Refine
Year of publication
- 2021 (158) (remove)
Document Type
- Article (121)
- Doctoral Thesis (25)
- Postprint (8)
- Conference Proceeding (3)
- Habilitation Thesis (1)
Is part of the Bibliography
- yes (158)
Keywords
- Polymer (6)
- dye removal (4)
- methyl orange (4)
- methylene blue (4)
- singlet oxygen (4)
- water treatment (4)
- Arenes (3)
- Organic Chemistry (3)
- activated carbon (3)
- block copolymers (3)
- charge transfer (3)
- degradation (3)
- electron transfer (3)
- photooxygenation (3)
- Actuation (2)
- Biomimetic (2)
- Birch reduction (2)
- C1N1 (2)
- Caenorhabditis elegans (2)
- DNA damage response (2)
- DNA origami (2)
- DNA repair (2)
- Hydrogenation (2)
- Janus droplets (2)
- LIBS (2)
- Membrane (2)
- NICS (2)
- Nanostructure (2)
- Niobium (2)
- PCA (2)
- Pickering emulsions (2)
- Polymers (2)
- RAFT polymerization (2)
- SERS (2)
- Second-Year Undergraduate (2)
- Shape memory (2)
- Shape-memory (2)
- Sulfonamides (2)
- Synthese (2)
- Synthetic methods (2)
- Thin film (2)
- Water (2)
- X-ray scattering (2)
- [4+2] cycloaddition (2)
- adsorption (2)
- augmented reality (2)
- auxiliary control (2)
- azobenzene (2)
- biomaterial (2)
- calcium carbonate (2)
- carbohydrates (2)
- catalysis (2)
- citric acid (2)
- core-shell (2)
- cryogel (2)
- dissociative electron attachment (2)
- dye adsorption (2)
- dye mixture (2)
- emulsion (2)
- endothelial cells (2)
- energy transfer (2)
- fluorescence (2)
- gold nanoparticles (2)
- iPLS regression (2)
- ionic liquid (2)
- magnetic manipulation (2)
- magnetite nanoparticles (2)
- manganese (2)
- mass spectrometry (2)
- mechanical (2)
- minerals (2)
- naphthalenes (2)
- negative ions (2)
- nitride materials (2)
- organic chemistry (2)
- oxaloacetic acid (2)
- oxidative stress (2)
- photochemistry (2)
- plasmonics (2)
- polymer (2)
- polymerization (2)
- properties (2)
- rare earth elements (2)
- semiconductors (2)
- spent coffee (2)
- stereoselectivity (2)
- surface interaction (2)
- surfactants (2)
- synthesis (2)
- synthetic biology (2)
- thermoresponsiv (2)
- thermoresponsive (2)
- water (2)
- "water-in-salt" (1)
- (NMR) (1)
- 1,2-diboretane-3-ylidene (1)
- 1-Arylnaphthalen-Lignane (1)
- 1-arylnaphthalene lignanes (1)
- 2D material (1)
- 2D materials (1)
- 2D-LC-MS/MS (1)
- 2D-Material (1)
- 3c,2e-bonding (1)
- ADC(2) (1)
- AOT (1)
- AR (1)
- Abbau (1)
- Actuator (1)
- Actuators (1)
- Additive manufacturing (1)
- Ag nanoparticles (1)
- Aggregation (1)
- Aktuator (1)
- Alcohols (1)
- Aminolyse (1)
- Analogies/Transfer (1)
- Analytische Ultrazentrifugation (1)
- Anisotropy effect (1)
- Anthracene (1)
- Antiviral (1)
- Augmented Reality (1)
- Bacteria (1)
- Basis sets (1)
- Beschichtungen (1)
- Beschichtungsanwendung (1)
- Biaryls (1)
- Biobased Polymers (1)
- Biobasierte Polymere (1)
- Biohybrid-Membran (1)
- Biomaterial (1)
- Biomaterials (1)
- Blockcopolymer (1)
- C-H activation (1)
- C2N (1)
- C3N (1)
- C3N5 (1)
- CO2 capture (1)
- CO2-Abscheidung (1)
- COVID-19 (1)
- CXNY (1)
- Cereals (1)
- Chemical calculations (1)
- Cluster (1)
- Coating Applications (1)
- Coherences (1)
- Collaborative/Cooperative Learning (1)
- Coumaronochromone (1)
- Coumestan (1)
- Curriculum (1)
- Cyclobutylcarbene (1)
- C− H activation (1)
- DBD (1)
- DBD-Farbstoffe (1)
- DBD-dyes (1)
- DNA (1)
- DNA Schädigung (1)
- DNA damage (1)
- DNA nanotechnology (1)
- Dative vs. coordinative NHC -> BR3 bond (1)
- Defects (1)
- Deformation (1)
- Degradable (1)
- Depsipeptide (1)
- Digitalisierung (1)
- Dissertation (1)
- Distance (1)
- Doppelstrangbruch (1)
- Durchflusschemie (1)
- Einkristalle (1)
- Einzelstrangbruch (1)
- Electrospinning (1)
- Emulsions (1)
- Energiespeicher (1)
- Energy (1)
- Energy storage (1)
- Erneuerbare Ressourcen (1)
- Excited state proton transfer (1)
- F(4)TCNQ (1)
- Farbstoff (1)
- Fiber (1)
- First-Year Undergraduate/General (1)
- Fluorescence (1)
- Fluoreszenzfarbstoffe (1)
- Formgedächtnis (1)
- Fragmentation (1)
- Function by design (1)
- Funktionalisierung (1)
- GOIP (1)
- Gas selective membranes (1)
- Gasselektive Membranen (1)
- Gastrennung (1)
- Genetics (1)
- Heck reactions (1)
- Heterocycles (1)
- High-throughput (1)
- Humor/Puzzles/Games (1)
- Hydrogels (1)
- Hydrogen Bonds (1)
- Hydrolyse (1)
- Hydroxyl (1)
- Imidazolate Frameworks Potsdam (1)
- Immersion (1)
- In situ (1)
- Indikator (1)
- Ionic liquid monomers (1)
- Ionic liquids (1)
- Ionization (1)
- Ionogel (1)
- Irradiation (1)
- Isocyanates (1)
- Katalysatoren (1)
- Kohlenstoff (1)
- Kristallisation (1)
- LED (1)
- Lactams (1)
- Lactones (1)
- Langmuir monolayers (1)
- Lasers (1)
- Learning/Chemistry Education Research (1)
- Leguminosae (1)
- Lernumgebung (1)
- Liquids (1)
- Lumineszenz (1)
- Löschung (1)
- MD simulations (1)
- Magnetite-gold nanoparticles (1)
- Mass spectrometry (1)
- Membran (1)
- Membranforschung bzw. Membranwissenschaften (1)
- Methacrylat (1)
- Microemulsions (1)
- Microstructure (1)
- Mikrofluidik (1)
- Millettia lasiantha (1)
- Mixed-Matrix-Membran (1)
- Modelling (1)
- Modified mycotoxins (1)
- Molecular orientation (1)
- Molecular structure (1)
- Morpholindione (1)
- Multi-method (1)
- Multiblock Copolymer (1)
- Multiblock copolymer (1)
- Multiblock copolymers (1)
- Mycotoxins (1)
- NHCs (1)
- Nanofiber (1)
- Nanoparticles (1)
- Natrium-Ionen-Akkumulator (1)
- Negative Poisson’s ratio (1)
- Negatives Poisson-Verhältnis (1)
- Nonadiabatic effects (1)
- Nuclear magnetic resonance (1)
- Nuclear magnetic resonance spectroscopy (1)
- Olefin Metathese (1)
- Olefin metathesis (1)
- On-demand Freisetzung (1)
- On-demand release (1)
- Organic chemistry (1)
- Organic structure (1)
- Organische Chemie (1)
- PDMS surface grafting (1)
- PISA (1)
- Palladium (1)
- Palladium ion (1)
- Percolation (1)
- Pesticides (1)
- Phase morphology (1)
- Photochemie (1)
- Photochemistry (1)
- Photodynamics (1)
- Photoinduzierte Polymerisation (1)
- Photoinitiierte Polymerisationen (1)
- Photopolymer (1)
- Photopolymerization (1)
- Photopolymers (1)
- Poly(2-oxazolin)-Blockcopolymer (1)
- Poly(methyl methacrylate (1)
- Poly(ε-caprolacton) (1)
- Polydisulfide (1)
- Polymer chemistry (1)
- Polymer films (1)
- Polymer physics (1)
- Polymerchemie (1)
- Polymere (1)
- Polymerfilme (1)
- Polymerionogel (1)
- Polymerisierbare ionische Flüssigkeiten (1)
- Polymerkristallisation (1)
- Polymerphysik (1)
- Polymethylmethacrylat (1)
- Polysulfon (1)
- Protein-NMR-Spektroskopie (1)
- Protein-Polymer-Konjugat (1)
- Proteincharakterisierung (1)
- Quantum dynamics (1)
- Quantum mechanics (1)
- RAFT dispersion polymerization (1)
- RAFT, Polymerisation (1)
- RAFT-Polymerisation (1)
- Raman spectroscopy (1)
- Random copolymer (1)
- Reaktion (1)
- Renewable Resources (1)
- Ring-opening polymerization (1)
- Robotic synthesis (1)
- Robotics (1)
- Ruthenium (1)
- SEC-MALS (1)
- Salzschmelze-Templating (1)
- Sauerstoff-Reduktionsreaktion (1)
- Scanning probe microscopy (SPM) (1)
- Scattering (1)
- Schmelz (1)
- Schulversuch (1)
- Schwefel (1)
- Second-Year undergraduate (1)
- Selbstassemblierung (1)
- Sequence structure (1)
- Shape-memory polymer (1)
- Spannungskonzentrationen (1)
- Spectroscopy (1)
- Spektroskopie (1)
- Stereocomplex (1)
- Stereokomplex (1)
- Stickstoff‑ und Kohlenstoffhaltige Materialien (1)
- Stress concentration (1)
- Structure Determination (1)
- Students (1)
- Substrat (1)
- Sulfated polymer (1)
- Surface reaction (1)
- Synthesis (1)
- Synthetische Biologie (1)
- TD-DFT (1)
- Telechel (1)
- Templated self-assembly (1)
- Thermoplastic elastomer (1)
- Thiol-En (1)
- Through-space NMR (1)
- Through-space NMR shieldings (TSNMRS) (1)
- Thymolblau (1)
- TiO2 (1)
- Tin octanoate (1)
- Transient (1)
- Transmembranprotein (1)
- Ultradünne Filme (1)
- Uranyl (1)
- Vesikel (1)
- Vesikel Forschung/Vesikel Studien (1)
- Vinylsulfonylverbindungen (1)
- Winsor phases (1)
- Wärmetransformationsanwendungen (1)
- Zanthoxylum leprieurii (1)
- acidic ionic liquids (1)
- active polymer (1)
- aerogel (1)
- aggregation (1)
- alkaloid (1)
- aminolysis (1)
- analytical ultracentrifugation (1)
- anodes (1)
- anorganisch-organische Hybrid-Nanopartikel (1)
- anthracene (1)
- antimycobacterial activity (1)
- arenes (1)
- artificial cells (1)
- assembly capabilities (1)
- batteries (1)
- biohybrid membrane materials (1)
- bioinspired composite (1)
- bioinspired materials (1)
- bioinspirierte Komposite (1)
- bioinstructive implants (1)
- biological membrane (1)
- biopolymer (1)
- bioprinting (1)
- block copolymer (1)
- bottom-up fabrication (1)
- brominated (1)
- calcination (1)
- capillary-active substrates (1)
- carbon (1)
- carbon nitrides (1)
- catalysts (1)
- cells (1)
- chiral sensing (1)
- chirality (1)
- circular dichroism (1)
- click chemistry (1)
- cluster (1)
- co-nonsolvency (1)
- coexisting phases (1)
- coffee by-products (1)
- computer literacy (1)
- controlled radical polymerization (1)
- coordination bonds (1)
- copper (1)
- crystallinity (1)
- crystallization (1)
- cyclic olefin copolymer (1)
- diblock copolymers (1)
- dielectric spectroscopy (1)
- digitalization (1)
- dimer (1)
- dissertation (1)
- double strand break (1)
- dye (1)
- electrochemical impedance spectroscopy (1)
- electrochemistry (1)
- electrode materials (1)
- electron microscopy (1)
- end-groups (1)
- endothelial basement membrane (1)
- energy materials (1)
- energy storage (1)
- engineering (1)
- enzyme (1)
- ethylene oxide (1)
- evolution (1)
- excited states (1)
- exciton (1)
- flow chemistry (1)
- fluorescence stimuli‐ responsivity (1)
- fluorescent dyes (1)
- form stability (1)
- fractal kinetics (1)
- fumaronitrile (1)
- functionalization (1)
- galactose-decorated monomer (1)
- gas supply conditions (1)
- glyco-inside nano-assemblies (1)
- gold surface (1)
- group-subgroup relations (1)
- group-subgroup relationships (1)
- halide perovskites (1)
- heat transformation application (1)
- heterocyclic ligand (1)
- high pressure (1)
- hole scavengers (1)
- hot electrons (1)
- hot-electrons (1)
- hybrid materials (1)
- hydrate formation process (1)
- hydrogels (1)
- hydrolysis (1)
- hydroxy (1)
- hysteresis (1)
- immersion (1)
- in (1)
- in vitro thrombogenicity testing (1)
- indicator (1)
- informatische Bildung (1)
- inorganic-organic hybrid nanoparticle (1)
- intercalations (1)
- intermediates (1)
- internal membrane-membrane adhesion (1)
- interne Membran-Membran Adhäsion (1)
- ion transport (1)
- ionic liquid crystals (1)
- ionic liquid precursors (1)
- ionische Flüssigkeit (1)
- ionisierende Strahlung (1)
- ionizing radiation (1)
- ionogel (1)
- isomerism (1)
- janus emulsion (1)
- kinetics (1)
- kontrollierte radikalische Polymerisationen (1)
- künstliche Zellen (1)
- l-cysteine (1)
- lanthanides (1)
- lanthanoid migration (1)
- learning environment (1)
- libraries (1)
- library (1)
- ligands (1)
- lithium sulfides (1)
- lithium-ion capacitors (1)
- low-energy electrons (1)
- luminescence (1)
- macrocycles (1)
- magnetic nanoparticles (1)
- maleonitrile (1)
- material characterization (1)
- melting (1)
- membrane (1)
- membrane science (1)
- metal (1)
- methacrylate (1)
- micelles (1)
- microcontact printing (1)
- microfluidics (1)
- microporous (1)
- mixed gas hydrates (1)
- mixed-matrix-membrane (1)
- morphology (1)
- multi-compartmentalised vesicles (1)
- multi-kompartmentalisierte Vesikel (1)
- multiblock copolymers (1)
- multiple functions (1)
- multiple light scattering (1)
- nano-optics (1)
- nanohole arrays (1)
- nanoparticle assemblies (1)
- nanoparticle dimers (1)
- nanoparticles (1)
- nanostructures (1)
- nanoswitches (1)
- naphthalene (1)
- naturwissenschaftliche Bildung (1)
- neutron reflectometry (1)
- niederenergetische Elektronen (1)
- nitrogen containing carbonaceous materials (1)
- nitrogen-doped carbon (1)
- optical sensors (1)
- organic compounds adsorption (1)
- organische Chemie (1)
- oxygen reduction reaction (1)
- pH-responsive (1)
- parchment (1)
- phase morphology (1)
- phase transfer (1)
- photo induced polymerization (1)
- photocatalysis (1)
- photon density wave spectroscopy (1)
- photoswitches (1)
- plasmon-driven catalysis (1)
- plasmonic (1)
- plasmonic nanoparticles (1)
- platelets (1)
- poly(2-oxazoline) (1)
- poly(disulfide)s (1)
- poly(e-caprolactone) (1)
- poly(tetrafluoroethylene) (1)
- poly(ε-caprolactone) (1)
- polydopamine (1)
- polymer crystallization (1)
- polymer ionogel (1)
- polysulfone (1)
- polyvinyl acetate (1)
- porous carbon (1)
- porous silicon (1)
- porphyrazine (1)
- process analytical technology (1)
- protein NMR spectroscopy (1)
- protein characterization (1)
- protein-polymer conjugate (1)
- proton hopping (1)
- protonation (1)
- purines (1)
- quenching (1)
- rate constants (1)
- reaction mechanisms (1)
- reactions (1)
- reactive (1)
- reshaping abilities (1)
- resonance Raman (1)
- rheology (1)
- rhodium(I)– phosphine (1)
- ring-opening (1)
- salt melt templating (1)
- scattering (1)
- school experiment (1)
- scientific literacy (1)
- self-assembly (1)
- sequence structures (1)
- shape change (1)
- shape-memory hydrogel (1)
- shieldings (TSNMRS) (1)
- shuttled RAFT-polymerization (1)
- silane chemistry (1)
- silica (1)
- single crystals (1)
- single strand break (1)
- situ Raman spectroscopy (1)
- sodium-ion batteries (1)
- solar (1)
- solid electrolyte interphase (1)
- solvent resistance (1)
- spectroscopy (1)
- spent coffee grounds (1)
- spin-orbit coupling (1)
- stereocomplexes (1)
- sterilization (1)
- stimul-responsive (1)
- stimul-responsive emulsion (1)
- stimuli-sensitive materials (1)
- structure elucidation (1)
- structure-property relationships (1)
- substrate (1)
- sulfation (1)
- sulfides (1)
- sulfones (1)
- sulfur (1)
- supercapacitor (1)
- superlattices (1)
- surface hopping (1)
- surface patterning (1)
- surface plasmon resonance (1)
- surface-enhanced Raman scattering (1)
- switch (1)
- synthetische Biologie (1)
- temperature effect (1)
- temperature-memory polymers (1)
- temperature-responsive (1)
- thermoplastic elastomer (1)
- thermoplastisches Elastomer (1)
- thin films (1)
- thiol-ene (1)
- thymol blue (1)
- tissue (1)
- trans-fagaramide (1)
- transient (1)
- transition density matrix (1)
- transition metal catalysis (1)
- transmembrane protein (1)
- tuberculosis (1)
- twinning (1)
- ultrathin film (1)
- upconversion nanoparticles (1)
- uranyl (1)
- valorization (1)
- vascular grafts (1)
- vesicle (1)
- vesicle studies (1)
- vinyl sulfonyl compounds (1)
- water vapor (1)
- wide angle x‐ ray scattering (1)
- wurtzite type (1)
- yolk-shell (1)
- Übergangsmetallkatalyse (1)
Institute
- Institut für Chemie (158) (remove)
Self-assembly of plasmonic nanoantenna-waveguide structures for subdiffractional chiral sensing
(2021)
Spin-momentum locking is a peculiar effect in the near-field of guided optical or plasmonic modes. It can be utilized to map the spinning or handedness of electromagnetic fields onto the propagation direction. This motivates a method to probe the circular dichroism of an illuminated chiral object. In this work, we demonstrate local, subdiffraction limited chiral coupling of light and propagating surface plasmon polaritons in a self-assembled system of a gold nanoantenna and a silver nanowire. A thin silica shell around the nanowire provides precise distance control and also serves as a host for fluorescent molecules, which indicate the direction of plasmon propagation. We characterize our nanoantenna-nanowire systems comprehensively through correlated electron microscopy, energy-dispersive X-ray spectroscopy, dark-field, and fluorescence imaging. Three-dimensional numerical simulations support the experimental findings. Besides our measurement of far-field polarization, we estimate sensing capabilities and derive not only a sensitivity of 1 mdeg for the ellipticity of the light field, but also find 10(3) deg cm(2)/dmol for the circular dichroism of an analyte locally introduced in the hot spot of the antenna-wire system. Thorough modeling of a prototypical design predicts on-chip sensing of chiral analytes. This introduces our system as an ultracompact sensor for chiral response far below the diffraction limit.
In vitro thrombogenicity test systems require co-cultivation of endothelial cells and platelets under blood flow-like conditions. Here, a commercially available perfusion system is explored using plasma-treated cyclic olefin copolymer (COC) as a substrate for the endothelial cell layer. COC was characterized prior to endothelialization and co-cultivation with platelets under static or flow conditions. COC exhibits a low roughness and a moderate hydrophilicity. Flow promoted endothelial cell growth and prevented platelet adherence. These findings show the suitability of COC as substrate and the importance of blood flow-like conditions for the assessment of the thrombogenic risk of drugs or cardiovascular implant materials.
Structure, mechanical properties and degradation behavior of electrospun PEEU fiber meshes and films
(2021)
The capability of a degradable implant to provide mechanical support depends on its degradation behavior. Hydrolytic degradation was studied for a polyesteretherurethane (PEEU70), which consists of poly(p-dioxanone) (PPDO) and poly(epsilon-caprolactone) (PCL) segments with a weight ratio of 70:30 linked by diurethane junction units. PEEU70 samples prepared in the form of meshes with average fiber diameters of 1.5 mu m (mesh1.5) and 1.2 mu m (mesh1.2), and films were sterilized and incubated in PBS at 37 degrees C with 5 vol% CO2 supply for 1 to 6 weeks. Degradation features, such as cracks or wrinkles, became apparent from week 4 for all samples. Mass loss was found to be 11 wt%, 6 wt%, and 4 wt% for mesh1.2, mesh1.5, and films at week 6. The elongation at break decreased to under 20% in two weeks for mesh1.2. In case of the other two samples, this level of degradation was achieved after 4 weeks. The weight average molecular weight of both PEEU70 mesh and film samples decreased to below 30 kg/mol when elongation at break dropped below 20%. The time period of sustained mechanical stability of PEEU70-based meshes depends on the fiber diameter and molecular weight.
Informatische Bildung spielt eine immer zentralere Rolle in der Bildung einer Gesellschaft des 21. Jahrhunderts. Für den Chemieunterricht ergeben sich daraus zwei Aspekte: Einerseits können Konzepte der informatischen Bildung dabei helfen, chemie- und naturwissenschaftsspezifische Denk- und Arbeitsweisen zu fördern. Andererseits kann der Chemieunterricht einen Beitrag für die informatische Bildung leisten. Dieser Artikel geht auf beide Aspekte ein und versucht die gegenseitigen Vorteile der informatischen Bildung und der naturwissenschaftlichen Bildung im Chemieunterricht darzustellen.
In this study, the kinetics of the adsorption of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) on the surface of Ag nanoparticles (Ag NPs) in chloroform has been intensively investigated, as molecular doping is known to play a crucial role in organic electronic devices. Based on the results obtained from UV-visible (vis)-near-infrared (NIR) absorption spectroscopy, cryogenic transmission electron microscopy, scanning nanobeam electron diffraction, and electron energy loss spectroscopy, a two-step interaction kinetics has been proposed for the Ag NPs and F(4)TCNQ molecules, which includes the first step of electron transfer from Ag NPs to F(4)TCNQ indicated by the ionization of F(4)TCNQ and the second step of the formation of a Ag-F(4)TCNQ complex. The whole process has been followed via UV-vis-NIR absorption spectroscopy, which reveals distinct kinetics at two stages: the instantaneous ionization and the long-term complex formation. The kinetics and the influence of the molar ratio of Ag NPs/F(4)TCNQ molecules on the interaction between Ag NPs and F(4)TCNQ molecules in an organic solution are reported herein for the first time. Furthermore, the control experiment with silica-coated Ag NPs manifests that the charge transfer at the surface between Ag NPs and F(4)TCNQ molecules is prohibited by a silica layer of 18 nm.
Sulfated biomolecules are known to influence numerous biological processes in all living organisms. Particularly, they contribute to prevent and inhibit the hypercoagulation condition. The failure of polymeric implants and blood contacting devices is often related to hypercoagulation and microbial contamination. Here, bioactive sulfated biomacromolecules are mimicked by sulfation of poly(glycerol glycidyl ether) (polyGGE) films. Autoclaving, gamma-ray irradiation and ethylene oxide (EtO) gas sterilization techniques were applied to functionalized materials. The sulfate group density and hydrophilicity of sulfated polymers were decreased while chain mobility and thermal degradation were enhanced post autoclaving when compared to those after EtO sterilization. These results suggest that a quality control after sterilization is mandatory to ensure the amount and functionality of functionalized groups are retained.
Binary III-V nitrides such as AlN, GaN and InN in the wurtzite-type structure have long been considered as potent semiconducting materials because of their optoelectronic properties, amongst others. With rising concerns over the utilization of scarce elements, a replacement of the trivalent cations by others in ternary and multinary nitrides has led to the development of different variants of nitrides and oxide nitrides crystallizing in lower-symmetry variants of wurtzite. This work presents the symmetry relationships between these structural types specific to nitrides and oxide nitrides and updates some prior work on this matter. The non-existence of compounds crystallizing in Pmc2(1), formally the highest subgroup of the wurtzite type fulfilling Pauling's rules for 1:1:2 stoichiometries, has been puzzling scientists for a while; a rationalization is given, from a crystallographic basis, of why this space group is unlikely to be adopted.
Quenching mechanism of uranyl(VI) by chloride and bromide in aqueous and non-aqueous solutions
(2021)
A major hindrance in utilizing uranyl(VI) luminescence as a standard analytical tool, for example, in environmental monitoring or nuclear industries, is quenching by other ions such as halide ions, which are present in many relevant matrices of uranyl(VI) speciation. Here, we demonstrate through a combination of time-resolved laser-induced fluorescence spectroscopy, transient absorption spectroscopy, and quantum chemistry that coordinating solvent molecules play a crucial role in U(VI) halide luminescence quenching. We show that our previously suggested quenching mechanism based on an internal redox reaction of the 1:2-uranyl-halide-complex holds also true for bromide-induced quenching of uranyl(VI). By adopting specific organic solvents, we were able to suppress the separation of the oxidized halide ligand X-2(center dot-) and the formed uranyl(V) into fully solvated ions, thereby "reigniting" U(VI) luminescence. Time-dependent density functional theory calculations show that quenching occurs through the outer-sphere complex of U(VI) and halide in water, while the ligand-to-metal charge transfer is strongly reduced in acetonitrile.
Halide perovskites
(2021)
To systematically add functionality to nanoscale polymer switches, an understanding of their responsive behavior is crucial. Herein, solvent vapor stimuli are applied to thin films of a diblock copolymer consisting of a short poly(methyl methacrylate) (PMMA) block and a long poly(N-isopropylmethacrylamide) (PNIPMAM) block for realizing ternary nanoswitches. Three significantly distinct film states are successfully implemented by the combination of amphiphilicity and co-nonsolvency effect. The exposure of the thin films to nitrogen, pure water vapor, and mixed water/acetone (90 vol%/10 vol%) vapor switches the films from a dried to a hydrated (solvated and swollen) and a water/acetone-exchanged (solvated and contracted) equilibrium state. These three states have distinctly different film thicknesses and solvent contents, which act as switch positions "off," "on," and "standby." For understanding the switching process, time-of-flight neutron reflectometry (ToF-NR) and spectral reflectance (SR) studies of the swelling and dehydration process are complemented by information on the local solvation of functional groups probed with Fourier-transform infrared (FTIR) spectroscopy. An accelerated responsive behavior beyond a minimum hydration/solvation level is attributed to the fast build-up and depletion of the hydration shell of PNIPMAM, caused by its hydrophobic moieties promoting a cooperative hydration character.
Vibrational relaxation of adsorbates is a sensitive tool to probe energy transfer at gas/solid and liquid/solid interfaces. The most direct way to study relaxation dynamics uses time-resolved spectroscopy. Here we report on a non-equilibrium ab initio molecular dynamics (NE-AIMD) methodology to model vibrational relaxation of OH vibrations on a hydroxylated, water-covered alpha-Al2O3(0001) surface. In our NE-AIMD approach, after exciting selected O-H bonds their coupling to surface phonons and to the water adlayer is analyzed in detail, by following both the energy flow in time, as well as the time-evolution of Vibrational Density of States (VDOS) curves. The latter are obtained from Time-dependent Correlation Functions (TCFs) and serve as prototypical, generic representatives of time-resolved vibrational spectra. As most important results, (i) we find a few-picosecond lifetime of the excited modes and (ii) identify both hydrogen-bonded aluminols and water molecules in the adsorbed water layer as main dissipative channels, while the direct coupling to Al2O3 surface phonons is of minor importance on the timescales of interest. Our NE-AIMD/TCF methodology is powerful for complex adsorbate systems, in principle even reacting ones, and opens a way towards time-resolved vibrational spectroscopy.
Elucidation of the reaction mechanism for the synthesis of ZnGeN2 through Zn2GeO4 ammonolysis
(2021)
Ternary II-IV-N-2 materials have been considered as a promising class of materials that combine photovoltaic performance with earth-abundance and low toxicity. When switching from binary III-V materials to ternary II-IV-N-2 materials, further structural complexity is added to the system that may influence its optoelectronic properties. Herein, we present a systematic study of the reaction of Zn2GeO4 with NH3 that produces zinc germanium oxide nitrides, and ultimately approach stoichiometric ZnGeN2, using a combination of chemical analyses, X-ray powder diffraction and DFT calculations. Elucidating the reaction mechanism as being dominated by Zn and O extrusion at the later reaction stages, we give an insight into studying structure-property relationships in this emerging class of materials.
This study deals with the facile synthesis of Fe1-xS nanoparticle-containing nitrogen-doped porous carbon membranes (denoted as Fe1-xS/N-PCMs) via vacuum carbonization of hybrid porous poly(ionic liquid) (PIL) membranes, and their successful use as a sulfur host material to mitigate the shuttle effect in lithium-sulfur (Li-S) batteries. The hybrid porous PIL membranes as the sacrificial template were prepared via ionic crosslinking of a cationic PIL with base-neutralized 1,1 '-ferrocenedicarboxylic acid, so that the iron source was molecularly incorporated into the template. The carbonization process was investigated in detail at different temperatures, and the chemical and porous structures of the carbon products were comprehensively analyzed. The Fe1-xS/N-PCMs prepared at 900 degrees C have a multimodal pore size distribution with a satisfactorily high surface area and well-dispersed iron sulfide nanoparticles to physically and chemically confine the LiPSs. The sulfur/Fe1-xS/N-PCM composites were then tested as electrodes in Li-S batteries, showing much improved capacity, rate performance and cycle stability, in comparison to iron sulfide-free, nitrogen-doped porous carbon membranes.
Toll-like receptor (TLR) can trigger an immune response against virus including SARS-CoV-2. TLR expression/distribution is varying in mesenchymal stromal cells (MSCs) depending on their culture environments. Here, to explore the effect of periodic thermomechanical cues on TLRs, thermally controlled shape-memory polymer sheets with programmable actuation capacity were created. The proportion of MSCs expressing SARS-CoV-2-associated TLRs was increased upon stimulation. The TLR4/7 colocalization was promoted and retained in the endoplasmic reticula. The TLR redistribution was driven by myosin-mediated F-actin assembly. These results highlight the potential of boosting the immunity for combating COVID-19 via thermomechanical preconditioning of MSCs.
Rapid migration of mesenchymal stem cells (MSCs) on device surfaces could support in vivo tissue integration and might facilitate in vitro organoid formation. Here, polydopamine (PDA) is explored as a biofunctional coating to effectively promote MSC motility. It is hypothesized that PDA stimulates fibronectin deposition and in this way enhances integrin-mediated migration capability. The random and directional cell migration was investigated by time-lapse microscopy and gap closure assay respectively, and analysed with softwares as computational tools. A higher amount of deposited fibronectin was observed on PDA substrate, compared to the non-coated substrate. The integrin beta 1 activation and focal adhesion kinase (FAK) phosphorylation at Y397 were enhanced on PDA substrate, but the F-actin cytoskeleton was not altered, suggesting MSC migration on PDA was regulated by integrin initiated FAK signalling. This study strengthens the biofunctionality of PDA coating for regulating stem cells and offering a way of facilitating tissue integration of devices.
Copolyesterurethanes (PDLCLs) based on oligo(epsilon-caprolactone) (OCL) and oligo(omega-pentadecalactone) (OPDL) segments are biodegradable thermoplastic temperature-memory polymers. The temperature-memory capability in these polymers with crystallizable control units is implemented by a thermomechanical programming process causing alterations in the crystallite arrangement and chain organization. These morphological changes can potentially affect degradation. Initial observations on the macroscopic level inspire the hypothesis that switching of the controlling units causes an accelerated degradation of the material, resulting in programmable degradation by sequential coupling of functions. Hence, detailed degradation studies on Langmuir films of a PDLCL with 40 wt% OPDL content are carried out under enzymatic catalysis. The temperature-memory creation procedure is mimicked by compression at different temperatures. The evolution of the chain organization and mechanical properties during the degradation process is investigated by means of polarization-modulated infrared reflection absorption spectroscopy, interfacial rheology and to some extend by X-ray reflectivity. The experiments on PDLCL Langmuir films imply that degradability is not enhanced by thermal switching, as the former depends on the temperature during cold programming. Nevertheless, the thin film experiments show that the leaching of OCL segments does not induce further crystallization of the OPDL segments, which is beneficial for a controlled and predictable degradation.
The water vapor-induced swelling, as well as subsequent phase-transition kinetics, of thin films of a diblock copolymer (DBC) loaded with different amounts of the salt NaBr, is investigated in situ. In dilute aqueous solution, the DBC features an orthogonally thermoresponsive behavior. It consists of a zwitterionic poly(sulfobetaine) block, namely, poly(4-(N-(3'-methacrylamidopropyl)-N, N-dimethylammonio) butane-1-sulfonate) (PSBP), showing an upper critical solution temperature, and a nonionic block, namely, poly(N-isopropylmethacrylamide) (PNIPMAM), exhibiting a lower critical solution temperature. The swelling kinetics in D2O vapor at 15 degrees C and the phase transition kinetics upon heating the swollen film to 60 degrees C and cooling back to 15 degrees C are followed with simultaneous time-of-flight neutron reflectometry and spectral reflectance measurements. These are complemented by Fourier transform infrared spectroscopy. The collapse temperature of PNIPMAM and the swelling temperature of PSBP are found at lower temperatures than in aqueous solution, which is attributed to the high polymer concentration in the thin-film geometry. Upon inclusion of sub-stoichiometric amounts (relative to the monomer units) of NaBr in the films, the water incorporation is significantly increased. This increase is mainly attributed to a salting-in effect on the zwitterionic PSBP block. Whereas the addition of NaBr notably shifts the swelling temperature of PSBP to lower temperatures, the collapse temperature of PNIPMAM remains unaffected by the presence of salt in the films.
Shape-memory hydrogels (SMH) are multifunctional, actively-moving polymers of interest in biomedicine. In loosely crosslinked polymer networks, gelatin chains may form triple helices, which can act as temporary net points in SMH, depending on the presence of salts. Here, we show programming and initiation of the shape-memory effect of such networks based on a thermomechanical process compatible with the physiological environment. The SMH were synthesized by reaction of glycidylmethacrylated gelatin with oligo(ethylene glycol) (OEG) alpha,omega-dithiols of varying crosslinker length and amount. Triple helicalization of gelatin chains is shown directly by wide-angle X-ray scattering and indirectly via the mechanical behavior at different temperatures. The ability to form triple helices increased with the molar mass of the crosslinker. Hydrogels had storage moduli of 0.27-23 kPa and Young's moduli of 215-360 kPa at 4 degrees C. The hydrogels were hydrolytically degradable, with full degradation to water-soluble products within one week at 37 degrees C and pH = 7.4. A thermally-induced shape-memory effect is demonstrated in bending as well as in compression tests, in which shape recovery with excellent shape-recovery rates R-r close to 100% were observed. In the future, the material presented here could be applied, e.g., as self-anchoring devices mechanically resembling the extracellular matrix.