TY - JOUR A1 - Adesina, Morenike O. A1 - Block, Inga A1 - Günter, Christina A1 - Unuabonah, Emmanuel Iyayi A1 - Taubert, Andreas T1 - Efficient Removal of Tetracycline and Bisphenol A from Water with a New Hybrid Clay/TiO2 Composite JF - ACS Omega N2 - New TiO2 hybrid composites were prepared fromkaolinclay, predried and carbonized biomass, and titanium tetraisopropoxideand explored for tetracycline (TET) and bisphenol A (BPA) removalfrom water. Overall, the removal rate is 84% for TET and 51% for BPA.The maximum adsorption capacities (q (m))are 30 and 23 mg/g for TET and BPA, respectively. These capacitiesare far greater than those obtained for unmodified TiO2. Increasing the ionic strength of the solution does not change theadsorption capacity of the adsorbent. pH changes only slightly changeBPA adsorption, while a pH > 7 significantly reduces the adsorptionof TET on the material. The Brouers-Sotolongo fractal modelbest describes the kinetic data for both TET and BPA adsorption, predictingthat the adsorption process occurs via a complex mechanism involvingvarious forces of attraction. Temkin and Freundlich isotherms, whichbest fit the equilibrium adsorption data for TET and BPA, respectively,suggest that adsorption sites are heterogeneous in nature. Overall,the composite materials are much more effective for TET removal fromaqueous solution than for BPA. This phenomenon is assigned to a differencein the TET/adsorbent interactions vs the BPA/adsorbent interactions:the decisive factor appears to be favorable electrostatic interactionsfor TET yielding a more effective TET removal. Y1 - 2023 U6 - https://doi.org/10.1021/acsomega.3c00184 SN - 2470-1343 VL - 8 IS - 24 SP - 21594 EP - 21604 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Mazarei, Elham A1 - Penschke, Christopher A1 - Saalfrank, Peter T1 - Band gap engineering in two-dimensional materials by functionalization BT - Methylation of graphene and graphene bilayers JF - ACS Omega N2 - Graphene is well-knownfor its unique combination of electricaland mechanical properties. However, its vanishing band gap limitsthe use of graphene in microelectronics. Covalent functionalizationof graphene has been a common approach to address this critical issueand introduce a band gap. In this Article, we systematically analyzethe functionalization of single-layer graphene (SLG) and bilayer graphene(BLG) with methyl (CH3) using periodic density functionaltheory (DFT) at the PBE+D3 level of theory. We also include a comparisonof methylated single-layer and bilayer graphene, as well as a discussionof different methylation options (radicalic, cationic, and anionic).For SLG, methyl coverages ranging from 1/8 to 1/1, (i.e.,the fully methylated analogue of graphane) are considered. We findthat up to a coverage theta of 1/2, graphene readily accepts CH3, with neighbor CH3 groups preferring trans positions. Above theta = 1/2, the tendency to accept further CH3 weakens and the lattice constant increases. The band gapbehaves less regularly, but overall it increases with increasing methylcoverage. Thus, methylated graphene shows potential for developingband gap-tuned microelectronics devices and may offer further functionalizationoptions. To guide in the interpretation of methylation experiments,vibrational signatures of various species are characterized by normal-modeanalysis (NMA), their vibrational density of states (VDOS), and infrared(IR) spectra, the latter two are obtained from ab initio moleculardynamics (AIMD) in combination with a velocity-velocity autocorrelationfunction (VVAF) approach. KW - Adsorption KW - Alkyls KW - Band structure KW - Electrical conductivity KW - Two dimensional materials Y1 - 2023 U6 - https://doi.org/10.1021/acsomega.3c02068 SN - 2470-1343 VL - 8 IS - 24 SP - 22026 EP - 22041 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - The multiple bond character of the carbon-boron bond in boron trapped N-heterocyclic carbenes (NHCs) and cyclic(alkyl)(amino) carbenes (CAACs) on the magnetic criterion JF - Tetrahedron N2 - Geometry, 11B, 13C chemical shifts and the spatial magnetic properties (Through-Space NMR Shieldings -TSNMRS) of both cations and anions of boron-trapped N-heterocyclic carbenes (NHCs) and cyclic (alkyl)(amino)carbenes (CAACs) and of the corresponding diborane/diborene/diboryne dis-carbene adducts have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept; the TSNMRS results are visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The ICSS of the TSNMRS (actually the anisotropy effects measurable in 1H NMR spectroscopy) are employed to qualify and quantify the present multiple bond character of the Carbene-Boron bond in the trapped NHCs and CAACs. Results are confirmed by bond length and 11B/13C chemical shift variations. Thus the partial multiple bond character of the Carbene-Boron bond cannot be expressed by the arrow of weak, much longer dative bonds and should be omitted as in other covalent lone pair-it or triel bonds. & COPY; 2023 Elsevier Ltd. All rights reserved. KW - NHCs KW - CAACs KW - Multiple NHC(CAAC)-Boron bonds KW - Through -space NMR KW - shieldings (TSNMRS) KW - NICS KW - Anisotropy effect KW - Ring current effect Y1 - 2023 U6 - https://doi.org/10.1016/j.tet.2023.133469 SN - 0040-4020 SN - 1464-5416 VL - 140 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Schlappa, Stephanie A1 - Bressel, Lena A1 - Reich, Oliver A1 - Münzberg, Marvin T1 - Advanced particle size analysis in high-solid-content polymer dispersions using photon density wave spectroscopy JF - Polymers N2 - High-solid-content polystyrene and polyvinyl acetate dispersions of polymer particles with a 50 nm to 500 nm mean particle diameter and 12-55% (w/w) solid content have been produced via emulsion polymerization and characterized regarding their optical and physical properties. Both systems have been analyzed with common particle-size-measuring techniques like dynamic light scattering (DLS) and static light scattering (SLS) and compared to inline particle size distribution (PSD) measurements via photon density wave (PDW) spectroscopy in undiluted samples. It is shown that particle size measurements of undiluted polystyrene dispersions are in good agreement between analysis methods. However, for polyvinyl acetate particles, size determination is challenging due to bound water in the produced polymer. For the first time, water-swelling factors were determined via an iterative approach of PDW spectroscopy error (X-2) minimization. It is shown that water-swollen particles can be analyzed in high-solid-content solutions and their physical properties can be assumed to determine the refractive index, density, and volume fraction in dispersion. It was found that assumed water swelling improved the reduced scattering coefficient fit by PDW spectroscopy by up to ten times and particle size determination was refined and enabled. Particle size analysis of the water-swollen particles agreed well with offline-based state-of-the-art techniques. KW - emulsion polymerization KW - multiple light scattering KW - photon density wave KW - spectroscopy KW - particle sizing KW - swelling of polymers Y1 - 2023 U6 - https://doi.org/10.3390/polym15153181 SN - 2073-4360 VL - 15 IS - 15 PB - MDPI CY - Basel ER - TY - JOUR A1 - Reitenbach, Julija A1 - Geiger, Christina A1 - Wang, Peixi A1 - Vagias, Apostolos N. A1 - Cubitt, Robert A1 - Schanzenbach, Dirk A1 - Laschewsky, André A1 - Papadakis, Christine M. A1 - Müller-Buschbaum, Peter T1 - Effect of magnesium salts with chaotropic anions on the swelling behavior of PNIPMAM thin films JF - Macromolecules : a publication of the American Chemical Society N2 - Poly(N-isopropylmethacrylamide) (PNIPMAM) is a stimuli responsive polymer, which in thin film geometry exhibits a volume-phase transition upon temperature increase in water vapor. The swelling behavior of PNIPMAM thin films containing magnesium salts in water vapor is investigated in view of their potential application as nanodevices. Both the extent and the kinetics of the swelling ratio as well as the water content are probed with in situ time-of-flight neutron reflectometry. Additionally, in situ Fourier-transform infrared (FTIR) spectroscopy provides information about the local solvation of the specific functional groups, while two-dimensional FTIR correlation analysis further elucidates the temporal sequence of solvation events. The addition of Mg(ClO4)2 or Mg(NO3)2 enhances the sensitivity of the polymer and therefore the responsiveness of switches and sensors based on PNIPMAM thin films. It is found that Mg(NO3)2 leads to a higher relative water uptake and therefore achieves the highest thickness gain in the swollen state. Y1 - 2023 U6 - https://doi.org/10.1021/acs.macromol.2c02282 SN - 0024-9297 SN - 1520-5835 VL - 56 IS - 2 SP - 567 EP - 577 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Nchiozem-Ngnitedem, Vaderament-Alexe A1 - Sperlich, Eric A1 - Matieta, Valaire Yemene A1 - Kuete, Jenifer Reine Ngnouzouba A1 - Kuete, Victor A1 - Omer, Ejlal A. A. A1 - Efferth, Thomas A1 - Schmidt, Bernd T1 - Synthesis and bioactivity of isoflavones from ficus carica and some non-natural analogues JF - Journal of natural products : Lloydia N2 - FicucariconeD (1) and its 4 '-demethyl congener 2 are isoflavones isolated from fruits of Ficus carica that share a 5,7-dimethoxy-6-prenyl-substituted A-ring. Both naturalproducts were, for the first time, obtained by chemical synthesisin six steps, starting from 2,4,6-trihydroxyacetophenone. Key stepsare a microwave-promoted tandem sequence of Claisen- and Cope-rearrangementsto install the 6-prenyl substituent and a Suzuki-Miyaura crosscoupling for installing the B-ring. By using various boronic acids,non-natural analogues become conveniently available. All compoundswere tested for cytotoxicity against drug-sensitive and drug-resistanthuman leukemia cell lines, but were found to be inactive. The compoundswere also tested for antimicrobial activities against a panel of eightGram-negative and two Gram-positive bacterial strains. Addition ofthe efflux pump inhibitor phenylalanine-arginine-beta-naphthylamide(PA beta N) significantly improved the antibiotic activity in mostcases, with MIC values as low as 2.5 mu M and activity improvementfactors as high as 128-fold. KW - Antimicrobial activity KW - Bacteria KW - Ethers KW - Flavonoids KW - Mixtures Y1 - 2023 U6 - https://doi.org/10.1021/acs.jnatprod.3c00219 SN - 0163-3864 SN - 1520-6025 VL - 86 IS - 6 SP - 1520 EP - 1528 PB - American Chemical Society CY - Washington, DC ER - TY - THES A1 - Margraf, Johannes T. T1 - Science-driven chemical machine learning Y1 - 2023 ER - TY - JOUR A1 - Sperlich, Eric A1 - Köckerling, Martin T1 - The double cluster compound [Nb6Cl14(MeCN)(4)] [Nb6Cl14(pyz)(4)].6MeCN (Me: methyl, pyz: pyrazine) with a layered structure resulting from weak intermolecular interactions JF - Zeitschrift für Naturforschung N2 - The synthesis and the crystal structure of the double cluster compound [Nb6Cl14(MeCN)(4)][Nb6Cl14(pyz)(4)]middot6CH(3)CN are described. The synthesis is based on a partial ligand exchange reaction, which proceeds upon dissolving [Nb6Cl14(pyz)(4)]middot2CH(2)Cl(2) in acetonitrile. The compound is built up of two discrete neutral cluster units, which consist of octahedra of Nb-6 atoms coordinated by 12 edge-bridging chlorido and two terminal chlorido ligands, and four acetonitrile ligands on one and four pyrazine ligands on the other cluster unit. Co-crystallized acetonitrile molecules are also present. The single-crystal structure determination has revealed a cluster arrangement in which the [Nb6Cl14(pyz)(4)] units are connected by (halogen) lone-pair-(pyrazine) pi interactions. These lead to chains of [Nb6Cl14(pyz)(4)] clusters. These chains are further connected to cluster layers by (nitrile-halogen) dipole-dipole interactions, in which the [Nb6Cl14(MeCN)(4)] and co-crystallized MeCN molecules are also involved. These cluster layers are arranged parallel to the crystallographic {011} plane. KW - cluster KW - crystal structure KW - dipole-dipole interaction KW - halide KW - lone-pair-pi interactions KW - niobium Y1 - 2023 U6 - https://doi.org/10.1515/znb-2023-0001 SN - 0932-0776 SN - 1865-7117 VL - 78 IS - 5 SP - 279 EP - 283 PB - De Gruyter CY - Berlin ER - TY - THES A1 - Savatieiev, Oleksandr T1 - Carbon nitride semiconductors: properties and application as photocatalysts in organic synthesis N2 - Graphitic carbon nitrides (g-CNs) are represented by melon-type g-CN, poly(heptazine imides) (PHIs), triazine-based g-CN and poly(triazine imide) with intercalated LiCl (PTI/Li+Cl‒). These materials are composed of sp2-hybridized carbon and nitrogen atoms; C:N ratio is close to 3:4; the building unit is 1,3,5-triazine or tri-s-triazine; the building units are interconnected covalently via sp2-hybridized nitrogen atoms or NH-moieties; the layers are assembled into a stack via weak van der Waals forces as in graphite. Due to medium band gap (~2.7 eV) g-CNs, such as melon-type g-CN and PHIs, are excited by photons with wavelength ≤ 460 nm. Since 2009 g-CNs have been actively studied as photocatalysts in evolution of hydrogen and oxygen – two half-reactions of full water splitting, by employing corresponding sacrificial agents. At the same time application of g-CNs as photocatalysts in organic synthesis has been remaining limited to few reactions only. Cumulative Habilitation summarizes research work conducted by the group ‘Innovative Heterogeneous Photocatalysis’ between 2017-2023 in the field of carbon nitride organic photocatalysis, which is led by Dr. Oleksandr Savatieiev. g-CN photocatalysts activate molecules, i.e. generate their more reactive open-shell intermediates, via three modes: i) Photoinduced electron transfer (PET); ii) Excited state proton-coupled electron transfer (ES-PCET) or direct hydrogen atom transfer (dHAT); iii) Energy transfer (EnT). The scope of reactions that proceed via oxidative PET, i.e. one-electron oxidation of a substrate to the corresponding radical cation, are represented by synthesis of sulfonylchlorides from S-acetylthiophenols. The scope of reactions that proceed via reductive PET, i.e. one-electron reduction of a substrate to the corresponding radical anion, are represented by synthesis of γ,γ-dichloroketones from the enones and chloroform. Due to abundance of sp2-hybridized nitrogen atoms in the structure of g-CN materials, they are able to cleave X-H bonds in organic molecules and store temporary hydrogen atom. ES-PCET or dHAT mode of organic molecules activation to the corresponding radicals is implemented for substrates featuring relatively acidic X-H bonds and those that are characterized by low bond dissociation energy, such as C-H bond next to the heteroelements. On the other hand, reductively quenched g-CN carrying hydrogen atom reduces a carbonyl compound to the ketyl radical via PCET that is thermodynamically more favorable pathway compared to the electron transfer. The scope of these reactions is represented by cyclodimerization of α,β-unsaturated ketones to cyclopentanoles. g-CN excited state demonstrates complex dynamics with the initial formation of singlet excited state, which upon intersystem crossing produces triplet excited state that is characterized by the lifetime > 2 μs. Due to long lifetime, g-CN activate organic molecules via EnT. For example, g-CN sensitizes singlet oxygen, which is the key intermediate in the dehydrogenation of aldoximes to nitrileoxides. The transient nitrileoxide undergoes [3+2]-cycloaddition to nitriles and gives oxadiazoles-1,2,4. PET, ES-PCET and EnT are fundamental phenomena that are applied beyond organic photocatalysis. Hybrid composite is formed by combining conductive polymers, such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) with potassium poly(heptazine imide) (K-PHI). Upon PET, K-PHI modulated population of polarons and therefore conductivity of PEDOT:PSS. The initial state of PEDOT:PSS is recovered upon material exposure to O2. K-PHI:PEDOT:PSS may be applied in O2 sensing. In the presence of electron donors, such as tertiary amines and alcohols, and irradiation with light, K-PHI undergoes photocharging – the g-CN material accumulates electrons and charge-compensating cations. Such photocharged state is stable under anaerobic conditions for weeks, but at the same time it is a strong reductant. This feature allows decoupling in time light harvesting and energy storage in the form of electron-proton couples from utilization in organic synthesis. The photocharged state of K-PHI reduces nitrobenzene to aniline, and enables dimerization of α,β-unsaturated ketones to hexadienones in dark. N2 - Graphitische Kohlenstoffnitride (g-CNs) werden durch g-CN vom Melonen-Typ, Poly(heptazinimide) (PHIs), g-CN auf Triazinbasis und Poly(triazinimid) mit interkaliertem LiCl (PTI/Li+Cl-) repräsentiert. Diese Materialien bestehen aus sp2-hybridisierten Kohlenstoff- und Stickstoffatomen; das C:N-Verhältnis liegt nahe bei 3:4; das Grundgerüst ist 1,3,5-Triazin oder Tri-s-Triazin; die Grundgerüste sind kovalent über sp2-hybridisierte Stickstoffatome oder NH-Moleküle miteinander verbunden; die Schichten werden über schwache van-der-Waals-Kräfte wie in Graphit zu einem Stapel zusammengefügt. Aufgrund der mittleren Bandlücke (~2,7 eV) werden g-CNs, wie z. B. g-CN vom Melonen-Typ und PHIs, durch Photonen mit einer Wellenlänge ≤ 460 nm angeregt. Seit 2009 werden g-CNs aktiv als Photokatalysatoren für die Entwicklung von Wasserstoff und Sauerstoff - zwei Halbreaktionen der vollständigen Wasserspaltung - untersucht, indem entsprechende Opferstoffe eingesetzt werden. Gleichzeitig ist die Anwendung von g-CNs als Photokatalysatoren in der organischen Synthese auf wenige Reaktionen beschränkt geblieben. Die kumulative Habilitation fasst die Forschungsarbeiten zusammen, die von der Gruppe "Innovative heterogene Photokatalyse" zwischen 2017 und 2023 auf dem Gebiet der organischen Photokatalyse mit Kohlenstoffnitrid durchgeführt wurden, die von Dr. Oleksandr Savatieiev geleitet wird. g-CN-Photokatalysatoren aktivieren Moleküle, d. h. sie erzeugen ihre reaktiveren Zwischenprodukte mit offener Schale über drei Modi: i) photoinduzierter Elektronentransfer (PET); ii) protonengekoppelter Elektronentransfer im angeregten Zustand (ES-PCET) oder direkter Wasserstoffatomtransfer (dHAT); iii) Energietransfer (EnT). Der Bereich der Reaktionen, die über oxidativen PET ablaufen, d. h. die Ein-Elektronen-Oxidation eines Substrats zum entsprechenden Radikalkation, wird durch die Synthese von Sulfonylchloriden aus S-Acetylthiophenolen dargestellt. Der Bereich der Reaktionen, die über reduktive PET ablaufen, d. h. Reduktion eines Substrats mit einem Elektron zum entsprechenden radikalischen Anion, wird durch die Synthese von γ,γ-Dichloroketonen aus Enonen und Chloroform repräsentiert. Aufgrund der zahlreichen sp2-hybridisierten Stickstoffatome in der Struktur der g-CN-Materialien können sie X-H-Bindungen in organischen Molekülen spalten und temporäre Wasserstoffatome speichern. Der ES-PCET- oder dHAT-Modus der Aktivierung organischer Moleküle zu den entsprechenden Radikalen wird bei Substraten mit relativ sauren X-H-Bindungen und solchen, die sich durch eine niedrige Bindungsdissoziationsenergie auszeichnen, wie z. B. die C-H-Bindung neben den Heteroelementen, durchgeführt. Andererseits reduziert reduktiv gequenchtes g-CN, das ein Wasserstoffatom trägt, eine Carbonylverbindung über PCET zum Ketylradikal, was im Vergleich zum Elektronentransfer der thermodynamisch günstigere Weg ist. Der Umfang dieser Reaktionen wird durch die Cyclodimerisierung von α,β-ungesättigten Ketonen zu Cyclopentanolen dargestellt. Der angeregte Zustand von g-CN zeigt eine komplexe Dynamik mit der anfänglichen Bildung eines angeregten Singulett-Zustands, der beim Übergang zwischen den Systemen einen angeregten Triplett-Zustand erzeugt, der durch eine Lebensdauer von > 2 μs gekennzeichnet ist. Aufgrund der langen Lebensdauer aktivieren g-CN organische Moleküle über EnT. So sensibilisiert g-CN beispielsweise Singulett-Sauerstoff, der das wichtigste Zwischenprodukt bei der Dehydrierung von Aldoximen zu Nitriloxiden ist. Das transiente Nitriloxid unterliegt einer [3+2]-Cycloaddition zu Nitrilen und ergibt Oxadiazole-1,2,4. PET, ES-PCET und EnT sind grundlegende Phänomene, die über die organische Photokatalyse hinaus Anwendung finden. Hybridkomposit wird durch die Kombination von leitfähigen Polymeren wie Poly(3,4-ethylendioxythiophen)polystyrolsulfonat (PEDOT:PSS) mit Kaliumpoly(heptazinimid) (K-PHI) gebildet. Nach PET modulierte K-PHI die Population der Polaronen und damit die Leitfähigkeit von PEDOT:PSS. Der Ausgangszustand von PEDOT:PSS wird wiederhergestellt, wenn das Material O2 ausgesetzt wird. K-PHI:PEDOT:PSS kann für die O2-Sensorik verwendet werden. In Gegenwart von Elektronendonatoren, wie tertiären Aminen und Alkoholen, und bei Lichteinstrahlung wird K-PHI photogeladen - das g-CN-Material sammelt Elektronen und ladungsausgleichende Kationen an. Dieser photogeladene Zustand ist unter anaeroben Bedingungen wochenlang stabil, gleichzeitig ist er aber ein starkes Reduktionsmittel. Diese Eigenschaft ermöglicht die zeitliche Entkopplung von Lichtsammlung und Energiespeicherung in Form von Elektron-Protonen-Paaren von der Nutzung in der organischen Synthese. Der photogeladene Zustand von K-PHI reduziert Nitrobenzol zu Anilin und ermöglicht die Dimerisierung von α,β-ungesättigten Ketonen zu Hexadienonen im Dunkeln. KW - carbon nitride KW - photocatalysis KW - photochemistry KW - photocharging KW - organic synthesis Y1 - 2023 ER - TY - JOUR A1 - Akampurira, Denis A1 - Akala, Hoseah M. A1 - Derese, Solomon A1 - Heydenreich, Matthias A1 - Yenesew, Abiy T1 - A new C-C linked benzophenathridine-2-quinoline dimer, and the antiplasmodial activity of alkaloids from Zanthoxylum holstzianum JF - Natural product research N2 - The CH2Cl2/MeOH (1:1) extract of Zanthoxylum holstzianum stem bark showed good antiplasmodial activity (IC50 2.5 +/- 0.3 and 2.6 +/- 0.3 mu g/mL against the W2 and D6 strains of Plasmodium falciparum, respectively). From the extract five benzophenanthridine alkaloids [8-acetonyldihydrochelerythrine (1), nitidine (2), dihydrochelerythine (3), norchelerythrine (5), arnottianamide (8)]; a 2-quinolone alkaloid [N-methylflindersine (4)]; a lignan [4,4 '-dihydroxy-3,3 '-dimethoxylignan-9,9 '-diyl diacetate (7)] and a dimer of a benzophenanthridine and 2-quinoline [holstzianoquinoline (6)] were isolated. The CH2Cl2/MeOH (1:1) extract of the root bark afforded 1, 3-6, 8, chelerythridimerine (9) and 9-demethyloxychelerythrine (10). Holstzianoquinoline (6) is new, and is the second dimer linked by a C-C bond of a benzophenanthridine and a 2-quinoline reported thus far. The compounds were identified based on spectroscopic evidence. Amongst five compounds (1-5) tested against two strains of P. falciparum, nitidine (IC50 0.11 +/- 0.01 mu g/mL against W2 and D6 strains) and norchelerythrine (IC50 value of 0.15 +/- 0.01 mu g/mL against D6 strain) were the most active. KW - Antiplasmodial KW - benzophenanthridine alkaloid KW - holstzianoquinoline; KW - rutaceae KW - Zanthoxylum holstzianum Y1 - 2022 U6 - https://doi.org/10.1080/14786419.2022.2034810 SN - 1478-6419 SN - 1478-6427 VL - 37 IS - 13 SP - 2161 EP - 2171 PB - Taylor & Francis CY - London [u.a.] ER - TY - THES A1 - Breternitz, Joachim T1 - Structural systematic investigations of photovoltaic absorber materials N2 - The direct conversion of light from the sun into usable forms of energy marks one of the central cornerstones of the change of our living from the use of fossil, non-renewable energy resources towards a more sustainable economy. Besides the necessary societal changes necessary, it is the understanding of the solids employed that is of particular importance for the success of this target. In this work, the principles and approaches of systematic-crystallographic characterisation and systematisation of solids is used and employed to allow a directed tuning of the materials properties. The thorough understanding of the solid-state forms hereby the basis, on which more applied approaches are founded. Two material systems, which are considered as promising solar absorber materials, are at the core of this work: halide perovskites and II-IV-N2 nitride materials. While the first is renowned for its high efficiencies and rapid development in the last years, the latter is putting an emphasis on true sustainability in that toxic and scarce elements are avoided. N2 - Die direkte Umwandlung der Energie der Sonne bildet einen zentralen Baustein im Umbau unserer Gesellschaft von der Nutzung fossiler, nicht nachhaltiger Energieträger zum Erreichen einer nachhaltigen Wirtschaft. Neben den gesellschaftlichen Veränderungen ist es insbesondere das Verständnis der genutzten Festkörper, das den Motor dieser Entwicklung bildet. In dieser Arbeit werden Prinzipien der systematisch-kristallographischen Untersuchung und Kategorisierung von Festkörpern genutzt, um die Eigenschaften der Materialien gezielt steuern zu können. Dabei bildet das Verständnis des kristallinen Zustands und seine Untersuchung die Basis, auf der angewandtere Forschungsansätze aufbauen. In dieser Arbeit werden vor allem zwei Materialsysteme betrachtet, die als Absorbermaterialien in Solarzellen in Betracht gezogen werden: Halid-Perowskite und II-IV-N2-Nitrid Materialien. Die ersteren zeichnen sich insbesondere durch ihre erstaunlich hohen Effizienzen und rapide Entwicklung in den letzten Jahren aus, während das letztere System in besonderer Weise auf Nachhaltigkeit optimiert ist, und giftige oder seltene Elemente zu vermeiden sucht. KW - Materials Chemistry KW - Crystallography KW - Photovoltaics Y1 - 2023 ER - TY - JOUR A1 - Hu, Neng A1 - Lin, Li A1 - Metwalli, Ezzeldin A1 - Bießmann, Lorenz A1 - Philipp, Martine A1 - Hildebrand, Viet A1 - Laschewsky, André A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Zhong, Qi A1 - Müller-Buschbaum, Peter T1 - Kinetics of water transfer between the LCST and UCST thermoresponsive blocks in diblock copolymer thin films monitored by in situ neutron reflectivity JF - Advanced materials interfaces N2 - The kinetics of water transfer between the lower critical solution temperature (LCST) and upper critical solution temperature (UCST) thermoresponsive blocks in about 10 nm thin films of a diblock copolymer is monitored by in situ neutron reflectivity. The UCST-exhibiting block in the copolymer consists of the zwitterionic poly(4((3-methacrylamidopropyl)dimethylammonio)butane-1-sulfonate), abbreviated as PSBP. The LCST-exhibiting block consists of the nonionic poly(N-isopropylacrylamide), abbreviated as PNIPAM. The as-prepared PSBP80-b-PNIPAM(400) films feature a three-layer structure, i.e., PNIPAM, mixed PNIPAM and PSBP, and PSBP. Both blocks have similar transition temperatures (TTs), namely around 32 degrees C for PNIPAM, and around 35 degrees C for PSBP, and with a two-step heating protocol (20 degrees C to 40 degrees C and 40 degrees C to 80 degrees C), both TTs are passed. The response to such a thermal stimulus turns out to be complex. Besides a three-step process (shrinkage, rearrangement, and reswelling), a continuous transfer of D2O from the PNIPAM to the PSBP block is observed. Due to the existence of both, LCST and UCST blocks in the PSBP80-b-PNIPAM(400 )film, the water transfer from the contracting PNIPAM, and mixed layers to the expanding PSBP layer occurs. Thus, the hydration kinetics and thermal response differ markedly from a thermoresponsive polymer film with a single LCST transition. KW - block copolymer KW - dual thermoresponsive KW - kinetic water transfer KW - neutron KW - reflectivity KW - thin film Y1 - 2022 U6 - https://doi.org/10.1002/admi.202201913 SN - 2196-7350 VL - 10 IS - 3 PB - Wiley-VCH CY - Weinheim ER - TY - THES A1 - Baryzewska, Agata W. T1 - Reconfigurable Janus emulsions as signal transducers for biosensing applications Y1 - 2023 ER - TY - THES A1 - Lian, Tingting T1 - Efficient activation of peroxymonosulfate by carbon-based catalysts for water purification N2 - The increasing global population has led to a growing demand for cost-effective and eco-friendly methods of water purification. This demand has reached a peak due to the increasing presence of impurities and pollutants in water and a growing awareness of waterborne diseases. Advanced oxidation processes (AOPs) are effective methods to address these challenges, due to the generation of highly reactive radicals, such as sulfate radical (SO4•-), hydroxyl radical (•OH), and/or superoxide radical (•O2-) in oxidation reactions. Relative to conventional hydrogen peroxide (H2O2)-based AOPs for wastewater treatment, the persulfate-related AOPs are receiving increasing attention over the past decades, due to their stronger oxidizing capability and a wider pH working window. Further deployment of the seemingly plausible technology as an alternative for the well-established one in industry, however, necessitates a careful evaluation of compounding factors, such as water matrix effects, toxicological consequences, costs, and engineering challenges, etc. To this end, rational design of efficient and environmentally friendly catalysts constitutes an indispensable pathway to advance persulfate activation efficacy and to elucidate the mechanisms in AOPs, the combined endeavors are expected to provide insightful understanding and guidelines for future studies in wastewater treatment. A dozens of transition metal-based catalysts have been developed for persulfate-related AOPs, while the undesirable metal leaching and poor stability in acidic conditions have been identified as major obstacles. Comparatively, the carbonaceous materials are emerging as alternative candidates, which are characterized by metal-free nature, wide availability, and exceptional resistance to acid and alkali, as well as tunable physicochemical and electronic properties, the combined merits make them an attractive option to overcome the aforementioned limitations in metal-based catalytic systems. This dissertation aims at developing novel carbonaceous materials to boost the activity in peroxymonosulfate (PMS) activation processes. Functionalized carbon materials with metal particles or heteroatoms were constructed and further evaluated in terms of their ability to activate PMS for AOPs. The main contents of this thesis are summarized as follows: (1) Iron oxide-loaded biochar: improving stability and alleviating metal leakage Metal leaching constitutes one of the main drawbacks in using transition metals as PMS activators, which is accompanied by the generation of metal-containing sludge, potentially leading to secondary pollution. Meanwhile, the metal nanoparticles are prone to aggregate, causing rapid decay of catalytic performance. The use of carbons as supports for transition metals could mitigate these deficiencies, because the interaction between metals and carbons could in turn disperse and stabilize metal nanoparticles, thus suppressing the metal leaching. In this work, the environmentally benign lignin with its abundant phenolic groups, which is well known to serve as carbon source with high yields and flexibility, was utilized to load Fe ions. The facile low-temperature pre-treatment pyrolytic strategy was employed to construct a green catalyst with iron oxides embedded in Kraft-lignin-derived biochar (termed as γ-Fe2O3@KC). The γ-Fe2O3@KC was capable of activating PMS to generate stable non-radical species (1O2 and Fe (V)=O) and to enhance electron transfer efficiency. A surface-bound reactive complex (catalyst-PMS*) was identified by electrochemical characterizations and discussed with primary surface-bound radical pairs to explain the contradictions between quenching and EPR detection results. The system also showed encouraging reusability for at least 5 times and high stability at pH 3-9. The low concentration of iron in γ-Fe2O3@KC/PMS system implied that the carbon scaffold of biochar substantially alleviated metal leakage. (2) MOF-derived nanocarbon: new carbon crystals Traditional carbon materials are of rather moderate performance in activation PMS, due to the poor electron transfer capacity within the amorphous structure and limited active sites for PMS adsorption. Herein, we established crystalline nanocarbon materials via a simple NaCl-templated strategy using the monoclinic zeolitic imidazolate framework-8 (ZIF-8) sealed with NaCl crystals as the precursors. Specifically, NaCl captured dual advantages in serving as structure-directing agent during hydrolysis and protective salt reactor to facilitate phase transformation during carbonization. The structure-directing agent NaCl provided a protective and confined space for the evolution of MOF upon carbonization, which led to high doping amounts of nitrogen (N) and oxygen elements (O) in carbon framework (N: 14.16 wt%, O: 9.6 wt%) after calcination at a high temperature of 950 oC. We found that N-O co-doping can activate the chemically inert carbon network and the nearby sp2-hybridized carbon atoms served as active sites for adsorption and activation. Besides, the highly crystallized structure with well-established carbon channels around activated carbon atoms could significantly accelerate electron transfer process after initial adsorption of PMS. As such, this crystalline nanocarbon exhibited excellent catalytic kinetics for various pollutants. (3) MOF-derived 2D carbon layers: enhanced mass/electron transfer The two-dimensional (2D) configuration of carbon-based nanosheets with inherent nanochannels and abundant active sites residing on the layer edges or in between the layers, allowed the accessible interaction and close contact between the substrates and reactants, as well as the dramatically improved electron- and mass-transfer kinetics. In this regard, we developed dual-templating strategy to afford 2D assembly of the crystalline carbons, which found efficiency in reinforcing the interactions between the catalyst surface and foreign pollutants. Specifically, we found that the ice crystals and NaCl promoted the evolution of MOF in a 2D fashion during the freezing casting stage, while the later further allowed the formation of a graphitic surface at high calcination temperature, by virtue of the templating effect of molten salt. Due to the highly retained co-doping amounts, N and O heteroatoms created abundant active sites for PMS activation, the 2D configuration of carbon-based nanosheets enable efficient interaction of PMS and pollutants on the surface, which further boosted the kinetics of degradation. KW - Carbon KW - Water treatment KW - PMS activation Y1 - 2023 ER - TY - JOUR A1 - Bhattacharyya, Biswajit A1 - Balischewski, Christian A1 - Sperlich, Eric A1 - Günter, Christina A1 - Mies, Stefan A1 - Kelling, Alexandra A1 - Taubert, Andreas T1 - N-Butyl Pyridinium Diiodido Argentate(I) BT - A One-Dimensional Ag-I Network with Superior Solid-State Ionic Conductivity at Room Temperature JF - Advanced materials interfaces N2 - A new solid-state material, N-butyl pyridinium diiodido argentate(I), is synthesized using a simple and effective one-pot approach. In the solid state, the compound exhibits 1D ([AgI2](-))(n) chains that are stabilized by the N-butyl pyridinium cation. The 1D structure is further manifested by the formation of long, needle-like crystals, as revealed from electron microscopy. As the general composition is derived from metal halide-based ionic liquids, the compound has a low melting point of 100-101 degrees C, as confirmed by differential scanning calorimetry. Most importantly, the compound has a conductivity of 10(-6) S cm(-1) at room temperature. At higher temperatures the conductivity increases and reaches to 10(-4 )S cm(-1) at 70 degrees C. In contrast to AgI, however, the current material has a highly anisotropic 1D arrangement of the ionic domains. This provides direct and tuneable access to fast and anisotropic ionic conduction. The material is thus a significant step forward beyond current ion conductors and a highly promising prototype for the rational design of highly conductive ionic solid-state conductors for battery or solar cell applications. KW - AgI KW - ionic conductivity KW - Ionic liquids KW - thermal properties Y1 - 2023 U6 - https://doi.org/10.1002/admi.202202363 SN - 2196-7350 VL - 10 IS - 12 PB - Wiley CY - Hoboken 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 - THES A1 - Frank, Bradley D. T1 - Complex and adaptive soft colloids BT - templated from reconfigurable jamus emulsions Y1 - 2023 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 - 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 - 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 -