic systems, where fabrication/programming and quantification methods are required to fully control and implement dynamic physical behavior. Here, programmable microcuboids with defined geometries are prepared by a template-based method from crosslinked poly[ethylene-co-(vinyl acetate)] elastomers. These microobjects could be programmed to exhibit a temperature-memory effect or a shape-memory polymer actuation capability. Switching temperaturesT(sw)during shape recovery of 55 +/- 2, 68 +/- 2, 80 +/- 2, and 86 +/- 2 degrees C are achieved by tuning programming temperatures to 55, 70, 85, and 100 degrees C, respectively. Actuation is achieved with a reversible strain of 2.9 +/- 0.2% to 6.7 +/- 0.1%, whereby greater compression ratios and higher separation temperatures induce a more pronounced actuation. Micro-geometry change is quantified using optical microscopy and atomic force microscopy. The realization and quantification of microparticles, capable of a tunable temperature responsive shape-change or reversible actuation, represent a key development in the creation of soft microscale devices for drug delivery or microrobotics.
KW  - actuation
KW  - atomic force microscopy
KW  - biomaterials
KW  - microparticles
KW  - shape-memory polymers
Y1  - 2020
U6  - https://doi.org/10.1002/mame.202000333
SN  - 1438-7492
SN  - 1439-2054
VL  - 305
IS  - 10
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Pacholski, Claudia
A1  - Rosencrantz, Sophia
A1  - Rosencrantz, Ruben R.
A1  - Balderas-Valadez, Ruth Fabiola
T1  - Plasmonic biosensors fabricated by galvanic displacement reactions for monitoring biomolecular interactions in real time
JF  - Analytical and bioanalytical chemistry : a merger of Fresenius' journal of analytical chemistry, Analusis and Quimica analitica
N2  - Optical sensors are prepared by reduction of gold ions using freshly etched hydride-terminated porous silicon, and their ability to specifically detect binding between protein A/rabbit IgG and asialofetuin/Erythrina cristagalli lectin is studied. The fabrication process is simple, fast, and reproducible, and does not require complicated lab equipment. The resulting nanostructured gold layer on silicon shows an optical response in the visible range based on the excitation of localized surface plasmon resonance. Variations in the refractive index of the surrounding medium result in a color change of the sensor which can be observed by the naked eye. By monitoring the spectral position of the localized surface plasmon resonance using reflectance spectroscopy, a bulk sensitivity of 296 nm +/- 3 nm/RIU is determined. Furthermore, selectivity to target analytes is conferred to the sensor through functionalization of its surface with appropriate capture probes. For this purpose, biomolecules are deposited either by physical adsorption or by covalent coupling. Both strategies are successfully tested, i.e., the optical response of the sensor is dependent on the concentration of respective target analyte in the solution facilitating the determination of equilibrium dissociation constants for protein A/rabbit IgG as well as asialofetuin/Erythrina cristagalli lectin which are in accordance with reported values in literature. These results demonstrate the potential of the developed optical sensor for cost-efficient biosensor applications.
KW  - Optical sensor
KW  - Gold nanostructure
KW  - Localized surface plasmon resonance
KW  - Surface functionalization
KW  - Biomolecular interactions
KW  - Lectin
Y1  - 2020
U6  - https://doi.org/10.1007/s00216-020-02414-0
SN  - 1618-2642
SN  - 1618-2650
VL  - 412
IS  - 14
SP  - 3433
EP  - 3445
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - López de Guereñu Kurganova, Anna
A1  - Klier, Dennis Tobias
A1  - Haubitz, Toni
A1  - Kumke, Michael Uwe
T1  - Influence of Gd3+ doping concentration on the properties of Na(Y,Gd)F-4
BT  - Yb3+, Tm3+ upconverting nanoparticles and their long-term aging behavior
JF  - Photochemical & photobiological sciences / European Society for Photobiology
N2  - We present a systematic study on the properties of Na(Y,Gd)F-4-based upconverting nanoparticles (UCNP) doped with 18% Yb3+, 2% Tm3+, and the influence of Gd3+ (10-50 mol% Gd3+). UCNP were synthesized via the solvothermal method and had a range of diameters within 13 and 50 nm. Structural and photophysical changes were monitored for the UCNP samples after a 24-month incubation period in dry phase and further redispersion. Structural characterization was performed by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as dynamic light scattering (DLS), and the upconversion luminescence (UCL) studies were executed at various temperatures (from 4 to 295 K) using time-resolved and steady-state spectroscopy. An increase in the hexagonal lattice phase with the increase of Gd3+ content was found, although the cubic phase was prevalent in most samples. The Tm3+-luminescence intensity as well as the Tm3+-luminescence decay times peaked at the Gd3+ concentration of 30 mol%. Although the general upconverting luminescence properties of the nanoparticles were preserved, the 24-month incubation period lead to irreversible agglomeration of the UCNP and changes in luminescence band ratios and lifetimes.
KW  - Upconversion luminescence
KW  - Lanthanides
KW  - Near infra-red
KW  - Ultra-low
KW  - temperature
KW  - Time-resolved spectroscopy
Y1  - 2022
U6  - https://doi.org/10.1007/s43630-021-00161-4
SN  - 1474-905X
SN  - 1474-9092
VL  - 21
IS  - 2
SP  - 235
EP  - 245
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - GEN
A1  - Behrens, Karsten
A1  - Balischewski, Christian
A1  - Sperlich, Eric
A1  - Menski, Antonia Isabell
A1  - Balderas-Valadez, Ruth Fabiola
A1  - Pacholski, Claudia
A1  - Günter, Christina
A1  - Lubahn, Susanne
A1  - Kelling, Alexandra
A1  - Taubert, Andreas
T1  - Mixed chloridometallate(ii) ionic liquids with tunable color and optical response for potential ammonia sensors
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Eight d-metal-containing N-butylpyridinium ionic liquids (ILs) with the nominal composition (C4Py)2[Ni0.5M0.5Cl4] or (C4Py)2[Zn0.5M0.5Cl4] (M = Cu, Co, Mn, Ni, Zn; C4Py = N-butylpyridinium) were synthesized, characterized, and investigated for their optical properties. Single crystal and powder X-ray analysis shows that the compounds are isostructural to existing examples based on other d-metal ions. Inductively coupled plasma optical emission spectroscopy measurements confirm that the metal/metal ratio is around 50 : 50. UV-Vis spectroscopy shows that the optical absorption can be tuned by selection of the constituent metals. Moreover, the compounds can act as an optical sensor for the detection of gases such as ammonia as demonstrated via a simple prototype setup.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1316 
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-587512
SN  - 1866-8372
IS  - 1316
SP  - 35072
EP  - 35082
ER  - 
TY  - JOUR
A1  - Behrens, Karsten
A1  - Balischewski, Christian
A1  - Sperlich, Eric
A1  - Menski, Antonia Isabell
A1  - Balderas-Valadez, Ruth Fabiola
A1  - Pacholski, Claudia
A1  - Günter, Christina
A1  - Lubahn, Susanne
A1  - Kelling, Alexandra
A1  - Taubert, Andreas
T1  - Mixed chloridometallate(ii) ionic liquids with tunable color and optical response for potential ammonia sensors
JF  - RSC Advances
N2  - Eight d-metal-containing N-butylpyridinium ionic liquids (ILs) with the nominal composition (C4Py)2[Ni0.5M0.5Cl4] or (C4Py)2[Zn0.5M0.5Cl4] (M = Cu, Co, Mn, Ni, Zn; C4Py = N-butylpyridinium) were synthesized, characterized, and investigated for their optical properties. Single crystal and powder X-ray analysis shows that the compounds are isostructural to existing examples based on other d-metal ions. Inductively coupled plasma optical emission spectroscopy measurements confirm that the metal/metal ratio is around 50 : 50. UV-Vis spectroscopy shows that the optical absorption can be tuned by selection of the constituent metals. Moreover, the compounds can act as an optical sensor for the detection of gases such as ammonia as demonstrated via a simple prototype setup.
Y1  - 2022
U6  - https://doi.org/10.1039/d2ra05581c
SN  - 2046-2069
VL  - 12
SP  - 35072
EP  - 35082
PB  - RSC
CY  - London
ER  - 
TY  - JOUR
A1  - Izraylit, Victor
A1  - Liu, Yue
A1  - Tarazona, Natalia A.
A1  - Machatschek, Rainhard Gabriel
A1  - Lendlein, Andreas
T1  - Crystallization and degradation behaviour of multiblock copolyester blends in Langmuir monolayers
JF  - MRS communications / a publication of the Materials Research Society
N2  - Supporting the wound healing of soft tissues requires fixation devices becoming more elastic while degrading. To address this unmet need, we designed a blend of degradable multiblock copolymers, which is cross-linked by PLA stereocomplexation combining two soft segments differing substantially in their hydrolytic degradation rate. The degradation path and concomitant structural changes are predicted by Langmuir monolayer technique. The fast hydrolysis of one soft segment leads to a decrease of the total polymer mass at constant physical cross-linking density. The corresponding increase of the average spacing between the network nodes suggests the targeted increase of the blend's flexibility.
KW  - Degradable
KW  - In situ
KW  - Microstructure
KW  - Thin film
Y1  - 2021
U6  - https://doi.org/10.1557/s43579-021-00107-y
SN  - 2159-6859
SN  - 2159-6867
VL  - 11
IS  - 6
SP  - 850
EP  - 855
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Izraylit, Victor
A1  - Heuchel, Matthias
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Non-woven shape-memory polymer blend actuators
JF  - MRS advances : a journal of the Materials Research Society (MRS)
N2  - The hierarchical design approach provides various opportunities to adjust the structural performance of polymer materials. Electrospinning processing techniques give access to molecular orientation as a design parameter, which we consider here in view of the shape-memory actuation performance. The aim of this work is to investigate how the reversible strain epsilon'(rev) can be affected by a morphology change from a bulk material to an electrospun mesh. epsilon'(rev) could be increased from 5.5 +/- 0.5% to 15 +/- 1.8% for a blend from a multiblock copolymer with poly(epsilon-caprolactone) (PCL) and poly(L-lactide) (PLLA) segments with oligo(D-lactide) (ODLA). This study demonstrates an effective design approach for enhancing soft actuator performance, which can be broadly applied in soft robotics and medicine.
Y1  - 2021
U6  - https://doi.org/10.1557/s43580-021-00063-8
SN  - 2059-8521
VL  - 6
IS  - 33
SP  - 781
EP  - 785
PB  - Springer Nature Switzerland AG
CY  - Cham
ER  - 
TY  - JOUR
A1  - Pilar Yeste, Maria
A1  - Carlos Hernandez-Garrido, Juan
A1  - Kumke, Michael Uwe
A1  - Alvarado, Sarah
A1  - Cauqui, Miguel Angel
A1  - Juan Calvino, Jose
A1  - Primus, Philipp-Alexander
T1  - Low-temperature growth of reactive pyrochlore nanostructures on Zirconia-supported ceria
BT  - implications for improved catalytic behavior
JF  - ACS applied nano materials
N2  - The use of a catalyst support for the design of nanoscale heterogeneous catalysts based on cerium oxide offers vast possibilities for future catalyst development, particularly with regard to an increased focus on the use of renewable biogas and an emerging hydrogen economy. In this study, zirconia-supported ceria catalysts were synthesized, activated by using different thermochemical treatments, and characterized by way of temperature-programmed reduction (TPR), oxygen storage capacity, Xray diffraction, electron microscopy, and luminescence spectroscopy using Eu3+ as a spectroscopic probe. Through reduction-oxidation pretreatment routines, reactive pyrochlore structures were created at temperatures as low as 600 degrees C and identified through TPR and electron microscopy experiments. A structural relationship and alignment of the crystal planes is revealed in high-resolution scanning transmission electron microscopy experiments through the digital diffraction patterns. Low-temperature pretreatment induces the formation of reactive pyrochlore domains under retention of the surface area of the catalyst system, and no further morphological changes are detected. Furthermore, the formation of pyrochlore domains achieved through severe reduction and mild reoxidation (SRMO) treatments is reversible. Over multiple alternating SRMO and severe reduction and severe reoxidation (SRSO) treatments, europium spectroscopy and TPR results indicate that pyrochlore structures are recreated over consecutive treatments, whenever the mild oxidation step at 500 degrees C is the last treatment (SRMO, SRMO-SRSO-SRMO, etc.).
KW  - pyrochlore
KW  - nanocomposite
KW  - ceria
KW  - zirconia
KW  - supported catalyst
KW  - oxygen
KW  - storage capacity
Y1  - 2022
U6  - https://doi.org/10.1021/acsanm.2c00416
SN  - 2574-0970
VL  - 5
IS  - 5
SP  - 6316
EP  - 6326
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Mazurek-Budzyńska, Magdalena
A1  - Behl, Marc
A1  - Neumann, Richard
A1  - Lendlein, Andreas
T1  - 4D-actuators by 3D-printing combined with water-based curing
JF  - Materials today. Communications
N2  - The shape and the actuation capability of state of the art robotic devices typically relies on multimaterial systems from a combination of geometry determining materials and actuation components. Here, we present multifunctional 4D-actuators processable by 3D-printing, in which the actuator functionality is integrated into the shaped body. The materials are based on crosslinked poly(carbonate-urea-urethane) networks (PCUU), synthesized in an integrated process, applying reactive extrusion and subsequent water-based curing. Actuation capability could be added to the PCUU, prepared from aliphatic oligocarbonate diol, isophorone diisocyanate (IPDI) and water, in a thermomechanical programming process. When programmed with a strain of epsilon(prog) = 1400% the PCUU networks exhibited actuation apparent by reversible elongation epsilon'(rev) of up to 22%. In a gripper a reversible bending epsilon'(rev)((be)(nd)()) in the range of 37-60% was achieved when the actuation temperature (T-high) was varied between 45 degrees C and 49 degrees C. The integration of actuation and shape formation could be impressively demonstrated in two PCUU-based reversible fastening systems, which were able to hold weights of up to 1.1 kg. In this way, the multifunctional materials are interesting candidate materials for robotic applications where a freedom in shape design and actuation is required as well as for sustainable fastening systems.
KW  - 4D-actuation
KW  - 3D-printing
KW  - Ink
KW  - Gripper
KW  - Fastener
Y1  - 2022
U6  - https://doi.org/10.1016/j.mtcomm.2021.102966
SN  - 2352-4928
VL  - 30
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Chemura, Sitshengisiwe
A1  - Haubitz, Toni
A1  - Primus, Philipp A.
A1  - Underberg, Martin
A1  - Hülser, Tim
A1  - Kumke, Michael Uwe
T1  - Europium-doped Ceria-Gadolinium mixed oxides
BT  - PARAFAC analysis and high-resolution emission spectroscopy under cryogenic conditions for structural analysis
JF  - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2  - Gadolinium-doped ceria or gadolinium-stabilized ceria (GDC) is an important technical material due to its ability to conduct O2- ions, e.g., used in solid oxide fuel cells operated at intermediate temperature as an electrolyte, diffusion barrier, and electrode component. We have synthesized Ce1-xGdxO2-y:Eu3+ (0 <= x <= 0.4) nanoparticles (11-15 nm) using a scalable spray pyrolysis method, which allows the continuous large-scale technical production of such materials. Introducing Eu3+ ions in small amounts into ceria and GDC as spectroscopic probes can provide detailed information about the atomic structure and local environments and allows us to monitor small structural changes. This study presents a novel approach to structurally elucidate europium-doped Ce1-xGdxO2-y:Eu3+ nanoparticles by way of Eu3+ spectroscopy, processing the spectroscopic data with the multiway decomposition method parallel factor (PARAFAC) analysis. In order to perform the deconvolution of spectra, data sets of excitation wavelength, emission wavelength, and time are required. Room temperature, time-resolved emission spectra recorded at lambda(ex) = 464 nm show that Gd3+ doping results in significantly altered emission spectra compared to pure ceria. The PARAFAC analysis for the pure ceria samples reveals a high-symmetry species (which can also be probed directly via the CeO2 charge transfer band) and a low-symmetry species. The GDC samples yield two low-symmetry spectra in the same experiment. High-resolution emission spectra recorded under cryogenic conditions after probing the D-5(0)-F-7(0) transition at lambda(ex) = 575-583 nm revealed additional variation in the low-symmetry Eu3+ sites in pure ceria and GDC. The total luminescence spectra of CeO2-y:Eu3+ showed Eu3+ ions located in at least three slightly different coordination environments with the same fundamental symmetry, whereas the overall hypsochromic shift and increased broadening of the D-5(0)-F-7(0) excitation in the GDC samples, as well as the broadened spectra after deconvolution point to less homogeneous environments. The data of the Gd3+-containing samples indicates that the average charge density around the Eu3+ ions in the lattice is decreased with increasing Gd3+ and oxygen vacancy concentration. For reference, the Judd-Ofelt parameters of all spectra were calculated. PARAFAC proves to be a powerful tool to analyze lanthanide spectra in crystalline solid materials, which are characterized by numerous Stark transitions and where measurements usually yield a superposition of different contributions to any given spectrum.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jpca.0c03188
SN  - 1089-5639
SN  - 1520-5215
VL  - 124
IS  - 24
SP  - 4972
EP  - 4983
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Rietze, Clemens
A1  - Titov, Evgenii
A1  - Granucci, Giovanni
A1  - Saalfrank, Peter
T1  - Surface hopping dynamics for azobenzene photoisomerization
BT  - effects of packing density on surfaces, fluorination, and excitation wavelength
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - Azobenzenes easily photoswitch in solution, while their photoisomerization at surfaces is often hindered. In recent work, it was demonstrated by nonadiabatic molecular dynamics with trajectory surface hopping [Titov et al., J. Phys. Chem. Lett. 2016, 7, 3591-3596] that the experimentally observed suppression of trans -> cis isomerization yields in azobenzenes in a densely packed SAM (self-assembled monolayer) [Gahl et al., J. Am. Chem. Soc. 2010, 132, 1831-1838] is dominated by steric hindrance. In the present work, we systematically study by ground-state Langevin and nonadiabatic surface hopping dynamics, the effects of decreasing packing density on (i) UV/vis absorption spectra, (ii) trans -> cis isomerization yields, and (iii) excited-state lifetimes of photoexcited azobenzene. Within the quantum mechanics/ molecular mechanics models adopted here, we find that above a packing density of similar to 3 molecules/nm(2), switching yields are strongly reduced, while at smaller packing densities, the "monomer limit" is quickly approached. The UV/vis absorption spectra, on the other hand, depend on packing density over a larger range (down to at least similar to 1 molecule/nm(2)). Trends for excited-state lifetimes are less obvious, but it is found that lifetimes of pi pi* excited states decay monotonically with decreasing coverage. Effects of fluorination of the switches are also discussed for single, free molecules. Fluorination leads to comparatively large trans -> cis yields, in combination with long pi pi* lifetimes. Furthermore, for selected systems, also the effects of n pi* excitation at longer excitation wavelengths have been studied, which is found to enhance trans -> cis yields for free molecules but can lead to an opposite behavior in densely packed SAMs.
KW  - Computational chemistry
KW  - Energy
KW  - Molecules
KW  - Monomers
KW  - Oligomers
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jpcc.0c08052
SN  - 1932-7447
SN  - 1932-7455
VL  - 124
IS  - 48
SP  - 26287
EP  - 26295
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Hess, Andreas
A1  - Schmidt, Bernhard Volkmar Konrad Jakob
A1  - Schlaad, Helmut
T1  - Aminolysis induced functionalization of (RAFT) polymer-dithioester with thiols and disulfides
JF  - Polymer Chemistry
N2  - A series of polystyrene- and poly(methyl methacrylate)-dithioesters was subjected to aminolysis under ambient atmospheric conditions, i.e., in the presence of oxygen. Polymer disulfide coupling by oxidation occurred within tens of minutes and the yield of disulfide-coupled polymer increased with decreasing polymer molar mass. Oxidation of thiolates is usually an unwanted side reaction, here it is employed to obtain exclusively polymeric mixed disulfides through in situ aminolysis/functionalization in the presence of a thiol. The in situ aminolysis/functionalization in the presence of a disulfide, Ellman's reagent or polymer disulfide, resulted in the exclusive formation of polymer-dithionitrobenzoic acid, which can be further reacted with a thiol to exchange the terminal functionality, or block copolymer with dynamic disulfide linker, respectively.
Y1  - 2020
U6  - https://doi.org/10.1039/d0py01365j
SN  - 1759-9954
SN  - 1759-9962
VL  - 11
IS  - 48
SP  - 7677
EP  - 7684
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Kwesiga, George
A1  - Kelling, Alexandra
A1  - Kersting, Sebastian
A1  - Sperlich, Eric
A1  - von Nickisch-Rosenegk, Markus
A1  - Schmidt, Bernd
T1  - Total syntheses of prenylated isoflavones from Erythrina sacleuxii and their antibacterial activity
BT  - 5-deoxy-3′-prenylbiochanin A and erysubin F
JF  - Journal of natural products
N2  - The prenylated isoflavones 5-deoxyprenylbiochanin A (7-hydroxy-4'-methoxy-3'-prenylisoflavone) and erysubin F (7,4'-dihydroxy-8,3'-diprenylisoflavone) were synthesized for the first time, starting from mono-or di-O-allylated chalcones, and the structure of 5-deoxy-3'-prenylbiochanin A was corroborated by single-crystal X-ray diffraction analysis. Flavanones are key intermediates in the synthesis. Their reaction with hypervalent iodine reagents affords isoflavones via a 2,3-oxidative rearrangement and the corresponding flavone isomers via 2,3-dehydrogenation. This enabled a synthesis of 7,4'-dihydroxy-8,3'-diprenylflavone, a non-natural regioisomer of erysubin F. Erysubin F (8), 7,4'-dihydroxy-8,3'-diprenylflavone (27), and 5-deoxy-3'prenylbiochanin A (7) were tested against three bacterial strains and one fungal pathogen. All three compounds are inactive against Salmonella enterica subsp. enterica (NCTC 13349), Escherichia coli (ATCC 25922), and Candida albicans (ATCC 90028), with MIC values greater than 80.0 mu M. The diprenylated natural product erysubin F (8) and its flavone isomer 7,4'-dihydroxy-8,3'diprenylflavone (27) show in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA, ATCC 43300) at MIC values of 15.4 and 20.5 mu M, respectively. In contrast, the monoprenylated 5-deoxy-3'-prenylbiochanin A (7) is inactive against this MRSA strain.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jnatprod.0c00932
SN  - 0163-3864
SN  - 1520-6025
VL  - 83
IS  - 11
SP  - 3445
EP  - 3453
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Rottke, Falko O.
A1  - Heyne, Marie-Victoria
A1  - Reinicke, Stefan
T1  - Switching enzyme activity by a temperature responsive inhibitor modified polymer
JF  - Chemical communications
N2  - A thermoresponsive NIPAAm-based polymer is combined with the selective acetylcholinesterase inhibitor tacrine in order to create a strict in sense on/off switch for enzymatic activity. This polymer-inhibitor conjugate inhibits AChE at room temperature and enables reactivation of AChE by heating above the cloud point of the conjugate.
Y1  - 2020
U6  - https://doi.org/10.1039/c9cc09385k
SN  - 1359-7345
SN  - 1364-548X
VL  - 56
IS  - 16
SP  - 2459
EP  - 2462
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Bressel, Katharina
A1  - Müller, Wenke
A1  - Leser, Martin Erwin
A1  - Reich, Oliver
A1  - Hass, Roland
A1  - Wooster, Tim J.
T1  - Depletion-induced flocculation of concentrated emulsions probed by photon density wave spectroscopy
JF  - Langmuir
N2  - Stable, creaming-free oil in water emulsions with high volume fractions of oil (phi = 0.05-0.40, density matched to water) and polysorbate 80 as an emulsifier were characterized without dilution by Photon Density Wave spectroscopy measuring light absorption and scattering behavior, the latter serving as the basis for droplet size distribution analysis. The emulsion with phi = 0.10 was used to investigate flocculation processes induced by xanthan as a semi-flexible linear nonabsorbing polymer. Different time regimes in the development of the reduced scattering coefficient mu(s)' could be identified. First, a rapid, temperature-dependent change in mu(s)' during the depletion process was observed. Second, the further decrease of mu(s)' follows a power law in analogy to a spinodal demixing behavior, as described by the Cahn-Hilliard theory.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.langmuir.9b03642
SN  - 0743-7463
VL  - 36
IS  - 13
SP  - 3504
EP  - 3513
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Fischer, Eric W.
A1  - Werther, Michael
A1  - Bouakline, Foudhil
A1  - Saalfrank, Peter
T1  - A hierarchical effective mode approach to phonon-driven multilevel vibrational relaxation dynamics at surfaces
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry
N2  - We discuss an efficient Hierarchical Effective Mode (HEM) representation of a high-dimensional harmonic oscillator bath, which describes phonon-driven vibrational relaxation of an adsorbate-surface system, namely, deuterium adsorbed on Si(100). Starting from the original Hamiltonian of the adsorbate-surface system, the HEM representation is constructed via iterative orthogonal transformations, which are efficiently implemented with Householder matrices. The detailed description of the HEM representation and its construction are given in the second quantization representation. The hierarchical nature of this representation allows access to the exact quantum dynamics of the adsorbate-surface system over finite time intervals, controllable via the truncation order of the hierarchy. To study the convergence properties of the effective mode representation, we solve the time-dependent Schrodinger equation of the truncated system-bath HEM Hamiltonian, with the help of the multilayer extension of the Multiconfigurational Time-Dependent Hartree (ML-MCTDH) method. The results of the HEM representation are compared with those obtained with a quantum-mechanical tier-model. The convergence of the HEM representation with respect to the truncation order of the hierarchy is discussed for different initial conditions of the adsorbate-surface system. The combination of the HEM representation with the ML-MCTDH method provides information on the time evolution of the system (adsorbate) and multiple effective modes of the bath (surface). This permits insight into mechanisms of vibration-phonon coupling of the adsorbate-surface system, as well as inter-mode couplings of the effective bath.
Y1  - 2020
U6  - https://doi.org/10.1063/5.0017716
SN  - 0021-9606
SN  - 1089-7690
VL  - 153
IS  - 6
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - THES
A1  - Kim, Jiyong
T1  - Synthesis of InP quantum dots and their applications
N2  - Technologically important, environmentally friendly InP quantum dots (QDs) typically used as green and red emitters in display devices can achieve exceptional photoluminescence quantum yields (PL QYs) of near-unity (95-100%) when the-state-of-the-art core/shell heterostructure of the ZnSe inner/ZnS outer shell is elaborately applied. Nevertheless, it has only led to a few industrial applications as QD liquid crystal display (QD–LCD) which is applied to blue backlight units, even though QDs has a lot of possibilities that able to realize industrially feasible applications, such as QD light-emitting diodes (QD‒LEDs) and luminescence solar concentrator (LSC), due to their functionalizable characteristics. 
Before introducing the main research, the theoretical basis and fundamentals of QDs are described in detail on the basis of the quantum mechanics and experimental synthetic results, where a concept of QD and colloidal QD, a type-I core/shell structure, a transition metal doped semiconductor QDs, the surface chemistry of QD, and their applications (LSC, QD‒LEDs, and EHD jet printing) are sequentially elucidated for better understanding. This doctoral thesis mainly focused on the connectivity between QD materials and QD devices, based on the synthesis of InP QDs that are composed of inorganic core (core/shell heterostructure) and organic shell (surface ligands on the QD surface). In particular, as for the former one (core/shell heterostructure), the ZnCuInS mid-shell as an intermediate layer is newly introduced between a Cu-doped InP core and a ZnS shell for LSC devices. As for the latter one (surface ligands), the ligand effect by 1-octanethiol and chloride ion are investigated for the device stability in QD‒LEDs and the printability of electro-hydrodynamic (EHD) jet printing system, in which this research explores the behavior of surface ligands, based on proton transfer mechanism on the QD surface. 
Chapter 3 demonstrates the synthesis of strain-engineered highly emissive Cu:InP/Zn–Cu–In–S (ZCIS)/ZnS core/shell/shell heterostructure QDs via a one-pot approach. When this unconventional combination of a ZCIS/ZnS double shelling scheme is introduced to a series of Cu:InP cores with different sizes, the resulting Cu:InP/ZCIS/ZnS QDs with a tunable near-IR PL range of 694–850 nm yield the highest-ever PL QYs of 71.5–82.4%. These outcomes strongly point to the efficacy of the ZCIS interlayer, which makes the core/shell interfacial strain effectively alleviated, toward high emissivity. The presence of such an intermediate ZCIS layer is further examined by comparative size, structural, and compositional analyses. The end of this chapter briefly introduces the research related to the LSC devices, fabricated from Cu:InP/ZCIS/ZnS QDs, currently in progress.  
Chapter 4 mainly deals with ligand effect in 1-octanethiol passivation of InP/ZnSe/ZnS QDs in terms of incomplete surface passivation during synthesis. This chapter demonstrates the lack of anionic carboxylate ligands on the surface of InP/ZnSe/ZnS quantum dots (QDs), where zinc carboxylate ligands can be converted to carboxylic acid or carboxylate ligands via proton transfer by 1-octanethiol. The as-synthesized QDs initially have an under-coordinated vacancy surface, which is passivated by solvent ligands such as ethanol and acetone. Upon exposure of 1-octanethiol to the QD surface, 1-octanthiol effectively induces the surface binding of anionic carboxylate ligands (derived from zinc carboxylate ligands) by proton transfer, which consequently exchanges ethanol and acetone ligands that bound on the incomplete QD surface. The systematic chemical analyses, such as thermogravimetric analysis‒mass spectrometry and proton nuclear magnetic resonance spectroscopy, directly show the interplay of surface ligands, and it associates with QD light-emitting diodes (QD‒LEDs). 
Chapter 5 shows the relation between material stability of QDs and device stability of QD‒LEDs through the investigation of surface chemistry and shell thickness. In typical III–V colloidal InP quantum dots (QDs), an inorganic ZnS outermost shell is used to provide stability when overcoated onto the InP core. However, this work presents a faster photo-degradation of InP/ZnSe/ZnS QDs with a thicker ZnS shell than that with a thin ZnS shell when 1-octanethiol was applied as a sulfur source to form ZnS outmost shell. Herein, 1-octanethiol induces the form of weakly-bound carboxylate ligand via proton transfer on the QD surface, resulting in a faster degradation at UV light even though a thicker ZnS shell was formed onto InP/ZnSe QDs. Detailed insight into surface chemistry was obtained from proton nuclear magnetic resonance spectroscopy and thermogravimetric analysis–mass spectrometry. However, the lifetimes of the electroluminescence devices fabricated from InP/ZnSe/ZnS QDs with a thick or a thin ZnS shell show surprisingly the opposite result to the material stability of QDs, where the QD light-emitting diodes (QD‒LEDs) with a thick ZnS shelled QDs maintained its luminance more stable than that with a thin ZnS shelled QDs. This study elucidates the degradation mechanism of the QDs and the QD light-emitting diodes based on the results and discuss why the material stability of QDs is different from the lifetime of QD‒LEDs. 
Chapter 6 suggests a method how to improve a printability of EHD jet printing when QD materials are applied to QD ink formulation, where this work introduces the application of GaP mid-shelled InP QDs as a role of surface charge in EHD jet printing technique. In general, GaP intermediate shell has been introduced in III–V colloidal InP quantum dots (QDs) to enhance their thermal stability and quantum efficiency in the case of type-I core/shell/shell heterostructure InP/GaP/ZnSeS QDs. Herein, these highly luminescent InP/GaP/ZnSeS QDs were synthesized and applied to EHD jet printing, by which this study demonstrates that unreacted Ga and Cl ions on the QD surface induce the operating voltage of cone jet and cone jet formation to be reduced and stabilized, respectively. This result indicates GaP intermediate shell not only improves PL QY and thermal stability of InP QDs but also adjusts the critical flow rate required for cone-jet formation. In other words, surface charges of quantum dots can have a significant role in forming cone apex in the EHD capillary nozzle. For an industrially convenient validation of surface charges on the QD surface, Zeta potential analyses of QD solutions as a simple method were performed, as well as inductively coupled plasma optical emission spectrometry (ICP-OES) for a composition of elements.
Beyond the generation of highly emissive InP QDs with narrow FWHM, these studies talk about the connection between QD material and QD devices not only to make it a vital jumping-off point for industrially feasible applications but also to reveal from chemical and physical standpoints the origin that obstructs the improvement of device performance experimentally and theoretically.
N2  - Umweltfreundliche InP Quantenpunkte (QDs) sind technologisch relevant und werden typischerweise als grüne und rote Emitter in Bildschirmen verwendet. Nach dem Stand der Technik kann eine sorgfältig hergestellte Kern-Schale-Heterostruktur (ZnSe innen/ZnS außen) zu außergewöhnlich hohen Photolumineszenz-Quantenausbeuten (PL-QYs) von nahezu Eins (95 - 100 %) führen. Dennoch gibt es bisher nur einige wenige industrielle Anwendungen wie QD-Flüssigkristall-Bildschirme (liquid crystal display, QD-LCD), in denen die Anregung durch eine blaue Hintergrundbeleuchtung realisiert wird. Dabei haben QDs aufgrund ihrer Modifizierbarkeit noch viele weitere industrielle Einsatzmöglichkeiten, beispielsweise QD basierte lichtemittierende Dioden (QD-LEDs) und lumineszierende Solarkollektoren (luminescence solar concentrator, LSC). 
Vor dem Hauptteil werden in den Kapiteln 1 und 2 die Grundlagen von QDs und die theoretischen Grundlagen basierend auf quantenmechanischer Beschreibung und experimentellen Ergebnissen eingeführt. Zum besseren Verständnis werden: das Konzept der QDs, kolloidale QDs, Kern-Schale-Strukturen vom Typ I, mit Übergangsmetallen dotierte Halbleiter-QDs, die Oberflächenchemie von QDs und ihre Anwendungen (LSC, QD-LEDs und electrohydrodynamic EHD-Jet-Printing), nacheinander eingeführt. Der Schwerpunkt dieser Doktorarbeit liegt hauptsächlich auf der Kombination von QD-Materialien und QD-Bauelementen, basierend auf der Synthese von InP QDs mit einem anorganischen Kern (Kern-Schale-Heterostruktur) und einer organischen Hülle (Oberflächenliganden auf der QD-Oberfläche). In die Kern-Schale-Heterostruktur wird eine ZnCuInS-Mittelschale als Zwischenschicht zwischen einem Cu-dotierten InP Kern und einer ZnS-Schale für LSC-Bauelemente neu eingeführt. Bei den Oberflächenliganden wird der Ligandeneffekt von 1-Oktanthiol und Chloridionen auf die Stabilität von QD-LEDs und die Druckbarkeit mit EHD-Jet-Printing hin untersucht. Dabei erhält der Protonentransfermechanismus auf der QD-Oberfläche ein besonderes Augenmerk.
In Kapitel 3 wird die Eintopfsynthese von hocheffizient  emittierenden QDs mit einer Cu:InP/Zn-Cu-In-S (ZCIS)/ZnS Kern/Schale/Schale-Heterostruktur beschrieben. Wenn diese neuartige Kombination einer ZCIS/ZnS-Doppelschalenstruktur mit eine Reihe von Cu:InP-Kerne mit unterschiedlichen Größen kombiniert wird, ergeben die daraus entstehenden Cu:InP/ZCIS/ZnS-QDs die bisher höchsten publizierten PL-QYs von 71,5 – 82,4 % im nahen IR-Bereich von 694 – 850 nm mit einstellbarer PL Wellenlänge. Diese Ergebnisse weisen auf die Wirksamkeit der ZCIS-Zwischenschicht hin, welche die Grenzflächenspannung zwischen Kern und Schale effektiv mildert und damit zu einem solch hohen Emissionsvermögen führt. Diese ZCIS-Zwischenschicht wird durch vergleichende Größen-, Struktur- und Zusammensetzungsanalysen weiter untersucht. Am Ende des Kapitels wird der aktuellen Stand der Forschung auf dem Gebiet der LSC-Bauelemente aus solchen Cu:InP/ZCIS/ZnS-QDs vorgestellt. 
Kapitel 4 befasst sich hauptsächlich mit dem Ligandeneffekt bei der Passivierung mit 1-Oktanthiol von InP/ZnSe/ZnS-QDs im Hinblick auf die unvollständige Oberflächenpassivierung während der Synthese. Es fehlen anionischen Carboxylat-Liganden auf der InP/ZnSe/ZnS-Oberfläche der QDs, an denen Zink Carboxylat Liganden durch Protonentransfer vom 1-Oktanthiol in Carbonsäure-Liganden umgewandelt werden könnten. Die so synthetisierten QDs haben zunächst eine unterkoordinierte Oberfläche mit Leerstellen, die durch Lösungsmittel-Liganden wie Ethanol oder Aceton passiviert werden. Wenn 1-Octanthiol an die QD-Oberfläche bindet bewirkt der Protonentransfer die Bindung von Carboxylat-Liganden (aus Zink-Carboxylat) an die Oberfläche, wobei Ethanol- oder Aceton-Liganden ausgetauscht werden. Systematische Analysen wie Thermogravimetrie (thermogravimetric analysis TGA), Massenspektrometrie (MS) und Protonen-Kernmagnetresonanz (proton nuclear magnetic resonance 1H-NMR) zeigen direkt den Zusammenhang zwischen Oberflächenliganden und QD-LEDs. 
Kapitel 5 zeigt den Zusammenhang zwischen der Materialstabilität von QDs und der Bauteilstabilität von QD-LEDs durch Untersuchung der Oberflächenchemie und der Schalendicke. In typischen kolloidalen III-V-InP-QDs wird eine anorganische ZnS-Außenhülle auf den InP Kern aufgetragen, um Stabilität zu gewährleisten. In dieser Arbeit wird jedoch eine schnellere Photodegradation von InP/ZnSe/ZnS-QDs mit einer dickeren statt einer dünneren ZnS-Schale gezeigt, wenn 1-Oktanthiol als Schwefelquelle zur Bildung der äußersten ZnS-Schale verwendet wurde. 1-Oktanthiol induziert die Bildung eines schwach gebundenen Carboxylatliganden durch Protonentransfer auf der QD-Oberfläche, was zu einem schnelleren Abbau unter UV-Licht trotz dickerer ZnS-Schale führt. Detailliertere Einblicke in die Oberflächenchemie werden durch 1H-NMR, TGA und MS gewonnen. Überraschenderweise zeigen jedoch die Lebensdauern der aus InP/ZnSe/ZnS-QDs mit dicken oder dünnen ZnS-Hüllen hergestellten EL-Bauelemente eine gegenteilige Stabilität: Die QD-LEDs mit QDs mit dicker ZnS-Hülle haben eine längere Lebensdauer, als jene mit dünner ZnS-Hülle. Es wird der Degradationsmechanismus der QDs und der QD-Leuchtdioden anhand der Ergebnisse erläutert und der Effekt auf die unterschiedlichen Lebensdauern von Material und Bauteil diskutiert. 
In Kapitel 6 wird eine Methode vorgeschlagen, wie die Druckbarkeit von QD-Tintenformulierungen beim EHD-Jet-Druck über die QD-Materialien verbessert werden kann. Dazu werden InP-QDs mit GaP-Zwischenschalen erweitert, um die Oberflächenladung zu beeinflussen. Darüber hinaus verbessern GaP-Zwischenschalen in III-V kolloidalen InP-QDs deren thermische Stabilität und PL-QY im Falle von Typ-I-Kern/Schale/Schale-Heterostrukturen (InP/GaP/ZnSeS-QDs). Diese stark lumineszierenden InP/GaP/ZnSeS-QDs wurden synthetisiert und für den EHD-Jet-Druck verwendet. Nicht umgesetzte Ga und Cl-Ionen auf der QD-Oberfläche reduzieren die benötigte Betriebsspannung zur Ausbildung eines Taylor-Kegels und eines stabilen Tinten-Jets. Dieses Ergebnis deutet darauf hin, dass die Oberflächenladungen der Quantenpunkte eine wichtige Rolle bei der Ausbildung des Taylor-Kegels spielen. Mittels Zeta-Potenzial-Messung von QD-Tinten wurde eine industriell erprobte und einfache Methode zur Untersuchung der Oberflächenladungen verwendet. Darüber hinaus wurde optische Emissionsspektrometrie mit induktiv gekoppeltem Plasma (inductively coupled plasma-atomic emission spectroscopy ICP-OES) zur Bestimmung der Elementzusammensetzung durchgeführt.
Diese Dissertation beschäftigt sich sowohl mit der Synthese von hocheffizienten InP QDs mit schmalbandiger Emission (full width at half maximum FWHM), als auch den Zusammenhängen zwischen QD-Material und QD-Bauelementen. Die Ergebnisse sind einerseits relevant für die breitere industrielle Anwendung dieser Materialien und andererseits für ein tieferes chemisch-physikalisches, theoretisches und experimentelles Verständnis der Prozesse, die zu langlebigen und stabilen Bauelementen führen.
KW  - colloidal quantum dot
KW  - Cu doped InP
KW  - surface chemistry
KW  - QD stability
KW  - QD device
KW  - kolloidaler Quantenpunkt
KW  - Cu-dotiertes InP
KW  - Oberflächenchemie
KW  - QD-Stabilität
KW  - QD-Gerät
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-585351
ER  - 
TY  - JOUR
A1  - Kar, Manaswita
A1  - Körzdörfer, Thomas
T1  - Computational high throughput screening of inorganic cation based halide perovskites for perovskite only tandem solar cells
JF  - Materials Research Express
N2  - We search for homovalent alternatives for A, B, and X-ions in ABX(3) type inorganic halide perovskites suitable for tandem solar cell applications. We replace the conventional A-site organic cation CH3NH3, by 3 inorganic cations, Cs, K, and Rb, and the B site consists of metals; Cd, Hg, Ge, Pb, and Sn This work is built on our previous high throughput screening of hybrid perovskite materials (Kar et al 2018 J. Chem. Phys. 149, 214701). By performing a systematic screening study using Density Functional Theory (DFT) methods, we found 11 suitable candidates; 2 Cs-based, 3 K-based and 6 Rb-based that are suitable for tandem solar cell applications.
KW  - inorganic perovskites
KW  - tandem solar cells
KW  - density functional theory
Y1  - 2020
U6  - https://doi.org/10.1088/2053-1591/ab8c0d
SN  - 2053-1591
VL  - 7
IS  - 5
SP  - 1
EP  - 10
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - GEN
A1  - Mayer, Dennis
A1  - Lever, Fabiano
A1  - Picconi, David
A1  - Metje, Jan
A1  - Ališauskas, Skirmantas
A1  - Calegari, Francesca
A1  - Düsterer, Stefan
A1  - Ehlert, Christopher
A1  - Feifel, Raimund
A1  - Niebuhr, Mario
A1  - Manschwetus, Bastian
A1  - Kuhlmann, Marion
A1  - Mazza, Tommaso
A1  - Robinson, Matthew Scott
A1  - Squibb, Richard James
A1  - Trabattoni, Andrea
A1  - Wallner, Måns
A1  - Saalfrank, Peter
A1  - Wolf, Thomas J. A.
A1  - Gühr, Markus
T1  - Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220–250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1301 
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-577442
SN  - 1866-8372
IS  - 1301
ER  - 
TY  - JOUR
A1  - Mayer, Dennis
A1  - Lever, Fabiano
A1  - Picconi, David
A1  - Metje, Jan
A1  - Ališauskas, Skirmantas
A1  - Calegari, Francesca
A1  - Düsterer, Stefan
A1  - Ehlert, Christopher
A1  - Feifel, Raimund
A1  - Niebuhr, Mario
A1  - Manschwetus, Bastian
A1  - Kuhlmann, Marion
A1  - Mazza, Tommaso
A1  - Robinson, Matthew Scott
A1  - Squibb, Richard James
A1  - Trabattoni, Andrea
A1  - Wallner, Måns
A1  - Saalfrank, Peter
A1  - Wolf, Thomas J. A.
A1  - Gühr, Markus
T1  - Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy
JF  - Nature Communications
N2  - The conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220–250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states.
Y1  - 2022
U6  - https://doi.org/10.1038/s41467-021-27908-y
SN  - 2041-1723
VL  - 13
PB  - Springer Nature
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Wang, Xuepu
A1  - Sperling, Marcel
A1  - Reifarth, Martin
A1  - Böker, Alexander
T1  - Shaping metallic nanolattices
BT  - Design by microcontact printing from wrinkled stamps
JF  - Small
N2  - A method for the fabrication of well-defined metallic nanostructures is presented here in a simple and straightforward fashion. As an alternative to lithographic techniques, this routine employs microcontact printing utilizing wrinkled stamps, which are prepared from polydimethylsiloxane (PDMS), and includes the formation of hydrophobic stripe patterns on a substrate via the transfer of oligomeric PDMS. Subsequent backfilling of the interspaces between these stripes with a hydroxyl-functional poly(2-vinyl pyridine) then provides the basic pattern for the deposition of citrate-stabilized gold nanoparticles promoted by electrostatic interaction. The resulting metallic nanostripes can be further customized by peeling off particles in a second microcontact printing step, which employs poly(ethylene imine) surface-decorated wrinkled stamps, to form nanolattices. Due to the independent adjustability of the period dimensions of the wrinkled stamps and stamp orientation with respect to the substrate, particle arrays on the (sub)micro-scale with various kinds of geometries are accessible in a straightforward fashion. This work provides an alternative, cost-effective, and scalable surface-patterning technique to fabricate nanolattice structures applicable to multiple types of functional nanoparticles. Being a top-down method, this process could be readily implemented into, e.g., the fabrication of optical and sensing devices on a large scale.
KW  - gold nanoparticle assembly
KW  - hydroxyl-functional poly(2-vinyl pyridine)
KW  - metallic nanolattices
KW  - microcontact printing
KW  - oligomeric
KW  - polydimethylsiloxane
KW  - polydimethylsiloxane wrinkles
KW  - wrinkled stamps
Y1  - 2020
U6  - https://doi.org/10.1002/smll.201906721
SN  - 1613-6810
SN  - 1613-6829
VL  - 16
IS  - 11
SP  - 1
EP  - 8
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Bastian, Philipp U.
A1  - Yu, Leixiao
A1  - de Guereñu Kurganova, Anna Lopez
A1  - Haag, Rainer
A1  - Kumke, Michael Uwe
T1  - Bioinspired confinement of upconversion nanoparticles for improved performance in aqueous solution
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - The resonance energy transfer (RET) from NaYF4:Yb,Er upconverting nanoparticles (UNCPs) to a dye (5-carboxytetramethylrhodamine (TAMRA)) was investigated by photoluminescence experiments and microscale thermophoresis (MST). The dye was excited via RET from the UCNPs which was excited in the near-infrared (NIR). The change of the dye diffusion speed (free vs coupled) was investigated by MST. RET shows significant changes in the decay times of the dye as well as of the UCNPs. MST reveals significant changes in the diffusion speed. A unique amphiphilic coating polymer (customized mussel protein (CMP) polymer) for UCNP surface coating was used, which mimics blood protein adsorption and mussel food protein adhesion to transfer the UCNP into the aqueous phase and to allow surface functionalization. The CMP provides very good water dispersibility to the UCNPs and minimizes ligand exchange and subsequent UCNP aging reactions because of the interlinkage of the CMP on the UCNP surface. Moreover, CMP provides N-3-functional groups for dick chemistry-based functionalization demonstrated with the dye 5-carboxytetramethylrhodamine (TAMRA). This establishes the principle coupling scheme for suitable biomarkers such as antibodies. The CMP provides very stable aqueous UCNP dispersions that are storable up to 3 years in a fridge at 5 degrees C without dissolution or coagulation. The outstanding properties of CMP in shielding the UCNP from unwanted solvent effects is reflected in the distinct increase of the photoluminescence decay times after UCNP functionalization. The UCNP-to-TAMRA energy transfer is also spectroscopically investigated at low temperatures (4-200 K), revealing that one of the two green Er(III) emission bands contributes the major part to the energy transfer. The TAMRA fluorescence decay time increases by a factor of 9500 from 2.28 ns up to 22 mu s due to radiationless energy transfer from the UCNP after NIR excitation of the latter. This underlines the unique properties of CMP as a versatile capping ligand for distinctly improving the UCNPs' performance in aqueous solutions, for coupling of biomolecules, and for applications for in vitro and in vivo experiments using UCNPs as optical probes in life science applications.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jpcc.0c09798
SN  - 1932-7447
SN  - 1932-7455
VL  - 124
IS  - 52
SP  - 28623
EP  - 28635
PB  - American Chemical Society
CY  - Washington, DC
ER  - 
TY  - GEN
A1  - Brinkmann, Pia
A1  - Köllner, Nicole
A1  - Merk, Sven
A1  - Beitz, Toralf
A1  - Altenberger, Uwe
A1  - Löhmannsröben, Hans-Gerd
T1  - Comparison of handheld and echelle spectrometer to assess copper in ores by means of laser-induced breakdown spectroscopy (LIBS)
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Its properties make copper one of the world’s most important functional metals. Numerous megatrends are increasing the demand for copper. This requires the prospection and exploration of new deposits, as well as the monitoring of copper quality in the various production steps. A promising technique to perform these tasks is Laser Induced Breakdown Spectroscopy (LIBS). Its unique feature, among others, is the ability to measure on site without sample collection and preparation. In this work, copper-bearing minerals from two different deposits are studied. The first set of field samples come from a volcanogenic massive sulfide (VMS) deposit, the second part from a stratiform sedimentary copper (SSC) deposit. Different approaches are used to analyze the data. First, univariate regression (UVR) is used. However, due to the strong influence of matrix effects, this is not suitable for the quantitative analysis of copper grades. Second, the multivariate method of partial least squares regression (PLSR) is used, which is more suitable for quantification. In addition, the effects of the surrounding matrices on the LIBS data are characterized by principal component analysis (PCA), alternative regression methods to PLSR are tested and the PLSR calibration is validated using field samples.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1311 
KW  - LIBS
KW  - copper-bearing minerals
KW  - UVR
KW  - PCA
KW  - PLSR
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-584742
SN  - 1866-8372
IS  - 1311
ER  - 
TY  - JOUR
A1  - Brinkmann, Pia
A1  - Köllner, Nicole
A1  - Merk, Sven
A1  - Beitz, Toralf
A1  - Altenberger, Uwe
A1  - Löhmannsröben, Hans-Gerd
T1  - Comparison of handheld and echelle spectrometer to assess copper in ores by means of laser-induced breakdown spectroscopy (LIBS)
JF  - Minerals
N2  - Its properties make copper one of the world’s most important functional metals. Numerous megatrends are increasing the demand for copper. This requires the prospection and exploration of new deposits, as well as the monitoring of copper quality in the various production steps. A promising technique to perform these tasks is Laser Induced Breakdown Spectroscopy (LIBS). Its unique feature, among others, is the ability to measure on site without sample collection and preparation. In this work, copper-bearing minerals from two different deposits are studied. The first set of field samples come from a volcanogenic massive sulfide (VMS) deposit, the second part from a stratiform sedimentary copper (SSC) deposit. Different approaches are used to analyze the data. First, univariate regression (UVR) is used. However, due to the strong influence of matrix effects, this is not suitable for the quantitative analysis of copper grades. Second, the multivariate method of partial least squares regression (PLSR) is used, which is more suitable for quantification. In addition, the effects of the surrounding matrices on the LIBS data are characterized by principal component analysis (PCA), alternative regression methods to PLSR are tested and the PLSR calibration is validated using field samples.
KW  - LIBS
KW  - copper-bearing minerals
KW  - UVR
KW  - PCA
KW  - PLSR
Y1  - 2023
U6  - https://doi.org/10.3390/min13010113
SN  - 2075-163X
VL  - 13
IS  - 1
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Dative or coordinative carbon-boron bond in boron trapped N-heterocyclic carbenes (NHCs)?
BT  - an answer given on the magnetic criterion
JF  - Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of isolated as well as B-C bond length varied model compounds (BR3 trapped NHCs) have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually the anisotropy effects measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the present dative vs. coordinative bond character of the boron-carbon bond in the trapped NHCs. Results are confirmed by bond lengths and B-11/C-13 chemical shift variations in the BR3 trapped NHCs.
KW  - NHCs
KW  - Dative vs. coordinative NHC -> BR3 bond
KW  - Through-space NMR
KW  - shieldings (TSNMRS)
KW  - NICS
KW  - Anisotropy effect
Y1  - 2021
U6  - https://doi.org/10.1016/j.tet.2020.131787
SN  - 0040-4020
SN  - 1464-5416
VL  - 80
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Yeste, Maria Pilar
A1  - Primus, Philipp-Alexander
A1  - Alcantara, Rodrigo
A1  - Cauqui, Miguel Angel
A1  - Calvino, Juan Jose
A1  - Pintado, José María
A1  - Blanco, Ginesa
T1  - Surface characterization of two Ce0.62Zr0.38O2 mixed oxides with different reducibility
JF  - Applied surface science : a journal devoted to applied physics and chemistry of surfaces and interfaces
N2  - This paper presents a study of the surface properties of two Ce/Zr mixed oxides with different reducibility, obtained by applying distinct thermal ageing treatments to an oxide with the composition Ce0.62Zr0.38O2. The surface composition was investigated by XPS. Chemical reactivity of the surface was studied by adsorption of the probe molecules CO2, D-2 and methanol. Nanostructural characterization was carried out by XRD, Raman and high-resolution Eu3+ spectroscopy (FLNS). The characterization showed only slight variations in surface composition and bulk Ce-Zr distribution, but hardy differences concerning the type and strength of acidic surface centres, as well as strong differences in the ability to dissociate hydrogen. Structural variations between both samples were identified by comparing the optical spectra of Eu3+ in surface doped samples.
KW  - Ce/Zr
KW  - Surface properties
KW  - Reactive adsorption
KW  - Hydrogen activation
Y1  - 2020
U6  - https://doi.org/10.1016/j.apsusc.2019.144255
SN  - 0169-4332
SN  - 1873-5584
VL  - 503
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Chepkirui, Carolyne
A1  - Ochieng, Purity J.
A1  - Sarkar, Biswajyoti
A1  - Hussain, Aabid
A1  - Pal, Chiranjib
A1  - Yang, Li Jun
A1  - Coghi, Paolo
A1  - Akala, Hoseah M.
A1  - Derese, Solomon
A1  - Ndakala, Albert
A1  - Heydenreich, Matthias
A1  - Wong, Vincent K. W.
A1  - Erdelyi, Mate
A1  - Yenesew, Abiy
T1  - Antiplasmodial and antileishmanial flavonoids from Mundulea sericea
JF  - Fitoterapia
N2  - Five known compounds (1-5) were isolated from the extract of Mundulea sericea leaves. Similar investigation of the roots of this plant afforded an additional three known compounds (6-8). The structures were elucidated using NMR spectroscopic and mass spectrometric analyses. The absolute configuration of 1 was established using ECD spectroscopy. In an antiplasmodial activity assay, compound 1 showed good activity with an IC50 of 2.0 mu M against chloroquine-resistant W2, and 6.6 mu M against the chloroquine-sensitive 3D7 strains of Plasmodium falciparum. Some of the compounds were also tested for antileishmanial activity. Dehydrolupinifolinol (2) and sericetin (5) were active against drug-sensitive Leishmania donovani (MHOM/IN/83/AG83) with IC50 values of 9.0 and 5.0 mu M, respectively. In a cytotoxicity assay, lupinifolin (3) showed significant activity on BEAS-2B (IC50 4.9 mu M) and HePG2 (IC50 10.8 mu M) human cell lines. All the other compounds showed low cytotoxicity (IC50 > 30 mu M) against human lung adenocarcinoma cells (A549), human liver cancer cells (HepG2), lung/bronchus cells (epithelial virus transformed) (BEAS-2B) and immortal human hepatocytes (LO2)
KW  - Mundulea sericea
KW  - leguminosae
KW  - flavanonol
KW  - flavonol
KW  - antiplasmodial
KW  - antileishmanial
KW  - cytotoxicity
Y1  - 2020
U6  - https://doi.org/10.1016/j.fitote.2020.104796
SN  - 0367-326X
SN  - 1873-6971
VL  - 149
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Erler, Alexander
A1  - Riebe, Daniel
A1  - Beitz, Toralf
A1  - Löhmannsröben, Hans-Gerd
A1  - Grothusheitkamp, Daniela
A1  - Kunz, Thomas
A1  - Methner, Frank-Jürgen
T1  - Characterization of volatile metabolites formed by molds on barley by mass and ion mobility spectrometry
JF  - Journal of mass spectrometr
N2  - The contamination of barley by molds on the field or in storage leads to the spoilage of grain and the production of mycotoxins, which causes major economic losses in malting facilities and breweries. Therefore, on-site detection of hidden fungus contaminations in grain storages based on the detection of volatile marker compounds is of high interest. In this work, the volatile metabolites of 10 different fungus species are identified by gas chromatography (GC) combined with two complementary mass spectrometric methods, namely, electron impact (EI) and chemical ionization at atmospheric pressure (APCI)-mass spectrometry (MS). The APCI source utilizes soft X-radiation, which enables the selective protonation of the volatile metabolites largely without side reactions. Nearly 80 volatile or semivolatile compounds from different substance classes, namely, alcohols, aldehydes, ketones, carboxylic acids, esters, substituted aromatic compounds, alkenes, terpenes, oxidized terpenes, sesquiterpenes, and oxidized sesquiterpenes, could be identified. The profiles of volatile and semivolatile metabolites of the different fungus species are characteristic of them and allow their safe differentiation. The application of the same GC parameters and APCI source allows a simple method transfer from MS to ion mobility spectrometry (IMS), which permits on-site analyses of grain stores. Characterization of IMS yields limits of detection very similar to those of APCI-MS. Accordingly, more than 90% of the volatile metabolites found by APCI-MS were also detected in IMS. In addition to different fungus genera, different species of one fungus genus could also be differentiated by GC-IMS.
KW  - APCI
KW  - fungus
KW  - gas chromatography
KW  - ion mobility spectrometry
KW  - mass
KW  - spectrometry
KW  - mold
KW  - soft X-ray
Y1  - 2020
U6  - https://doi.org/10.1002/jms.4501
SN  - 1076-5174
SN  - 1096-9888
VL  - 55
IS  - 5
SP  - 1
EP  - 10
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Schneider, Matthias
A1  - Fritzsche, Nora
A1  - Puciul-Malinowska, Agnieszka
A1  - Baliś, Andrzej
A1  - Mostafa, Amr
A1  - Bald, Ilko
A1  - Zapotoczny, Szczepan
A1  - Taubert, Andreas
T1  - Surface etching of 3D printed poly(lactic acid) with NaOH
BT  - a systematic approach
JF  - Polymers
N2  - The article describes a systematic investigation of the effects of an aqueous NaOH treatment of 3D printed poly(lactic acid) (PLA) scaffolds for surface activation. The PLA surface undergoes several morphology changes and after an initial surface roughening, the surface becomes smoother again before the material dissolves. Erosion rates and surface morphologies can be controlled by the treatment. At the same time, the bulk mechanical properties of the treated materials remain unaltered. This indicates that NaOH treatment of 3D printed PLA scaffolds is a simple, yet viable strategy for surface activation without compromising the mechanical stability of PLA scaffolds.
KW  - surface modification
KW  - sodium hydroxide etching
KW  - poly(lactic acid)
KW  - 3D
KW  - printing
KW  - roughness
KW  - wettability
KW  - erosion
Y1  - 2020
U6  - https://doi.org/10.3390/polym12081711
SN  - 2073-4360
VL  - 12
IS  - 8
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Perovic, Milena
A1  - Qin, Qing
A1  - Oschatz, Martin
T1  - From molecular precursors to nanoparticles
BT  - tailoring the adsorption properties of porous carbon materials by controlled chemical functionalization
JF  - Advanced functional materials
N2  - Nanoporous carbon materials (NCMs) provide the "function" of high specific surface area and thus have large interface area for interactions with surrounding species, which is of particular importance in applications related to adsorption processes. The strength and mechanism of adsorption depend on the pore architecture of the NCMs. In addition, chemical functionalization can be used to induce changes of electron density and/or electron density distribution in the pore walls, thus further modifying the interactions between carbons and guest species. Typical approaches for functionalization of nanoporous materials with regular atomic construction like porous silica, metal-organic frameworks, or zeolites, cannot be applied to NCMs due to their less defined local atomic construction and abundant defects. Therefore, synthetic strategies that offer a higher degree of control over the process of functionalization are needed. Synthetic approaches for covalent functionalization of NCMs, that is, for the incorporation of heteroatoms into the carbon backbone, are critically reviewed with a special focus on strategies following the concept "from molecules to materials." Approaches for coordinative functionalization with metallic species, and the functionalization by nanocomposite formation between pristine carbon materials and heteroatom-containing carbons, are introduced as well. Particular focus is given to the influences of these functionalizations in adsorption-related applications.
KW  - composites
KW  - heteroatoms
KW  - metal species
KW  - porous carbon materials
KW  - surface
KW  - functionalization
Y1  - 2020
U6  - https://doi.org/10.1002/adfm.201908371
SN  - 1616-301X
SN  - 1616-3028
VL  - 30
IS  - 41
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Prüfert, Chris
A1  - Urban, Raphael David
A1  - Fischer, Tillmann Georg
A1  - Villatoro, José Andrés
A1  - Riebe, Daniel
A1  - Beitz, Toralf
A1  - Belder, Detlev
A1  - Zeitler, Kirsten
A1  - Löhmannsröben, Hans-Gerd
T1  - In situ monitoring of photocatalyzed isomerization reactions on a microchip flow reactor by IR-MALDI ion mobility spectrometry
JF  - Analytical and bioanalytical chemistry : a merger of Fresenius' journal of analytical chemistry, Analusis and Quimica analitica
N2  - The visible-light photocatalyticE/Zisomerization of olefins can be mediated by a wide spectrum of triplet sensitizers (photocatalysts). However, the search for the most efficient photocatalysts through screenings in photo batch reactors is material and time consuming. Capillary and microchip flow reactors can accelerate this screening process. Combined with a fast analytical technique for isomer differentiation, these reactors can enable high-throughput analyses. Ion mobility (IM) spectrometry is a cost-effective technique that allows simple isomer separation and detection on the millisecond timescale. This work introduces a hyphenation method consisting of a microchip reactor and an infrared matrix-assisted laser desorption ionization (IR-MALDI) ion mobility spectrometer that has the potential for high-throughput analysis. The photocatalyzedE/Zisomerization of ethyl-3-(pyridine-3-yl)but-2-enoate (E-1) as a model substrate was chosen to demonstrate the capability of this device. Classic organic triplet sensitizers as well as Ru-, Ir-, and Cu-based complexes were tested as catalysts. The ionization efficiency of theZ-isomer is much higher at atmospheric pressure which is due to a higher proton affinity. In order to suppress proton transfer reactions by limiting the number of collisions, an IM spectrometer working at reduced pressure (max. 100 mbar) was employed. This design reduced charge transfer reactions and allowed the quantitative determination of the reaction yield in real time. Among 14 catalysts tested, four catalysts could be determined as efficient sensitizers for theE/Zisomerization of ethyl cinnamate derivativeE-1. Conversion rates of up to 80% were achieved in irradiation time sequences of 10 up to 180 s. With respect to current studies found in the literature, this reduces the acquisition times from several hours to only a few minutes per scan.
KW  - microchip
KW  - reaction monitoring
KW  - IR-MALDI
KW  - ion mobility spectrometry
KW  - photochemistry
KW  - photocatalysis
KW  - Olefin isomerization
Y1  - 2020
U6  - https://doi.org/10.1007/s00216-020-02923-y
SN  - 1618-2642
SN  - 1618-2650
VL  - 412
IS  - 28
SP  - 7899
EP  - 7911
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Qin, Qing
A1  - Oschatz, Martin
T1  - Overcoming chemical inertness under ambient conditions
BT  - a critical view on recent developments in Ammonia synthesis via electrochemical N-2 reduction by asking five questions
JF  - ChemElectroChem
N2  - Ammonia (NH3) synthesis by the electrochemical N-2 reduction reaction (NRR) is increasingly studied and proposed as an alternative process to overcome the disadvantages of Haber-Bosch synthesis by a more energy-efficient, carbon-free, delocalized, and sustainable process. An ever-increasing number of scientists are working on the improvement of the faradaic efficiency (FE) and NH3 production rate by developing novel catalysts, electrolyte concepts, and/or by contributing theoretical studies. The present Minireview provides a critical view on the interplay of different crucial aspects in NRR from the electrolyte, over the mechanism of catalytic activation of N-2, to the full electrochemical cell. Five critical questions are asked, discussed, and answered, each coupled with a summary of recent developments in the respective field. This article is not supposed to be a complete summary of recent research about NRR but provides a rather critical personal view on the field. It is the major aim to give an overview over crucial influences on different length scales to shine light on the sweet spots into which room for revolutionary instead of incremental improvements may exist.
KW  - N-2 reduction
KW  - ammonia synthesis
KW  - catalysis
KW  - catalysts
KW  - electrolytes
Y1  - 2022
U6  - https://doi.org/10.1002/celc.201901970
SN  - 2196-0216
VL  - 7
IS  - 4
SP  - 878
EP  - 889
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - THES
A1  - Störmann, Florian Konstantin
T1  - Multifunctional Microballoons for the active and passive control of fluid-flows
N2  - Functional materials, also called "Smart Materials", are described by their ability to fulfill a desired task through targeted interaction with its environment. Due to this functional integration, such materials are of increased interest, especially in areas where the increasing micronization of components is required. Modern manufacturing processes (e.g. microfluidics) and the availability of a wide variety of functional materials (e.g. shape memory materials) now enable the production of particle-based switching components. This category includes micropumps and microvalves, whose basic function is the active control of liquid flows. One approach in realizing those microcomponents as pursued by this work, enables variable size-switching of water-filled microballoons by implementing a stimulus-sensitive switching motif in the capsule's membrane shell, while being under the influence of a constant driving force. The switching motif with its gatekeeper function has a critical influence on one or more material parameters, which modulate the capsule's resistance against the driving force in microballoon expansion process. The advantage of this concept is that even non-variable analyte conditions, such as concentration levels of ions, can be capitalized to generate external force fields that, under the control of the membrane, cause an inflation of the microballoon by an osmotically driven water influx. In case of osmotic pressure gradients as the driving force for the capsule expansion, material parameters associated with the gatekeeper function are specifically the permeability and the mechanical stiffness of the shell material. While a modulation of the shell permeability could be utilized to kinetically impede the water influx on large time scales, a modulation of the shell's mechanical stiffness even might be utilized to completely prevent the capsule inflation due to a possible non-deformability beneath a certain threshold pressure. In polymer networks, which are a suitable material class for the demanded capsule shell because of their excellent elasticity, both the permeability and the mechanical properties are strongly influenced by the crystallinity of the material. Since the permeability is effectively reduced with increasing crystallinity, while the mechanical stiffness is simultaneously greatly increased, both effects point in the same direction in terms of their functional relationship. For this reason and due to a reversible and contactless modulation of the membrane crystallinity by heat input, crystallites may be suitable switching motifs for controlling the capsule expansion. As second design element of reversible expandable microballoons, the capsule geometry, defined by an aqueous core enveloped by the temperature-sensitive polymer network membrane, should allow an osmotic pressure gradient across the membrane layer. The strength of the inflation pressure and the associated inflation velocity upon membrane melting should be controlled by the salt concentration within the aqueous core, while a turn in the osmotic gradient should furthermore allow the reversible process of capsule deflation. Therefore, it should be possible to build either microvalves and micropumps, while their intended action of either pumping or valving is determined by their state of expansion and the direction of the osmotic pressure gradient.. Microballoons of approximately 300 µm in diameter were formed via droplet-based microfluidics from double-emulsion templates (w/o/w). The elastomeric capsule membrane was formed by photo-crosslinking of methacrylate (MA) functionalized oligo(ε-caprolactone) precursors (≈ 3.8 MA-arms, Mn ≈ 12000 g mol-1) within the organic medium layer (o) via UV-exposure after droplet-formation. After removal of the toluene/chloroform mixture by slow extraction via the continuous aqueous phase, the capsules solidified under the development of a characteristic "mushroom"-like shape at specific experimental conditions (e.g. λ = 308 nm, 57 mJ·s-1·cm-2, 16 min). It could be furthermore shown that in dependency to the process parameters: oligomer concentration and curing-time also spherical capsules were accessible. Long curing-times and high oligomer concentrations at a fixed light-intensity favored the formation of "mushroom"-like capsules, whereas the contrary led to spherical shaped capsules. A comparative study on thin polymer network films of same composition and equal treatment proved a correlation between the film's crosslink density and their contraction capability, while stronger crosslinked polymer networks showed a stronger contraction after solvent removal. In combination with observations during capsule solidification via light-microscopy, where a continuous shaping from almost spherical crosslinked templates to "mushroom"-shaped and solidified capsules was stated, the following mechanism was proposed. In case of low oligomer contents and short curing-times, the contraction of the capsule shell during solvent removal is strongly diminished due to a low degree of crosslinking. Therefore, the solidifying shell could freely collapse onto the aqueous core. In the other case, high oligomer concentrations and long curing-times will favor the formation of highly crosslinked capsule membranes with a strong contraction capability. Due to an observed decentered location of the aqueous core within the swollen polymer network, an uneven radial stress along the capsule's circumference is exerted to the incompressible core. This lead to an uneven contraction during solvent removal and a directed flow of the core fluid into the direction of the minimal stress vector. In consequence, the initially thicker spherical cap contracts, whereas the opposing thinner spherical cap get stretched. The "mushroom"-shape over some advantages over their spherical shaped counterparts, why they were selected for the further experiments. Besides the necessity of a high density of crosslinking for the purpose of extraordinary elasticity and toughness, the form-anisotropy promotes a faster microballoon expandability due to a partial reduction of the membrane thickness. Additionally, pre-stretched regions of thin thickness might provide a better resistance against inflation pressure than spherical but non-stretched capsules of equal membrane thickness. The resulting "mushroom"-shaped microcapsules exhibited a melting point of Tm ≈ 50 - 60 °C and a degree of crystallinity of Xc ≈ 29 - 38 % depending on the membrane thickness and internal salt content, which is slightly lower than for the non-crosslinked oligomer and reasoned by a limited chain mobility upon crosslinking. Nonetheless, the melting transition of the polymer network was associated with a strong drop in its mechanical stiffness, which was shown to have a strong influence on the osmotic driven expansion of the microcapsules. Capsules that were subjected to osmotic pressures between 1.5 and 4.7 MPa did not expand if the temperature was well below the melting point of the capsule's membrane, i.e. at room temperature. In contrast, a continuous expansion, while approaching asymptotically to a final capsule size, was observed if the temperature exceeded the melting point, i.e. 60 °C. Microballoons, which were kept for 56 days at ∆Π = 1.5 MPa and room temperature, did not change significantly in diameter, why the impact of the mechanical stiffness on the expansion behavior is considered to be the greater than the influence of the shell permeability. The time-resolved expansion behavior of the microballoons above their Tm was subsequently modeled, using difusion equations that were corrected for shape anisotropy and elastic restoring forces. A shape-related and expansion dependent pre-factor was used to dynamically address the influence of the shell thickness differences along the circumference on the inflation velocity, whereas the microballoon's elastic contraction upon inflation was rendered by the inclusion of a hyperelastic constitutive model. An important finding resulting from this model was the pronounced increase in inflation velocity compared to hypothetical capsules with a homogeneous shell thickness, which stresses the benefit of employing shape anisotropic balloon-like capsules in this study. Furthermore, the model was able to predict the finite expandability on basis of entropy-elastic recovery forces and strain-hardening effects. A comparison of six different microballoons with different shell thicknesses and internal salt contents showed the linear relationship between the volumetric expansion, the shell thickness and the applied osmotic pressure, as represented by the model. As the proposed model facilitates the prediction of the expansion kinetics depending on the membranes mechanical and diffusional characteristics, it might be a screening tool for future material selections. In course of the microballoon expansion process, capsules of intermediate diameters could be isolated by recrystallization of the membrane, which is mainly caused by a restoration of the membrane's mechanical stiffness and is otherwise difficult to achieve with other stimuli-sensitive systems. The capsule's crystallinity of intermediate expansion states was nearly unchanged, whereas the lamellar crystal size tends to decreased with the expansion ratio. Therefore, it was assumed that the elastic modulus was only minimally altered and might increased due to the networks segment-chain extension. In addition to the volume increase achieved by inflation, a turn in the osmotic gradient also facilitated the reversible deflation, which was shown in inflation/deflation cycles. These both characteristics of the introduced microballoons are important parameter regarding the realization of micropumps and microvalves. The fixation of expanded microcapsules via recrystallization enabled the storage of entropy-elastic strain-energy, which could be utilized for pumping actions in non-aqueous media. Here, the pumping velocity depended on both, the type of surrounding medium and the applied temperature. Surrounding media that supported the fast transport of pumped liquid showed an accelerated deflation, while high temperatures further accelerate the pumping velocity. Very fast rejection of the incorporated payload was furthermore realized with pierced expanded microballoons, which were subjected to temperatures above their Tm. The possible fixation of intermediate particle sizes provide opportunities for vent constructions that allowed the precise adjustment of specific flow-rates and multiple valve openings and closings. A valve construction was realized by the insertion of a single or multiple microballoons in a microfluidic channel. A complete and a partial closing of the microballoon-valves was demonstrated as a function of the heating period. In this context, a difference between the inflation and deflation velocity was stated, summarizing slower expansion kinetics. Overall, microballoons, which presented both on-demand pumping and reversible valving by a temperature-triggered change in the capsule's volume, might be suitable components that help to design fully integrated LOC devices, due to the implementation of the control switch and controllable inflation/deflation kinetics. In comparison to other state of the art stimuli-sensitive materials, one has to highlight the microballoons capability of stabilizing almost continuously intermediate capsule sizes by simple recrystallization of the microballoon's membrane.
N2  - Funktionsmaterialien, auch "Smart Materials" genannt, werden durch ihre Fähigkeit, durch die gezielte Interaktion mit seiner Umgebung eine gewünschte Aufgabe zu erfüllen, beschrieben. Aufgrund dieser Funktionsintegration sind solche Materialien vor allem in Bereichen, in denen die zunehmende Mikronisierung von Bauteilen benötigt wird, von gesteigerten Interesse. Moderne Fertigungsverfahren (z..B. Mikrofluidik) und die Verfügbarkeit verschiedenster Funktionsmaterialien (z.B. Formgedächtnismaterialien) ermöglichen heutzutage die Herstellung partikelbasierter Schaltkomponenten. In diese Kategorie fallen unter anderem Mikropumpen und Mikroventile, deren grundsätzliche Funktion die aktive Steuerung von Flüssigkeitsströmen ist. Ein Ansatz zur Realisierung solcher Mikroschalter, der von dieser Arbeit verfolgt wurde, basiert auf wassergefüllten Mikroballons mit einem integrierten stimuli-sensitiven Schaltelement, welche unter dem Einfluss einer konstanten Antriebskraft eine Gröÿenänderung erfahren. Das Schaltmotiv als kontrollierende Instanz entscheidet dabei über die Auswirkung der einwirkenden Kraft auf die Gröÿenänderung durch ihren Einfluss auf einen oder mehrere Materialparameter. Dies ermöglicht die Ausnutzung nicht-variabler Analytbedingungen, wie zum Beispiel Ionenkonzentrationsunterschiede, zur Erzeugung von Kraftfeldern, welche eine Expansion der Mikroballons durch Osmose hervorrufen. Materialparameter welche mit osmotischen Volumenströmen assoziiert sind und diese steuern, sind im Speziellen die Permeabilität und die mechanische Steifigkeit der Kapselmembran. Durch eine Verringerung der Permeabilität kann die Expansionsgeschwindigkeit der Kapseln kinetisch gehemmt und zu langen Zeitperioden hin verschoben werden, wohingegen eine Verstärkung der mechanischen Steifigkeit die Expansion der Kapseln komplett unterbinden kann, indem der angelegte osmotische Druck unterhalb des zur Dehnung notwendigen Schwellendruck liegt.. In Verbindung mit Polymernetzwerken, welche aufgrund ihrer herausragenden Elastizität und Zähfestigkeit eine geeignete Materialklasse für die Herstellung der Kapselmembran darstellen, sind sowohl die Permeabilität als auch die mechanische Steifigkeit mit der Kristallinität des Materials assoziiert. Grundsätzlich kann festgestellt werden, dass die Permeabilität mit der Kristallinität sinkt, wohingegen die Steifigkeit mit ihr steigt. Die Expansion der Kapseln sollte demnach in Abhängigkeit der Kristallinität des Hüllmaterials ermöglicht oder unterbunden werden können, weswegen sich Kristallite als temperatur-sensitive Schaltmotive eignen sollten. Das zweite Designelement von reversibel expandierbaren Mikroballons wird durch die Kapselgeometrie beschrieben, welche sowohl einen wässrigen Kern als auch eine elastomere, semi-permeable Membran aufweist. Diese Kompartimentierung ermöglicht zum einen die Generierung eines osmotischen Druckgradientens zwischen Kapselkern und Umgebung und zum anderen die Erzeugung einer dünnen und umspannenden Polymermembran. Der osmotische Druck als auch die hiermit einhergehende Expansionsgeschwindigkeit nach Aufschmelzen der Kapselmembran sollte durch das Einstellen des Salzgehaltes des Partikelkerns möglich sein. Eine reversible Kapselschrumpfung nach erfolgter Expansion sollte durch Änderungen des äußeren Salzgehaltes zugänglich sein. Auf Basis dieses Konzepts sollten demnach reversibel schaltbare Mikropumpen und Mikroventile realisierbar sein, wobei die Art ihrer Funktion sowohl von ihrem Expansionszustand als auch von der Richtung des osmotischen Druckgradienten abhängt. Die templat-basierte Erzeugung von Mikroballons mit einem Durchmesser von ca. 300 µm erfolgte aus (w/o/w) Doppelemulsionströpfchen mittels Mikrofluidik. Die elastomere Kapselmembran wurde durch Photovernetzung von Methacrylat funktionalisierten oligo(ϵ-caprolacton) Vorläufern (≈ 3.8 MA-Arme, Mn ≈ 12000 g mol-1) aus der organischen Phase (o) und nach Abschluss der Tröpfchenformierung erzeugt. Nach Verfestigung der Kapselmembran durch langsames extrahieren des Lösungsmittelgemisches (Toluol/Chloroform) über die kontinuierliche wässrige Phase, wurden unter bestimmten Reaktionsbedingungen während der Photovernetzung (e.g. λ = 308 nm, 57 mJ·s-1·cm-2, 16 min) formanisotrope "pilzförmige" Mikrokapseln erhalten. Es wurde festgestellt, dass über die Syntheseparameter der Oligomerkonzentration und Belichtungszeit, die Formgebung zwischen kugelförmigen und "pilzförmigen" Kapseln gesteuert werden konnte. Im Fall von niedrigen Oligomerkonzentrationen und kurzen Belichtungszeiten wurden kugelförmige Mikrokapseln und ansonsten "pilzförmige" Kapseln erzeugt. In einer vergleichenden Studie an dünnen Polymernetzwerkfilmen gleicher Zusammensetzung und Behandlung konnte ein Zusammenhang zwischen den beiden Syntheseparametern und der Kontraktilität der Filme bestätigt werden, wobei im Falle höherer Oligomerkonzentrationen und längeren Belichtungszeiten eine stärkere Kontraktion der Filme nach Abdampfen des Lösungsmittelgemisches beobachtet werden konnte. Zusammen mit Beobachtungen eines kontinuierlichen Ausprägens der "Pilzform" von initial annähernd kugelförmigen Kapseln im Laufe des Verfestigungsprozesses mittels Lichtmikroskopie wird folgender Mechanismus der Formausprägung vorgeschlagen. Kapseln mit niedriger Vernetzungsdichte zeigen nur eine geringe Kontraktilität, wodurch das Polymernetzwerk nach Extraktion des Lösungsmittelgemisches frei auf der Kernoberfläche kollabieren kann. Stark vernetzte Kapseln weisen hingegen eine sehr starke Schrumpfung infolge des Lösungsmittelverlustes auf. Aufgrund der nicht mittigen Positionierung des wässrigen Kerns mit Abschluss der Tröpfchenbildung und der darauf ausgebildeten inhomogenen Schichtdickenverteilung ergeben sich unterschiedlich starke radiale Spannungsunterschiede entlang der Membran. Bereiche großer Materialstärke kontrahieren infolge stärker und sorgen für eine Verformung des inkompressiblen wässrigen Kerns in Richtung dünnerer Membransegmente, welche daraufhin gedehnt werden. Nach Abschluss der Membranverfestigung liegen demnach entspannte und stark vorgedehnte Membransegmente vor, die aufgrund der Kristallisation konserviert werden. Die "Pilzform" bietet hinsichtlich der Expansionseigenschaften der Mikroballons einige Vorteile gegenüber ihrem kugelförmigen Pendant, weswegen diese für die weiteren Experimente verwendet wurden. Neben den Anforderung hoher Vernetzungsdichten zum Zwecke der geforderten Elastizität, wird durch die Formanisotropie und der damit verbundenen Schichtdickenunterschiede die Expansionsgeschwindigkeit der Kapseln gesteigert. Weiterhin könnte die Vorstreckung der dünnen Membranschichten eine zusätzliche Stabilität gegenüber dem angelegten osmotischen Drucks aufweisen und somit ein ungewolltes Expandieren unterhalb der Schmelztemperatur erschweren. Die resultierenden "pilzförmigen" Mikroballons wiesen je nach eingestellter Schichtdicke und innerer Salzkonzentration, einen Schmelzpunkt von Tm ≈ 50 - 60 °C und einen Kristallisationsgrad von Xc ≈ 29 - 38 % auf, welche verglichen mit dem unvernetzten PCL Homopolymer geringfügig kleiner waren. Dies liegt zum einen an der erhöhten Anzahl von Kettenenden und zum anderen an der eingeschränkten Kettenmobilität infolge der Oligomervernetzung. Es konnte jedoch weiterhin eine starke Verringerung der mechanischen Steifigkeit nach dem Überschreiten der Schmelztemperatur beobachtet werden. Der große Einfluss der Temperatur auf die Expansion der Mikroballons konnte für mehrere Kapseln bestätigt werden. Kapseln welche einem osmotischen Druck von 1.5 bis 4.7 MPa ausgesetzt waren zeigten keine Größenveränderung bei Raumtemperatur, d.h. weit unterhalb der Schmelztemperatur. Im Gegensatz hierzu wurde eine starke Volumenzunahme aller Kapseln nach dem Überschreiten der Schmelztemperatur, bei 60 °C festgestellt. Mikroballons welche für 56 Tage einem osmotischen Druck von 1.5 MPa bei Raumtemperatur ausgesetzt waren zeigten keine signifikanten Volumenänderungen, weswegen insbesondere der Effekt der mechanischen Erweichung ausschlaggebend für das Schaltprinzip gemacht werden kann. Das zeitaufgelöste Expansionsverhalten der Mikroballons oberhalb ihres Schmelzpunktes wurde daraufhin unter Verwendung von Diffusionsgleichungen, welche für die Formanisotropie und elastische Rückstellkräfte korrigiert wurden, modelliert. Ein formabhängiger Vorfaktor, der die Expansionsgeschwindigkeit in Abhängigkeit der Schichtdickenunterschiede und des Expansionszustandes beschreibt, wurde ebenso eingeführt wie ein Term zur Beschreibung der mechanischen Rückstellkräfte auf Basis eines hyperelastischen Materialmodells. Das Model ermöglichte zum einen eine Beschreibung der endlichen Expandierfähigkeit aufgrund entropie-elastischer Rückstellkräfte sowie aufgrund von Kaltverfestigungen, und zum anderen eine deutliche Beschleunigung des Expandiervorganges aufgrund der Kapselanisotropie. Der Vergleich sechs unterschiedlicher Kapseln mit unterschiedlichen Schichtdicken und inneren Salzgehalten zeigte zudem, in Übereinstimmung mit dem Modell, eine lineare Abhängigkeit von Schichtdicke, osmotischen Druck und der Volumenzunahme. Die mit dem Modell einhergehende Vorhersagemöglichkeit der Expansionskinetik hinsichtlich der mechanischen und diffusionsbedingten Materialcharakteristika stellen somit möglicherweise eine Hilfestellung dar, eine zukünftige Materialauswahl zu treffen. Weiterhin konnte gezeigt werden, dass durch Rekristallisation der Kapselmembran und der damit verbundenen Wiederherstellung der mechanischen Steifigkeit, intermediäre Kapselgrößen isoliert werden konnten, was nach besten Wissen des Standes-der-Technik andernfalls nur schwer zu erreichen ist. Ungeachtet des Expansionsgrades konnten nur geringe Änderungen der Kristallinität festgestellt werden, wohingegen die Kristallgröße mit zunehmender Expansion abnahm. Diesbezüglich wird angenommen dass der Elastizitätsmodulus nur geringfügigen Veränderungen unterliegt oder sogar aufgrund einer Kettenversteifung tendenziell zunimmt. Zusätzlich der Betrachtung einer Volumenzunahme, konnte durch die Änderung des Druckgradienten ebenfalls ein Schrumpfen der Kapseln erreicht werden. Die Reversibilität dieses Prozesses wurde in Expansions/Deflations-Zyklen bestätigt und ist eine wichtige Eigenschaft der Mikroballons hinsichtlich ihrer Verwendung als Mikropumpe und Mikroventil. Die Fixierung expandierter Mikrokapseln durch Rekristallisierung der Membran ermöglichte weiterhin eine Pumpfunktion in nicht-wässrigen Medien. Dabei konnte festgestellt werden, dass die Pumpleistung sowohl von dem umgebenden Medium als auch von der applizierten Temperatur abhingen. Medien, die einen schnellen Abtransport der freigesetzten Flüssigkeit ermöglichten, als auch hohe Temperaturen steigerten hierbei die Pumpleistung. Mikroballons mit einer sehr großen Auswurfleistung konnten durch das Einbringen einer Öffnung in die Membran erzeugt werden. Die Fixierung intermediärer Kapselgrößen ermöglichte Ventilkonstruktionen, welche eine präzise Flussrateneinstellung und ein vielfaches öffnen und Schließen des Ventils ermöglichte. Diese Konstruktionen wurden durch das Einbringen eines oder mehrerer Mikroballons realisiert. Ein teilweises und vollkommenes Schließen dieser Mikroballon-basierten Ventilen wurde mit einem periodischen Versuchsaufbau in Abhängigkeit der Heizperiode gezeigt. Dabei wurden unterschiedliche Expansions- und Deflationskinetiken mit einem schnelleren Schrumpfverhalten bestätigt. Zusammenfassend wurden Mikroballons entwickelt, welche sowohl eine "on-demand" Pumpfunktion als auch eine reversible Ventilfunktion aufweisen. Die Implementierung des Schaltmotives in die Partikelmembran sowie die kontrollierbaren Expansions/Deflationskinetiken machen die Mikroballons gegebenenfalls zu geeigneten Komponenten für hochintegrierbare LOC-Systeme. Im Vergleich zu anderen Stimuli-sensitiven Materialien ist die Möglichkeit der nahezu kontinuierlichen Stabilisierung von intermediärer Partikelgrößen hervorzuheben. Dieses Verhalten wird dabei durch Wechselspiel zwischen Materialeigenschaften und Kapselgeometrie erzeugt.
KW  - microcapsules
KW  - expansion
KW  - stimuli-sensitivity
KW  - microfluidics
KW  - polymer network
KW  - Mikrokapseln
KW  - expandierbar
KW  - Stimuli-Sensitivität
KW  - Mikrofluidik
KW  - Polymernetzwerk
Y1  - 2023
ER  - 
TY  - JOUR
A1  - Hossain, Mohammad Delwar
A1  - Chakraborty, Chanchal
A1  - Rana, Utpal
A1  - Mondal, Sanjoy
A1  - Holdt, Hans-Jürgen
A1  - Higuchi, Masayoshi
T1  - Green-to-black electrochromic copper(I)-based metallo-supramolecular polymer with a perpendicularly twisted structure
JF  - ACS applied polymer materials
N2  - A Cu(I)-based metallo-supramolecular polymer with a perpendicularly twisted structure was synthesized by a 1:1 complexation of tetrakis(acetonitrile)copper(I) triflate with the pi-conjugated dibenzoeilatin ligand. Stepwise complexation behavior of Cu(I) with the ligand was revealed by titrimetric ultraviolet- visible (UV-vis) spectroscopic analysis. Formation of a high-molecular-weight polymer (M-w = 1.21 x 10(5) Da) was confirmed by a size-exclusion chromatography-viscometry-right-angle laser light scattering study. A bundle structure of the polymer chains was observed by scanning electron microscopy. A cyclic voltammogram of the polymer film showed reversible redox waves at a negative potential. A device consisting of indium tin oxide (ITO) glass coated with a film of the polymer exhibited reversible green-to-black electrochromism upon alternate application of -3 and +1 V.
KW  - electrochromism
KW  - metallo-supramolecular polymers
KW  - stepwise complexation
KW  - metal-to-ligand charge transfer
KW  - copper
KW  - dibenzoeilatin
Y1  - 2020
U6  - https://doi.org/10.1021/acsapm.0c00559
SN  - 2637-6105
VL  - 2
IS  - 11
SP  - 4449
EP  - 4454
PB  - American Chemical Society
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Neffe, Axel T.
A1  - Zhang, Quanchao
A1  - Hommes-Schattmann, Paul J.
A1  - Lendlein, Andreas
T1  - Ethylene oxide sterilization of electrospun poly(L-lactide)/poly(D-lactide) core/shell nanofibers
JF  - MRS advances
N2  - The application of polymers in medicine requires sterilization while retaining material structure and properties. This demands detailed analysis, which we show exemplarily for the sterilization of PLLA/PDLA core-shell nanofibers with ethylene oxide (EtO). The electrospun patch was exposed to EtO gas (6 vol% in CO2, 1.7 bar) for 3 h at 45 degrees C and 75% rel. humidity, followed by degassing under pressure/vacuum cycles for 12 h. GC-MS analysis showed that no residual EtO was retained. Fiber diameters (similar to 520 +/- 130 nm) of the patches remained constant as observed by electron microscopy. Young's modulus slightly increased and the elongation at break slightly decreased, determined at 37 degrees C. No changes were detected in H-1-NMR spectra, in molar mass distribution (GPC) or in crystallinity measured for annealed samples with comparable thermal history (Wide Angle X-Ray Scattering). Altogether, EtO emerged as suitable sterilization method for polylactide nanofibers with core-shell morphology.
Y1  - 2021
U6  - https://doi.org/10.1557/s43580-021-00058-5
SN  - 2059-8521
VL  - 6
IS  - 33
SP  - 786
EP  - 789
PB  - Springer
CY  - Cham
ER  - 
TY  - THES
A1  - Esen, Cansu
T1  - Carbon nitride incorporation in polymer networks
T1  - Inkorporation von Kohlenstoffnitrid in Polymernetzwerke
BT  - light-driven integration and utilization of graphitic carbon nitride into macroscale polymeric networks
N2  - The urge of light utilization in fabrication of materials is as encouraging as challenging. Steadily increasing energy consumption in accordance with rapid population growth, is requiring a corresponding solution within the same rate of occurrence speed. Therefore, creating, designing and manufacturing materials that can interact with light and in further be applicable as well as disposable in photo-based applications are very much under attention of researchers. In the era of sustainability for renewable energy systems, semiconductor-based photoactive materials have received great attention not only based on solar and/or hydrocarbon fuels generation from solar energy, but also successful stimulation of photocatalytic reactions such as water splitting, pollutant degradation and organic molecule synthesisThe turning point had been reached for  water splitting with an electrochemical cell consisting of TiO2-Pt electrode illuminated by UV light as energy source rather than an external voltage, that successfully pursued water photolysis by Fujishima and Honda in 1972. Ever since, there has been a great deal of interest in research of semiconductors (e.g. metal oxide, metal-free organic, noble-metal complex) exhibiting effective band gap for photochemical reactions. In the case of environmental friendliness, toxicity of metal-based semiconductors brings some restrictions in possible applications. Regarding this, very robust and ‘earth-abundant’ organic semiconductor, graphitic carbon nitride has been synthesized and successfully applied in photoinduced applications as novel photocatalyst. Properties such as suitable band gap, low charge carrier recombination and feasibility for scaling up, pave the way of advance combination with other catalysts to gather higher photoactivity based on compatible heterojunction. 
This dissertation aims to demonstrate a series of combinations between organic semiconductor g-CN and polymer materials that are forged through photochemistry, either in synthesis or in application. Fabrication and design processes as well as applications performed in accordance to the scope of thesis will be elucidated in detail. In addition to UV light, more attention is placed on visible light as energy source with a vision of more sustainability and better scalability in creation of novel materials and solar energy based applications.
N2  - Die Nutzung von Licht bei der Herstellung von Materialien ist ebenso vielversprechend wie herausfordernd. Der stetig steigende Energieverbrauch in Kombination mit dem rasanten Bevölkerungswachstum erfordert Lösungen in der entsprechenden Geschwindigkeit. Daher stehen Materialien, die mit Licht interagieren können und darüber hinaus in fotobasierten Anwendungen einsetzbar sind, im Mittelpunkt des Interesses der Forscher. In der Ära der Nachhaltigkeit und erneuerbarer Energiesysteme haben halbleiterbasierte photoaktive Materialien nicht nur aufgrund der Erzeugung von Solarenergie oder der Herstellung von Brennstoffen aus Sonnenenergie große Aufmerksamkeit erhalten, sondern auch aufgrund des erfolgreichen Einsatzes in photokatalytischen Reaktionen wie zum Beispiel der Wasserspaltung, des Schadstoffabbaus und der Synthese organischer Moleküle. Die Wasserspaltung mit einer elektrochemischen Zelle führte hier zu einem Wendepunkt in der Forschung. Die Zelle bestand aus einer TiO2-Pt-Elektrode, welche mit UV-Licht als Energiequelle anstatt einer sonst üblichen externen Spannung betrieben wurde. 1972 führten Fujishima und Honda somit erfolgreich die Photolyse von Wasser durch. Seitdem besteht ein großes Interesse an der Erforschung von Halbleitern (z. B. Metalloxide, metallfreie organische Stoffe, Edelmetallkomplexe), die eine effektive Bandlücke für photochemische Reaktionen aufweisen. Was jedoch die Umweltfreundlichkeit anbelangt, so bringt die Toxizität von Halbleitern auf Metallbasis einige Einschränkungen mit sich.  Um diese Toxizität zu vermeiden wurde der sehr robuste und bezüglich seiner Ausgangsstoffe häufig vorkommende organische Halbleiter Graphitkohlenstoffnitrid synthetisiert und erfolgreich in photoinduzierten Anwendungen als neuartiger Photokatalysator eingesetzt. Eigenschaften wie eine geeignete Bandlücke, geringe Ladungsträgerrekombination und die Möglichkeit der Skalierung ebnen somit den Weg für  Kombinationen mit anderen Katalysatoren, um eine höhere Photoaktivität auf der Grundlage einer kompatiblen Heteroverbindung zu erreichen. 
Diese Dissertation zielt darauf ab, eine Reihe von Kombinationen zwischen dem organischen Halbleitern g-CN und Polymermaterialien zu demonstrieren. Diese werden entweder durch photochemische Reaktionen synthetisiert oder in solchen angewendet. Die Herstellungs- und Designprozesse sowie die Anwendungen, die im Rahmen dieser Arbeit durchgeführt wurden, werden im Detail erläutert. Neben UV-Licht wird auch dem sichtbarem Licht als Energiequelle mehr Aufmerksamkeit gewidmet. Durch die Verwendung von sichtbaren Licht können die Materialen in solarenergetischen Anwendungen genutzt werden und die Nachhaltigkeit und Skalierbarkeit der Materialien wird verbessert.
KW  - polymer chemistry
KW  - Polymerchemie
KW  - carbon nitride
KW  - Kohlenstoffnitriden
KW  - heterogeneous photocatalysis
KW  - heterogene Photokatalyse
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-576253
ER  - 
TY  - THES
A1  - Lepre, Enrico
T1  - Nitrogen-doped carbonaceous materials for energy and catalysis
N2  - Facing the environmental crisis, new technologies are needed to sustain our society. In this context, this thesis aims to describe the properties and applications of carbon-based sustainable materials. In particular, it reports the synthesis and characterization of a wide set of porous carbonaceous materials with high nitrogen content obtained from nucleobases. These materials are used as cathodes for Li-ion capacitors, and a major focus is put on the cathode preparation, highlighting the oxidation resistance of nucleobase-derived materials. Furthermore, their catalytic properties for acid/base and redox reactions are described, pointing to the role of nitrogen speciation on their surfaces. Finally, these materials are used as supports for highly dispersed nickel loading, activating the materials for carbon dioxide electroreduction.
N2  - Angesichts der Umweltkrise werden neue Technologien benötigt, um unsere Gesellschaft zu erhalten. In diesem Zusammenhang zielt diese Arbeit darauf ab, die Eigenschaften und Anwendungen von nachhaltigen Materialien auf Kohlenstoffbasis zu untersuchen. Insbesondere wird über die Synthese und Charakterisierung eines breiten Spektrums poröser, kohlenstoffhaltiger Materialien berichtet, welche einen hohen Stickstoffgehalt, besitzen und aus Nukleobasen gewonnen werden. Diese Materialien werden als Kathoden für Li-Ionen-Kondensatoren verwendet, wobei der Schwerpunkt auf der Kathodenherstellung liegt und die Oxidationsbeständigkeit, der aus Nukleobasen gewonnenen Materialien, hervorgehoben wird. Darüber hinaus werden ihre katalytischen Eigenschaften für Säure/Base- und Redoxreaktionen beschrieben, wobei die Rolle der Speziierung des Stickstoffs auf ihren Oberflächen hervorgehoben wird. Schließlich werden diese Materialien als Träger für eine hochdisperse Beladung mit Nickel verwendet, wodurch die Materialien für die Kohlendioxid Elektroreduktion aktiviert werden.
KW  - heteroatom-doped carbons
KW  - heteroatom-dotierte Kohlenstoffe
KW  - porous materials
KW  - poröse Materialien
KW  - salt melt templating
KW  - Salzschmelze-Templating
KW  - heterogeneous catalysis
KW  - heterogene Katalyse
KW  - single-atom catalysis
KW  - Einzelatomkatalyse
KW  - Li-ion capacitor
KW  - Li-Ionen-Kondensator
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-577390
ER  - 
TY  - THES
A1  - Henschel, Cristiane
T1  - Thermoresponsive polymers with co-nonsolvency behavior
T1  - Thermoresponsive Polymere mit "Co-Nonsolvency" Verhalten
N2  - Despite the popularity of thermoresponsive polymers, much is still unknown about their behavior, how it is triggered, and what factors influence it, hindering the full exploitation of their potential. One particularly puzzling phenomenon is called co-nonsolvency, in which a polymer is soluble in two individual solvents, but counter-intuitively becomes insoluble in mixtures of both. Despite the innumerous potential applications of such systems, including actuators, viscosity regulators and as carrier structures, this field has not yet been extensively studied apart from the classical example of poly(N isopropyl acrylamide) (PNIPAM) in mixtures of water and methanol. Therefore, this thesis focuses on evaluating how changes in the chemical structure of the polymers impact the thermoresponsive, aggregation and co-nonsolvency behaviors of both homopolymers and amphiphilic block copolymers.  Within this scope, both the synthesis of the polymers and their characterization in solution is investigated. Homopolymers were synthesized by conventional free radical polymerization, whereas block copolymers were synthesized by consecutive reversible addition fragmentation chain transfer (RAFT) polymerizations. The synthesis of the monomers N isopropyl methacrylamide (NIPMAM) and N vinyl isobutyramide (NVIBAM), as well as a few chain transfer agents is also covered. Through turbidimetry measurements, the thermoresponsive and co-nonsolvency behavior of PNIPMAM and PNVIBAM homopolymers is then compared to the well-known PNIPAM, in aqueous solutions with 9 different organic co-solvents. Additionally, the effects of end-groups, molar mass, and concentration are investigated. Despite the similarity of their chemical structures, the 3 homopolymers show significant differences in transition temperatures and some divergences in their co-nonsolvency behavior. More complex systems are also evaluated, namely amphiphilic di- and triblock copolymers of PNIPAM and PNIPMAM with polystyrene and poly(methyl methacrylate) hydrophobic blocks. Dynamic light scattering is used to evaluate their aggregation behavior in aqueous and mixed aqueous solutions, and how it is affected by the chemical structure of the blocks, the chain architecture, presence of cosolvents and polymer concentration. The results obtained shed light into the thermoresponsive, co-nonsolvency and aggregation behavior of these polymers in solution, providing valuable information for the design of systems with a desired aggregation behavior, and that generate targeted responses to temperature and solvent mixture changes.
N2  - Trotz der Popularität thermoresponsiver Polymere ist noch vieles über ihr Verhalten, sowie dessen Auslöser und Einflüsse darauf unbekannt, was die volle Nutzung ihres Potenzials behindert. Ein besonders ungewöhnliches Phänomen ist die so genannte Co-Nonsolvency, bei der ein Polymer in zwei reinen Lösungsmitteln löslich ist, aber in Mischungen aus beiden unlöslich wird. Trotz der zahlreichen potenziellen Anwendungen solcher Systeme, wie z.B. Aktuatoren, Viskositätsregulatoren und als Transportmedien, ist dieses Feld, abgesehen vom klassischen Beispiel von Poly(N isopropylacrylamid) (PNIPAM) in Mischungen aus Wasser und Methanol, bisher nicht umfassend untersucht worden. Diese Arbeit untersucht daher, welche Auswirkungen die chemische Struktur der Polymere auf das thermoresponsive, Aggregations- und Co-Nonsolvency Verhalten sowohl von Homopolymeren als auch von amphiphilen Blockcopolymeren hat. Dazu wurden sowohl die Synthese der Polymere als auch deren Verhalten in Lösung untersucht. Die Homopolymere wurden durch konventionelle radikalische Polymerisation hergestellt, wogegen die Blockcopolymere durch konsekutive Reversible Addition Fragmentation Chain Transfer Polymerisationen (RAFT) synthetisiert wurden. Die Synthese der Monomere N-Isopropylmethacrylamid (NIPMAM) und N Vinylisobutyramid (NVIBAM) sowie einiger Kettenüberträger wird ebenfalls beschrieben. Mittels Trübungs-Messungen wird das thermoresponsive und Co-Nonsolvency Verhalten von PNIPMAM- und PNVIBAM-Homopolymeren mit dem bekannten PNIPAM in wässrigen Lösungen mit 9 verschiedenen organischen Co-Lösungsmitteln verglichen. Außerdem werden die Auswirkungen der Endgruppen, der Molmasse und der Konzentration der Polymere diskutiert. Trotz der Ähnlichkeit ihrer chemischen Strukturen zeigen die drei Homopolymere signifikante Unterschiede bei den Übergangstemperaturen und einige Divergenzen in ihrem Co-Nonsolvency Verhalten. Es wurden auch komplexere Systeme untersucht, nämlich amphiphile Di- und Triblock-Copolymere von PNIPAM und PNIPMAM mit hydrophoben Blöcken aus Polystyrol und Polymethylmethacrylat. Mittels dynamischer Lichtstreuung wird ihr Aggregationsverhalten in wässrigen und gemischten wässrigen Lösungen bewertet und untersucht, wie es von der chemischen Struktur der Blöcke, der Kettenarchitektur, den Co-Lösungsmitteln und der Polymerkonzentration beeinflusst wird. Die Ergebnisse dokumentieren das thermoresponsive, Co-Nonsolvency und Aggregationsverhalten dieser Polymere in Lösung und liefern wertvolle Informationen für die Entwicklung von Systemen mit einem gewünschten Aggregationsverhalten, die gezielt auf Temperatur- und Lösungsmittelgemischänderungen reagieren.
KW  - thermoresponsive polymer
KW  - co-nonsolvency
KW  - amphiphilic block copolymer
KW  - poly(N-isopropyl acrylamide)
KW  - poly(N-isopropyl methacrylamide)
KW  - poly(N-vinyl isobutyramide)
KW  - lower critical solution temperature
KW  - phase transition
KW  - amphiphile Blockcopolymere
KW  - Co-Nonsolvency
KW  - untere kritische Lösungstemperatur
KW  - Phasenübergang
KW  - Poly(N-Isopropylacrylamid)
KW  - Poly(N-Isopropylmethacrylamid)
KW  - Poly(N-Vinylisobutyramid)
KW  - thermoresponsive Polymere
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-577161
ER  - 
TY  - JOUR
A1  - Penschke, Christopher
A1  - Edler von Zander, Robert
A1  - Beqiraj, Alkit
A1  - Zehle, Anna
A1  - Jahn, Nicolas
A1  - Neumann, Rainer
A1  - Saalfrank, Peter
T1  - Water on porous, nitrogen-containing layered carbon materials
BT  - the performance of computational model chemistries
JF  - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies / RSC, Royal Society of Chemistry
N2  - Porous, layered materials containing sp(2)-hybridized carbon and nitrogen atoms, offer through their tunable properties, a versatile route towards tailormade catalysts for electrochemistry and photochemistry. A key molecule interacting with these quasi two-dimensional materials (2DM) is water, and a photo(electro)chemical key reaction catalyzed by them, is water splitting into H-2 and O-2, with the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) as half reactions. The complexity of some C/N-based 2DM in contact with water raises special needs for their theoretical modelling, which in turn is needed for rational design of C/N-based catalysts. In this work, three classes of C/N-containing porous 2DM with varying pore sizes and C/N ratios, namely graphitic carbon nitride (g-C3N4), C2N, and poly(heptazine imides) (PHI), are studied with various computational methods. We elucidate the performance of different models and model chemistries (the combination of electronic structure method and basis set) for water and water fragment adsorption in the low-coverage regime. Further, properties related to the photo(electro)chemical activity like electrochemical overpotentials, band gaps, and optical excitation energies are in our focus. Specifically, periodic models will be tested vs. cluster models, and density functional theory (DFT) vs. wavefunction theory (WFT). This work serves as a basis for a systematic study of trends for the photo(electro)chemical activity of C/N-containing layered materials as a function of water content, pore size and density.
Y1  - 2022
U6  - https://doi.org/10.1039/d2cp00657j
SN  - 1463-9076
SN  - 1463-9084
VL  - 24
IS  - 24
SP  - 14709
EP  - 14726
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Lood, Kajsa
A1  - Tikk, Triin
A1  - Krüger, Mandy
A1  - Schmidt, Bernd
T1  - Methylene capping facilitates cross-metathesis reactions of enals
BT  - a short synthesis of 7-methoxywutaifuranal from the xylochemical isoeugenol
JF  - The journal of organic chemistry
N2  - Four combinations of type-I olefins isoeugenol and 4-hydroxy-3-methoxystyrene with type-II olefins acrolein and crotonaldehyde were investigated in cross-metathesis (CM) reactions. While both type-I olefins are suitable CM partners for this transformation, we observed synthetically useful conversions only with type-II olefin crotonaldehyde. For economic reasons, isoeugenol, a cheap xylochemical available from renewable lignocellulose or from clove oil, is the preferred type-I CM partner. Nearly quantitative conversions to coniferyl aldehyde by the CM reaction of isoeugenol and crotonaldehyde can be obtained at ambient temperature without a solvent or at high substrate concentrations of 2 mol.L-1 with the second-generation Hoveyda-Grubbs catalyst. Under these conditions, the ratio of reactants can be reduced to 1:1.5 and catalyst loadings as low as 0.25 mol % are possible. The high reactivity of the isoeugenol/crotonaldehyde combination in olefin metathesis reactions was demonstrated by a short synthesis of the natural product 7-methoxywutaifuranal, which was obtained from isoeugenol in a 44% yield over five steps. We suggest that the superior performance of crotonaldehyde in the CM reactions investigated can be rationalized by "methylene capping", i.e., the steric stabilization of the propagating Ru-alkylidene species.
KW  - Aldehydes
KW  - Catalysts
KW  - Hydrocarbons
KW  - Metathesis
KW  - Mixtures
Y1  - 2022
U6  - https://doi.org/10.1021/acs.joc.1c02851
SN  - 0022-3263
SN  - 1520-6904
VL  - 87
IS  - 5
SP  - 3079
EP  - 3088
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ebel, Kenny
A1  - Bald, Ilko
T1  - Low-energy (5-20 eV) electron-induced single and double strand breaks in well-defined DNA sequences
JF  - The journal of physical chemistry letters / American Chemical Society
N2  - Ionizing radiation is used in cancer radiation therapy to effectively damage the DNA of tumors. The main damage is due to generation of highly reactive secondary species such as low-energy electrons (LEEs). The accurate quantification of DNA radiation damage of well-defined DNA target sequences in terms of absolute cross sections for LEE-induced DNA strand breaks is possible by the DNA origami technique; however, to date, it is possible only for DNA single strands. In the present work DNA double strand breaks in the DNA sequence 5'-d(CAC)(4)/5'd(GTG)(4) are compared with DNA single strand breaks in the oligonucleotides 5'-d(CAC)(4) and 5'-d(GTG)(4) upon irradiation with LEEs in the energy range from 5 to 20 eV. A maximum of strand break cross section was found around 7 and 10 eV independent of the DNA sequence, indicating that dissociative electron attachment is the underlying mechanism of strand breakage and confirming previous studies using plasmid DNA.
Y1  - 2022
U6  - https://doi.org/10.1021/acs.jpclett.2c00684
SN  - 1948-7185
VL  - 13
IS  - 22
SP  - 4871
EP  - 4876
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Picconi, David
T1  - Nonadiabatic quantum dynamics of the coherent excited state intramolecular proton transfer of 10-hydroxybenzo[h]quinoline
JF  - Photochemical & photobiological sciences
N2  - The photoinduced nonadiabatic dynamics of the enol-keto isomerization of 10-hydroxybenzo[h]quinoline (HBQ) are studied computationally using high-dimensional quantum dynamics. The simulations are based on a diabatic vibronic coupling Hamiltonian, which includes the two lowest pi pi* excited states and a n pi* state, which has high energy in the Franck-Condon zone, but significantly stabilizes upon excited state intramolecular proton transfer. A procedure, applicable to large classes of excited state proton transfer reactions, is presented to parametrize this model using potential energies, forces and force constants, which, in this case, are obtained by time-dependent density functional theory. The wave packet calculations predict a time scale of 10-15 fs for the photoreaction, and reproduce the time constants and the coherent oscillations observed in time- resolved spectroscopic studies performed on HBQ. In contrast to the interpretation given to the most recent experiments, it is found that the reaction initiated by 1 pi pi* <- S-0 photoexcitation proceeds essentially on a single potential energy surface, and the observed coherences bear signatures of Duschinsky mode-mixing along the reaction path. The dynamics after the 2 pi pi* <- S-0 excitation are instead nonadiabatic, and the n pi* state plays a major role in the relaxation process. The simulations suggest a mainly active role of the proton in the isomerization, rather than a passive migration assisted by the vibrations of the benzoquinoline backbone. <br /> [GRAPHICS] <br /> .
KW  - Excited state proton transfer
KW  - Quantum dynamics
KW  - Nonadiabatic effects
KW  - Spectroscopy
KW  - Coherences
Y1  - 2021
U6  - https://doi.org/10.1007/s43630-021-00112-z
SN  - 1474-905X
SN  - 1474-9092
VL  - 20
IS  - 11
SP  - 1455
EP  - 1473
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Quantification of sigma-acceptor and pi-donor stabilization in O, S and Hal analogues of N-heterocyclic carbenes (NHCs) on the magnetic criterion
JF  - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRSs), of stable O, S and Hal analogues of N-heterocyclic carbenes (NHCs) have been calculated using the GIAO perturbation method employing the nucleus-independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSSs) of various sizes and directions. The TSNMRS values (actually the anisotropy effects measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the position of the present mesomeric equilibria (carbenes <-> ylides). The results are confirmed by geometry (bond angles and bond lengths), IR spectra, UV spectra, and C-13 chemical shifts of the electron-deficient carbon centers.
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jpca.1c05257
SN  - 1089-5639
SN  - 1520-5215
VL  - 125
IS  - 33
SP  - 7235
EP  - 7245
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Riemer, Janine
T1  - Highly K+ selective probes with fluorescence emission wavelengths higher than 500 nm in water
JF  - ChemistrySelect
N2  - Herein, we report on the synthesis of highly K+/Na+ selective fluorescent probes in a feasible number of synthetic steps. These K+ selective fluorescent probes, so called fluoroionophores, 1 and 2 consists of different highly K+/Na+ selective building blocks the alkoxy-substituted N-phenylaza-18-crown-6 lariat ethers (ionophores) and "green" (cf. coumarin unit in 1) or "red" (cf. nile red unit in 2) fluorescent moieties (fluorophores). The fluorescent probes 1 and 2 show K+ induced fluorescence enhancement factors of 4.1 for 1 and 1.9 for 2 and dissociation constants for the corresponding K+ complexes of 43 mM (1+K+) and 18 mM (2+K+) in buffered aqueous solution. The fluorescence signal of 1 and 2 is changed by less than 5 % by pH values in the range of 6.8 to 8.8. Thus, 1 and 2 are capable fluorescent tools to determine extracellular K+ levels by fluorescence enhancements at wavelengths higher than 500 nm.
KW  - potassium
KW  - sodium
KW  - fluorescence
KW  - selectivity
KW  - probes
Y1  - 2020
U6  - https://doi.org/10.1002/slct.202003785
SN  - 2365-6549
VL  - 5
IS  - 42
SP  - 13174
EP  - 13178
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Hermanns, Jolanda
A1  - Keller, David
T1  - School-related content knowledge in organic chemistry
BT  - How does the Bachelor and Master studies?
JF  - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society
N2  - In this paper the development, use, and evaluation of tasks based on the construct of school-related content knowledge are described. The tasks were used in seminars on organic chemistry for bachelor and master preservice chemistry teachers at a German university. For the evaluation a questionnaire with open and closed items was used. The tasks were rated by the preservice chemistry teachers as relevant for their future profession as a chemistry teacher if the content of the tasks is part of the school curriculum. If the content does not belong to the school curriculum, they rated the nature of the tasks still as relevant; they seem to recognize the importance of conceptual knowledge for their future profession. However, the master's preservice teachers argued with this conceptual knowledge more often than the bachelor's preservice teachers. Although the study is cross-sectional, a certain shift from the focus on the content to conceptual knowledge from bachelor's to master's preservice teachers can be observed.
KW  - Organic Chemistry
KW  - Second-Year Undergraduate
KW  - Analogies/Transfer
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jchemed.0c01415
SN  - 0021-9584
SN  - 1938-1328
VL  - 98
IS  - 3
SP  - 763
EP  - 773
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Marques, Telma S.
A1  - Smialek, Malgorzata A.
A1  - Schürmann, Robin
A1  - Bald, Ilko
A1  - Raposo, Maria
A1  - Eden, Sam
A1  - Mason, Nigel J.
T1  - Decomposition of halogenated nucleobases by surface plasmon resonance excitation of gold nanoparticles
JF  - The European physical journal : D, Atomic, molecular, optical and plasma physics
N2  - Halogenated uracil derivatives are of great interest in modern cancer therapy, either as chemotherapeutics or radiosensitisers depending on their halogen atom. This work applies UV-Vis spectroscopy to study the radiation damage of uracil, 5-bromouracil and 5-fluorouracil dissolved in water in the presence of gold nanoparticles upon irradiation with an Nd:YAG ns-pulsed laser operating at 532 nm at different fluences. Gold nanoparticles absorb light efficiently by their surface plasmon resonance and can significantly damage DNA in their vicinity by an increase of temperature and the generation of reactive secondary species, notably radical fragments and low energy electrons. A recent study using the same experimental approach characterized the efficient laser-induced decomposition of the pyrimidine ring structure of 5-bromouracil mediated by the surface plasmon resonance of gold nanoparticles. The present results show that the presence of irradiated gold nanoparticles decomposes the ring structure of uracil and its halogenated derivatives with similar efficiency. In addition to the fragmentation of the pyrimidine ring, for 5-bromouracil the cleavage of the carbon-halogen bond could be observed, whereas for 5-fluorouracil this reaction channel was inhibited. Locally-released halogen atoms can react with molecular groups within DNA, hence this result indicates a specific mechanism by which doping with 5-bromouracil can enhance DNA damage in the proximity of laser irradiated gold nanoparticles.
Y1  - 2020
U6  - https://doi.org/10.1140/epjd/e2020-10208-3
SN  - 1434-6060
SN  - 1434-6079
VL  - 74
IS  - 11
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Intramolecular carbene stabilization via 3c,2e bonding on basis of the magnetic criterion
JF  - Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of bent cyclobutylcarbene 8, 1,2-diboretane-3-ylidene 9, and some carbene analogues of boron 14-18 as most intriguing examples of carbenes, which can be stabilized as homoaromatic systems with 3c,2e bonding, have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually, ring current effect/anisotropy effects as measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the degree of present 3c,2e-homoaromaticity. Results are confirmed by geometry (bond angles and bond lengths) and spectroscopic data, the delta(B-11)/ppm data and the C-13 chemical shifts of the carbene electron-deficient centre.
KW  - Cyclobutylcarbene
KW  - 1,2-diboretane-3-ylidene
KW  - 3c,2e-bonding
KW  - Through-space NMR shieldings (TSNMRS)
KW  - NICS
Y1  - 2021
U6  - https://doi.org/10.1016/j.tet.2021.132357
SN  - 0040-4020
SN  - 1464-5416
VL  - 95
PB  - Elsevier Science
CY  - Amsterdam
ER  - 
TY  - THES
A1  - Chea, Sany
T1  - Glycomaterials: From synthesis of glycoconjugates to potential biomedical applications
T1  - Glykomaterialien: Von der Synthese von Glykokonjugaten zu potenziellen biomedizinischen Anwendungen
N2  - The importance of carbohydrate structures is enormous due to their ubiquitousness in our lives. The development of so-called glycomaterials is the result of this tremendous significance. These are not exclusively used for research into fundamental biological processes, but also, among other things, as inhibitors of pathogens or as drug delivery systems. This work describes the development of glycomaterials involving the synthesis of glycoderivatives, -monomers and -polymers. Glycosylamines were synthesized as precursors in a single synthesis step under microwave irradiation to significantly shorten the usual reaction time. Derivatization at the anomeric position was carried out according to the methods developed by Kochetkov and Likhorshetov, which do not require the introduction of protecting groups. Aminated saccharide structures formed the basis for the synthesis of glycomonomers in β-configuration by methacrylation. In order to obtain α-Man-based monomers for interactions with certain α-Man-binding lectins, a monomer synthesis by Staudinger ligation was developed in this work, which also does not require protective groups. Modification of the primary hydroxyl group of a saccharide was accomplished by enzyme-catalyzed synthesis. Ribose-containing cytidine was transesterified using the lipase Novozym 435 and microwave irradiation. The resulting monomer synthesis was optimized by varying the reaction partners. To create an amide bond instead of an ester bond, protected cytidine was modified by oxidation followed by amide coupling to form the monomer. This synthetic route was also used to isolate the monomer from its counterpart guanosine. After obtaining the nucleoside-based monomers, they were block copolymerized using the RAFT method. Pre-synthesized pHPMA served as macroCTA to yield cytidine- or guanosine-containing block copolymer. These isolated block copolymers were then investigated for their self-assembly behavior using UV-Vis, DLS and SEM to serve as a potential thermoresponsive drug delivery system.
N2  - Die Bedeutung von Kohlenhydratstrukturen ist immens, da sie in unserem Leben allgegenwärtig sind. Die Entwicklung sogenannter Glykomaterialien ist das Ergebnis dieser großen Bedeutung. Diese werden nicht nur zur Erforschung grundlegender biologischer Prozesse eingesetzt, sondern unter anderem auch als Hemmstoffe für Krankheitserreger oder als Wirkstofftransportsysteme. Die vorliegende Arbeit beschreibt die Entwicklung von Glycomaterialien durch die Synthese von Glycoderivaten, -monomeren und -polymeren. Glycosylamine wurden als Vorstufen in einem einzigen Syntheseschritt unter Mikrowellenbestrahlung synthetisiert, um die übliche Reaktionszeit deutlich zu verkürzen. Die Derivatisierung an der anomeren Position wurde nach den von Kochetkov und Likhorshetov entwickelten Methoden durchgeführt, die keine Einführung von Schutzgruppen erfordern. Die aminierten Saccharidstrukturen bildeten die Grundlage für die Synthese von Glycomonomeren in β-Konfiguration durch Methacrylierung. Um α-Man-basierte Monomere für Interaktionen mit bestimmten α-Man-bindenden Lektinen zu erhalten, wurde in dieser Arbeit eine Monomersynthese durch Staudinger-Ligation entwickelt, die ebenfalls keine Schutzgruppen erfordert. Die Modifizierung der primären Hydroxylgruppe eines Saccharids wurde durch enzymkatalysierte Synthese erreicht. Ribosehaltiges Cytidin wurde mit Hilfe der Lipase Novozym 435 und Mikrowellenbestrahlung umgeestert. Die resultierende Monomersynthese wurde durch Variation der Reaktionspartner optimiert. Um eine Amidbindung anstelle einer Esterbindung zu erzeugen, wurde geschütztes Cytidin durch Oxidation und anschließende Amidkupplung modifiziert, um das Monomer zu bilden. Dieser Syntheseweg wurde auch zur Isolierung des Monomers aus seinem Gegenstück Guanosin verwendet. Nach der Gewinnung der nukleosidbasierten Monomere wurden diese mit Hilfe der RAFT-Methode blockcopolymerisiert. Vorsynthetisiertes pHPMA diente als MakroCTA, um Cytidin- oder Guanosin-haltige Blockcopolymere zu erhalten. Diese isolierten Blockcopolymere wurden dann mit UV-Vis, DLS und SEM auf ihr Selbstorganisationsverhalten untersucht, um als potenzielles thermoresponsives Drug-Delivery-System zu dienen.
KW  - polymer chemistry
KW  - glyco chemistry
KW  - glycomonomer
KW  - glycopolymer
KW  - lectin
KW  - drug delivery
KW  - thermoresponsive
KW  - glycoconjugate
KW  - Glykochemie
KW  - Glykokonjugat
KW  - Glykomonomer
KW  - Glykopolymer
KW  - Lektin
KW  - Polymerchemie
KW  - thermoresponsiv
KW  - Drug Delivery
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-574240
ER  - 
TY  - THES
A1  - Simsek, Ibrahim
T1  - Ink-based preparation of chalcogenide perovskites as thin films for PV applications
T1  - Präparation von Chalkogeniden Perowskiten auf Basis von molekularer Tinte als Dünnschichten für PV Anwendungen
N2  - The increasing demand for energy in the current technological era and the recent political decisions about giving up on nuclear energy diverted humanity to focus on alternative environmentally friendly energy sources like solar energy. Although silicon solar cells are the product of a matured technology, the search for highly efficient and easily applicable materials is still ongoing. These properties made the efficiency of halide perovskites comparable with silicon solar cells for single junctions within a decade of research. However, the downside of halide perovskites are poor stability and lead toxicity for the most stable ones.
On the other hand, chalcogenide perovskites are one of the most promising absorber materials for the photovoltaic market, due to their elemental abundance and chemical stability against moisture and oxygen. In the search of the ultimate solar absorber material, combining the good optoelectronic properties of halide perovskites with the stability of chalcogenides could be the promising candidate.
Thus, this work investigates new techniques for the synthesis and design of these novel chalcogenide perovskites, that contain transition metals as cations, e.g., BaZrS3, BaHfS3, EuZrS3, EuHfS3 and SrHfS3. There are two stages in the deposition techniques of this study: In the first stage, the binary compounds are deposited via a solution processing method. In the second stage, the deposited materials are annealed in a chalcogenide atmosphere to form the perovskite structure by using solid-state reactions.
The research also focuses on the optimization of a generalized recipe for a molecular ink to deposit precursors of chalcogenide perovskites with different binaries. The implementation of the precursor sulfurization resulted in either binaries without perovskite formation or distorted perovskite structures, whereas some of these materials are reported in the literature as they are more favorable in the needle-like non-perovskite configuration.
Lastly, there are two categories for the evaluation of the produced materials: The first category is about the determination of the physical properties of the deposited layer, e.g., crystal structure, secondary phase formation, impurities, etc. For the second category, optoelectronic properties are measured and compared to an ideal absorber layer, e.g., band gap, conductivity, surface photovoltage, etc.
N2  - Der stetig wachsende Energieverbrauch in der aktuellen technologischen Ära und die kürzliche Entscheidung der Politik auf Nuklearenergie zu verzichten hat die Menschheit dazu geleitet sich auf alternative umweltfreundliche Energiequellen wie Solare Energie zu fokussieren. Obwohl Silizium Solarzellen das Produkt einer ausgereiften Technologie sind geht die Suche nach hocheffizienten Materialien, die einfach umzusetzen sind weiter. Diese Eigenschaften führten zur Vergleichbarkeit von Halogeniden Perowskiten mit Silizium in Einfachsolarzellen innerhalb eines Jahrzehnts der Forschung. Allerdings mangelt es bei Halogeniden Perowskiten an Stabilität und jene stabile haben eine Blei-Toxizität.
Andererseits bieten Chalkogenide Perowskite aussichtsreiche Eigenschaften als Absorber Materialien für den Photovoltaik Markt auf Grund des hohen Vorkommens der Elemente auf dem Planeten und ihrer chemischen Stabilität in Luft. Auf der Suche nach dem ultimativen Absorber Material für Solarzellen könnte sich eine Kombination der guten optoelektronischen Eigenschaften von Halogeniden Perowskiten mit der Stabilität von Chalkogeniden als guter Kandidat herausstellen.
Infolgedessen untersucht diese Arbeit neue Methoden für die Synthese und das Design dieser neuartigen Chalkogeniden Perowskite, welche Übergangsmetalle als Kationen enthalten, z.B. BaZrS3, BaHfS3, EuZrS3, EuHfS3 and SrHfS3. Es gibt zwei Schritte in den Methoden der Deposition in dieser Untersuchung: Im ersten Schritt werden die binären Verbindungen durch eine Lösungsmittelprozessierung auf dem Substrat aufgebracht. Daraufhin wird im zweiten Schritt das aufgetragene Material in einer Chalkogeniden Atmosphäre getempert, um die Perowskit Struktur durch Festkörperreaktion zu bilden.
Die Untersuchung fokussiert sich außerdem auf die Optimierung eines generalisierten Rezeptes für molekulare Tinte zur Deposition eines Präkursors aus unterschiedlichen binären Verbindungen. Die Implementierung der Präkursor Schwefelung führt entweder zu einer Formation der binären Verbindungen ohne Perowskit Struktur oder in der verzerrten Perowskit Struktur, obwohl für manche dieser Materialien laut Literatur die nadelförmige nicht-Perowskit Struktur günstiger sein sollte.
Zuletzt gibt es zwei Kategorien für die Evaluierung der hergestellten Materialien: Die erste Kategorie behandelt die Determinierung der physikalischen Eigenschaften der deponierten Dünnschicht, z.B. Kristallstruktur, Sekundärphasen, Unreinheiten. In der zweiten Kategorie werden die optoelektronischen Eigenschaften gemessen und mit einem idealen Absorber verglichen, z.B. Bandlücke, Leitfähigkeit, Oberflächen Photospannung, etc.
KW  - chalcogenide
KW  - perovskite
KW  - Perowskite
KW  - Chalkogenide
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-572711
ER  - 
TY  - JOUR
A1  - Krüger, Tobias
A1  - Linker, Torsten
T1  - Synthesis of gamma-spirolactams by Birch reduction of arenes
JF  - European journal of organic chemistry
N2  - A convenient method for the synthesis of gamma-spirolactams in only three steps is described. Birch reduction of inexpensive and commercially available aromatic carboxylic acids in the presence of chloroacetonitrile affords nitriles in moderate to good yields. Suitable precursors are methyl-substituted benzoic acids, naphthoic, and anthroic acid. Subsequent catalytic hydrogenation proceeds smoothly with PtO2 or Raney Ni as catalysts and lactams are isolated in excellent yields and stereoselectivities. Thus, up to 3 new stereogenic centers can be constructed as sole diastereomers from achiral benzoic acids. Furthermore, it is possible to control the degree of saturation at different pressures, affording products with 0, 1, or 2 double bonds. Overall, more than 15 new gamma-spirolactams have been synthesized in analytically pure form.
KW  - Arenes
KW  - Birch reduction
KW  - Hydrogenation
KW  - Lactams
KW  - Synthetic methods
Y1  - 2021
U6  - https://doi.org/10.1002/ejoc.202100056
SN  - 1099-0690
VL  - 2021
IS  - 10
SP  - 1585
EP  - 1591
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - THES
A1  - Djalali, Saveh Arman
T1  - Multiresponsive complex emulsions: Concepts for the design of active and adaptive liquid colloidal systems
T1  - Multiresponsive komplexe Emulsionen: Konzepte für das Design von aktiven und adaptiven flüssig-kolloidalen Systemen
N2  - Complex emulsions are dispersions of kinetically stabilized multiphasic emulsion droplets comprised of two or more immiscible liquids that provide a novel material platform for the generation of active and dynamic soft materials. In recent years, the intrinsic reconfigurable morphological behavior of complex emulsions, which can be attributed to the unique force equilibrium between the interfacial tensions acting at the various interfaces, has become of fundamental and applied interest. As such, particularly biphasic Janus droplets have been investigated as structural templates for the generation of anisotropic precision objects, dynamic optical elements or as transducers and signal amplifiers in chemo- and bio-sensing applications. In the present thesis, switchable internal morphological responses of complex droplets triggered by stimuli-induced alterations of the balance of interfacial tensions have been explored as a universal building block for the design of multiresponsive, active, and adaptive liquid colloidal systems. A series of underlying principles and mechanisms that influence the equilibrium of interfacial tensions have been uncovered, which allowed the targeted design of emulsion bodies that can alter their shape, bind and roll on surfaces, or change their geometrical shape in response to chemical stimuli. Consequently, combinations of the unique triggerable behavior of Janus droplets with designer surfactants, such as a stimuli-responsive photosurfactant (AzoTAB) resulted for instance in shape-changing soft colloids that exhibited a jellyfish inspired buoyant motion behavior, holding great promise for the design of biological inspired active material architectures and transformable soft robotics.
In situ observations of spherical Janus emulsion droplets using a customized side-view microscopic imaging setup with accompanying pendant dropt measurements disclosed the sensitivity regime of the unique chemical-morphological coupling inside complex emulsions and enabled the recording of calibration curves for the extraction of critical parameters of surfactant effectiveness. The deduced new "responsive drop" method permitted a convenient and cost-efficient quantification and comparison of the critical micelle concentrations (CMCs) and effectiveness of various cationic, anionic, and nonionic surfactants. Moreover, the method allowed insightful characterization of stimuli-responsive surfactants and monitoring of the impact of inorganic salts on the CMC and surfactant effectiveness of ionic and nonionic surfactants. Droplet functionalization with synthetic crown ether surfactants yielded a synthetically minimal material platform capable of autonomous and reversible adaptation to its chemical environment through different supramolecular host-guest recognition events. Addition of metal or ammonium salts resulted in the uptake of the resulting hydrophobic complexes to the hydrocarbon hemisphere, whereas addition of hydrophilic ammonium compounds such as amino acids or polypeptides resulted in supramolecular assemblies at the hydrocarbon-water interface of the droplets. The multiresponsive material platform enabled interfacial complexation and
thus triggered responses of the droplets to a variety of chemical triggers including metal ions, ammonium compounds, amino acids, antibodies, carbohydrates as well as amino-functionalized solid surfaces.
In the final chapter, the first documented optical logic gates and combinatorial logic circuits based on complex emulsions are presented. More specifically, the unique reconfigurable and multiresponsive properties of complex emulsions were exploited to realize droplet-based logic gates of varying complexity using different stimuli-responsive surfactants in combination with diverse readout methods. In summary, different designs for multiresponsive, active, and adaptive liquid colloidal systems were presented and investigated, enabling the design of novel transformative chemo-intelligent soft material platforms.
N2  - Komplexe Emulsionen sind Dispersionen kinetisch stabilisierter mehrphasiger Emulsionströpfchen, die aus zwei oder mehreren nicht mischbaren Flüssigkeiten bestehen und eine neuartige Materialplattform für die Herstellung aktiver und dynamischer weicher Materialien darstellen. In den letzten Jahren haben komplexe Emulsionen aufgrund ihres intrinsisch rekonfigurierbaren morphologischen Verhaltens, dass auf ein einzigartiges Kräftegleichgewicht zwischen den an den verschiedenen Grenzflächen wirkenden Grenzflächenspannungen zurückzuführen ist, zunehmendes wissenschaftliches Interesse erfahren. So wurden insbesondere zweiphasige Janus-Tropfen als strukturelle Vorlagen für die Erzeugung anisotroper Präzisionsobjekte, dynamischer optischer Elemente oder als Wandler und Signalverstärker in Chemo- und Bio-Sensorik-Anwendungen untersucht. In der vorliegenden Arbeit wurden schaltbare interne morphologische Veränderungen komplexer Tröpfchen erforscht, die durch Stimulus-induzierte Verschiebungen des Grenzflächenspannungsgleichgewichts ausgelöst werden. Diese können als universelle Bausteine für das Design multiresponsiver, aktiver und adaptiver flüssiger kolloidaler Systeme dienen. Es wurde eine Reihe von grundlegenden Prinzipien und Mechanismen zur Beeinflussung des Grenzflächenspannungsgleichgewichtes erforscht, die die gezielte Entwicklung von formverändernden, sich an Oberflächen bindenden und in Reaktion auf chemische Stimuli verändernden Emulsionskörpern ermöglicht. Die Kombination des einzigartigen responsiven Verhaltens von Janus-Tropfen mit maßgeschneiderten Tensiden erlaubt die Erschließung von biologisch inspirierten aktiven Materialarchitekturen. So führte beispielsweise die Funktionalisierung von Janus-Tropfen mit einem photo-responsiven Tensid (AzoTAB) zu formverändernden weichen Kolloiden, die ein von Quallen inspiriertes Schwimmverhalten zeigten und damit vielversprechend für die Anwendung im Forschungsfeld der transformierbaren „soft-robotics“ sind.
Die In-situ-Beobachtung von sphärischen Janus-Emulsionströpfchen mit einem Seitenansichts-Mikroskop und begleitenden Pendant-Drop-Messungen ermöglichten es das Empfindlichkeitsregime der einzigartigen chemisch-morphologischen Kopplung innerhalb komplexer Emulsionen offenzulegen. Die resultierende Kalibrierungskurve erlaubt die Extraktion von kritischen Parametern der Tensidwirksamkeit. Die daraus abgeleitete neue "responsive drop"-Methode ermöglicht eine einfache, kosteneffiziente Quantifizierung der kritischen Mizellenkonzentrationen (CMCs) und einen Vergleich der Wirksamkeit verschiedener kationischer, anionischer und nichtionischer Tenside. Darüber hinaus ermöglichte die Methode eine aufschlussreiche Charakterisierung Stimuli-responsiver Tenside und die Überwachung des Einflusses anorganischer Salze auf die CMC und die Tensidwirksamkeit ionischer und nichtionischer Tenside. Die Funktionalisierung von Tröpfchen mit synthetischen Kronenether-Tensiden führte zu einer synthetisch minimalen Materialplattform, die in der Lage ist, sich durch verschiedene supramolekulare Wirts-Gast-Erkennungsereignisse selbständig und reversibel an ihre chemische Umgebung anzupassen. Die Zugabe von Metall- oder Ammoniumsalzen hatte eine Aufnahme der resultierenden hydrophoben Komplexe in die Kohlenwasserstoff-Hemisphäre zur Folge, während die Zugabe von hydrophilen Ammoniumverbindungen wie Aminosäuren oder Polypeptiden zu supramolekularen Assemblierungen an der Kohlenwasserstoff-Wasser-Grenzfläche der Tröpfchen führte. Die multiresponsive Materialplattform ermöglicht die Grenzflächenkomplexierung und damit die morphologische Reaktion der Tröpfchen auf eine Vielzahl von chemischen Triggern, darunter Metallionen, Ammoniumverbindungen, Aminosäuren, Antikörper, Kohlenhydrate sowie aminofunktionalisierte feste Oberflächen. 
Im letzten Kapitel werden die ersten dokumentierten optischen Logikgatter und kombinatorischen Logikschaltungen auf der Grundlage von komplexen Emulsionen vorgestellt. Zur Realisierung von Tropfen-basierten Logikgattern unterschiedlicher Komplexität wurden die einzigartigen rekonfigurierbaren und multiresponsiven Eigenschaften komplexer Emulsionen ausgenutzt. Dabei wurden Stimuli-responsive Tenside in Kombination mit unterschiedlichen Auslesemethoden verwendet. Zusammenfassend wurden verschiedene Designs für multiresponsive, aktive und adaptive flüssige kolloidale Systeme vorgestellt und untersucht, die die Entwicklung neuartiger chemo-intelligenter weicher Materialplattformen ermöglichen.
KW  - complex emulsion
KW  - emulsion
KW  - multiresponsive
KW  - komplexe Emulsion
KW  - Emulsion
KW  - multiresponsiv
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-575203
ER  - 
TY  - JOUR
A1  - Wessig, Pablo
A1  - Badetko, Dominik
A1  - Czarnecki, Maciej
A1  - Wichterich, Lukas
A1  - Schmidt, Peter
A1  - Brudy, Cosima
A1  - Sperlich, Eric
A1  - Kelling, Alexandra
T1  - Studies toward the total synthesis of arylnaphthalene lignans via a Photo-Dehydro-Diels-Alder (PDDA) reaction
JF  - The journal of organic chemistry
N2  - An efficient method for the preparation of arylnaphthalene lignans (ANLs) was developed, which is based on thePhoto-Dehydro-DIELS-ALDER(PDDA) reaction. While intermolecular PDDA reactions turned out to be inefficient, theintramolecular variant using suberic acid as tether linking two aryl propiolic esters smoothly provided naphthalenophanes. Theirradiations were performed with a previously developed annular continuous-flow reactor and UVB lamps. In this way, the naturalproducts Alashinol D, Taiwanin C, and an unnamed ANL could be prepared.
Y1  - 2022
U6  - https://doi.org/10.1021/acs.joc.2c00195
SN  - 0022-3263
SN  - 1520-6904
VL  - 87
IS  - 9
SP  - 5904
EP  - 5915
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Titov, Evgenii
T1  - On the low-lying electronically excited states of azobenzene dimers
BT  - Transition density matrix analysis
JF  - Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International
N2  - Azobenzene-containing molecules may associate with each other in systems such as self-assembled monolayers or micelles. The interaction between azobenzene units leads to a formation of exciton states in these molecular assemblies. Apart from local excitations of monomers, the electronic transitions to the exciton states may involve charge transfer excitations. Here, we perform quantum chemical calculations and apply transition density matrix analysis to quantify local and charge transfer contributions to the lowest electronic transitions in azobenzene dimers of various arrangements. We find that the transitions to the lowest exciton states of the considered dimers are dominated by local excitations, but charge transfer contributions become sizable for some of the lowest pi pi* electronic transitions in stacked and slip-stacked dimers at short intermolecular distances. In addition, we assess different ways to partition the transition density matrix between fragments. In particular, we find that the inclusion of the atomic orbital overlap has a pronounced effect on quantifying charge transfer contributions if a large basis set is used.
KW  - azobenzene
KW  - dimer
KW  - transition density matrix
KW  - exciton
KW  - charge transfer
KW  - excited states
KW  - TD-DFT
KW  - ADC(2)
Y1  - 2021
U6  - https://doi.org/10.3390/molecules26144245
SN  - 1420-3049
VL  - 26
IS  - 14
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Fischer, Eric W.
A1  - Saalfrank, Peter
T1  - A thermofield-based multilayer multiconfigurational time-dependent Hartree approach to non-adiabatic quantum dynamics at finite temperature
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry
N2  - We introduce a thermofield-based formulation of the multilayer multiconfigurational time-dependent Hartree (MCTDH) method to study finite temperature effects on non-adiabatic quantum dynamics from a non-stochastic, wave function perspective. Our approach is based on the formal equivalence of bosonic many-body theory at zero temperature with a doubled number of degrees of freedom and the thermal quasi-particle representation of bosonic thermofield dynamics (TFD). This equivalence allows for a transfer of bosonic many-body MCTDH as introduced by Wang and Thoss to the finite temperature framework of thermal quasi-particle TFD. As an application, we study temperature effects on the ultrafast internal conversion dynamics in pyrazine. We show that finite temperature effects can be efficiently accounted for in the construction of multilayer expansions of thermofield states in the framework presented herein. Furthermore, we find our results to agree well with existing studies on the pyrazine model based on the pMCTDH method.
Y1  - 2021
U6  - https://doi.org/10.1063/5.0064013
SN  - 0021-9606
SN  - 1089-7690
VL  - 155
IS  - 13
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Linker, Torsten
T1  - Structural motives controlling the binding affinity of 9,10-bis(methylpyridinium)anthracenes towards DNA
JF  - Bioorganic & medicinal chemistry : a Tetrahedron publication for the rapid dissemination of full original research papers and critical reviews on biomolecular chemistry, medicinal chemistry and related disciplines
N2  - In the search of new DNA groove binding agents a series of substituted 9,10-methylpyridiniumanthracenes have been synthesized and their interactions with DNA have been studied by UV/vis absorption, CD and fluorescence spectroscopy. A minor groove binding mode is confirmed by DNA melting studies, strong CD effects, the dependence of the binding affinity on ionic strength, and the differentiation between AT and GC base pairs. No binding occurs to GC sequences. Binding constants to calf thymus DNA (ct-DNA) and poly(dA:dT) in the range between 1 x 10(4) and 3 x 10(5) M-1 have been determined. The binding strength decreases with the size of substituents attached at the anthracene site. Variation of the substitution pattern of the charged groups shows that methyl groups in meta position cause slightly stronger binding than methyl groups in para position. In contrast, with these groups in ortho position, no binding interaction has been observed. The strongest binding is achieved with an expansion of the peripheral heterocycle from pyridine to quinoline. Molecular modeling reveals the pivotal role of the substitution pattern: Anthracenes with para and meta pyridines align along the minor grooves. On the other hand, the ortho derivative adopts no groove-alignment.
KW  - groove binding
KW  - anthracenes
KW  - ct-DNA
KW  - fluorescence enhancement
KW  - docking
Y1  - 2020
U6  - https://doi.org/10.1016/j.bmc.2020.115432
SN  - 0968-0896
SN  - 1464-3391
VL  - 28
IS  - 8
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Krause, Andreas
A1  - Sperlich, Eric
A1  - Schmidt, Bernd
T1  - Matsuda-Heck arylation of itaconates
BT  - a versatile approach to heterocycles from a renewable resource
JF  - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry
N2  - Itaconic acid esters and hemiesters undergo Pd-catalyzed coupling reactions with arene diazonium salts in high to excellent yields. The coupling products of ortho-nitro arene diazonium salts can be converted in one or two steps to benzazepine-2-ones.
Y1  - 2021
U6  - https://doi.org/10.1039/d1ob00392e
SN  - 1477-0520
SN  - 1477-0539
VL  - 19
IS  - 19
SP  - 4292
EP  - 4302
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Hermanns, Jolanda
T1  - The task navigator following the STRAKNAP concept
BT  - Development, application, and evaluation of a new scaffold to support nonmajor chemistry students while solving tasks in organic chemistry
JF  - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society
N2  - Educational Scaffolding was first mentioned in 1976 by Wood et al. Several examples for scaffolding in chemistry are also known from the literature. As written scaffolds, stepped supporting tools to support students while solving problems in organic chemistry were developed, applied, and evaluated. Although the students rated the tool as very helpful, a think-aloud study showed that the support given by this scaffold was not sufficient. As a further development of stepped supporting tools, task navigators were therefore developed, applied, and evaluated. This new scaffold gives tips on strategy, knowledge, and application of knowledge after the STRAKNAP concept. The evaluation of this tool shows that the students rated the tool as being very helpful. A think-aloud study showed that the scaffold supports the students while they solve a problem. Because of the stepwise construction of the task navigators and the providing of the knowledge needed for the application, the students can solve parts of the task successfully even if they do not solve all parts correctly; the students can always start from scratch. When students use the tool regularly, their knowledge of organic chemistry increases compared to students who did not use the tool at all. The task navigator is not only a scaffold for the content of the task but also for the development of methodological competences on the field of strategies and applying knowledge.
KW  - First-Year Undergraduate/General
KW  - Organic Chemistry
KW  - Distance
KW  - Learning/Chemistry Education Research
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jchemed.0c01162
SN  - 0021-9584
SN  - 1938-1328
VL  - 98
IS  - 4
SP  - 1077
EP  - 1087
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Matic, Aleksandar
A1  - Hess, Andreas
A1  - Schanzenbach, Dirk
A1  - Schlaad, Helmut
T1  - Epoxidized 1,4-polymyrcene
JF  - Polymer chemistry
N2  - 1,4-Polymyrcene was synthesized by anionic polymerization and epoxidized using meta-chloroperbenzoic acid. Samples with different degrees of epoxidation (25%, 49%, 74%, and 98%) were prepared and examined according to their chemical and thermal properties. Epoxidation was found to increase the glass transition temperature (T-g = 14 degrees C for the 98% epoxidized 1,4-polymyrcene) as well as the shelf live (>10 months). The trisubstituted epoxide groups were remarkably stable against nucleophiles under basic conditions but cross-linked or hydrolyzed in the presence of an acid. Also, highly epoxidized 1,4-polymyrcene readily cross-linked upon annealing at 260 degrees C to produce an epoxy resin.
KW  - comb poly(beta-myrcene)-graft-poly(l-lactide) copolymers
KW  - thermoplastic elastomer synthesis
KW  - myrcen
KW  - polymerization
KW  - epoxidation
Y1  - 2020
U6  - https://doi.org/10.1039/c9py01783f
SN  - 1759-9954
SN  - 1759-9962
VL  - 11
IS  - 7
SP  - 1364
EP  - 1368
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Balischewski, Christian
A1  - Behrens, Karsten
A1  - Zehbe, Kerstin
A1  - Günter, Christina
A1  - Mies, Stefan
A1  - Sperlich, Eric
A1  - Kelling, Alexandra
A1  - Taubert, Andreas
T1  - Ionic liquids with more than one metal
BT  - optical and rlectrochemical properties versus d-block metal vombinations
JF  - Chemistry - a European journal
N2  - Thirteen N-butylpyridinium salts, including three monometallic [C4Py](2)[MCl4], nine bimetallic [C4Py](2)[(M1-xMxCl4)-M-a-Cl-b] and one trimetallic compound [C4Py](2)[(M1-y-zMyMz (c) Cl4)-M-a-M-b] (M=Co, Cu, Mn; x=0.25, 0.50 or 0.75 and y=z=0.33), were synthesized and their structure and thermal and electrochemical properties were studied. All compounds are ionic liquids (ILs) with melting points between 69 and 93 degrees C. X-ray diffraction proves that all ILs are isostructural. The conductivity at room temperature is between 10(-4) and 10(-8) S cm(-1). Some Cu-based ILs reach conductivities of 10(-2) S cm(-1), which is, however, probably due to IL dec. This correlates with the optical bandgap measurements indicating the formation of large bandgap semiconductors. At elevated temperatures approaching the melting points, the conductivities reach up to 1.47x10(-1) S cm(-1) at 70 degrees C. The electrochemical stability windows of the ILs are between 2.5 and 3.0 V.
KW  - bandgap
KW  - electrochemistry
KW  - ionic liquids
KW  - metal-containing ionic
KW  - liquids
KW  - tetrahalido metallates
Y1  - 2020
U6  - https://doi.org/10.1002/chem.202003097
SN  - 0947-6539
SN  - 1521-3765
VL  - 26
IS  - 72
SP  - 17504
EP  - 17513
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Bouakline, Foudhil
T1  - Umbrella inversion of ammonia redux
JF  - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies
N2  - Umbrella inversion of ammonia is a prototypical example of large-amplitude vibrational motion, described with a symmetric double-well potential. The transition state of the latter corresponds to a planar (D-3h) molecular geometry, whereas the two equilibrium configurations are equivalent (C-3v) pyramidal structures, with the nitrogen atom being either 'above' or 'below' the plane of the hydrogen atoms. As commonly understood, inversion motion of ammonia corresponds to the coherent, anharmonic, vibrational motion of the molecule, which shuttles back and forth between the two potential wells; that is, oscillation of the nitrogen atom from one side of the H-3 plane to the other, via coherent tunneling. However, this intuitively appealing view of umbrella inversion results from a reduced description of the dynamics, which includes only the inversion vibrational coordinate and fully neglects all the other molecular degrees of freedom. As such, this textbook picture of inversion motion ignores the fact that the two equilibrium structures of ammonia are superimposable, and can only be distinguished by labelling the identical hydrogen nuclei. A correct description of umbrella inversion, which incorporates nuclear permutations, requires the inclusion of other molecular modes. Indeed, it is well known that the quantum symmetrization postulate engenders entanglement between ammonia's nuclear-spin, inversion, and rotation. Using the explicit expressions of the corresponding zeroth-order eigenstates, we clearly show that the inversion density of any multilevel wavepacket of ammonia, including the case of perfectly aligned molecules, is symmetrically distributed between the two potential wells, at all times. This follows from a rigorous demonstration based on the evaluation of the expectation values of the inversion coordinate or equivalent projection operators. However, provided that these wavepackets involve inversion-rotation levels with opposite parity, the inversion density may exhibit dynamical spatial localization. In the latter case, the space-fixed inversion density or, equivalently, the expectation values of the projections of the inversion coordinate on the space-fixed axes, may oscillate between opposite directions in the space-fixed frame. Nevertheless, in all cases, localization of ammonia in a single potential well is impossible, even partially or transiently. This is equivalent to saying that the nitrogen atom has the same probability (one-half) to be on either side of the H-3 plane, for any wavepacket of the molecule and at all times-a conclusion which is in perfect accord with the principle of the indistinguishability of identical particles (nuclei).
Y1  - 2021
U6  - https://doi.org/10.1039/d1cp01991k
SN  - 1463-9076
SN  - 1463-9084
VL  - 23
IS  - 36
SP  - 20509
EP  - 20523
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Al-Naji, Majd
A1  - Schlaad, Helmut
A1  - Antonietti, Markus
T1  - New (and old) monomers from biorefineries to make polymer chemistry more sustainable
JF  - Macromolecular rapid communications
N2  - This opinion article describes recent approaches to use the "biorefinery" concept to lower the carbon footprint of typical mass polymers, by replacing parts of the fossil monomers with similar or even the same monomer made from regrowing dendritic biomass. Herein, the new and green catalytic synthetic routes are for lactic acid (LA), isosorbide (IS), 2,5-furandicarboxylic acid (FDCA), and p-xylene (pXL). Furthermore, the synthesis of two unconventional lignocellulosic biomass derivable monomers, i.e., alpha-methylene-gamma-valerolactone (MeGVL) and levoglucosenol (LG), are presented. All those have the potential to enter in a cost-effective way, also the mass market and thereby recover lost areas for polymer materials. The differences of catalytic unit operations of the biorefinery are also discussed and the challenges that must be addressed along the synthesis path of each monomers.
KW  - biodegradable polymers
KW  - biorefineries
KW  - carbohydrate‐ based
KW  - monomers
KW  - green polymers
KW  - lignocellulosic biomass
Y1  - 2020
U6  - https://doi.org/10.1002/marc.202000485
SN  - 1022-1336
SN  - 1521-3927
VL  - 42
IS  - 3
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Youk, Sol
A1  - Hofmann, Jan P.
A1  - Badamdorj, Bolortuya
A1  - Volkel, Antje
A1  - Antonietti, Markus
A1  - Oschatz, Martin
T1  - Controlling pore size and pore functionality in sp(2)-conjugated microporous materials by precursor chemistry and salt templating
JF  - Journal of materials chemistry : A, Materials for energy and sustainability
N2  - The synthesis of sp(2)-conjugated, heteroatom-rich, "carbonaceous" materials from economically feasible raw materials and salt templates is reported. Low cost citrazinic acid (2,6-dihydroxy-4-pyridinecarboxylic acid) and melamine are used as components to form a microporous, amorphous framework, where edges of the covalent frameworks are tightly terminated with nitrogen and oxygen moieties. ZnCl2 as the porogen stabilizes structural microporosity as well as nitrogen and oxygen heteroatoms up to comparably high condensation temperatures of 750 and 950 degrees C. The specific surface area up to 1265 m(2) g(-1) is mainly caused by micropores and typical of heteroatom-rich carbon materials with such structural porosity. The unusually high heteroatom content reveals that the edges and pores of the covalent structures are tightly lined with heteroatoms, while C-C or C-H bonds are expected to have a minor contribution as compared to typical carbon materials without or with minor content of heteroatoms. Adsorption of water vapor and carbon dioxide are exemplarily chosen to illustrate the impact of this heteroatom functionalization under salt-templating conditions on the adsorption properties of the materials. 27.10 mmol g(-1) of H2O uptake (at p/p(0) = 0.9) can be achieved, which also proves the very hydrophilic character of the pore walls, while the maximum CO2 uptake (at 273 K) is 5.3 mmol g(-1). At the same time the CO2/N-2 adsorption selectivity at 273 K can reach values of up to 60. All these values are beyond those of ordinary high surface area carbons, also differ from those of N-doped carbons, and are much closer to those of organized framework species, such as C2N.
Y1  - 2020
U6  - https://doi.org/10.1039/d0ta05856d
SN  - 2050-7488
SN  - 2050-7496
VL  - 8
IS  - 41
SP  - 21680
EP  - 21689
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Hermanns, Jolanda
A1  - Schmidt, Bernd
A1  - Glowinski, Ingrid
A1  - Keller, David
T1  - Online teaching in the course "organic chemistry" for nonmajor chemistry students
BT  - from necessity to opportunity
JF  - Journal of chemical education
N2  - In this communication the development of an online course on the topic organic chemistry for nonmajor chemistry students is described and discussed. For this online course, the existing classroom course was further developed. New elements such as podcasts, task navigators, and a forum for discussing the solving of tasks or problems with the content were added. This new online course was evaluated. Therefore, a questionnaire was developed. This consists of questions with regard to the longtime learning behavior of the students and to the online learning. The results of this evaluation show that a preference for online learning and a preference for classroom teaching can be measured separately in two scales. Students values on the scale representing a preference for online learning correlate positively and significantly with confidence in the choice of the study subject, enthusiasm about the subject, and the ability to organize their learning, learning environment, and time management. They correlate also with the satisfaction concerning the materials provided. Students values for one of those teaching methods also correlate with their rating with regard to their exam preparation. Values representing a preference for online teaching correlate positively with students better feeling of exam preparation. Values representing a preference for classroom teaching show negative correlations with the values representing students similar or even better preparation for the exams as a result of online teaching. It is therefore not surprising that the ratings for the two scales correlate with the wish for a combination of online teaching and classroom teaching in the future. As a solution, a new course concept for the time after the corona virus crisis that suits all students is outlined in the outlook.
KW  - first-year undergraduate/general
KW  - organic chenlistry
KW  - computer-based
KW  - learning
KW  - distance learning/self instruction
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jchemed.0c00658
SN  - 0021-9584
SN  - 1938-1328
VL  - 97
IS  - 9
SP  - 3140
EP  - 3146
PB  - American Chemical Society
CY  - Washington
ER  -