Refine
Has Fulltext
- yes (427) (remove)
Year of publication
Document Type
- Postprint (225)
- Doctoral Thesis (192)
- Habilitation Thesis (8)
- Monograph/Edited Volume (1)
- Master's Thesis (1)
Language
- English (427) (remove)
Keywords
- Nanopartikel (19)
- nanoparticles (15)
- Selbstorganisation (12)
- self-assembly (11)
- DNA origami (9)
- thermoresponsive (7)
- Polymerchemie (6)
- RAFT (6)
- Synthese (6)
- block copolymer (6)
- ionic liquids (6)
- porous materials (6)
- synthesis (6)
- water (6)
- Blockcopolymer (5)
- Blockcopolymere (5)
- biomaterials (5)
- block copolymers (5)
- green chemistry (5)
- hydrogel (5)
- luminescence (5)
- polymer (5)
- Bioraffinerie (4)
- DNA Origami (4)
- Elektrokatalyse (4)
- FRET (4)
- Katalyse (4)
- Korrosion (4)
- LIBS (4)
- Lumineszenz (4)
- Polymer (4)
- Tenside (4)
- adsorption (4)
- anomalous diffusion (4)
- biomass (4)
- carbon nitride (4)
- copolymers (4)
- corrosion (4)
- energy storage (4)
- heterogeneous catalysis (4)
- living cells (4)
- nachhaltige Chemie (4)
- nanoparticle (4)
- nanostructures (4)
- polymer chemistry (4)
- polyzwitterion (4)
- poröse Materialien (4)
- ring-opening polymerization (4)
- surfactants (4)
- thermoresponsiv (4)
- Adsorption (3)
- Biomasse (3)
- Chitooligosaccharide (3)
- Chitooligosaccharides (3)
- Diodenlaserspektroskopie (3)
- Energiespeicher (3)
- Fluoreszenz-Resonanz-Energie-Transfer (3)
- Förster resonance energy transfer (3)
- Immunoassay (3)
- Kohlendioxid (3)
- Kohlenhydrate (3)
- Kohlenstoff (3)
- Kohlenstoffnitriden (3)
- Kolloid (3)
- Massenspektrometrie (3)
- Metallnitride (3)
- Nanoparticles (3)
- Photochemie (3)
- Photoionisation (3)
- Photokatalyse (3)
- Polyelektrolyte (3)
- Polymere (3)
- SERS (3)
- Vesikel (3)
- binding (3)
- biomineralization (3)
- biorefinery (3)
- carbohydrates (3)
- carbon (3)
- carbon nitrides (3)
- catalysis (3)
- composites (3)
- controlled radical polymerization (3)
- crystal structure (3)
- crystallization (3)
- glucose oxidation (3)
- heterogene Katalyse (3)
- heterogene Photokatalyse (3)
- heterogeneous photocatalysis (3)
- hydrogels (3)
- infection pathway (3)
- ionic liquid (3)
- ionothermal synthesis (3)
- ligand (3)
- low-energy electrons (3)
- lower critical solution temperature (3)
- mass spectrometry (3)
- metal nitrides (3)
- metal-organic frameworks (3)
- micelle (3)
- micelles (3)
- models (3)
- nucleation (3)
- perovskite solar cells (3)
- photocatalysis (3)
- polyelectrolyte (3)
- polymerization (3)
- polymers (3)
- polypeptide (3)
- quantum dots (3)
- selectivity (3)
- shape (3)
- sol-gel (3)
- surface (3)
- surface modification (3)
- sustainable chemistry (3)
- theoretical chemistry (3)
- theoretische Chemie (3)
- zinc (3)
- 3D printing (2)
- ATRP (2)
- Abbau (2)
- Ammoniak (2)
- Antifouling (2)
- Beschichtungen (2)
- Bindung (2)
- Cellulose (2)
- Chitinase (2)
- Chitosan (2)
- Colloid Chemistry (2)
- DNA radiation damage (2)
- Electrocatalysis (2)
- Elektronendynamik (2)
- Emulsion (2)
- Energietransfer (2)
- Europium (2)
- Fluorescence spectroscopy (2)
- Formgedächtnis (2)
- Funktionalisierung (2)
- Funktionalisierung <Chemie> (2)
- Förster-Resonanzenergietransfer (2)
- Gasadsorption (2)
- Glycosylation (2)
- Grenzflächen (2)
- Grüne Chemie (2)
- Hydrogel (2)
- Hydrothermale Karbonisierung (2)
- Ion mobility spectrometry (2)
- Ionenmobilitätsspektrometrie (2)
- Ionic liquids (2)
- Ionische Flüssigkeiten (2)
- Isotopenverhältnis (2)
- Juvenile hormone (2)
- Katalysatoren (2)
- Kohlenstoffmaterialien (2)
- Kohlenstoffnitride (2)
- Kolloidchemie (2)
- Komposite (2)
- Kristallisation (2)
- Lanthanoide (2)
- Leguminosae (2)
- Lignin (2)
- Lipide (2)
- Mesokristalle (2)
- Mizelle (2)
- Mizellen (2)
- Molekulardynamik (2)
- Monoschicht (2)
- NCA (2)
- Nanostrukturen (2)
- Nanotechnologie (2)
- Oberflächenchemie (2)
- PCA (2)
- Peptide (2)
- Peptides (2)
- Perowskit-Solarzellen (2)
- Plasmonik (2)
- Polyelektrolyt (2)
- Polymer chemistry (2)
- Polymerisation (2)
- Polypeptid (2)
- Polyzwitterion (2)
- Porous carbon (2)
- Quantenpunkt (2)
- Quantenpunkte (2)
- RAFT-Polymerisation (2)
- Raman (2)
- SAXS (2)
- Salts (2)
- Salz (2)
- Salzschmelze-Templating (2)
- Selektivität (2)
- Sol-Gel (2)
- Solarzellen (2)
- Spektroskopie (2)
- Struktur (2)
- Synthesis (2)
- Transmembranprotein (2)
- Ultrazentrifuge (2)
- Wasser (2)
- Zwitterionen (2)
- air-water interface (2)
- antifouling (2)
- aqueous-solution (2)
- arsenolipids present (2)
- assemblies (2)
- assembly (2)
- azobenzene (2)
- biodegradable polymers (2)
- biomaterial (2)
- boronic acid (2)
- calcium carbonate (2)
- calcium phosphate (2)
- carbon dioxide (2)
- carbon dots (2)
- carbon materials (2)
- carbon monoxide (2)
- carbon-dioxide (2)
- carbon-dioxide capture (2)
- catalysts (2)
- cellulose (2)
- chitosan (2)
- clusters (2)
- cod-liver (2)
- colloid (2)
- colloids (2)
- complexes (2)
- controlled polymerization (2)
- degradation (2)
- detector development (2)
- diode laser spectroscopy (2)
- dissociative electron attachment (2)
- dye (2)
- dye removal (2)
- dynamics (2)
- electrocatalysis (2)
- electrochemistry (2)
- electron dynamics (2)
- enzyme (2)
- europium (2)
- fatty-acids (2)
- films (2)
- functionalization (2)
- gas adsorption (2)
- gold nanoparticles (2)
- graphene (2)
- grüne Chemie (2)
- heteroatom-doped carbons (2)
- heteroatoms (2)
- hierarchical porosity (2)
- hierarchische Porosität (2)
- hydrolysis (2)
- hydrothermal (2)
- identification (2)
- in-situ (2)
- intracellular-transport (2)
- ion mobility spectrometry (2)
- ionic conductivity (2)
- ionische Flüssigkeiten (2)
- isomerization (2)
- kontrollierte Polymerisation (2)
- kontrollierte radikalische Polymerisationen (2)
- langevin equation (2)
- lanthanides (2)
- liquid-phase catalysis (2)
- magnetic nanoparticles (2)
- manganese (2)
- mesocrystals (2)
- metal oxides (2)
- methyl orange (2)
- methylene blue (2)
- microcontact printing (2)
- microwave synthesis (2)
- miniemulsion (2)
- mixtures (2)
- molecular dynamics (2)
- molecular switches (2)
- molecules (2)
- molekulare Schalter (2)
- nanolenses (2)
- nonaqueous synthesis (2)
- organic chemistry (2)
- organic synthesis (2)
- organische Synthese (2)
- organosilica (2)
- oxygen reduction reaction (2)
- perovskite (2)
- phase-transitions (2)
- photochemistry (2)
- photoionization (2)
- photoisomerization (2)
- physiological consequences (2)
- plasmonics (2)
- poly(N-isopropyl acrylamide) (2)
- poly(lactic acid) (2)
- polyelectrolytes (2)
- polyesters (2)
- polysoaps (2)
- polysulfobetaine (2)
- polyzwitterions (2)
- porous carbon (2)
- protein (2)
- protein-polymer conjugate (2)
- proteins (2)
- quantum dynamics (2)
- random-walks (2)
- redox chemistry (2)
- reduction (2)
- reference material (2)
- resonance energy-transfer (2)
- ringöffnende Polymerisation (2)
- salt (2)
- salt melt templating (2)
- salts (2)
- sclerotization (2)
- sensitivity (2)
- simulations (2)
- single-particle tracking (2)
- size (2)
- soil (2)
- solar cells (2)
- sorption (2)
- spectroscopy (2)
- structure (2)
- structure elucidation (2)
- sulfur (2)
- supercapacitors (2)
- surfaces (2)
- synthetic biology (2)
- system (2)
- systems (2)
- thermoresponsive Polymere (2)
- thermoresponsive polymer (2)
- thermoresponsive polymers (2)
- transmembrane protein (2)
- upconversion (2)
- vesicle (2)
- vesicles (2)
- visible-light (2)
- water treatment (2)
- wettability (2)
- "Reactive Flux" Ratenkonstanten (1)
- "Spacer"-Gruppe (1)
- (S)-Elatadihydrochalcone (1)
- (S)-Lupinifolin 4´-methyl ether (1)
- 1,2-dithiooxalate (1)
- 11-mercaptoundecanoic acid (1)
- 2-Azaspiro[4.5]deca-1-ones (1)
- 2-Thiodisaccharide (1)
- 2-Thiodisaccharides (1)
- 2D material (1)
- 2D-LC-MS/MS (1)
- 2D-Material (1)
- 3-color fret (1)
- 3-mercaptopropionic acid (1)
- 315 nm (1)
- 473 nm (1)
- 5'-neolignane (1)
- 8 (1)
- 946 nm (1)
- ABC triblock copolymer (1)
- ACC (1)
- ADMET (1)
- AOT bilayer (1)
- ATCUN motif (1)
- Acids (1)
- Actuator (1)
- Additive (1)
- Adsorbatschwingungen (1)
- Adsorptionsaktivität (1)
- Aerogele (1)
- Aerogels (1)
- African medicinal plants (1)
- Afrikanische Heilpflanzen (1)
- AgI (1)
- Aggregation (1)
- Aktivierungsentropie (1)
- Aktuator (1)
- Alkylpyridinium salts (1)
- Alkylpyridinium-Salze (1)
- All-Carbon-Kompositen (1)
- Aluminiumlegierung (1)
- Aluminiumoberfläche (1)
- Amin (1)
- Amine (1)
- Aminosäuren (1)
- Ammonia (1)
- Amphiphile (1)
- Amphiphilic Polymers (1)
- Amphiphilic diblock copolymers (1)
- Amphiphilic polymers (1)
- Amyloid peptide (1)
- Analytische Ultrazentrifugation (1)
- Anisotrope Kolloide (1)
- Anode (1)
- Antikörper-Färbung (1)
- Assemblierung (1)
- Atom Transfer Radical Polymerization (1)
- Aufarbeitung von Fruktose (1)
- Aufkonversion (1)
- Azobenzene (1)
- Azobenzol (1)
- Bariumtitanat (1)
- Benetzung (1)
- Benzoboroxol (1)
- Beschallung (1)
- Beschichtungsanwendung (1)
- Beta-Lactoglobulin (1)
- Betulin (1)
- Biobased Polymers (1)
- Biobasierte Polymere (1)
- Biochromophore (1)
- Bioconjugation (1)
- Biohybrid-Membran (1)
- Bioinspiration (1)
- Biokompatibilität (1)
- Biokonjugate (1)
- Biokonjugation (1)
- Biological activity (1)
- Biomass (1)
- Biomasseverwertung (1)
- Biomaterial (1)
- Biomaterialien (1)
- Biomineralisation (1)
- Biomineralisierung (1)
- Biomodification (1)
- Biophotonik (1)
- Biorefinery (1)
- Biosensoren (1)
- Biosynthesis (1)
- Block Copolymer (1)
- Block-Copolymere (1)
- Block-copolymer (1)
- Blockcopolymervesikel (1)
- Bodengas (1)
- Boronsäure (1)
- Brewsterwinkel-Mikroskopie (1)
- Brownian motion (1)
- C-C Bindungsknüpfung (1)
- C-C bond formation (1)
- C-reactive (1)
- C1N1 (1)
- CN (1)
- CN materials (1)
- CN-Materialien (1)
- CO2 capture (1)
- CO2-Abscheidung (1)
- Caenorhabditis elegans (1)
- Calcium (1)
- Calciumcarbonat (1)
- Carbide (1)
- Carbides (1)
- Carbohydrate (1)
- Carbohydrates (1)
- Carbon (1)
- Carbon materials (1)
- Carbonitrides (1)
- Carbonization (1)
- Catalysis (1)
- Cd-free (1)
- Cer Ammonium Nitrat (CAN) (1)
- Cereals (1)
- Ceric Ammonium Nitrate (CAN) (1)
- Ceroxid (1)
- Chalkogenide (1)
- Characterisation (1)
- Charakterisierung (1)
- Chemical Sensors (1)
- Chemical Synthesis (1)
- Chemie (1)
- Chemische Synthese (1)
- Chiralität <Chemie> (1)
- Chitolectins (1)
- Chitolektine (1)
- Cholesterin (1)
- Chromatographie (1)
- Cis- and trans-form (1)
- Citrazinsäure (1)
- Click Chemistry (1)
- Click chemistry (1)
- Cluster (1)
- Co-Nonsolvency (1)
- Coating Applications (1)
- Cobalt (1)
- Cobalt Nanopartikeln (1)
- Collagen (1)
- Collagenase (1)
- Collision cross-section (1)
- Composites (1)
- Configuration (1)
- Confinement (1)
- Confocal microscopy (1)
- Conformation (1)
- Copolymere (1)
- Corpora allata (1)
- CsPbI3 (1)
- Cu doped InP (1)
- Cu-dotiertes InP (1)
- DBD (1)
- DFT (1)
- DFTB3 (1)
- DNA (1)
- DNA Nanostrukturen (1)
- DNA Schädigung (1)
- DNA damage (1)
- DNA damage response (1)
- DNA nanostructures (1)
- DNA repair (1)
- DNA strand breaks (1)
- DNA-Origami (1)
- DNS (1)
- Debus-Radziszewski polymerization (1)
- Decorin (1)
- Defektchemie (1)
- Defekte (1)
- Degradation (1)
- Deoxyfructosazin (1)
- Derris trifoliata (1)
- Design (1)
- Detektor (1)
- Detektor-Entwicklung (1)
- Detektorentwicklung (1)
- Diamondoide (1)
- Dichtematrixtheorie offener Systeme (1)
- Differential mobility analysis (DMA) (1)
- Differentielle Mobilitätsanalyse (DMA) (1)
- Diffusionsbarriere (1)
- Dihydrobenzofurane (1)
- Dihydroxyaceton (1)
- Dilatations-Viskoelastizität (1)
- Dimensionsstabilität (1)
- Dissoziation (1)
- Dissoziative Elektronenanlagerung (1)
- Disulfide (1)
- Doppelschichtstruktur (1)
- Doppelstrangbruch (1)
- Doppelt hydrophile Blockcopolymere (1)
- Drug Delivery (1)
- Dynamik der Adsorption (1)
- Einkapselung (1)
- Einkristalle (1)
- Einzelatomkatalyse (1)
- Einzelmoleküldetektion (1)
- Einzelstrangbruch (1)
- Eisen (1)
- Eisen-Kohlenstoff-Nanoröhrchen-Katalysatoren (1)
- Electrochemistry (1)
- Electronic materials (1)
- Elektrochemie (1)
- Elektrolytempfindlichkeit (1)
- Elektronenkorrelation (1)
- Elektronentomographie (1)
- Elektrospinnen (1)
- Emulsion Polymerization (1)
- Emulsionen (1)
- Emulsionspolymerisation (1)
- Enegieanwendungen (1)
- Energiespeichermechanismus (1)
- Energieumwandlung (1)
- Energy Applications (1)
- Energy Transfer (1)
- Enzym (1)
- Enzyme (1)
- Enzyme inhibitor (1)
- Equisetum hyemale (1)
- Erneuerbare Ressourcen (1)
- Falten (1)
- Farbstoff (1)
- Faser (1)
- Ferrofluid (1)
- Festkörperstruktur (1)
- Festphasensynthese (1)
- Fettsäure (1)
- Fettsäuren (1)
- FhuA (1)
- Fischer-Tropsch Synthesis (1)
- Fischer-Tropsch-Synthese (1)
- Flavanone (1)
- Fluorchemie (1)
- Fluorescence imaging (1)
- Fluorescent probes (1)
- Fluoreszenz (1)
- Fluorierte Blockcopolymere (1)
- Fluorpolymere (1)
- Flüssig-/flüssig-Grenzflächen (1)
- Flüssigkeitszerstäubung (1)
- Flüssigphasenkatalyse (1)
- Fokker-Planck equations (1)
- Formate (1)
- Formose (1)
- Freistehende Membranen (1)
- Frequenzaufkonversion (1)
- Functionalization (1)
- Fungi (1)
- Funktionalisierung von Katalysatoren (1)
- Fällungsreaktion (1)
- Förster Resonanz Energie Transfer (1)
- Förster-Resonanz-Energie-Transfer (1)
- G quadruplexes (1)
- GIXD (1)
- Gadolinium (1)
- Gas Sorption (1)
- Gaspermeation (1)
- Gelatin (1)
- Gelatine (1)
- Gele (1)
- Gelieren (1)
- Gleichgewicht der Adsorption (1)
- Glucose (1)
- Glukose Oxidation (1)
- Glukoseoxidation (1)
- Glycopeptoid (1)
- Glycosylierung (1)
- Glykochemie (1)
- Glykogele (1)
- Glykokonjugat (1)
- Glykokonjugate (1)
- Glykolipide (1)
- Glykomonomer (1)
- Glykopeptid (1)
- Glykopolymer (1)
- Glykopolymer-Elektrolyt (1)
- Glykopolymere (1)
- Glykosylierung (1)
- Gold nanoparticles (1)
- Gold-Kohlenstoff-Katalysatoren (1)
- Goldnanopartikel (1)
- Graphen (1)
- Green Chemistry (1)
- Grenzfläche Lösung/Tetradecan (1)
- Grenzflächenaktivität (1)
- Grenzflächenchemie (1)
- Group Transfer polymerisation (1)
- HDAC1 (1)
- HER (1)
- HPLC (1)
- Halogenid-Perowskite (1)
- Helicen (1)
- Hepcidin (1)
- Heptazine (1)
- Heteroatom Doping (1)
- Heteroatom-Dotierung (1)
- Heteroatom-Modifikation (1)
- Heteroatom-dotierte Kohlenstoffe (1)
- Heterophase Polymerization (1)
- Heterophasenpolymerisation (1)
- Hofmeister (1)
- Hohlkugeln (1)
- Hollow Spheres (1)
- Holzmodifikation (1)
- Hyalophora cecropia (1)
- Hyaluronic acid (1)
- Hyaluronsäure (1)
- Hybrid material (1)
- Hydroborierung (1)
- Hydrogele (1)
- Hydrogelen (1)
- Hydrogenolyse (1)
- Hydrolyse (1)
- Hydrophobizität (1)
- Hydrothermal Carbonization (1)
- Hydrothermal carbonisation (1)
- Hydrothermalkohle (1)
- Hydrotrope (1)
- Hydroxyapatit (1)
- Hydroxyl (1)
- Hydroxymethylfurfural (1)
- IR excitation (1)
- IR-Anregung (1)
- IR-MALDI (1)
- IRRAS (1)
- ISA (1)
- ITC (1)
- Imidazolium (1)
- In vitro (1)
- InP (1)
- InPZnS (1)
- Infrared matrix-assisted laser desorption ionization (IR-MALDI) (1)
- Ion mobility spectrometry (IMS) (1)
- Ionen (1)
- Ionenmigration (1)
- Ionenmobilitäts-Berechnungen (1)
- Ionenmobilitätspektrometrie (1)
- Ionenmobilitätsspektrometry (IMS) (1)
- Ionic Liquid (1)
- Ionic liquid (1)
- Ionisationspotential (1)
- Ionisierungsenergie (1)
- Isoflavonoide (1)
- Isothermal Titration Calorimetry (1)
- Isotherme Titrationskalorimetrie (1)
- Isothermen (1)
- Isotop (1)
- Isotope ratio (1)
- JH-III-specific carrier protein (1)
- Janus (1)
- Janus droplets (1)
- Juvenile hormone analogue (1)
- Karbonisierung (1)
- Karbonnitrid Ionothermalsynthese (1)
- Katalysator (1)
- Kathode (1)
- Keramik (1)
- Kern-Schale Aufkonvertierende Nanopartikel (1)
- Kerndynamik (1)
- Kinetically controlled nanocrystal growth (1)
- Kinetics (1)
- Kinetik (1)
- Klassiche Simulationen (1)
- Kleinwinkelstreuung (1)
- Klick-Chemie (1)
- Klickchemie (1)
- Koaleszenz (1)
- Kohlenmaterialien (1)
- Kohlenmonoxid (1)
- Kohlenstoff-Nanopunkte (1)
- Kohlenstoff-Punkte (1)
- Kohlenstoffe auf Biomasse-Basis (1)
- Kohlenstoffmaterial (1)
- Kohlenstoffnitrid (1)
- Kohlenstoffnitrid (CN) (1)
- Kohlenstoffträger (1)
- Kol (1)
- Kollagen (1)
- Kollagenase (1)
- Komplexe (1)
- Kompositmaterial (1)
- Konformationsänderungen (1)
- Koordinationskomplexe (1)
- Korrelationsfunktion (1)
- Kraft lignin hydrogenolysis (1)
- Kraftlignin (1)
- Kraftsensoren (1)
- Kristallisation von Dünnschichten (1)
- Kryo-Elektronenmikroskopie (1)
- LCPs (1)
- LCST (1)
- LCST and UCST (1)
- LCST und UCST (1)
- Lactams (1)
- Ladung Transport (1)
- Langmuir Monoschicht (1)
- Langmuir monolayers (1)
- Lanthanide (1)
- Lanthanides (1)
- Lanthano (1)
- Laser (1)
- Laser-Carbonization (1)
- Laserinduzierte Inkandeszenz (LII) (1)
- Laserinduzierte Plasmaspektroskopie (LIBS) (1)
- Laserkarbonisierung (1)
- Laserpulse (1)
- Laserpulskontrolle (1)
- Layer-by-Layer Glykopolymerbeschichtung (1)
- Legierungen (1)
- Lektin (1)
- Leptinotarsa decemlineata (1)
- Levoglucosenol (1)
- Li-Ionen-Akkus (1)
- Li-Ionen-Kondensator (1)
- Li-S batteries (1)
- Li-S-Batterien (1)
- Li-ion batteries (1)
- Li-ion capacitor (1)
- LiFePO4 (1)
- Ligation (1)
- Lignane (1)
- Linienspannung (1)
- Liquid dispersion (1)
- Lithiophilizität (1)
- Lithium-Ionen-Kondensatoren (1)
- Locust (1)
- Locusta migratoria (1)
- Luminescence (1)
- Lupinifolin (1)
- Lävulinsäure (1)
- Löschung (1)
- Lösungsmittel (1)
- Lösungsmittel-thermisches Tempern (1)
- Lösungsmitteleffekte (1)
- Lösungsprozess (1)
- MALDI-TOF mass spectrometry (1)
- MS (1)
- Magnetic (1)
- Magnetisch (1)
- Magnetit Nanopartikel (1)
- Makrozyklen (1)
- Marangoni flow (1)
- Marangoni-Fluss (1)
- Mass Spectrometry (1)
- Materialwissenschaft (1)
- Matrix-unterstützte Laser-Desorption/Ionisation (IR-MALDI) (1)
- Membranforschung bzw. Membranwissenschaften (1)
- Mesoporosity (1)
- Mesoporosität (1)
- Mesoporöse Materialien (1)
- Metal Chalcogenides (1)
- Metal-organic framework (1)
- Metall (1)
- Metall-organische Gerüste (1)
- Metallcarbide (1)
- Metallchalkogenide (1)
- Metallnitrid-Kohlenstoff Komposite (1)
- Metallorganischen (1)
- Metalloxide (1)
- Methacrylat (1)
- Micellar polymers (1)
- Micr (1)
- Microalgae (1)
- Mikroalgen (1)
- Mikroemulsion (1)
- Mikroemulsionen (1)
- Mikrofluidik (1)
- Mikrogel-Array (1)
- Mikrogele (1)
- Mikrogelketten (1)
- Mikrogelstränge (1)
- Mikrokontaktdruck (1)
- Mikrotomographie (1)
- Mikrowellensynthese (1)
- Miniemulsion (1)
- Mizellbildung (1)
- Modellierung (1)
- Modified mycotoxins (1)
- Modifizierung von Polymeren (1)
- Molecular dynamics (1)
- Monolayers (1)
- Monolith (1)
- Morphologie von Kapseln (1)
- Multi-Wellenlängen (1)
- Multi-method (1)
- Multiblock Copolymer (1)
- Multiblock copolymer (1)
- Muschelnachahmend (1)
- Mycotoxins (1)
- N-Alkylglycin (1)
- N-acetyldopamine (1)
- N-alkyl-glycine (1)
- N-carboxyanhydrid (1)
- N-carboxyanhydride (1)
- N-doped carbon (1)
- N-dotierter Kohlenstoff (1)
- N2 fixation (1)
- N2-Fixierung (1)
- NHC (1)
- NIR spectroscopy (1)
- NMR (1)
- NMR structure (1)
- Nachhaltigkeit (1)
- Nanofluidik (1)
- Nanokapseln (1)
- Nanokomposit (1)
- Nanokomposite (1)
- Nanolinsen (1)
- Nanoparticle (1)
- Nanopartikeln (1)
- Nanopartikeln-Anordnung (1)
- Nanoplastik (1)
- Nanoplättchen (1)
- Nanospindeln (1)
- Nanostructure (1)
- Nanostruktur (1)
- Nanotechnology (1)
- Nanotriangles (1)
- Natrium-Ionen-Akkumulator (1)
- Natrium-Ionen-Batterie (1)
- Naturstoff (1)
- Negative Poisson’s ratio (1)
- Negatives Poisson-Verhältnis (1)
- Neodym-YAG-Laser (1)
- Neutronen Diffraktion (1)
- Neutronen Reflektometrie (1)
- NiTi (1)
- Nichtlineare Spektroskopie (1)
- Nichtwässrige Synthese (1)
- Nickel-Kohlenstoff-Katalysatoren (1)
- Nitrogen Physisorption (1)
- Nukleation (1)
- Nukleierung (1)
- O-methyltransferase (1)
- OER (1)
- OLED (1)
- ORR (1)
- OTDR (1)
- Oberflächen (1)
- Oberflächenkräfte (1)
- Oberflächenmodifizierung (1)
- Oberflächenpotential (1)
- Oberflächentopografie (1)
- Oberfächen (1)
- Olefin Metathese (1)
- Olefin metathesis (1)
- Oligomere (1)
- Oligosaccharides (1)
- On-demand Freisetzung (1)
- On-demand release (1)
- On.Line Monitoring (1)
- Open Source (1)
- Optimale Kontrolltheorie (1)
- Optode (1)
- Organic photovoltaic Cell (1)
- Organische Photovoltaikzelle (1)
- Organo-Silikate (1)
- Organogel (1)
- Organosilica (1)
- Orthoptera (1)
- Oscillating Bubble (1)
- Oxalat-Fällung (1)
- Oxidkeramik (1)
- Oxo-Kohlenstoff (1)
- PAH (1)
- PARAFAC (1)
- PEG brushes (1)
- PEG-Funktionalisierung (1)
- PEI coating (1)
- PLA (1)
- PLS regression (1)
- PLSR (1)
- POF; Reliabilität; Abbau; Chemilumineszenz (1)
- POF; reliability; degradation; chemiluminescence (1)
- PZT (1)
- Palladium (1)
- Patchy Partikel (1)
- Peptid (1)
- Peptid-Polymer-Konjugate (1)
- Peptiden (1)
- Perovskite (1)
- Perowskit (1)
- Perowskit Solarzellen (1)
- Perowskit Vorläuferstadien (1)
- Perowskite (1)
- Perylen (1)
- Pesticides (1)
- Phase transitions (1)
- Phasenübergang (1)
- Phasenübergänge (1)
- Phospholipid (1)
- Photochemische Reaktionen (1)
- Photodesorption (1)
- Photoelektronenspektroskopie (1)
- Photoinitiierte Polymerisationen (1)
- Photon density waves (1)
- Photonendichtewellen (1)
- Photopolymer (1)
- Photopolymerization (1)
- Photopolymers (1)
- Physical Crosslinking (1)
- Physikalische Vernetzung (1)
- Phytopathogens (1)
- Pickering Emulsion (1)
- Pickering emulsions (1)
- Podanthus mitiqui (1)
- Poly(2-oxazoline) (1)
- Poly(N-Isopropylacrylamid) (1)
- Poly(N-Isopropylmethacrylamid) (1)
- Poly(N-Vinylisobutyramid) (1)
- Poly(ionische Flüssigkeit) (1)
- Poly(lactic acid) (1)
- Poly(ε-caprolacton) (1)
- Polyampholytes (1)
- Polyeste r (1)
- Polyester (1)
- Polyglycin (1)
- Polykondensation (1)
- Polylactid (1)
- Polymer Modification (1)
- Polymer physics (1)
- Polymerizable surfactant (1)
- Polymerphysik (1)
- Polymersynthese (1)
- Polymertenside (1)
- Polymilchsäure (1)
- Polyolefin (1)
- Polypeptoide (1)
- Polysulfobetaine (1)
- Poröse Materialien (1)
- Poröser Kohlenstoff (1)
- Poröser Stoff (1)
- Porösität (1)
- Post-Modifikationen (1)
- Precipitation (1)
- Protein Microcapsules (1)
- Protein-NMR-Spektroskopie (1)
- Protein-Polymer Konjugaten (1)
- Protein-Polymer-Konjugat (1)
- Proteinadsorption (1)
- Proteincharakterisierung (1)
- Proteinmikrokapseln (1)
- QD device (1)
- QD stability (1)
- QD-Gerät (1)
- QD-Stabilität (1)
- QDs (1)
- QM/MM Molekulardynamik (1)
- QM/MM stochastic dynamics (1)
- Quadratsäure (1)
- Quantenchemie (1)
- Quantendynamik (1)
- Quantendynamische Simulationen (1)
- Quantum Dot (1)
- Quantum Dots (1)
- Quantum dynamics (1)
- Quantumdots (1)
- Quartz Crystal (1)
- Química de Coloides (1)
- RAFT polymerization (1)
- RAFT, Polymerisation (1)
- RAFT-Polymerization (1)
- RAFT/MADIX Polymerisation (1)
- RAFT/MADIX polymerization (1)
- REMPI (1)
- ROMP (1)
- ROP (1)
- RP-HPLC (1)
- RUNX2 (1)
- Radikalreaktionen (1)
- Radiosensibilisator (1)
- Reaktion (1)
- Reaktionsmechanismen (1)
- Reaktionsmechanismus (1)
- Redoxchemie (1)
- Renewable Resources (1)
- Rerenzmaterial (1)
- Resonante Energie Transfer (1)
- Resonanz-Raman-Spektroskopie (1)
- Rheologie (1)
- Ringöffnungspolymerisation (1)
- Rod-like Polymers (1)
- Röntgenbeugung (1)
- Röntgenstrahlung (1)
- SEC-MALS (1)
- SEM (1)
- SERS enhancement factor (1)
- SLS (1)
- STM (1)
- Saccharide Recognition (1)
- Salze (1)
- Salzschmelze (1)
- Sauerstoff (1)
- Sauerstoff Reduktion (1)
- Sauerstoff-Reduktionsreaktion (1)
- Schaum (1)
- Schaumfilme (1)
- Schmelz (1)
- Schwefel (1)
- Schwefelwirt (1)
- Schwingungsanregung (1)
- Schwingungsaufgelöste UV/VIS-Spektroskopie (1)
- Schwingungsspektroskopie (1)
- Seedpods (1)
- Sekundärstruktur (1)
- Selbstassemblierung (1)
- Selbstheilende Beschichtungen (1)
- Serum (1)
- Shadowgraphie (1)
- Shadowgraphy (1)
- Shape-memory (1)
- Silbernanopartikel (1)
- Silicate (1)
- Siliciumdioxid (1)
- Silika (1)
- Silika Partikel (1)
- Simulation (1)
- Soft-Templaten (1)
- Solid phase synthesis (1)
- Solution phase synthesis (1)
- Solvothermalsynthese (1)
- Sonication (1)
- Spannungskonzentrationen (1)
- Spectroscopy (1)
- Spermidin (1)
- Spezies (1)
- Sprengstoffe (1)
- Spritzgießen (1)
- Stability of LB Films (1)
- Stabilität von Emulsionen (1)
- Stabilität von Schäumen (1)
- Stereocomplex (1)
- Stereokomplex (1)
- Stereokomplexierung (1)
- Stickstoff Physisorption (1)
- Stickstoffdotiert (1)
- Stickstoff‑ und Kohlenstoffhaltige Materialien (1)
- Stoßquerschnitt (1)
- Stress concentration (1)
- Structure elucidation (1)
- Strukturaufklärung (1)
- Strukturbildung (1)
- Strömungschemie (1)
- Substrat (1)
- Superkondensator (1)
- Superkondensatoren (1)
- Supramolecular Interactions (1)
- Supramolekular (1)
- Supramolekularen Wechselwirkungen (1)
- Surface Hopping Dynamik (1)
- Surfactant (1)
- Surfactants (1)
- Sustainability (1)
- Syngas Hydrogenation (1)
- Syngashydrierung (1)
- Synthesemethoden (1)
- Synthesis and processing (1)
- Synthetic methods (1)
- Synthetische Biologie (1)
- Tandemmassenspektrometrie (1)
- Teilchenbildung (1)
- Templat (1)
- Templatierung (1)
- Templating (1)
- Tensid (1)
- Tephrosia elata (1)
- Thermodynamische Eigenschaft (1)
- Thermoplastic elastomer (1)
- Thiazol-Salze (1)
- Thiole (1)
- TiO2 nanoparticles (1)
- Time-resolved Immunoassay (1)
- Transient (1)
- Transitionmetals (1)
- Triazin (1)
- Triblock Copolymers (1)
- Triblock-Copolymere (1)
- Trichloracetimidate (1)
- Trichloroacetimidates (1)
- Tropfen (1)
- Tropfenoszillationen (1)
- Tropfenprofil-Analysen-Tensiometrie (1)
- UV/VIS (1)
- UVR (1)
- Ultradünne Filme (1)
- Umweltreaktion (1)
- Upgrade of Fructose (1)
- Uranyl (1)
- Valerolacton (1)
- Verbindungen auf Eisenbasis (1)
- Verdunstung (1)
- Vernetzung (1)
- Vesikel Forschung/Vesikel Studien (1)
- WAXS (1)
- Wasser auf Aluminiumoxid (1)
- Wasser/Luft Grenzflächen (1)
- Wasser/Öl-Grenzfläche (1)
- Wassergehalt (1)
- Wasseroberfläche (1)
- Wasserspaltung (1)
- Weitwinkelröntgenstreuung (1)
- Winterschachtelhalm (1)
- Wirkung des Ionenstärken (1)
- Wirkung des pH-Werten (1)
- Wärmetransformationsanwendungen (1)
- X-ray (1)
- X-ray diffraction (1)
- X-ray structure (1)
- Zeitabhängige Dichtefunktionaltheorie (1)
- Zeitaufgelöste Lumineszenz (1)
- Zeitaufgelöster Immunoassay (1)
- Zellulose (1)
- Zinc (1)
- Zuckererkennung (1)
- [4+2] cycloaddition (1)
- [N]phenylene dyads (1)
- [N]phenylenes (1)
- abbaubares Polymer (1)
- absorbtion fine-structure (1)
- acceptors (1)
- acid (1)
- acids (1)
- acinar-cells (1)
- acoustically levitated droplets (1)
- acrylic acid esters (1)
- actinide, organic ligand, sorption, cementitious material, concrete, luminescence (1)
- activated carbon (1)
- activated urethane (1)
- activated urethane derivatives (1)
- activation entropy (1)
- adamantane (1)
- additive Fertigung (1)
- additive manufacturing (1)
- additives (1)
- adduct formation (1)
- adenoassociated virus (1)
- adhesive (1)
- adsorbate vibrations (1)
- aggregation (1)
- air-water-interface (1)
- aktiviertes Urethan (1)
- akustisch schwebende Tropfen (1)
- alignment (1)
- alkynol cycloisomerization (1)
- all-carbon composites (1)
- alumina (1)
- aluminum alloy (1)
- amine (1)
- amino acids (1)
- ammonia (1)
- amorphes Calciumcarbonat (1)
- amorphous carbon (1)
- amorphous polymers (1)
- amphiphile Blockcopolymere (1)
- amphiphilic block copolymer (1)
- amphiphilic block copolymers (1)
- analytical ultracentrifugation (1)
- anchor peptides (1)
- anionic polymerizations (1)
- anisotropic colloids (1)
- anisotropic microgels (1)
- anode (1)
- anti-fouling (1)
- anti-fouling materials (1)
- antibodies (1)
- antibody staining (1)
- antimalarial activity (1)
- aptamers (1)
- aqueous dispersion (1)
- aqueous systems (1)
- arenediazonium salts (1)
- arsenious acid (1)
- artificial cells (1)
- artificial muscles (1)
- arylboronic acids (1)
- aryldiazonium salts (1)
- aspect-ratio (1)
- associating polymers (1)
- assoziative Photodesorption (1)
- asymmetric (1)
- asymmetrisch (1)
- atomic force microscopy (1)
- atropisomerism (1)
- attachment (1)
- augmented-wave method (1)
- auxiliary control (1)
- beer (1)
- begrenzte Polymerisation (1)
- behavior (1)
- benzoboroxole (1)
- beta-lactoglobulin (1)
- betaine (1)
- bilayer system (1)
- bio-modification (1)
- bioactive (1)
- bioaktiv (1)
- bioanalysis (1)
- biochromophores (1)
- biocompatibility (1)
- bioconjugate (1)
- biohybrid membrane materials (1)
- bioinspiration (1)
- biological membranes (1)
- biologische Membranen (1)
- biomass valorization (1)
- biomass-derived carbons (1)
- biomimetics and semiconducting polymers (1)
- biophotonics (1)
- biopolymers (1)
- biorefineries (1)
- biorelevant (1)
- biosensors (1)
- bladder-cancer (1)
- bleifreie Perowskit-Solarzellen (1)
- block copolymer vesicles (1)
- block-copolymer (1)
- block-copolymers (1)
- blockcopolymer (1)
- blockcopolymere (1)
- bone tissue engineering (1)
- brownian-motion (1)
- brushite (1)
- bubble-bubble interaction (1)
- building-blocks (1)
- cadmium-free (1)
- calcium (1)
- calcium influx (1)
- calcium phosphate hybrid material (1)
- capacity (1)
- capillary pressure tensiometry (1)
- capsule morphology (1)
- carbohydrate derivatives (1)
- carbohydrate esters (1)
- carbohydrate-based oxepines (1)
- carbohydrate‐ based (1)
- carbon material (1)
- carbon nanodots (1)
- carbon supports (1)
- carbonyl-compounds (1)
- carbothermal (1)
- carbothermisch (1)
- carboxyanhydrides (1)
- carcinogen exposure (1)
- catalyst (1)
- catalyst functionalization (1)
- catalytic application (1)
- catalyzed cross metathesis (1)
- catalyzed redox isomerization (1)
- cathode (1)
- cationic surfactants (1)
- cell-death (1)
- cement admixtures (1)
- cement hydration (1)
- cementitious material (1)
- ceramics (1)
- cerium oxide (1)
- chain azobenzene polymers (1)
- chalcogenide (1)
- charge transport (1)
- chelates (1)
- chemical-synthesis (1)
- chemische Sensoren (1)
- chemistry (1)
- chemoradiation therapy (1)
- chiral recognition (1)
- chiral separation (1)
- chiral switches (1)
- chirale Erkennung (1)
- chirale Schalter (1)
- chirale Trennung (1)
- chirality (1)
- chromatography (1)
- chromoionophore (1)
- citrazinic acid (1)
- citric acid (1)
- classical dynamics (1)
- click chemistry (1)
- co-nonsolvency (1)
- coalescence (1)
- coating (1)
- coatings (1)
- cobalt (1)
- cobalt nanoparticles (1)
- cockroach salivary-glands (1)
- colloid chemistry (1)
- colloidal quantum dot (1)
- coloring agents (1)
- complex (1)
- complex emulsion (1)
- composite materials (1)
- concrete (1)
- configuration (1)
- confined polymerization (1)
- confinement (1)
- confocal raman microscopy (1)
- conformation (1)
- conformational-changes (1)
- construction (1)
- continuous-flow (1)
- contrast agents (1)
- controlled-release (1)
- coordination complexes (1)
- coordination polymer (1)
- copper (1)
- copper complex (1)
- copper(II) (1)
- copper(II) halide salts (1)
- copper-bearing minerals (1)
- core-shell UCNP (1)
- correlation function (1)
- covalent frameworks (1)
- covalent organic framework (1)
- critical solution temperature (1)
- cross-linking (1)
- crosslinking (1)
- crown compounds (1)
- cryo-electron microscopy (1)
- cryogel (1)
- crystals (1)
- cytoplasm (1)
- cytosine methylation (1)
- damage (1)
- data-storage (1)
- de-novo synthesis (1)
- decay dynamics (1)
- deep eutectic solvents (1)
- defect chemistry (1)
- degradable polymer (1)
- delivery (1)
- density functional theory (1)
- deoxyfructosazine (1)
- design of experiments (1)
- diamondoid (1)
- diels-alder reaction (1)
- diffusion barrier (1)
- dihydrobenzofurans (1)
- dihydroxyacetone (1)
- diimine-complexes (1)
- dilute aqueous-solutions (1)
- dimensional stability (1)
- dimerization of 4-nitrothiophenol (1)
- dip-coating (1)
- discotics (1)
- disordered media (1)
- disulfide (1)
- dna coiling (1)
- double hydrophilic block copolymers (1)
- double strand break (1)
- drop (1)
- drop and bubble coalescence (1)
- drop profile analysis tensiometry (1)
- drop-drop interaction (1)
- drug delivery (1)
- drug delivery system (1)
- drugs (1)
- dye adsorption (1)
- dye mixture (1)
- dyes (1)
- dynamic HPLC (1)
- dynamic NMR (1)
- dynamic interfacial tensions (1)
- dünne Filme (1)
- efficient (1)
- electrolyte sensitivity (1)
- electrolytes (1)
- electron correlation (1)
- electron paramagnetic resonance (1)
- electron tomography (1)
- electron-spin resonance (1)
- electron-transfer (1)
- electrospinning (1)
- elektroaktive Polymere (1)
- elektronische Materialien (1)
- elemental composition (1)
- emperical potential structure refinement (1)
- emulsion (1)
- emulsion polymerization (1)
- emulsions (1)
- enantioselectivity (1)
- encapsulation (1)
- end-groups (1)
- endosomal escape (1)
- endothelization (1)
- energy conversion (1)
- energy density (1)
- energy storage mechanism (1)
- ensamblaje de nanopartículas (1)
- enthalpy-entropy compensation (EEC) (1)
- environmental response (1)
- enzymatic degradation (1)
- enzymatic esterification (1)
- enzyme reactions (1)
- epsilon-caprolactone (1)
- erosion (1)
- escence correlation spectroscopy (1)
- escherichia-coli (1)
- estructuras templadas blandas (1)
- ether methacrylates (1)
- evaporation (1)
- exchange (1)
- excision-repair (1)
- excitation (1)
- excluded volume (1)
- explosives (1)
- exposure (1)
- extracellular matrix proteins (1)
- extraction (1)
- ferroelectricity (1)
- ferrofluid (1)
- fiber (1)
- fiber Bragg gratings (1)
- fiber actuators (1)
- fiber etching (1)
- fiber-optical sensors (1)
- fine-structure (1)
- fish (1)
- flexibility (1)
- flight search patterns (1)
- flow chemistry (1)
- fluctuation-dissipation theorem (1)
- fluorescence (1)
- fluorescence immunoassay (1)
- fluorescence lifetime (1)
- fluorescence photobleaching recovery (1)
- fluorescence quenching (1)
- fluorescent dyemonomers (1)
- fluorescent dyes (1)
- fluorescent probes (1)
- fluorinated Blockcopolymers (1)
- fluorinated polymers (1)
- fluorocarbon polymers (1)
- fluoroimmunoassay (1)
- fluorous chemistry (1)
- flux de Marangoni (1)
- foam (1)
- foam analysis (1)
- foam films (1)
- folding kinetics (1)
- force sensors (1)
- formose (1)
- fourier-transform spectroscopy (1)
- fractional dynamics (1)
- fractional dynamics approach (1)
- frameworks (1)
- fronts (1)
- fulgides (1)
- functional (1)
- functionalized (1)
- funktional (1)
- funktionalisiert (1)
- g-quadruplex (1)
- gadolinium (1)
- gas (1)
- gas permeation (1)
- gas sorption (1)
- gas-phase (1)
- gases (1)
- gaussian processes (1)
- gelatin (1)
- gelation (1)
- gels (1)
- gene-expression (1)
- gene-regulation kinetics (1)
- genomic dna methylation (1)
- gepulster DPSS Laser (1)
- germacrane sesquiterpene lactone (1)
- glass-transition temperature (1)
- glyco chemistry (1)
- glycoconjugate (1)
- glycoconjugates (1)
- glycogels (1)
- glycolipids (1)
- glycomonomer (1)
- glycopeptide (1)
- glycopeptoid (1)
- glycopolymer (1)
- glycopolymer electrolytes (1)
- glycopolymers (1)
- gold nanoparticle assembly (1)
- gold-carbon catalysts (1)
- gouttes (1)
- gouttes sessiles (1)
- grafting-from (1)
- graphite (1)
- green (1)
- green polymers (1)
- halide perovskite (1)
- halide-ions (1)
- heat transformation application (1)
- heiße Elektronen (1)
- hela-cells (1)
- helicene (1)
- hemocompatibility (1)
- hepcidin (1)
- hepcidin-25 (1)
- heptazine (1)
- heteroatom (1)
- heteroatom modification (1)
- heteroatom-dotierte Kohlenstoffe (1)
- heterocycles (1)
- hierarchical pore structure (1)
- hierarchische Porenstruktur (1)
- high energy density (1)
- high quantum yield (1)
- hohe Energiedichte (1)
- hohe Quantenausbeute (1)
- holmium(III) (1)
- holographic diffraction gratings (1)
- human-cells (1)
- hybrid nanostructures (1)
- hybrid perovskites (1)
- hybride Nanostrukturen (1)
- hydraulic oils (1)
- hydrogen (1)
- hydrogen storage (1)
- hydrogenation (1)
- hydrophil (1)
- hydrophilic (1)
- hydrophilic polymers (1)
- hydrophobe Moleküle (1)
- hydrophobic molecules (1)
- hydrophobicity (1)
- hydrothermal carbon (1)
- hydrothermal carbonization (1)
- hydrothermale Carbonisierung (1)
- hydrotropes (1)
- hydroxy (1)
- hydroxyapatite (1)
- hydroxyl-functional poly(2-vinyl pyridine) (1)
- hydroyxapatite (1)
- iPLS regression (1)
- imidazolium (1)
- imidazolium salts (1)
- immunoassay (1)
- implementation (1)
- in-operando SAXS (1)
- in-vitro (1)
- indicators (1)
- induced malignant-transformation (1)
- inhomogeneous-media (1)
- initio molecular-dynamics (1)
- injection molding (1)
- inner surface (1)
- inorganic chemistry (1)
- inorganic perovskites (1)
- intercomparison (1)
- interfaces (1)
- interfacial dynamics (1)
- interfacial forces (1)
- intermittent chaotic systems (1)
- internal membrane-membrane adhesion (1)
- interne Membran-Membran Adhäsion (1)
- intracellular na+ (1)
- intramolecular charge-transfer (1)
- intrinsic microporosity (1)
- inverse Opale (1)
- inverse opal (1)
- ion migration (1)
- ion mobility calculations (1)
- ion optodes (1)
- ion selective electrode (1)
- ionenselektive Elektrode (1)
- ionic defects (1)
- ionic polymers (1)
- ionic strength effect (1)
- ionische Flüssigkeit (1)
- ionischen Polymere (1)
- ionisierende Strahlung (1)
- ionization energy (1)
- ionization potential (1)
- ionizing radiation (1)
- ionogel (1)
- ionogels (1)
- ionophore (1)
- ionothermale Synthese (1)
- ions (1)
- iron (1)
- iron-based compounds (1)
- iron-carbon nanotube catalysts (1)
- isoflavonoids (1)
- isotope (1)
- isotope ratios (1)
- joziknipholones (1)
- juvenile hormone biosynthesis (1)
- kinetics (1)
- klassische Diffusionstheorie (1)
- klebend (1)
- kolloidaler Quantenpunkt (1)
- kolloidchemie (1)
- komplexe Emulsion (1)
- kontrollierte radikalische Polymerisation (1)
- kovalente Rahmenbedingungen (1)
- künstliche Zellen (1)
- labels (1)
- lanthanide (1)
- lanthanide luminescence (1)
- laser induced (1)
- laser pulse control (1)
- laser pulses (1)
- laser-induced breakdown spectroscopy (1)
- laser-induced breakdown spectroscopy (LIBS) (1)
- laser-induced incandescence (LII) (1)
- lasso (1)
- layer-by-layer (1)
- layer-by-layer glycopolymer coating (1)
- layered compounds (1)
- lead-free perovskites (1)
- lectin (1)
- levoglucosenol (1)
- levulinic acid (1)
- levy flights (1)
- liegende Tropfen (1)
- lifetime microscopy (1)
- ligand exchange (1)
- light (1)
- light-programmable viscosity (1)
- lignin (1)
- lignocellulosic biomass (1)
- lipids (1)
- liquid crystals (1)
- liquid-crystal precursors (1)
- lithiophilicity (1)
- lithium ion capacitors (1)
- lower (1)
- lubricant (1)
- lubricants (1)
- lösungsmittelfreie Synthese (1)
- macrocycles (1)
- magnetic manipulation (1)
- magnetic-properties (1)
- magnetische Nanopartikel (1)
- magnetite (1)
- magnetite nanoparticles (1)
- magnetosome (1)
- magnetotactic bacteria (1)
- magnetotaktische Bakterien (1)
- marine oils (1)
- mass-spectrometry (1)
- material science (1)
- mechanical properties (1)
- mechanical strength (1)
- mechanical-properties (1)
- mehrschichtige Verbindungen (1)
- melting (1)
- membrane (1)
- membrane science (1)
- membranes (1)
- mercaptocarboxylic acids (1)
- mesenchymal stem cells (1)
- mesoporous (1)
- mesoporous materials (1)
- mesoporös (1)
- mesostructure (1)
- metabolites (1)
- metal (1)
- metal alloys (1)
- metal carbides (1)
- metal complex (1)
- metal nanoparticles (1)
- metal nitride carbon composites (1)
- metal organic framework (1)
- metal peptide (1)
- metal species (1)
- metal-organic framework (1)
- metallic nanolattices (1)
- metallopeptide (1)
- metalloprotein (1)
- metallorganischen Gerüstverbindungen (1)
- methacrylate (1)
- methylmercury (1)
- methyltransferases dnmt3a (1)
- micellization (1)
- micro (1)
- microbalance (1)
- microemulsion (1)
- microemulsiones (1)
- microemulsions (1)
- microfluidics (1)
- microgel array (1)
- microgel chains (1)
- microgel strands (1)
- microgels (1)
- microporous organic polymers (1)
- microporous polymers (1)
- microscopy (1)
- microstructure (1)
- microtomography (1)
- mikroporöse Polymere (1)
- mikrowellengestützte Synthese (1)
- mineralization beneath (1)
- minerals (1)
- mixed-matrix membranes (1)
- modelling (1)
- modulation (1)
- modulus (1)
- moisture content (1)
- molecular oxygen (1)
- molecular rods (1)
- molecular thermometers (1)
- molecular-dynamics (1)
- molecular-mechanisms (1)
- molecular-reorientation (1)
- molecular-structure (1)
- monolayer (1)
- monolith (1)
- monomer (1)
- monomers (1)
- morphological transformation (1)
- morphology (1)
- motif périodique (1)
- multi-compartmentalised vesicles (1)
- multi-kompartmentalisierte Vesikel (1)
- multicompartment micelle (1)
- multiresponsiv (1)
- multiresponsive (1)
- multishell (1)
- multiwavelength (1)
- mussel-mimicking (1)
- n-heterocyclic carbenes (1)
- n-isopropylacrylamide (1)
- nachhaltige Energiespeichermaterialien (1)
- nachwachsende Rohstoffe (1)
- nano (1)
- nanocapsules (1)
- nanocarriers (1)
- nanoclusters (1)
- nanocomposite (1)
- nanoestructuras (1)
- nanoestructuras híbridas (1)
- nanoflowers (1)
- nanofluidics (1)
- nanoparticle assembly (1)
- nanoparticle dimers (1)
- nanopartículas (1)
- nanoplastic (1)
- nanoporous carbon particles (1)
- nanoporöser Kohlenstoffpartikel (1)
- nanoprisms (1)
- nanorods (1)
- nanospindles (1)
- nanostructure fabrication (1)
- nanostructured composite (1)
- nanotechnology (1)
- nanotriangles (1)
- nanowires (1)
- naphthalenes (1)
- naphthalenophanes (1)
- naphthalimide (1)
- natural products (1)
- negative ions (1)
- neolignans (1)
- neurodegenerative diseases (1)
- neurotoxicity (1)
- neutron diffraction (1)
- neutron reflectometry (1)
- nhc (1)
- nichtlineare Mechanik (1)
- nichtwässrige Synthese (1)
- nickel (1)
- nickel(II) (1)
- nickel-carbon catalysts (1)
- niederenergetische Elektronen (1)
- nitrogen containing carbonaceous materials (1)
- nitrogen doped carbons (1)
- nitrogen-doped (1)
- non-linear mechanics (1)
- nonlinear optics (1)
- nutrients (1)
- o bond formation (1)
- o-quinone isomerase (1)
- obere kritische Lösetemperatur (1)
- oberflächenverstärkte Raman-Streuung (1)
- off-specular scattering (1)
- oil (1)
- olefin-metathesis (1)
- oligo(ethylene glycol) (1)
- oligo(ethylene glycol) methacrylate (1)
- oligo(ethyleneglycol) (1)
- oligomeric polydimethylsiloxane (1)
- oligomers (1)
- opal (1)
- open source (1)
- open system density matrix theory (1)
- optical oil sensor (1)
- optical sensing (1)
- optical-properties (1)
- optimal control theory (1)
- optode (1)
- organic dye pigments (1)
- organic ligand (1)
- organic-inorganic c (1)
- organic–inorganic hybrid (1)
- organische Chemie (1)
- organogel (1)
- organometallics (1)
- orthophosphates (1)
- oscillating bubble (1)
- oxalic precipitation (1)
- oxaloacetic acid (1)
- oxidation (1)
- oxidative stress (1)
- oxides (1)
- oxocarbon (1)
- oxygen (1)
- pH effect (1)
- palladium (1)
- palladium catalyst (1)
- paper (1)
- paramagnetic (1)
- paramagnetic-resonance (1)
- paramagnetisch (1)
- particle formation (1)
- patchy particles (1)
- peptide (1)
- peptide-polymer conjugate (1)
- perfluorocarbon emulsion (1)
- periodic pattern (1)
- periodisches Muster (1)
- periplaneta-americana (1)
- perovskite precursors (1)
- perylene (1)
- phase separation (1)
- phase transfer (1)
- phase transition (1)
- phenanthrenes (1)
- phosgene-free synthesis (1)
- photo ionization (1)
- photo-dehydro-Diels-Alder reaction (1)
- photochemical reactions (1)
- photochemical synthesis (1)
- photoelectron spectroscopy (1)
- photoinduced electron transfer (1)
- photoinduced nonadiabatic dynamics (1)
- photon density wave spectroscopy (1)
- photon-counting statistics (1)
- photonic wires (1)
- photooxidation (1)
- photooxygenation (1)
- photophysics (1)
- photoredox catalysis (1)
- photovoltaic materials (1)
- photovoltaische Materialien (1)
- physical (1)
- physikalisch (1)
- physiolgischer pH (1)
- physiological pH (1)
- pickering emulsion (1)
- plasmonic chemistry (1)
- plasmonische Chemie (1)
- platform chemicals (1)
- poly(2-oxazoline)s (1)
- poly(ADP-ribose) polymerase-1 (1)
- poly(N-isopropyl methacrylamide) (1)
- poly(N-isopropylacrylamide) (1)
- poly(N-vinyl isobutyramide) (1)
- poly(N-vinylcaprolactam) (1)
- poly(dimethylsiloxane) (1)
- poly(ester amide)s (1)
- poly(ethyleneimine) (1)
- poly(ionic liquid) (1)
- poly(ionic liquid)s (1)
- poly(ionische Flüssigkeiten) (1)
- poly(ε-caprolactone) (1)
- polyacrylamide (1)
- polyamine (1)
- polyammonium salt (1)
- polyampholyte (1)
- polybutadiene (1)
- polycarboxylate (1)
- polycationic monolayer (1)
- polycondensation (1)
- polydimethylsiloxane wrinkles (1)
- polyelectrolyte membranes (1)
- polyglycine (1)
- polylactide (1)
- polymer amphiphile (1)
- polymer degradation (1)
- polymer synthesis (1)
- polymeric sensors (1)
- polymerised ionic liquids (1)
- polymersomes (1)
- polyolefin (1)
- polypeptides (1)
- polypeptoids (1)
- polypropylene yarns (1)
- polysoap (1)
- polysulfabetaine (1)
- poly‐ ε ‐ caprolactone (1)
- porosity (1)
- porous (1)
- porous carbon materials (1)
- porous carbon-based materials (1)
- porous carbons (1)
- porös (1)
- poröse Kohlenstoffe (1)
- poröse Kohlenstoffmaterialien (1)
- poröse Struktur (1)
- porösen Materialien auf Kohlenstoffbasis (1)
- poröser Kohlenstoff (1)
- post-modification (1)
- post-polymerization modification (1)
- precatalysts (1)
- precision agriculture (1)
- pressure (1)
- process analytical technology (1)
- programmable friction (1)
- protein NMR spectroscopy (1)
- protein adsorption (1)
- protein binding (1)
- protein characterization (1)
- protein interactions (1)
- protein stabilized foams (1)
- protein-kinase inhibitors (1)
- proximal soil sensing (1)
- précipitation (1)
- précipitation oxalique (1)
- pulsed DPSS laser (1)
- purity (1)
- quantum chemistry (1)
- quenching (1)
- quinone (1)
- quinone methide (1)
- racemization (1)
- radical reactions (1)
- radicals (1)
- radiosensitizer (1)
- rare earth elements (1)
- rat (1)
- ratiometric (1)
- ray absorption-spectroscopy (1)
- reactions (1)
- reactive flux rate constants (1)
- reactive templating (1)
- reactivity (1)
- recognition (1)
- recombinant protein (1)
- renewable resources (1)
- renewables (1)
- repair (1)
- resistive heating (1)
- resonance Raman spectroscopy (1)
- resonance energy transfer (1)
- resonance energy-tansfer (1)
- resonant formation (1)
- responsive (1)
- responsive polymer (1)
- responsive polymers (1)
- responsive systems (1)
- reversible addition fragmentation chain transfer (RAFT) (1)
- reversible addition-fragmentation chain transfer (1)
- reversible shape-memory actuator (1)
- review (1)
- rheology (1)
- ring-closing metathesis (1)
- ring-closure (1)
- rising bubble (1)
- roughness (1)
- rp-hplc (1)
- ruthenium carbene (1)
- salt melt (1)
- samples (1)
- scale (1)
- schaltbare Materialien (1)
- schaltbare Polymere (1)
- schizophrenes Verhalten (1)
- schizophrenic behavior (1)
- secondary structure (1)
- sel (1)
- selbstassemblierende Monolagen (1)
- self-assembled monolayers (1)
- self-healing coatings (1)
- self-organisation (1)
- semiempirical methods (1)
- sensor (1)
- sensors (1)
- separation (1)
- sequence dependence (1)
- sers (1)
- sessile droplet (1)
- shape-memory (1)
- shape‐memory polymer actuators (1)
- sichtbares Licht Photokatalyse (1)
- silica (1)
- silica nanoparticles (1)
- silica particles (1)
- silver (1)
- silver nanoparticles (1)
- silver nanowires (1)
- sinefungin (1)
- single crystals (1)
- single strand break (1)
- single-atom catalysis (1)
- single-molecule analysis (1)
- single-molecule detection (1)
- single-strand breaks (1)
- singlet oxygen (1)
- small-angle scattering (1)
- smart materials (1)
- sodium (1)
- sodium green (1)
- sodium hydroxide etching (1)
- sodium-ion batteries (1)
- sodium-ion battery (1)
- soft and hard templating (1)
- soft robotics (1)
- soft template (1)
- soft-templates (1)
- soil gas (1)
- soil nutrients (1)
- solid-state structure (1)
- solubility (1)
- solubilization (1)
- solution process (1)
- solvatochromic fluorophore (1)
- solvatochromism (1)
- solvent (1)
- solvent effect (1)
- solvent-free reactions (1)
- solvo-thermal annealing (1)
- solvothermal synthesis (1)
- sortase-mediated ligation (1)
- spacer (1)
- spacer group (1)
- spatial-organization (1)
- speciation (1)
- species (1)
- specific interactions (1)
- spectra (1)
- spent coffee (1)
- spermidine (1)
- spezifische Wechselwirkungen (1)
- spherical polyelectrolyte brushes (1)
- spider silk (1)
- spiked and crumble gold nanotriangles (1)
- spiropyran copolymer (1)
- square planar (1)
- squaric acid (1)
- stability (1)
- stannous octoate (1)
- stark eutektisches Lösungsmittel (1)
- state (1)
- states (1)
- statistische Versuchsplanung (Design of Experiments) (1)
- steigende Blasen (1)
- step (1)
- stereocomplexation (1)
- stereoselective-synthesis (1)
- stereoselectivity (1)
- stickstoffdotierte Kohlenstoffe (1)
- stimuli-response (1)
- stimuli-sensitive (1)
- stokes shift (1)
- strand breakage (1)
- structural-characterization (1)
- substituted stilbenes (1)
- substrate (1)
- sulfobetain (1)
- sulfoxides (1)
- sulfur host (1)
- supercapacitor (1)
- supercritical carbon dioxide (scCO₂) (1)
- superparamagnetic (1)
- superparamagnetisch (1)
- supported gold (1)
- supramolecular (1)
- supramolecular chemistry (1)
- supramolekulare Chemie (1)
- surface chemistry (1)
- surface functionalization (1)
- surface hopping dynamics (1)
- surface rheology (1)
- surface science (1)
- surface topography (1)
- surface-enhanced Raman scattering (1)
- surface-plasmon resonance (1)
- surfaces and interfaces (1)
- surfactant (1)
- sustainability (1)
- sustainable energy storage materials (1)
- switchable block copolymer (1)
- switches (1)
- synthetische Biologie (1)
- sättigbarer Absorber (1)
- tamplat unterstütze Anordnung von weichen Partikeln (1)
- tandem mass spectrometry (1)
- tandem solar cells (1)
- tannic acid (1)
- tanning agents (1)
- temperature (1)
- temperature phase (1)
- temperaturschaltbar (1)
- template (1)
- template assisted alignment of soft particles (1)
- tensioactivos (1)
- tetrabromidocuprate(II) (1)
- tetrachlorocuprate(II) salts (1)
- thermal isomerization of azobenzene (1)
- thermal properties (1)
- thermisch angeregte Isomerisierung von Azobenzolen (1)
- thermisch schaltbar (1)
- thermisch schaltbare Polymere (1)
- thermo-responsive polymers (1)
- thermochemistry (1)
- thermodynamics (1)
- thermometer (1)
- thermoplastisches Elastomer (1)
- thermosensitive (1)
- thermosensitive polymers (1)
- thiazolium (1)
- thimerosal (1)
- thin film crystallization (1)
- thin films (1)
- thin-films (1)
- thio-dimethylarsinic acid (1)
- tight-binding (1)
- time random-walks (1)
- time-dependent density functional theory (1)
- time-resolved luminescence (1)
- tin perovskites (1)
- to-coil transition (1)
- trafficking (1)
- trans-stilbenes (1)
- transformation (1)
- transient (1)
- transition (1)
- transition metal (1)
- transition path sampling (1)
- transition-metal-complexes (1)
- transparent-leitendes Oxid (1)
- triangular-[4] phenylene (1)
- triazine (1)
- trivalent (1)
- tropical infectious diseases (1)
- tropische Infektionskrankheiten (1)
- tunable diode laser (TDL) (1)
- tyrosinase; o-quinones (1)
- ultra-fast laser inscription (1)
- ultra-thin membrane (1)
- ultracentrifuge (1)
- ultradünne Membranen (1)
- ultrafast (1)
- ultrathin film (1)
- undulated (1)
- untere kritische Entmischungstemperatur (1)
- untere kritische Lösungstemperatur (1)
- upconverting nanoparticles (1)
- upper critical solution temperature (1)
- uranium (VI) (1)
- uranyl (1)
- valerolactone (1)
- ventricular myocytes (1)
- vesicle studies (1)
- vibrational control (1)
- vibrational excitation (1)
- vibrational spectroscopy (1)
- vibrationally resolved electronic spectroscopy (1)
- viologen (1)
- visible light photocatalysis (1)
- vitro toxicological characterization (1)
- wasser (1)
- water at alumina (1)
- water splitting reaction (1)
- water-soluble polymers (1)
- water/tetradecane interface (1)
- wavelength (1)
- weak ergodicity breaking (1)
- weiche Vorlage (1)
- weiche und harte Templatierung (1)
- weißer Kohlenstoff (1)
- wetting (1)
- white carbon (1)
- wide-angle x-ray scattering (1)
- wood modification (1)
- wrinkled stamps (1)
- wrinkles (1)
- wässrige Systeme (1)
- ytterbium (1)
- zeolitic imidazolate frameworks (1)
- zweifach schaltbare Blockcopolymere (1)
- zwitterionic group (1)
- zwitterions (1)
- Übergangsmetall (1)
- Übergangsmetalle (1)
- Überstrukturierte Komposite (1)
- ß-Lactoglobulin (1)
- überkritisches Kohlendioxid (scCO₂) (1)
- β-Hydroxydihydrochalcone (1)
Institute
- Institut für Chemie (427) (remove)
The incorporation of proteins in artificial materials such as membranes offers great opportunities to avail oneself the miscellaneous qualities of proteins and enzymes perfected by nature over millions of years. One possibility to leverage proteins is the modification with artificial polymers. To obtain such protein-polymer conjugates, either a polymer can be grown from the protein surface (grafting-from) or a pre-synthesized polymer attached to the protein (grafting-to). Both techniques were used to synthesize conjugates of different proteins with thermo-responsive polymers in this thesis.
First, conjugates were analyzed by protein NMR spectroscopy. Typical characterization techniques for conjugates can verify the successful conjugation and give hints on the secondary structure of the protein. However, the 3-dimensional structure, being highly important for the protein function, cannot be probed by standard techniques. NMR spectroscopy is a unique method allowing to follow even small alterations in the protein structure. A mutant of the carbohydrate binding module 3b (CBM3bN126W) was used as model protein and functionalized with poly(N-isopropylacrylamide). Analysis of conjugates prepared by grafting-to or grafting-from revealed a strong impact of conjugation type on protein folding. Whereas conjugates prepared by grafting a pre-formed polymer to the protein resulted in complete preservation of protein folding, grafting the polymer from the protein surface led to (partial) disruption of the protein structure.
Next, conjugates of bovine serum albumin (BSA) as cheap and easily accessible protein were synthesized with PNIPAm and different oligoethylene glycol (meth)acrylates. The obtained protein-polymer conjugates were analyzed by an in-line combination of size exclusion chromatography and multi-angle laser light scattering (SEC-MALS). This technique is particular advantageous to determine molar masses, as no external calibration of the system is needed. Different SEC column materials and operation conditions were tested to evaluate the applicability of this system to determine absolute molar masses and hydrodynamic properties of heterogeneous conjugates prepared by grafting-from and grafting-to. Hydrophobic and non-covalent interactions of conjugates lead to error-prone values not in accordance to expected molar masses based on conversions and extents of modifications.
As alternative to this method, conjugates were analyzed by sedimentation velocity analytical ultracentrifugation (SV-AUC) to gain insights in the hydrodynamic properties and how they change after conjugation. Within a centrifugal field, a sample moves and fractionates according to the mass, density, and shape of its individual components. Conjugates of BSA with PNIPAm were analyzed below and above the cloud point temperature of the thermo-responsive polymer component. It was identified that the polymer characteristics were transferred to the conjugate molecule which than showed a decreased ideality – defined as increased deviation from a perfect sphere model – below and increased ideality above the cloud point temperature. This effect can be attributed to an arrangement of the polymer chain pointing towards the solvent (expanded state) or snuggling around the protein surface depending on the applied temperature.
The last project dealt with the synthesis of ferric hydroxamate uptake protein component A (FhuA)-polymer conjugates as building blocks for novel membrane materials. The shape of FhuA can be described as barrel and removal of a cork domain inside the protein results in a passive channel aimed to be utilized as pores in the membrane system. The polymer matrix surrounding the membrane protein is composed of a thermo-responsive and a UV-crosslinkable part. Therefore, an external trigger for covalent immobilization of these building blocks in the membrane and switchability of the membrane between different states was incorporated. The overall performance of membranes prepared by a drying-mediated self-assembly approach was evaluated by permeability and size exclusion experiments. The obtained membranes displayed an insufficiency in interchain crosslinking and therefore a lack in performance. Furthermore, the aimed switch between a hydrophilic and hydrophobic state of the polymer matrix did not occur. Correspondingly, size exclusion experiments did not result in a retention of analytes larger than the pores defined by the dimension of the used FhuA variant.
Overall, different paths to generate protein-polymer conjugates by either grafting-from or grafting-to the protein surface were presented paving the way to the generation of new hybrid materials. Different analytical methods were utilized to describe the folding and hydrodynamic properties of conjugates providing a deeper insight in the overall characteristics of these seminal building blocks.
Polymeric films and coatings derived from semi-crystalline oligomers are of relevance for medical and pharmaceutical applications. In this context, the material surface is of particular importance, as it mediates the interaction with the biological system. Two dimensional (2D) systems and ultrathin films are used to model this interface. However, conventional techniques for their preparation, such as spin coating or dip coating, have disadvantages, since the morphology and chain packing of the generated films can only be controlled to a limited extent and adsorption on the substrate used affects the behavior of the films. Detaching and transferring the films prepared by such techniques requires additional sacrificial or supporting layers, and free-standing or self supporting domains are usually of very limited lateral extension. The aim of this thesis is to study and modulate crystallization, melting, degradation and chemical reactions in ultrathin films of oligo(ε-caprolactone)s (OCL)s with different end-groups under ambient conditions. Here, oligomeric ultrathin films are assembled at the air-water interface using the Langmuir technique. The water surface allows lateral movement and aggregation of the oligomers, which, unlike solid substrates, enables dynamic physical and chemical interaction of the molecules. Parameters like surface pressure (π), temperature and mean molecular area (MMA) allow controlled assembly and manipulation of oligomer molecules when using the Langmuir technique. The π-MMA isotherms, Brewster angle microscopy (BAM), and interfacial infrared spectroscopy assist in detecting morphological and physicochemical changes in the film. Ultrathin films can be easily transferred to the solid silicon surface via Langmuir Schaefer (LS) method (horizontal substrate dipping). Here, the films transferred on silicon are investigated using atomic force microscopy (AFM) and optical microscopy and are compared to the films on the water surface.
The semi-crystalline morphology (lamellar thicknesses, crystal number densities, and lateral crystal dimensions) is tuned by the chemical structure of the OCL end-groups (hydroxy or methacrylate) and by the crystallization temperature (Tc; 12 or 21 °C) or MMAs. Compression to lower MMA of ~2 Å2, results in the formation of a highly crystalline film, which consists of tightly packed single crystals. Preparation of tightly packed single crystals on a cm2 scale is not possible by conventional techniques. Upon transfer to a solid surface, these films retain their crystalline morphology whereas amorphous films undergo dewetting.
The melting temperature (Tm) of OCL single crystals at the water and the solid surface is found proportional to the inverse crystal thickness and is generally lower than the Tm of bulk PCL. The impact of OCL end-groups on melting behavior is most noticeable at the air-solid interface, where the methacrylate end-capped OCL (OCDME) melted at lower temperatures than the hydroxy end-capped OCL (OCDOL). When comparing the underlying substrate, melting/recrystallization of OCL ultrathin films is possible at lower temperatures at the air water interface than at the air-solid interface, where recrystallization is not visible. Recrystallization at the air-water interface usually occurs at a higher temperature than the initial Tc.
Controlled degradation is crucial for the predictable performance of degradable polymeric biomaterials. Degradation of ultrathin films is carried out under acidic (pH ~ 1) or enzymatic catalysis (lipase from Pseudomonas cepcia) on the water surface or on a silicon surface as transferred films. A high crystallinity strongly reduces the hydrolytic but not the enzymatic degradation rate. As an influence of end-groups, the methacrylate end-capped linear oligomer, OCDME (~85 ± 2 % end-group functionalization) hydrolytically degrades faster than the hydroxy end capped linear oligomer, OCDOL (~95 ± 3 % end-group functionalization) at different temperatures. Differences in the acceleration of hydrolytic degradation of semi-crystalline films were observed upon complete melting, partial melting of the crystals, or by heating to temperatures close to Tm. Therefore, films of densely packed single crystals are suitable as barrier layers with thermally switchable degradation rates.
Chemical modification in ultrathin films is an intricate process applicable to connect functionalized molecules, impart stability or create stimuli-sensitive cross-links. The reaction of end-groups is explored for transferred single crystals on a solid surface or amorphous monolayer at the air-water interface. Bulky methacrylate end-groups are expelled to the crystal surface during chain-folded crystallization. The density of end-groups is inversely proportional to molecular weight and hence very pronounced for oligomers. The methacrylate end-groups at the crystal surface, which are present at high concentration, can be used for further chemical functionalization. This is demonstrated by fluorescence microscopy after reaction with fluorescein dimethacrylate. The thermoswitching behavior (melting and recrystallization) of fluorescein functionalized single crystals shows the temperature-dependent distribution of the chemically linked fluorescein moieties, which are accumulated on the surfaces of crystals, and homogeneously dispersed when the crystals are molten. In amorphous monolayers at the air-water interface, reversible cross-linking of hydroxy-terminated oligo(ε-caprolactone) monolayers using dialdehyde (glyoxal) lead to the formation of 2D networks. Pronounced contraction in the area occurred for 2D OCL films in dependence of surface pressure and time indicating the reaction progress. Cross linking inhibited crystallization and retarded enzymatic degradation of the OCL film. Altering the subphase pH to ~2 led to cleavage of the covalent acetal cross-links. Besides as model systems, these reversibly cross-linked films are applicable for drug delivery systems or cell substrates modulating adhesion at biointerfaces.
To achieve a sustainable energy economy, it is necessary to turn back on the combustion of fossil fuels as a means of energy production and switch to renewable sources. However, their temporal availability does not match societal consumption needs, meaning that renewably generated energy must be stored in its main generation times and allocated during peak consumption periods. Electrochemical energy storage (EES) in general is well suited due to its infrastructural independence and scalability. The lithium ion battery (LIB) takes a special place, among EES systems due to its energy density and efficiency, but the scarcity and uneven geological occurrence of minerals and ores vital for many cell components, and hence the high and fluctuating costs will decelerate its further distribution.
The sodium ion battery (SIB) is a promising successor to LIB technology, as the fundamental setup and cell chemistry is similar in the two systems. Yet, the most widespread negative electrode material in LIBs, graphite, cannot be used in SIBs, as it cannot store sufficient amounts of sodium at reasonable potentials. Hence, another carbon allotrope, non-graphitizing or hard carbon (HC) is used in SIBs. This material consists of turbostratically disordered, curved graphene layers, forming regions of graphitic stacking and zones of deviating layers, so-called internal or closed pores.
The structural features of HC have a substantial impact of the charge-potential curve exhibited by the carbon when it is used as the negative electrode in an SIB. At defects and edges an adsorption-like mechanism of sodium storage is prevalent, causing a sloping voltage curve, ill-suited for the practical application in SIBs, whereas a constant voltage plateau of relatively high capacities is found immediately after the sloping region, which recent research attributed to the deposition of quasimetallic sodium into the closed pores of HC.
Literature on the general mechanism of sodium storage in HCs and especially the role of the closed pore is abundant, but the influence of the pore geometry and chemical nature of the HC on the low-potential sodium deposition is yet in an early stage. Therefore, the scope of this thesis is to investigate these relationships using suitable synthetic and characterization methods. Materials of precisely known morphology, porosity, and chemical structure are prepared in clear distinction to commonly obtained ones and their impact on the sodium storage characteristics is observed. Electrochemical impedance spectroscopy in combination with distribution of relaxation times analysis is further established as a technique to study the sodium storage process, in addition to classical direct current techniques, and an equivalent circuit model is proposed to qualitatively describe the HC sodiation mechanism, based on the recorded data. The obtained knowledge is used to develop a method for the preparation of closed porous and non-porous materials from open porous ones, proving not only the necessity of closed pores for efficient sodium storage, but also providing a method for effective pore closure and hence the increase of the sodium storage capacity and efficiency of carbon materials.
The insights obtained and methods developed within this work hence not only contribute to the better understanding of the sodium storage mechanism in carbon materials of SIBs, but can also serve as guidance for the design of efficient electrode materials.
The key to reduce the energy required for specific transformations in a selective manner is the employment of a catalyst, a very small molecular platform that decides which type of energy to use. The field of photocatalysis exploits light energy to shape one type of molecules into others, more valuable and useful.
However, many challenges arise in this field, for example, catalysts employed usually are based on metal derivatives, which abundance is limited, they cannot be recycled and are expensive. Therefore, carbon nitrides materials are used in this work to expand horizons in the field of photocatalysis.
Carbon nitrides are organic materials, which can act as recyclable, cheap, non-toxic, heterogeneous photocatalysts. In this thesis, they have been exploited for the development of new catalytic methods, and shaped to develop new types of processes.
Indeed, they enabled the creation of a new photocatalytic synthetic strategy, the dichloromethylation of enones by dichloromethyl radical generated in situ from chloroform, a novel route for the making of building blocks to be used for the productions of active pharmaceutical compounds.
Then, the ductility of these materials allowed to shape carbon nitride into coating for lab vials, EPR capillaries, and a cell of a flow reactor showing the great potential of such flexible technology in photocatalysis.
Afterwards, their ability to store charges has been exploited in the reduction of organic substrates under dark conditions, gaining new insights regarding multisite proton coupled electron transfer processes.
Furthermore, the combination of carbon nitrides with flavins allowed the development of composite materials with improved photocatalytic activity in the CO2 photoreduction.
Concluding, carbon nitrides are a versatile class of photoactive materials, which may help to unveil further scientific discoveries and to develop a more sustainable future.
The self-assembly of amphiphilic polymers in aqueous systems is important for a plethora of applications, in particular in the field of cosmetics and detergents. When introducing thermoresponsive blocks, the aggregation behavior of these polymers can be controlled by changing the temperature. While confined to simple diblock copolymer systems for long, the complexity - and thus the versatility - of such smart systems can be strongly enlarged, once designed monomers, specific block sizes, different architectures, or additional functional groups such as hydrophobic stickers are implemented. In this work, the structure-property relationship of such thermoresponsive amphiphilic block copolymers was investigated by varying their structure systematically. The block copolymers were generally composed of a permanently hydrophobic sticker group, a permanently hydrophilic block, and a thermoresponsive block exhibiting a Lower Critical Solution Temperature (LCST) behavior. While the hydrophilic block consisted of N,N dimethylacrylamide (DMAm), different monomers were used for the thermoresponsive block, such as N n propylacrylamide (NPAm), N iso propylacrylamide (NiPAm), N,N diethylacrylamide (DEAm), N,N bis(2 methoxyethyl)acrylamide (bMOEAm), or N acryloylpyrrolidine (NAP) with different reported LCSTs of 25, 32, 33, 42 and 56 °C, respectively. The block copolymers were synthesized by successive reversible addition fragmentation chain transfer (RAFT) polymerization. For the polymers with the basic linear, the twinned hydrophobic and the symmetrical quasi miktoarm architectures, the results were well defined block sizes and end groups as well as narrow molar mass distributions (Ɖ ≤ 1.3). More complex architectures, such as the twinned thermoresponsive and the non-symmetrical quasi miktoarm one, were achieved by combining RAFT polymerization with a second technique, namely atom transfer radical polymerization (ATRP) or single unit monomer insertion (SUMI), respectively. The obtained block copolymers showed well defined block sizes, but due to the complexity of these reaction paths, the dispersities were generally higher (Ɖ ≤ 1.8) and some end groups were lost.
The thermoresponsive behavior of the block copolymers was investigated by turbidimetry and dynamic light scattering (DLS). Below the phase transition temperature, the polymers were soluble in water and small micellar structures were visible. However, above the phase transition temperature, the aggregation behavior was strongly dependent on the architecture and the chemical structure of the thermoresponsive block. Thermoresponsive blocks comprising PNAP and PbMOEAm with DPn = 40 showed no cloud point (CP), since their already high LCSTs were further increased by the attached hydrophilic block. Depending on the architecture as well as on the block size, block copolymers with PNiPAm, PDEAm and PNPAm showed different CP’s. Large aggregates were visible for block copolymers with PNiPAm and PDEAm above their CP. For PNPAm containing block copolymers, the phase transition was very sensitive towards the architecture resulting in either small or large aggregates.
In addition, fluorescence studies were performed using PDMAm and PNiPAm homo and block copolymers with linear architecture, functionalized with complementary fluorescence dyes introduced at the opposite chain ends. The thermoresponsive behavior was studied in pure aqueous solution as well as in an oil in water (o/w) microemulsion. The findings indicate that the block copolymer behaves as polymeric surfactant at low temperatures, with one relatively small hydrophobic end group and an extended hydrophilic chain forming ‘hairy micelles’ similar as the other synthesized architectures. Above the phase transition temperature of the PNiPAm block, however, the copolymer behaves as associative telechelic polymer with two non-symmetrical hydrophobic end groups, which do not mix. Thus, instead of a network of bridged ‘flower micelles’, large dynamic aggregates are formed. These are connected alternatingly by the original micellar cores as well as by clusters of the collapsed PNiPAm blocks. This type of bridged micelles is even more favored in the o/w microemulsion than in pure aqueous solution.
Natural products have proved to be a major resource in the discovery and development of many pharmaceuticals that are in use today. There is a wide variety of biologically active natural products that contain conjugated polyenes or benzofuran structures. Therefore, new synthetic methods for the construction of such building blocks are of great interest to synthetic chemists. The recently developed one-pot tethered ring-closing metathesis approach allows for the formation of Z,E-dienoates in high stereoselectivity. The extension of this method with a Julia-Kocienski olefination protocol would allow for the formation of conjugated trienes in a stereoselective manner. This strategy was applied in the total synthesis of conjugated triene containing (+)-bretonin B. Additionally, investigations of cross metathesis using methyl substituted olefins were pursued. This methodology was applied, as a one-pot cross metathesis/ring-closing metathesis sequence, in the total synthesis of benzofuran containing 7-methoxywutaifuranal. Finally, the design and synthesis of a catalyst for stereoretentive metathesis in aqueous media was investigated.
The world energy consumption has constantly increased every year due to economic development and population growth. This inevitably caused vast amount of CO2 emission, and the CO2 concentration in the atmosphere keeps increasing with economic growth. To reduce CO2 emission, various methods have been developed but there are still many bottlenecks to be solved. Solvents easily absorbing CO2 such as monoethanol-amine (MEA) and diethanolamine, for example, have limitations of solvent loss, amine degradation, vulnerability to heat and toxicity, and the high cost of regeneration which is especially caused due to chemisorption process. Though some of these drawbacks can be compensated through physisorption with zeolites and metal-organic frameworks (MOFs) by displaying significant adsorption selectivity and capacity even in ambient conditions, limitations for these materials still exist. Zeolites demand relatively high regeneration energy and have limited adsorption kinetics due to the exceptionally narrow pore structure. MOFs have low stability against heat and moisture and high manufacturing cost.
Nanoporous carbons have recently received attention as an attractive functional porous material due to their unique properties. These materials are crucial in many applications of modern science and industry such as water and air purification, catalysis, gas separation, and energy storage/conversion due to their high chemical and thermal stability, and in particular electronic conductivity in combination with high specific surface areas. Nanoporous carbons can be used to adsorb environmental pollutants or small gas molecules such as CO2 and to power electrochemical energy storage devices such as batteries and fuel cells. In all fields, their pore structure or electrical properties can be modified depending on their purposes.
This thesis provides an in-depth look at novel nanoporous carbons from the synthetic and the application point of view. The interplay between pore structure, atomic construction, and the adsorption properties of nanoporous carbon materials are investigated. Novel nanoporous carbon materials are synthesized by using simple precursor molecules containing heteroatoms through a facile
templating method. The affinity, and in turn the adsorption capacity, of carbon materials toward polar gas molecules (CO2 and H2O) is enhanced by the modification of their chemical construction. It is also shown that these properties are important in electrochemical energy storage, here especially for supercapacitors with aqueous electrolytes which are basically based on the physisorption of ions on carbon surfaces. This shows that nanoporous carbons can be a “functional” material with specific physical or chemical interactions with guest species just like zeolites and MOFs.
The synthesis of sp2-conjugated materials with high heteroatom content from a mixture of citrazinic acid and melamine in which heteroatoms are already bonded in specific motives is illustrated. By controlling the removal procedure of the salt-template and the condensation temperature, the role of salts in the formation of porosity and as coordination sites for the stabilization of heteroatoms is proven. A high amount of nitrogen of up to 20 wt. %, oxygen contents of up to 19 wt.%, and a high CO2/N2 selectivity with maximum CO2 uptake at 273 K of 5.31 mmol g–1 are achieved. Besides, the further controlled thermal condensation of precursor molecules and advanced functional properties on applications of the synthesized porous carbons are described. The materials have different porosity and atomic construction exhibiting a high nitrogen content up to 25 wt. % as well as a high porosity with a specific surface area of more than 1800 m2 g−1, and a high performance in selective CO2 gas adsorption of 62.7. These pore structure as well as properties of surface affect to water adsorption with a remarkably high Qst of over 100 kJ mol−1 even higher than that of zeolites or CaCl2 well known as adsorbents. In addition to that, the pore structure of HAT-CN-derived carbon materials during condensation in vacuum is fundamentally understood which is essential to maximize the utilization of porous system in materials showing significant difference in their pore volume of 0.5 cm3 g−1 and 0.25 cm3 g−1 without and with vacuum, respectively.
The molecular designs of heteroatom containing porous carbon derived from abundant and simple molecules are introduced in the presented thesis. Abundant precursors that already containing high amount of nitrogen or oxygen are beneficial to achieve enhanced interaction with adsorptives. The physical and chemical properties of these heteroatom-doped porous carbons are affected by mainly two parameters, that is, the porosity from the pore structure and the polarity from the atomic composition on the surface. In other words, controlling the porosity as well as the polarity of the carbon materials is studied to understand interactions with different guest species which is a fundamental knowledge for the utilization on various applications.
The development and optimization of carbonaceous materials is of great interest for several applications including gas sorption, electrochemical storage and conversion, or heterogeneous catalysis. In this thesis, the exploration and optimization of nitrogen containing carbonaceous materials by direct condensation of smart chosen, molecular precursors will be presented. As suggested with the concept of noble carbons, the choice of a stable, nitrogen-containing precursor will lead to an even more stable, nitrogen doped carbonaceous material with a controlled structure and electronic properties. Molecules fulfilling this requirement are for example nucleobases. The direct condensation of nucleobases leads to highly nitrogen containing carbonaceous materials without any further post or pretreatment. By using salt melt templating, pore structure adjustment is possible without the use of hazardous or toxic reagents and the template can be reused.
Using these simple tools, the synergetic effect of the pore structure and nitrogen content of the materials can be explored. Within this thesis, the influence of the condensation parameters will be correlated to the structure and performance of the materials. First, the influence of the condensation temperature to the porosity and nitrogen content of guanine will be discussed and the exploration of highly CO2 selective structural pores in C1N1 materials will be shown. Further tuning the pore structure of the materials by salt melt templating will be then explored, the potential of the prepared materials as heterogeneous catalysts and their basic catalytic strength will be correlated to their nitrogen content and pore morphology. A similar approach is used to explore the water sorption behavior of uric acid derived carbonaceous materials as potential sorbents for heat transformation applications. Changes in maximum water uptake and hydrophilicity of the prepared materials will be correlated to the nitrogen content and pore architecture. Due to the high thermal stability, porosity, and nitrogen content of ionic liquid derived nitrogen doped carbonaceous materials, a simple impregnation and calcination route can be conducted to obtain copper nano cluster decorated nitrogen-doped carbonaceous materials. The activity as catalyst for the oxygen reduction reaction of the obtained materials will be shown and structure performance relations are discussed.
In conclusion, the versatility of nitrogen doped carbonaceous materials with a nitrogen to carbon ratio of up to one will be shown. The possibility to tune the pore structure as well as the nitrogen content by using a simple procedure including salt melt templating as well as the use of molecular precursors and their effect on the performance will be discussed.
The negative impact of crude oil on the environment has led to a necessary transition toward alternative, renewable, and sustainable resources. In this regard, lignocellulosic biomass (LCB) is a promising renewable and sustainable alternative to crude oil for the production of fine chemicals and fuels in a so-called biorefinery process. LCB is composed of polysaccharides (cellulose and hemicellulose), as well as aromatics (lignin). The development of a sustainable and economically advantageous biorefinery depends on the complete and efficient valorization of all components. Therefore, in the new generation of biorefinery, the so-called biorefinery of type III, the LCB feedstocks are selectively deconstructed and catalytically transformed into platform chemicals. For this purpose, the development of highly stable and efficient catalysts is crucial for progress toward viability in biorefinery. Furthermore, a modern and integrated biorefinery relies on process and reactor design, toward more efficient and cost-effective methodologies that minimize waste. In this context, the usage of continuous flow systems has the potential to provide safe, sustainable, and innovative transformations with simple process integration and scalability for biorefinery schemes.
This thesis addresses three main challenges for future biorefinery: catalyst synthesis, waste feedstock valorization, and usage of continuous flow technology. Firstly, a cheap, scalable, and sustainable approach is presented for the synthesis of an efficient and stable 35 wt.-% Ni catalyst on highly porous nitrogen-doped carbon support (35Ni/NDC) in pellet shape. Initially, the performance of this catalyst was evaluated for the aqueous phase hydrogenation of LCB-derived compounds such as glucose, xylose, and vanillin in continuous flow systems. The 35Ni/NDC catalyst exhibited high catalytic performances in three tested hydrogenation reactions, i.e., sorbitol, xylitol, and 2-methoxy-4-methylphenol with yields of 82 mol%, 62 mol%, and 100 mol% respectively. In addition, the 35Ni/NDC catalyst exhibited remarkable stability over a long time on stream in continuous flow (40 h). Furthermore, the 35Ni/NDC catalyst was combined with commercially available Beta zeolite in a dual–column integrated process for isosorbide production from glucose (yield 83 mol%).
Finally, 35Ni/NDC was applied for the valorization of industrial waste products, namely sodium lignosulfonate (LS) and beech wood sawdust (BWS) in continuous flow systems. The LS depolymerization was conducted combining solvothermal fragmentation of water/alcohol mixtures (i.e.,methanol/water and ethanol/water) with catalytic hydrogenolysis/hydrogenation (SHF). The depolymerization was found to occur thermally in absence of catalyst with a tunable molecular weight according to temperature. Furthermore, the SHF generated an optimized cumulative yield of lignin-derived phenolic monomers of 42 mg gLS-1. Similarly, a solvothermal and reductive catalytic fragmentation (SF-RCF) of BWS was conducted using MeOH and MeTHF as a solvent. In this case, the optimized total lignin-derived phenolic monomers yield was found of 247 mg gKL-1.
The optical properties of chromophores, especially organic dyes and optically active inorganic molecules, are determined by their chemical structures, surrounding media, and excited state behaviors. The classical optical go-to techniques for spectroscopic investigations are absorption and luminescence spectroscopy. While both techniques are powerful and easy to apply spectroscopic methods, the limited time resolution of luminescence spectroscopy and its reliance on luminescent properties can make its application, in certain cases, complex, or even impossible. This can be the case when the investigated molecules do not luminesce anymore due to quenching effects, or when they were never luminescent in the first place. In those cases, transient absorption spectroscopy is an excellent and much more sophisticated technique to investigate such systems. This pump-probe laser-spectroscopic method is excellent for mechanistic investigations of luminescence quenching phenomena and photoreactions. This is due to its extremely high time resolution in the femto- and picosecond ranges, where many intermediate or transient species of a reaction can be identified and their kinetic evolution can be observed. Furthermore, it does not rely on the samples being luminescent, due to the active sample probing after excitation. In this work it is shown, that with transient absorption spectroscopy it was possible to identify the luminescence quenching mechanisms and thus luminescence quantum yield losses of the organic dye classes O4-DBD, S4-DBD, and pyridylanthracenes. Hence, the population of their triplet states could be identified as the competitive mechanism to their luminescence. While the good luminophores O4-DBD showed minor losses, the S4-DBD dye luminescence was almost entirely quenched by this process. However, for pyridylanthracenes, this phenomenon is present in both the protonated and unprotonated forms and moderately effects the luminescence quantum yield. Also, the majority of the quenching losses in the protonated forms are caused by additional non-radiative processes introduced by the protonation of the pyridyl rings. Furthermore, transient absorption spectroscopy can be applied to investigate the quenching mechanisms of uranyl(VI) luminescence by chloride and bromide. The reduction of the halides by excited uranyl(VI) leads to the formation of dihalide radicals X^(·−2). This excited state redox process is thus identified as the quenching mechanism for both halides, and this process, being diffusion-limited, can be suppressed by cryogenically freezing the samples or by observing these interactions in media with a lower dielectric constant, such as ACN and acetone.
Eukaryotic cells can be regarded as complex microreactors capable of performing various biochemical reactions in parallel which are necessary to sustain life. An essential prerequisite for these complex metabolic reactions to occur is the evolution of lipid membrane-bound organelles enabling compartmental- ization of reactions and biomolecules. This allows for a spatiotemporal control over the metabolic reactions within the cellular system. Intracellular organi- zation arising due to compartmentalization is a key feature of all living cells and has inspired synthetic biologists to engineer such systems with bottom-up approaches.
Artificial cells provide an ideal platform to isolate and study specific re- actions without the interference from the complex network of biomolecules present in biological cells. To mimic the hierarchical architecture of eukaryotic cells, multi-compartment assemblies with nested liposomal structures also re- ferred to as multi-vesicular vesicles (MVVs) have been widely adopted. Most of the previously reported multi-compartment systems adopt bulk method- ologies which suffer from low yield and poor control over size. Microfluidic strategies help circumvent these issues and facilitate a high-throughput and robust technique to assemble MVVs of uniform size distribution.
In this thesis, firstly, the bulk methodologies are explored to build MVVs and implement a synthetic signalling cascade. Next, a polydimethylsiloxane (PDMS)-based microfluidic platform is introduced to build MVVs and the significance of PEGylated lipids for the successful encapsulation of inner com- partments to generate stable multi-compartment systems is highlighted.
Next, a novel two-inlet channel PDMS-based microfluidic device to create MVVs encompassing a three-step enzymatic reaction cascade is presented. A directed reaction pathway comprising of the enzymes α-glucosidase (α-Glc), glucose oxidase (GOx), and horseradish peroxidase (HRP) spanning across three compartments via reconstitution of size-selective membrane proteins is described. Furthermore, owing to the monodispersity of our MVVs due to microfluidic strategies, this platform is employed to study the effect of com- partmentalization on reaction kinetics.
Further integration of cell-free expression module into the MVVs would allow for gene-mediated signal transduction within artificial eukaryotic cells. Therefore, the chemically inducible cell-free expression of a membrane protein alpha-hemolysin and its further reconstitution into liposomes is carried out.
In conclusion, the present thesis aims to build artificial eukaryotic cells to achieve size-selective chemical communication that also show potential for applications as micro reactors and as vehicles for drug delivery.
The controlled dosage of substances from a device to its environment, such as a tissue or an organ in medical applications or a reactor, room, machinery or ecosystem in technical, should ideally match the requirements of the applications, e.g. in terms of the time point at which the cargo is released. On-demand dosage systems may enable such a desired release pattern, if the device contain suitable features that can translate external signals into a release function. This study is motivated by the opportunities arising from microsystems capable of an on-demand release and the contributions that geometrical design may have in realizing such features. The goals of this work included the design, fabrication, characterization and experimental proof-of-concept of geometry-assisted triggerable dosing effect (a) with a sequential dosing release and (b) in a self-sufficient dosage system. Structure-function relationships were addressed on the molecular, morphological and, with a particular attention, the device design level, which is on the micrometer scale. Models and/or computational tools were used to screen the parameter space and provide guidance for experiments.
Membrane contact sites are of particular interest in the field of synthetic biology and biophysics. They are involved in a great variety of cellular functions. They form in between two cellular organelles or an organelle and the plasma membrane in order to establish a communication path for molecule transport or signal transmission.
The development of an artificial membrane system which can mimic membrane contact sites using bottom up synthetic biology was the goal of this research study. For this, a multi - compartmentalised giant unilamellar vesicle (GUV) system was created with the membrane of the outer vesicle mimicking the plasma membrane and the inner GUVs posing as cellular organelles.
In the following steps, three different strategies were used to achieve an internal membrane - membrane adhesion.
The article describes a systematic investigation of the effects of an aqueous NaOH treatment of 3D printed poly(lactic acid) (PLA) scaffolds for surface activation. The PLA surface undergoes several morphology changes and after an initial surface roughening, the surface becomes smoother again before the material dissolves. Erosion rates and surface morphologies can be controlled by the treatment. At the same time, the bulk mechanical properties of the treated materials remain unaltered. This indicates that NaOH treatment of 3D printed PLA scaffolds is a simple, yet viable strategy for surface activation without compromising the mechanical stability of PLA scaffolds.
Excellent conversion efficiencies of over 20% and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials, with CH3NH3PbI3 being an archetypal compound. The question why CH3NH3PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated, with ferroelectricity being a promising candidate. This does, however, require the crystal structure to be non-centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic and, therefore, long-range level. Although the molecular cation CH3NH3+ is intrinsically polar, it is heavily disordered and this cannot be the sole reason for the ferroelectricity. We show that it, nonetheless, plays an important role, as it distorts the neighboring iodide positions from their centrosymmetric positions.
Nanoporous carbon materials (NCMs) provide the "function" of high specific surface area and thus have large interface area for interactions with surrounding species, which is of particular importance in applications related to adsorption processes. The strength and mechanism of adsorption depend on the pore architecture of the NCMs. In addition, chemical functionalization can be used to induce changes of electron density and/or electron density distribution in the pore walls, thus further modifying the interactions between carbons and guest species. Typical approaches for functionalization of nanoporous materials with regular atomic construction like porous silica, metal-organic frameworks, or zeolites, cannot be applied to NCMs due to their less defined local atomic construction and abundant defects. Therefore, synthetic strategies that offer a higher degree of control over the process of functionalization are needed. Synthetic approaches for covalent functionalization of NCMs, that is, for the incorporation of heteroatoms into the carbon backbone, are critically reviewed with a special focus on strategies following the concept "from molecules to materials." Approaches for coordinative functionalization with metallic species, and the functionalization by nanocomposite formation between pristine carbon materials and heteroatom-containing carbons, are introduced as well. Particular focus is given to the influences of these functionalizations in adsorption-related applications.
The impact of the orientation of zwitterionic groups, with respect to the polymer backbone, on the antifouling performance of thin hydrogel films made of polyzwitterions is explored. In an extension of the recent discussion about differences in the behavior of polymeric phosphatidylcholines and choline phosphates, a quasi-isomeric set of three poly(sulfobetaine methacrylate)s is designed for this purpose. The design is based on the established monomer 3-[N-2-(methacryloyloxy)ethyl-N,N-dimethyl]ammonio-propane-1-sulfonate and two novel sulfobetaine methacrylates, in which the positions of the cationic and the ionic groups relative to the polymerizable group, and thus also to the polymer backbone, are altered. The effect of the varied segmental dipole orientation on their water solubility, wetting behavior by water, and fouling resistance is compared. As model systems, the adsorption of the model proteins bovine serum albumin (BSA), fibrinogen, and lysozyme onto films of the various polyzwitterion surfaces is studied, as well as the settlement of a diatom (Navicula perminuta) and barnacle cyprids (Balanus improvisus) as representatives of typical marine fouling communities. The results demonstrate the important role of the zwitterionic group's orientation on the polymer behavior and fouling resistance
A thermodynamic study of the adsorption of Human Serum Albumin (HSA) onto spherical polyelectrolyte brushes (SPBs) by isothermal titration calorimetry (ITC) is presented. The SPBs are composed of a solid polystyrene core bearing long chains of poly(acrylic acid). ITC measurements done at different temperatures and ionic strengths lead to a full set of thermodynamicbinding constants together with the enthalpies and entropies of binding. The adsorption of HSA onto SPBs is described with a two-step model. The free energy of binding Delta Gb depends only weakly on temperature because of a marked compensation of enthalpy by entropy. Studies of the adsorbed HSA by Fourier transform infrared spectroscopy (FT-IR) demonstrate no significant disturbance in the secondary structure of the protein. The quantitative analysis demonstrates that counterion release is the major driving force for adsorption in a process where proteins become multivalent counterions of the polyelectrolyte chains upon adsorption. A comparison with the analysis of other sets of data related to the binding of HSA to polyelectrolytes demonstrates that the cancellation of enthalpy and entropy is a general phenomenon that always accompanies the binding of proteins to polyelectrolytes dominated by counterion release.
Effects of manganese on genomic integrity in the multicellular model organism Caenorhabditis elegans
(2021)
Although manganese (Mn) is an essential trace element, overexposure is associated with Mn-induced toxicity and neurological dysfunction. Even though Mn-induced oxidative stress is discussed extensively, neither the underlying mechanisms of the potential consequences of Mn-induced oxidative stress on DNA damage and DNA repair, nor the possibly resulting toxicity are characterized yet. In this study, we use the model organism Caenorhabditis elegans to investigate the mode of action of Mn toxicity, focusing on genomic integrity by means of DNA damage and DNA damage response. Experiments were conducted to analyze Mn bioavailability, lethality, and induction of DNA damage. Different deletion mutant strains were then used to investigate the role of base excision repair (BER) and dePARylation (DNA damage response) proteins in Mn-induced toxicity. The results indicate a dose- and time-dependent uptake of Mn, resulting in increased lethality. Excessive exposure to Mn decreases genomic integrity and activates BER. Altogether, this study characterizes the consequences of Mn exposure on genomic integrity and therefore broadens the molecular understanding of pathways underlying Mn-induced toxicity. Additionally, studying the basal poly(ADP-ribosylation) (PARylation) of worms lacking poly(ADP-ribose) glycohydrolase (PARG) parg-1 or parg-2 (two orthologue of PARG), indicates that parg-1 accounts for most of the glycohydrolase activity in worms.
In this contribution the dissociative electron attachment to metabolites found in aerobic organisms, namely oxaloacetic and citric acids, was studied both experimentally by means of a crossed-beam setup and theoretically through density functional theory calculations. Prominent negative ion resonances from both compounds are observed peaking below 0.5 eV resulting in intense formation of fragment anions associated with a decomposition of the carboxyl groups. In addition, resonances at higher energies (3–9 eV) are observed exclusively from the decomposition of the oxaloacetic acid. These fragments are generated with considerably smaller intensities. The striking findings of our calculations indicate the different mechanism by which the near 0 eV electron is trapped by the precursor molecule to form the transitory negative ion prior to dissociation. For the oxaloacetic acid, the transitory anion arises from the capture of the electron directly into some valence states, while, for the citric acid, dipole- or multipole-bound states mediate the transition into the valence states. What is also of high importance is that both compounds while undergoing DEA reactions generate highly reactive neutral species that can lead to severe cell damage in a biological environment.
Carbon Adsorbents from Spent Coffee for Removal of
Methylene Blue and Methyl Orange from Water
(2021)
Activated carbons (ACs) were prepared from dried spent coffee (SCD), a biological waste product, to produce adsorbents for methylene blue (MB) and methyl orange (MO) from aqueous solution. Pre-pyrolysis activation of SCD was achieved via treatment of the SCD with aqueous sodium hydroxide solutions at 90 °C. Pyrolysis of the pretreated SCD at 500 °C for 1 h produced powders with typical characteristics of AC suitable and effective for dye adsorption. As an alternative to the rather harsh base treatment, calcium carbonate powder, a very common and abundant resource, was also studied as an activator. Mixtures of SCD and CaCO3 (1:1 w/w) yielded effective ACs for MO and MB removal upon pyrolysis needing only small amounts of AC to clear the solutions. A selectivity of the adsorption process toward anionic (MO) or cationic (MB) dyes was not observed.
The present work focuses on minimising the usage of toxic chemicals by integration of the biobased monomers, derived from fatty acid esters, to photopolymerization processes, which are known to be nature friendly. Internal double bond present in the oleic acid was converted to more reactive (meth)acrylate or epoxy group. Biobased starting materials, functionalized by different pendant groups, were used for photopolymerizing formulations to design of new polymeric structures by using ultraviolet light emitting diode (UV-LED) (395 nm) via free radical polymerization or cationic polymerization.
New (meth)acrylates (2,3 and 4) consisting of two isomers, methyl 9-((meth)acryloyloxy)-10-hydroxyoctadecanoate / methyl 9-hydroxy-10-((meth)acryloyloxy)octadecanoate (2 and 3) and methyl 9-(1H-imidazol-1-yl)-10-(methacryloyloxy)octadecanoate / methyl 9-(methacryloyloxy)-10-(1H-imidazol-1-yl)octadecanoate (4), modified from oleic acid mix, and ionic liquid monomers (1a and 1b) bearing long alkyl chain were polymerized photochemically. New (meth)acrylates are based on vegetable oil, and ionic liquids (ILs) have nonvolatile behaviour. Therefore, both monomer types have green approach. Photoinitiated polymerization of new (meth)acrylates and ionic liquids was investigated in the presence of ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (Irgacure® TPO−L) or di(4-methoxybenzoyl)diethylgermane (Ivocerin®) as photoinitiator (PI). Additionally, the results were discussed in comparison with those obtained from commercial 1,6-hexanediol di(meth)acrylate (5 and 6) for deeper investigation of biobased monomer’s potential to substitute petroleum derived materials with renewable resources for possible coating applications. Kinetic study shows that methyl 9-(1H-imidazol-1-yl)-10-(methacryloyloxy)octadecanoate / methyl 9-(methacryloyloxy)-10-(1H-imidazol-1-yl)octadecanoate (4) and ionic liquids (1a and 1b) have quantitative conversion after irradiation process which is important for practical applications. On the other hand, heat generation occurs in a longer time during the polymerization of biobased systems or ILs.
The poly(meth)acrylates modified from (meth)acrylated fatty acid methyl ester monomers generally show a low glass transition temperature because of the presence of long aliphatic chain in the polymer structure. However, poly(meth)acrylates containing aromatic group have higher glass transition temperature. Therefore, new 4-(4-methacryloyloxyphenyl)-butan-2-one (7) was synthesized which can be a promising candidate for the green techniques, such as light induced polymerization. Photokinetic investigation of the new monomer, 4-(4-methacryloyloxyphenyl)-butan-2-one (7), was discussed using Irgacure® TPO−L or Ivocerin® as photoinitiator. The reactivity of that monomer was compared to commercial 2-phenoxyethyl methacrylate (8) and phenyl methacrylate (9) basis of the differences on monomer structures. The photopolymer of 4-(4-methacryloyloxyphenyl)-butan-2-one (7) might be an interesting candidate for the coating application with the properties of quantitative conversion and high molecular weight. It also shows higher glass transition temperature.
In addition to the linear systems based on renewable materials, new crosslinked polymers were also designed in this thesis. Therefore, isomer mixture consisting of ethane-1,2-diyl bis(9-methacryloyloxy-10-hydroxy octadecanoate), ethane-1,2-diyl 9-hydroxy-10-methacryloyloxy-9’-methacryloyloxy10’-hydroxy octadecanoate and ethane-1,2-diyl bis(9-hydroxy-10-methacryloyloxy octadecanoate) (10) was synthesized by derivation of the oleic acid which has not been previously described in the literature. Crosslinked material based on this biobased monomer was produced by photoinitiated free radical polymerization using Irgacure® TPO−L or Ivocerin® as photoinitiator. Furthermore, material properties were diversified by copolymerization of 10 with 4-(4-methacryloyloxyphenyl)-butan-2-one (7) or methyl 9-(1H-imidazol-1-yl)-10-(methacryloyloxy)octadecanoate / methyl 9-(methacryloyloxy)-10-(1H-imidazol-1-yl)octadecanoate (4). In addition to this, influence of comonomer with different chemical structure on the network system was investigated by analysis of thermo-mechanical properties, crosslink density and molecular weight between two crosslink junctions. An increase in the glass transition temperature caused by copolymerization of biobased monomer 10 with the excess amount of 4-(4-methacryloyloxyphenyl)-butan-2-one (7) was confirmed by both techniques, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). On the other hand, crosslink density decreased as a result of copolymerization reactions due to the reduction in the mean functionality of the system. Furthermore, surface characterization has been tested by contact angle measurements using solvents with different polarity.
This work also contributes to the limited data reported about cationic photopolymerization of the epoxidized vegetable oils in the literature in contrast to the widely investigation of thermal curing of the biorenewable epoxy monomers. In addition to the 9,10-epoxystearic acid methyl ester (11), a new monomer of bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) has been synthesized from oleic acid. These two biobased epoxies have been polymerized via cationic photoinitiated polymerization in the presence of bis(t-butyl)-iodonium-tetrakis(perfluoro-t-butoxy)aluminate ([Al(O-t-C4F9)4]-) and isopropylthioxanthone (ITX) as photinitiating system. Polymerization kinetic of 9,10-epoxystearic acid methyl ester (11) and bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) was investigated and compared with the kinetic of commercial monomers being 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexane carboxylate (13), 1,4-butanediol diglycidyl ether (14), and diglycidylether of bisphenol-A (15). Both biobased epoxies (11 and 12) showed higher conversion than cycloaliphatic epoxy (13), and lower reactivity than 1,4-butanediol diglycidyl ether (14). Additional network systems were designed by copolymerization of bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) and diglycidylether of bisphenol-A (15) in different molar ratios (1:1; 1:5; 1:9). It addresses that, final conversion is dependent on polymerization rate as well as physical processes such as vitrification during polymerization. Moreover, low glass transition temperature of homopolymer derived from bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) was successfully increased by copolymerization with diglycidylether bisphenol-A (15). On the other hand, the surface produced from bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) shows hydrophobic character. Higher concentration of biobased diepoxy (12) in the copolymerizing mixture decreases surface free energy. Network systems were also investigated according to the rubber elasticity theory. Crosslinked polymer derived from the mixture of bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) and diglycidylether of bisphenol-A (15) (molar ratio=1:5) exhibits almost ideal polymer network.
Soft actuators have drawn significant attention due to their relevance for applications, such as artificial muscles in devices developed for medicine and robotics. Tuning their performance and expanding their functionality are frequently done by means of chemical modification. The introduction of structural elements rendering non-synthetic modification of the performance possible, as well as control over physical appearance and facilitating their recycling is a subject of a great interest in the field of smart materials. The primary aim of this thesis was to create a shape-memory polymeric actuator, where the capability for non-synthetic tuning of the actuation performance is combined with reprocessability. Physically cross-linked polymeric matrices provide a solid material platform, where the in situ processing methods can be employed for modification of the composition and morphology, resulting in the fine tuning of the related mechanical properties and shape-memory actuation capability.
The morphological features, required for shape-memory polymeric actuators, namely two crystallisable domains and anchoring points for physical cross-links, were embedded into a multiblock copolymer with poly(ε-caprolactone) and poly(L-lactide) segments (PLLA-PCL). Here, the melting transition of PCL was bisected into the actuating and skeleton-forming units, while the cross-linking was introduced via PLA stereocomplexation in blends with oligomeric poly(D-lactide) (ODLA). PLLA segment number average length of 12-15 repeating units was experimentally defined to be capable of the PLA stereocomplexes formation, but not sufficient for the isotactic crystallisation. Multiblock structure and phase dilution broaden the PCL melting transition, facilitating its separation into two conditionally independent crystalline domains. Low molar mass of the PLA stereocomplex components and a multiblock structure enables processing and reprocessing of the PLLA-PCL / ODLA blends with common non-destructive techniques. The modularity of the PLLA-PCL structure and synthetic approach allows for independent tuning of the properties of its components. The designed material establishes a solid platform for non-synthetic tuning of thermomechanical and structural properties of thermoplastic elastomers.
To evaluate the thermomechanical stability of the formed physical network, three criteria were appraised. As physical cross-links, PLA stereocomplexes have to be evenly distributed within the material matrix, their melting temperature shall not overlap with the thermal transitions of the PCL domains and they have to maintain the structural integrity within the strain ε ranges further applied in the shape-memory actuation experiments. Assigning PCL the function of the skeleton-forming and actuating units, and PLA stereocomplexes the role of physical netpoints, shape-memory actuation was realised in the PLLA-PCL / ODLA blends. Reversible strain of shape-memory actuation was found to be a function of PLA stereocomplex crystallinity, i.e. physical cross-linking density, with a maximum of 13.4 ± 1.5% at PLA stereocomplex content of 3.1 ± 0.3 wt%. In this way, shape-memory actuation can be tuned via adjusting the composition of the PLLA-PCL / ODLA blend. This makes the developed material a valuable asset in the production of cost-effective tunable soft polymeric actuators for the applications in medicine and soft robotics.
DNA origami nanostructures allow for the arrangement of different functionalities such as proteins, specific DNA structures, nanoparticles, and various chemical modifications with unprecedented precision. The arranged functional entities can be visualized by atomic force microscopy (AFM) which enables the study of molecular processes at a single-molecular level. Examples comprise the investigation of chemical reactions, electron-induced bond breaking, enzymatic binding and cleavage events, and conformational transitions in DNA. In this paper, we provide an overview of the advances achieved in the field of single-molecule investigations by applying atomic force microscopy to functionalized DNA origami substrates.
Ionizing radiation is used in cancer radiation therapy to effectively damage the DNA of tumors leading to cell death and reduction of the tumor tissue. The main damage is due to generation of highly reactive secondary species such as low-energy electrons (LEE) with the most probable energy around 10 eV through ionization of water molecules in the cells. A simulation of the dose distribution in the patient is required to optimize the irradiation modality in cancer radiation therapy, which must be based on the fundamental physical processes of high-energy radiation with the tissue. In the present work the accurate quantification of DNA radiation damage in the form of absolute cross sections for LEE-induced DNA strand breaks (SBs) between 5 and 20 eV is done by using the DNA origami technique. This method is based on the analysis of well-defined DNA target sequences attached to DNA origami triangles with atomic force microscopy (AFM) on the single molecule level. The present work focuses on poly-adenine sequences (5'-d(A4), 5'-d(A8), 5'-d(A12), 5'-d(A16), and 5'- d(A20)) irradiated with 5.0, 7.0, 8.4, and 10 eV electrons. Independent of the DNA length, the strand break cross section shows a maximum around 7.0 eV electron energy for all investigated oligonucleotides confirming that strand breakage occurs through the initial formation of negative ion resonances. Additionally, DNA double strand breaks from a DNA hairpin 5'-d(CAC)4T(Bt-dT)T2(GTG)4 are examined for the first time and are compared with those of DNA single strands 5'-d(CAC)4 and 5'- d(GTG)4. The irradiation is made in the most likely energy range of 5 to 20 eV with an anionic resonance maximum around 10 eV independently of the DNA sequence. There is a clear difference between σSSB and σDSB of DNA single and double strands, where the strand break for ssDNA are always higher in all electron energies compared to dsDNA by the factor 3. A further part of this work deals with the characterization and analysis of new types of radiosensitizers used in chemoradiotherapy, which selectively increases the DNA damage upon radiation. Fluorinated DNA sequences with 2'-fluoro-2'-deoxycytidine (dFC) show an increased sensitivity at 7 and 10 eV compared to the unmodified DNA sequences by an enhancement factor between 2.1 and 2.5. In addition, light-induced oxidative damage of 5'-d(GTG)4 and 5'-d((CAC)4T(Bt-dT)T2(GTG)4) modified DNA origami triangles by singlet oxygen 1O2 generated from three photoexcited DNA groove binders [ANT994], [ANT1083] and [Cr(ddpd)2][BF4]3 illuminated in different experiments with UV-Vis light at 430, 435 and 530 nm wavelength is demonstrated. The singlet oxygen induced generation of DNA damage could be detected in both aqueous and dry environments for [ANT1083] and [Cr(ddpd)2][BF4]3.
Over the years, we developed highly selective fluorescent probes for K+ in water, which show K+-induced fluorescence intensity enhancements, lifetime changes, or a ratiometric behavior at two emission wavelengths (cf. Scheme 1, K1-K4). In this paper, we introduce selective fluorescent probes for Na+ in water, which also show Na+ induced signal changes, which are analyzed by diverse fluorescence techniques. Initially, we synthesized the fluorescent probes 2, 4, 5, 6 and 10 for a fluorescence analysis by intensity enhancements at one wavelength by varying the Na+ responsive ionophore unit and the fluorophore moiety to adjust different K-d values for an intra- or extracellular Na+ analysis. Thus, we found that 2, 4 and 5 are Na+ selective fluorescent tools, which are able to measure physiologically important Na+ levels at wavelengths higher than 500 nm. Secondly, we developed the fluorescent probes 7 and 8 to analyze precise Na+ levels by fluorescence lifetime changes. Herein, only 8 (K-d=106 mm) is a capable fluorescent tool to measure Na+ levels in blood samples by lifetime changes. Finally, the fluorescent probe 9 was designed to show a Na+ induced ratiometric fluorescence behavior at two emission wavelengths. As desired, 9 (K-d=78 mm) showed a ratiometric fluorescence response towards Na+ ions and is a suitable tool to measure physiologically relevant Na+ levels by the intensity change of two emission wavelengths at 404 nm and 492 nm.
Stereoselective [4+2] Cycloaddition of Singlet Oxygen to Naphthalenes Controlled by Carbohydrates
(2021)
Stereoselective reactions of singlet oxygen are of current interest. Since enantioselective photooxygenations have not been realized efficiently, auxiliary control is an attractive alternative. However, the obtained peroxides are often too labile for isolation or further transformations into enantiomerically pure products. Herein, we describe the oxidation of naphthalenes by singlet oxygen, where the face selectivity is controlled by carbohydrates for the first time. The synthesis of the precursors is easily achieved starting from naphthoquinone and a protected glucose derivative in only two steps. Photooxygenations proceed smoothly at low temperature, and we detected the corresponding endoperoxides as sole products by NMR. They are labile and can thermally react back to the parent naphthalenes and singlet oxygen. However, we could isolate and characterize two enantiomerically pure peroxides, which are sufficiently stable at room temperature. An interesting influence of substituents on the stereoselectivities of the photooxygenations has been found, ranging from 51:49 to up to 91:9 dr (diastereomeric ratio). We explain this by a hindered rotation of the carbohydrate substituents, substantiated by a combination of NOESY measurements and theoretical calculations. Finally, we could transfer the chiral information from a pure endoperoxide to an epoxide, which was isolated after cleavage of the sugar chiral auxiliary in enantiomerically pure form.
Interfacial properties of morpholine-2,5-dione-based oligodepsipeptides and multiblock copolymers
(2019)
Oligodepsipeptides (ODPs) with alternating amide and ester bonds prepared by ring-opening polymerization of morpholine-2,5-dione derivatives are promising matrices for drug delivery systems and building blocks for multifunctional biomaterials. Here, we elucidate the behavior of three telechelic ODPs and one multiblock copolymer containing ODP blocks at the air-water interface. Surprisingly, whereas the oligomers and multiblock copolymers crystallize in bulk, no crystallization is observed at the air-water interface. Furthermore, polarization modulation infrared reflection absorption spectroscopy is used to elucidate hydrogen bonding and secondary structures in ODP monolayers. The results will direct the development of the next ODP-based biomaterial generation with tailored properties for highly sophisticated applications.
Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(ethylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 degrees C and subsequent cooling, whereby a flat substrate was achieved by compression at 72 degrees C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads. optical storage, or cell instructive substrates.
New cryogels for selective dye removal from aqueous solution were prepared by free radical polymerization from the highly water-soluble crosslinker N,N,N’,N’-tetramethyl-N,N’-bis(2-ethylmethacrylate)-propyl-1,3-diammonium dibromide and the sulfobetaine monomer 2-(N-3-sulfopropyl-N,N-dimethyl ammonium)ethyl methacrylate. The resulting white and opaque cryogels have micrometer sized pores with a smaller substructure. They adsorb methyl orange (MO) but not methylene blue (MB) from aqueous solution. Mixtures of MO and MB can be separated through selective adsorption of the MO to the cryogels while the MB remains in solution. The resulting cryogels are thus candidates for the removal of hazardous organic substances, as exemplified by MO and MB, from water. Clearly, it is possible that the cryogels are also potentially interesting for removal of other compounds such as pharmaceuticals or pesticides, but this must be investigated further.
The hydrolytic stability of polymers to be used for coatings in aqueous environments, for example, to confer anti-fouling properties, is crucial. However, long-term exposure studies on such polymers are virtually missing. In this context, we synthesized a set of nine polymers that are typically used for low-fouling coatings, comprising the well-established poly(oligoethylene glycol methylether methacrylate), poly(3-(N-2-methacryloylethyl-N,N-dimethyl) ammoniopropanesulfonate) (“sulfobetaine methacrylate”), and poly(3-(N-3-methacryamidopropyl-N,N-dimethyl)ammoniopropanesulfonate) (“sulfobetaine methacrylamide”) as well as a series of hitherto rarely studied polysulfabetaines, which had been suggested to be particularly hydrolysis-stable. Hydrolysis resistance upon extended storage in aqueous solution is followed by ¹H NMR at ambient temperature in various pH regimes. Whereas the monomers suffered slow (in PBS) to very fast hydrolysis (in 1 M NaOH), the polymers, including the polymethacrylates, proved to be highly stable. No degradation of the carboxyl ester or amide was observed after one year in PBS, 1 M HCl, or in sodium carbonate buffer of pH 10. This demonstrates their basic suitability for anti-fouling applications. Poly(sulfobetaine methacrylamide) proved even to be stable for one year in 1 M NaOH without any signs of degradation. The stability is ascribed to a steric shielding effect. The hemisulfate group in the polysulfabetaines, however, was found to be partially labile.
In many biological and environmental applications spatially resolved sensing of molecular oxygen is desirable. A powerful tool for distributed measurements is optical time domain reflectometry (OTDR) which is often used in the field of telecommunications. We combine this technique with a novel optical oxygen sensor dye, triangular-[4] phenylene (TP), immobilized in a polymer matrix. The TP luminescence decay time is 86 ns. The short decay time of the sensor dye is suitable to achieve a spatial resolution of some meters. In this paper we present the development and characterization of a reflectometer in the UV range of the electromagnetic spectrum as well as optical oxygen sensing with different fiber arrangements.
Femtosecond-pulsed laser written and etched fiber bragg gratings for fiber-optical biosensing
(2018)
We present the development of a label-free, highly sensitive fiber-optical biosensor for online detection and quantification of biomolecules. Here, the advantages of etched fiber Bragg gratings (eFBG) were used, since they induce a narrowband Bragg wavelength peak in the reflection operation mode. The gratings were fabricated point-by-point via a nonlinear absorption process of a highly focused femtosecond-pulsed laser, without the need of prior coating removal or specific fiber doping. The sensitivity of the Bragg wavelength peak to the surrounding refractive index (SRI), as needed for biochemical sensing, was realized by fiber cladding removal using hydrofluoric acid etching. For evaluation of biosensing capabilities, eFBG fibers were biofunctionalized with a single-stranded DNA aptamer specific for binding the C-reactive protein (CRP). Thus, the CRP-sensitive eFBG fiber-optical biosensor showed a very low limit of detection of 0.82 pg/L, with a dynamic range of CRP detection from approximately 0.8 pg/L to 1.2 µg/L. The biosensor showed a high specificity to CRP even in the presence of interfering substances. These results suggest that the proposed biosensor is capable for quantification of CRP from trace amounts of clinical samples. In addition, the adaption of this eFBG fiber-optical biosensor for detection of other relevant analytes can be easily realized.
Luminescent Ionogels with Excellent Transparency, High Mechanical Strength, and High Conductivity
(2020)
The paper describes a new kind of ionogel with both good mechanical strength and high conductivity synthesized by confining the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide ([Bmim][NTf₂]) within an organic–inorganic hybrid host. The organic–inorganic host network was synthesized by the reaction of methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS), and methyl methacrylate (MMA) in the presence of a coupling agent, offering the good mechanical strength and rapid shape recovery of the final products. The silane coupling agent 3-methacryloxypropyltrimethoxysilane (KH-570) plays an important role in improving the mechanical strength of the inorganic–organic hybrid, because it covalently connected the organic component MMA and the inorganic component SiO₂. Both the thermal stability and mechanical strength of the ionogel significantly increased by the addition of IL. The immobilization of [Bmim][NTf₂] within the ionogel provided the final ionogel with an ionic conductivity as high as ca. 0.04 S cm⁻¹ at 50 °C. Moreover, the hybrid ionogel can be modified with organosilica-modified carbon dots within the network to yield a transparent and flexible ionogel with strong excitation-dependent emission between 400 and 800 nm. The approach is, therefore, a blueprint for the construction of next-generation multifunctional ionogels.
The article describes the surface modification of 3D printed poly(lactic acid) (PLA) scaffolds with calcium phosphate (CP)/gelatin and CP/chitosan hybrid coating layers. The presence of gelatin or chitosan significantly enhances CP co-deposition and adhesion of the mineral layer on the PLA scaffolds. The hydrogel/CP coating layers are fairly thick and the mineral is a mixture of brushite, octacalcium phosphate, and hydroxyapatite. Mineral formation is uniform throughout the printed architectures and all steps (printing, hydrogel deposition, and mineralization) are in principle amenable to automatization. Overall, the process reported here therefore has a high application potential for the controlled synthesis of biomimetic coatings on polymeric biomaterials.
The impact that catalysis has on global economy and environment is substantial, since 85% of all chemical industrial processes are catalytic. Among those, 80% of the processes are heterogeneously catalyzed, 17% make use of homogeneous catalysts, and 3% are biocatalytic processes. Especially in the pharmaceutical and agrochemical industry, a significant part of these processes involves chiral compounds. Obtaining enantiomerically pure compounds is necessary and it is usually accomplished by asymmetric synthesis and catalysis, as well as chiral separation. The efficiency of these processes may be vastly improved if the chiral selectors are positioned on a porous solid support, thereby increasing the available surface area for chiral recognition. Similarly, the majority of commercial catalysts are also supported, usually comprising of metal nanoparticles (NPs) dispersed on highly porous oxide or nanoporous carbon material.
Materials that have exceptional thermal and chemical stability, and are electrically conductive are porous carbons. Their stability in extreme pH regions and temperatures, the possibility to tailor their pore architecture and chemical functionalization, and their electric conductivity have already established these materials in the fields of separation and catalysis. However, their heterogeneous chemical structure with abundant defects make it challenging to develop reliable models for the investigation of structure-performance relationships. Therefore, there is a necessity for expanding the fundamental understanding of these robust materials under experimental conditions to allow for their further optimization for particular applications. This thesis gives a contribution to our knowledge about carbons, through different aspects, and in different applications.
On the one hand, a rather exotic novel application was investigated by attempts in synthesizing porous carbon materials with an enantioselective surface. Chapter 4.1 described an approach for obtaining mesoporous carbons with an enantioselective surface by direct carbonization of a chiral precursor. Two enantiomers of chiral ionic liquids (CIL) based on amino acid tyrosine were used as carbon precursors and ordered mesoporous silica SBA-15 served as a hard template for obtaining porosity. The chiral recognition of the prepared carbons has been tested in the solution by isothermal titration calorimetry with enantiomers of Phenylalanine as probes, as well as chiral vapor adsorption with 2-butanol enantiomers. Measurements in both solution and the gas phase revealed the differences in the affinity of carbons towards two enantiomers.
The atomic efficiency of the CIL precursors was increased in Chapter 4.2, and the porosity was developed independently from the development of chiral carbons, through the formation of stable composites of pristine carbon and CIL-derived coating. After the same set of experiments for the investigation of chirality, the enantiomeric ratios of the composites reported herein were even higher than in the previous chapter.
On the other hand, the structure‒activity relationship of carbons as supports for gold nanoparticles in a rather traditional catalytic model reaction, on the interface between gas, liquid, and solid, was studied. In Chapter 5.1 it was shown on the series of catalysts with different porosities that the kinetics of ᴅ-glucose oxidation reaction can be enhanced by increasing the local concentration of the reactants around the active phase of the catalyst. A large amount of uniform narrow mesopores connected to the surface of the Au catalyst supported on ordered mesoporous carbon led to the water confinement, which increased the solubility of the oxygen in the proximity of the catalyst and thereby increased the apparent catalytic activity of this catalyst.
After increasing the oxygen concentration in the internal area of the catalyst, in Chapter 5.2 the concentration of oxygen was increased in the external environment of the catalyst, by the introduction of less cohesive liquids that serve as efficient solvent for oxygen, perfluorinated compounds, near the active phase of the catalyst. This was achieved by a formation of catalyst particle-stabilized emulsions of perfluorocarbon in aqueous ᴅ-glucose solution, that further promoted the catalytic activity of gold-on-carbon catalyst.
The findings reported within this thesis are an important step in the understanding of the structure-related properties of carbon materials.
The structures and synthesis of polyzwitterions ("polybetaines") are reviewed, emphasizing the literature of the past decade. Particular attention is given to the general challenges faced, and to successful strategies to obtain polymers with a true balance of permanent cationic and anionic groups, thus resulting in an overall zero charge. Also, the progress due to applying new methodologies from general polymer synthesis, such as controlled polymerization methods or the use of "click" chemical reactions is presented. Furthermore, the emerging topic of responsive ("smart") polyzwitterions is addressed. The considerations and critical discussions are illustrated by typical examples.
Various 1,6- and 1,8-naphthalenophanes were synthesized by using the Photo-Dehydro-Diels-Alder (PDDA) reaction of bis-ynones. These compounds are easily accessible from omega-(3-iodophenyl)carboxylic acids in three steps. The obtained naphthalenophanes are axially chiral and the activation barrier for the atropisomerization could be determined in some cases by means of dynamic NMR (DNMR) and/or dynamic HPLC (DHPLC) experiments.
In the present thesis, self-assembly of hydrophilic polymers, reinforced hydrogels and inorganic/polymer hybrids were examined. The thesis describes an avenue from polymer synthesis via various methods over polymer self-assembly to the formation of polymer materials that have promising properties for future applications.
Hydrophilic polymers were utilized to form multi-phase systems, water-in-water emulsions and self-assembled structures, e.g. particles/aggregates or hollow structures from completely water-soluble building blocks. The structuring of aqueous environments by hydrophilic homo and block copolymers was further utilized in the formation of supramolecular hydrogels with compartments or specific thermal behavior. Furthermore, inorganic graphitic carbon nitride (g-CN) was utilized as photoinitiator for hydrogel formation and as reinforcer for hydrogels. As such, hydrogels with remarkable mechanical properties were synthesized, e.g. high compressibility, high storage modulus or lubricity. In addition, g-CN was combined with polymers for a broad range of materials, e.g. coatings, films or latex, that could be utilized in photocatalytic applications. Another inorganic material class was combined with polymers in the present thesis as well, namely metal-organic frameworks (MOFs). It was shown that the pore structure of MOFs enables improved control over tacticity and achievement of high molar masses. Furthermore, MOF-based polymerization catalysis was introduced with improved control for coordinating monomers, catalyst recyclability and decreased metal contamination in the product. Finally, the effect of external influence on MOF morphology was studied, e.g. via solvent or polymer additives, which allowed the formation of various MOF structures.
Overall, advances in several areas of polymer science are presented in here. A major topic of the thesis was hydrophilic polymers and hydrogels that currently constitute significant materials in the polymer field due to promising future applications in biomedicine. Moreover, the combination of polymers with materials from other areas of research, i.e. g-CN and MOFs, provided various new materials with remarkable properties also of interest for applications in the future, e.g. coatings, particle structures and catalysis.
Highly luminescent indium phosphide zinc sulfide (InPZnS) quantum dots (QDs), with zinc selenide/zinc sulfide (ZnSe/ZnS) shells, were synthesized. The QDs were modified via a post-synthetic ligand exchange reaction with 3-mercaptopropionic acid (MPA) and 11-mercaptoundecanoic acid (MUA) in different MPA:MUA ratios, making this study the first investigation into the effects of mixed ligand shells on InPZnS QDs. Moreover, this article also describes an optimized method for the correlation of the QD size vs. optical absorption of the QDs. Upon ligand exchange, the QDs can be dispersed in water. Longer ligands (MUA) provide more stable dispersions than short-chain ligands. Thicker ZnSe/ZnS shells provide a better photoluminescence quantum yield (PLQY) and higher emission stability upon ligand exchange. Both the ligand exchange and the optical properties are highly reproducible between different QD batches. Before dialysis, QDs with a ZnS shell thickness of ~4.9 monolayers (ML), stabilized with a mixed MPA:MUA (mixing ratio of 1:10), showed the highest PLQY, at ~45%. After dialysis, QDs with a ZnS shell thickness of ~4.9 ML, stabilized with a mixed MPA:MUA and a ratio of 1:10 and 1:100, showed the highest PLQYs, of ~41%. The dispersions were stable up to 44 days at ambient conditions and in the dark. After 44 days, QDs with a ZnS shell thickness of ~4.9 ML, stabilized with only MUA, showed the highest PLQY, of ~34%.
A surface modification of ultraflat gold nanotriangles (AuNTs) with different shaped nanoparticles is of special relevance for surface-enhanced Raman scattering (SERS) and the photo-catalytic activity of plasmonic substrates. Therefore, different approaches are used to verify the flat platelet morphology of the AuNTs by oriented overgrowth with metal nanoparticles. The most important part for the morphological transformation of the AuNTs is the coating layer, containing surfactants or polymers. By using well established AuNTs stabilized by a dioctyl sodium sulfosuccinate (AOT) bilayer, different strategies of surface modification with noble metal nanoparticles are possible. On the one hand undulated superstructures were synthesized by in situ growth of hemispherical gold nanoparticles in the polyethyleneimine (PEI)-coated AOT bilayer of the AuNTs. On the other hand spiked AuNTs were obtained by a direct reduction of Au³⁺ ions in the AOT double layer in presence of silver ions and ascorbic acid as reducing agent. Additionally, crumble topping of the smooth AuNTs can be realized after an exchange of the AOT bilayer by hyaluronic acid, followed by a silver-ion mediated reduction with ascorbic acid. Furthermore, a decoration with silver nanoparticles after coating the AOT bilayer with the cationic surfactant benzylhexadecyldimethylammonium chloride (BDAC) can be realized. In that case the ultraviolet (UV)-absorption of the undulated Au@Ag nanoplatelets can be tuned depending on the degree of decoration with silver nanoparticles. Comparing the Raman scattering data for the plasmon driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4′-dimercaptoazobenzene (DMAB) one can conclude that the most important effect of surface modification with a 75 times higher enhancement factor in SERS experiments becomes available by decoration with gold spikes.
Ammonia is a chemical of fundamental importance for nature`s vital nitrogen cycle. It is crucial for the growth of living organisms as well as food and energy source. Traditionally, industrial ammonia production is predominated by Haber- Bosch process (HBP) which is based on direct conversion of N2 and H2 gas under high temperature and high pressure (~500oC, 150-300 bar). However, it is not the favorite route because of its thermodynamic and kinetic limitations, and the need for the energy intense production of hydrogen gas by reforming processes. All these disfavors of HBP open a target to search for an alternative technique to perform efficient ammonia synthesis via electrochemical catalytic processes, in particular via water electrolysis, using water as the hydrogen source to save the process from gas reforming.
In this study, the investigation of the interface effects between imidazolium-based ionic liquids and the surface of porous carbon materials with a special interest in the nitrogen absorption capability. As the further step, the possibility to establish this interface as the catalytically active area for the electrochemical N2 reduction to NH3 has been evaluated. This particular combination has been chosen because the porous carbon materials and ionic liquids (IL) have a significant importance in many scientific fields including catalysis and electrocatalysis due to their special structural and physicochemical properties. Primarily, the effects of the confinement of ionic liquid (EmimOAc, 1-Ethyl-3-methylimidazolium acetate) into carbon pores have been investigated. The salt-templated porous carbons, which have different porosity (microporous and mesoporous) and nitrogen species, were used as model structures for the comparison of the IL confinement at different loadings. The nitrogen uptake of EmimOAc can be increased by about 10 times by the confinement in the pores of carbon materials compared to the bulk form. In addition, the most improved nitrogen absorption was observed by IL confinement in micropores and in nitrogen-doped carbon materials as a consequence of the maximized structural changes of IL. Furthermore, the possible use of such interfaces between EmimOAc and porous carbon for the catalytic activation of dinitrogen during the kinetically challenging NRR due to the limited gas absorption in the electrolyte, was examined. An electrocatalytic NRR system based on the conversion of water and nitrogen gas to ammonia at ambient operation conditions (1 bar, 25 °C) was performed in a setup under an applied electric potential with a single chamber electrochemical cell, which consists of the combination of EmimOAc electrolyte with the porous carbon-working electrode and without a traditional electrocatalyst. Under a potential of -3 V vs. SCE for 45 minutes, a NH3 production rate of 498.37 μg h-1 cm-2 and FE of 12.14% were achieved. The experimental observations show that an electric double-layer, which serves the catalytically active area, occurs between a microporous carbon material and ions of the EmimOAc electrolyte in the presence of sufficiently high provided electric potential. Comparing with the typical NRR systems which have been reported in the literature, the presented electrochemical ammonia synthesis approach provides a significantly higher ammonia production rate with a chance to avoid the possible kinetic limitations of NRR. In terms of operating conditions, ammonia production rate and the faradic efficiency without the need for any synthetic electrocatalyst can be resulted of electrocatalytic activation of nitrogen in the double-layer formed between carbon and IL ions.
In recent years people have realised non-renewability of our modern society which relays on spending huge amounts of energy mostly produced from fosil fuels, such as oil and coal, and the shift towards more sustainable energy sources has started. However, sustainable sources of energy, such as wind-, solar- and hydro-energy, produce primarily electrical energy and can not just be poured in canister like many fosil fuels, creating necessity for rechragable batteries. However, modern Li-ion batteries are made from toxic heavy metals and sustainable alternatives are needed. Here we show that naturally abundant catecholic and guaiacyl groups can be utilised to replace heavy metals in Li-ion batteries.
Foremost vanillin, a naturally occurring food additive that can be sustainably synthesised from industrial biowaste, lignin, was utilised to synthesise materials that showed extraordinary performance as cathodes in Li-ion batteries. Furthermore, behaviour of catecholic and guiacyl groups in Li-ion system was compared, confirming usability of guiacayl containing biopolymers as cathodes in Li-ion batteries. Lastly, naturally occurring polyphenol, tannic acid, was incorporated in fully bioderived hybrid material that shows performance comparable to commercial Li-ion batteries and good stability.
This thesis presents an important advancement in understanding of biowaste derived cathode materials for Li-ion batteries. Further research should be conducted to better understand behaviour of guaiacyl groups during Li-ion battery cycling. Lastly, challenges of incorporation of lignin, an industrial biowaste, have to be addressed and lignin should be incorporated as a cathode material in Li-ion batteries.
Abstract. Catalysis is one of the most effective tools for the highly efficient assembly of complex molecular structures. Nevertheless, it is mainly represented by transition metal-based catalysts and typically is an energy consuming process. Therefore, photocatalysis utilizing solar energy is one of the appealing approaches to overcome these problems. A great alternative to classic transition metal-based photocatalysts, carbon nitrides, a group of organic polymeric semiconductors, have already shown their efficiency in water splitting, CO2 reduction, and organic pollutants degradation. However, these materials have also a great potential for the use in functionalization of complex organic molecules for synthetic needs as it was shown in recent years.
This work addresses the challenge to develop efficient system for heterogeneous organic photocatalysis, employing cheap and environmentally benign photocatalysts – carbon nitrides. Herein, fundamental properties of semiconductors are studied from the organic chemistry standpoint; the inherent properties of carbon nitrides, such as ability to accumulate electrons, are deeply investigated and their effect on the reaction outcome is established. Thus, understanding of the electron charging processes allowed for the synthesis of otherwise hardly-achieved diazetidines-1,3 by tetramerization of benzylamines. Furthermore, the high electron capacity of Potassium Poly(heptazine imide)s (K-PHI) made possible a multi-electron reduction of aromatic nitro compounds to bare or formylated anilines. Additionally, two deep eutectic solvents (DES) were designed as a sustainable reaction media and reducing reagent for this reaction. Eventually, the high oxidation ability of carbon nitride K-PHI is employed in a challenging reaction of halide anion oxidation (Cl―, Br―) to accomplish electrophilic substitution in aromatic ring. The possibility to utilize NaCl solution (seawater mimetic) for the chlorination of electron rich arenes was shown. Eventually, light itself is used as a tool in a chromoselective photocatalytic oxidation of aromatic thiols and thioacetatas to three different compounds, using UV, blue, and red LEDs.
All in all, the work enhances understanding the mechanism of heterogeneous photocatalysis in synthetic organic reactions and therefore, is a step forward to the sustainable methods of synthesis in organic chemistry.
Metal halide perovskites have merged as an attractive class of materials for photovoltaic applications due to their excellent optoelectronic properties. However, the long term stability is a roadblock for this class of material’s industrial pathway. Increasing evidence shows that intrinsic defects in perovskite promote material degradation. Consequently, understanding defect behaviours in perovskite materials is essential to further improve device stability and performance. This dissertation, hence, focuses on the topic of defect chemistry in halide perovskites.
The first part of the dissertation gives a brief overview of the defect properties in halide perovskite. Subsequently, the second part shows that doping methylammonium lead iodide with a small amount of alkaline earth metals (Sr and Mg) creates a higher quality, less defective material resulted in high open circuit voltages in both n-i-p and p-i-n architecture. It has been found that the mechanism of doping has two distinct regimes in which a low doping concentration enables the inclusion of the dopants into the lattice whereas higher doping concentrations lead to phase segregation. The material can be more n-doped in the low doping regime while being less n-doped in the high doping regime. The threshold of these two regimes is based on the atomic size of the dopants.
The next part of the dissertation examines the photo-induced degradation in methylammonium lead iodide. This degradation mechanism links closely to the formation and migration of ionic defects. After they are formed, these ionic defects can migrate, however, not freely depending on the defect concentration and their distribution. In fact, a highly concentrated defect region such as the grain boundaries can inhibit the migration of ionic defects. This has implications for material design as perovskite solar cells normally employ a polycrystalline thin-film which has a high density of grain boundary.
The final study presented in this PhD dissertation focuses on the stability of the state-of-the-art triple cation perovskite-based solar devices under external bias. Prolonged bias (more than three hours) is found to promote amorphization in halide perovskite. The amorphous phase is suspected to accumulate at the interfaces especially between the hole selective layer and perovskite. This amorphous phase inhibits the charge collection and severely affects the device performance. Nonetheless, the devices can recover after resting without bias in the dark. This amorphization is attributed to ionic defect migration most likely halides. This provides a new understanding of the potential degradation mechanisms in perovskite solar cells under operational conditions.
Lately, the integration of upconverting nanoparticles (UCNP) in industrial, biomedical and scientific applications has been increasingly accelerating, owing to the exceptional photophysical properties that UCNP offer. Some of the most promising applications lie in the field of medicine and bioimaging due to such advantages as, among others, deeper tissue penetration, reduced optical background, possibility for multicolor imaging, and lower toxicity, compared to many known luminophores. However, some questions regarding not only the fundamental photophysical processes, but also the interaction of the UCNP with other luminescent reporters frequently used for bioimaging and the interaction with biological media remain unanswered. These issues were the primary motivation for the presented work.
This PhD thesis investigated several aspects of various properties and possibilities for bioapplications of Yb3+,Tm3+-doped NaYF4 upconverting nanoparticles. First, the effect of Gd3+ doping on the structure and upconverting behaviour of the nanocrystals was assessed. The ageing process of the UCNP in cyclohexane was studied over 24 months on the samples with different Gd3+ doping concentrations. Structural information was gathered by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), and discussed in relation to spectroscopic results, obtained through multiparameter upconversion luminescence studies at various temperatures (from 4 K to 295 K). Time-resolved and steady-state emission spectra recorded over this ample temperature range allowed for a deeper understanding of photophysical processes and their dependence on structural changes of UCNP.
A new protocol using a commercially available high boiling solvent allowed for faster and more controlled production of very small and homogeneous UCNP with better photophysical properties, and the advantages of a passivating NaYF4 shell were shown.
Förster resonance energy transfer (FRET) between four different species of NaYF4: Yb3+, Tm3+ UCNP (synthesized using the improved protocol) and a small organic dye was studied. The influence of UCNP composition and the proximity of Tm3+ ions (donors in the process of FRET) to acceptor dye molecules have been assessed. The brightest upconversion luminescence was observed in the UCNP with a protective inert shell. UCNP with Tm3+ ions only in the shell were the least bright, but showed the most efficient energy transfer.
In the final part, two surface modification strategies were applied to make UCNP soluble in water, which simultaneously allowed for linking them via a non-toxic copper-free click reaction to the liposomes, which served as models for further cell experiments. The results were assessed on a confocal microscope system, which was made possible by lesser known downshifting properties of Yb3+, Tm3+-doped UCNP. Preliminary antibody-staining tests using two primary and one dye-labelled secondary antibodies were performed on MDCK-II cells.
Hybrid organic-inorganic perovskites have attracted attention in recent years, caused by the incomparable increase in efficiency in energy convergence, which implies the application as an absorber material for solar cells. A disadvantage of these materials is, among others, the instability to moisture and UV-radiation. One possible solution for these problems is the reduction of the size towards the nano world. With that nanosized perovskites are showing superior stability in comparison to e.g. perovskite layers. Additionally to this the nanosize even enables stable perovskite structures, which could not be achieved otherwise at
room temperature.
This thesis is separated into two major parts. The separation is done by the composition and the band gap of the material and at the same time the shape and size of the nanoparticles. Here the division is made by the methylammonium lead tribromide nanoplatelets and the caesium lead triiodide nanocubes.
The first part is focusing on the hybrid organic-inorganic perovskite (methylammonium lead tribromide) nanoplatelets with a band gap of 2.35 eV and their thermal behaviour. Due to the challenging character of this material, several analysis methods are used to investigate the sub nano and nanostructures under the influence of temperature. As a result, a shift of phase-transition temperatures towards higher temperatures is observed. This unusual behaviour can be explained by the ligand, which is incorporated in the perovskite outer structure and adds phase-stability into the system.
The second part of this thesis is focusing on the inorganic caesium lead triiodide nanocubes with a band gap of 1.83 eV. These nanocrystals are first investigated and compared by TEM, XRD and other optical methods. Within these methods, a cuboid and orthorhombic structure are revealed instead of the in literature described cubic shape and structure. Furthermore, these cuboids are investigated towards their self-assembly on a substrate. Here a high degree in self-assembly is shown. As a next step, the ligands of the nanocuboids are exchanged against other ligands to increase the charge carrier mobility. This is further investigated by the above-mentioned methods. The last section is dealing with the enhancement of the CsPbI3 structure, by incorporating potassium in the crystal structure. The results are suggesting here an increase in stability.
"How Wenzel and Cassie were wrong" – this was the eye-catching title of an article published by Lichao Gao and Thomas McCarthy in 2007, in which fundamental interpretations of wetting behavior were put into question. The authors initiated a discussion on a subject, which had been generally accepted a long time ago and they showed that wetting phenomena were not as fully understood as imagined. Similarly, this thesis tries to put a focus on certain aspects of liquid wetting, which so far have been widely neglected in terms of interpretation and experimental proof. While the effect of surface roughness on the macroscopically observed wetting behavior is commonly and reliably interpreted according to the well-known models of Wenzel and Cassie/Baxter, the size-scale of the structures responsible for the surface's rough texture has not been of further interest. Analogously, the limits of these models have not been described and exploited. Thus, the question arises, what will happen when the size of surface structures is reduced to the size of the contacting liquid molecules itself? Are common methods still valid or can deviations from macroscopic behavior be observed?
This thesis wants to create a starting point regarding these questions. In order to investigate the effect of smallest-scale surface structures on liquid wetting, a suitable model system is developed by means of self-assembled monolayer (SAM) formation from (fluoro)organic thiols of differing lengths of the alkyl chain. Surface topographies are created which rely on size differences of several Ångströms and exhibit surprising wetting behavior depending on the choice of the individual precursor system. Thus, contact angles are experimentally detected, which deviate considerably from theoretical calculations based on Wenzel and Cassie/Baxter models and confirm that sub-nm surface topographies affect wetting. Moreover, experimentally determined wetting properties are found to correlate well to an assumed scale-dependent surface tension of the contacting liquid. This behavior has already been described for scattering experiments taking into account capillary waves on the liquid surface induced by temperature and had been predicted earlier by theoretical calculations.
However, the investigation of model surfaces requires the provision of suitable precursor molecules, which are not commercially available and opens up a door to the exotic chemistry of fluoro-organic materials. During the course of this work, the synthesis of long-chain precursors is examined with a particular focus put on oligomerically pure semi-fluorinated n-alkyl thiols and n-alkyl trichlorosilanes. For this, general protocols for the syntheses of the desired compounds are developed and product mixtures are assayed to be separated into fractions of individual chain lengths by fluorous-phase high-performance liquid chromatography (F-HPLC).
The transition from model systems to technically more relevant surfaces and applications is initiated through the deposition of SAMs from long-chain fluorinated n-alkyl trichlorosilanes. Depositions are accomplished by a vapor-phase deposition process conducted on a pilot-scale set-up, which enables the exact control of relevant process parameters. Thus, the influence of varying deposition conditions on the properties of the final coating is examined and analyzed for the most important parameters. The strongest effect is observed for the partial pressure of reactive water vapor, which directly controls the extent of precursor hydrolysis during the deposition process. Experimental results propose that the formation of ordered monolayers rely on the amount of hydrolyzed silanol species present in the deposition system irrespective of the exact grade of hydrolysis. However, at increased amounts of species which are able to form cross-linked molecules due to condensation reactions, films deteriorate in quality. This effect is assumed to be caused by the introduction of defects within the film and the adsorption of cross linked agglomerates. Deposition conditions are also investigated for chain extended precursor species and reveal distinct differences caused by chain elongation.
Aluminum oxide is an Earth-abundant geological material, and its interaction with water is of crucial importance for geochemical and environmental processes. Some aluminum oxide surfaces are also known to be useful in heterogeneous catalysis, while the surface chemistry of aqueous oxide interfaces determines the corrosion, growth and dissolution of such materials. In this doctoral work, we looked mainly at the (0001) surface of α-Al 2 O 3 and its reactivity towards water. In particular, a great focus of this work is dedicated to simulate and address the vibrational spectra of water adsorbed on the α-alumina(0001) surface in various conditions and at different coverages. In fact, the main source of comparison and inspiration for this work comes from the collaboration with the “Interfacial Molecular Spectroscopy” group led by Dr. R. Kramer Campen at the Fritz-Haber Institute of the MPG in Berlin. The expertise of our project partners in surface-sensitive Vibrational Sum Frequency (VSF) generation spectroscopy was crucial to develop and adapt specific simulation schemes used in this work. Methodologically, the main approach employed in this thesis is Ab Initio Molecular Dynamics (AIMD) based on periodic Density Functional Theory (DFT) using the PBE functional with D2 dispersion correction. The analysis of vibrational frequencies from both a static and a dynamic, finite-temperature perspective offers the ability to investigate the water / aluminum oxide interface in close connection to experiment.
The first project presented in this work considers the characterization of dissociatively adsorbed deuterated water on the Al-terminated (0001) surface. This particular structure is known from both experiment and theory to be the thermodynamically most stable surface termination of α-alumina in Ultra-High Vacuum (UHV) conditions. Based on experiments performed by our colleagues at FHI, different adsorption sites and products have been proposed and identified for D 2 O. While previous theoretical investigations only looked at vibrational frequencies of dissociated OD groups by staticNormal Modes Analysis (NMA), we rather employed a more sophisticated approach to directly assess vibrational spectra (like IR and VSF) at finite temperature from AIMD. In this work, we have employed a recent implementation which makes use of velocity-velocity autocorrelation functions to simulate such spectral responses of O-H(D) bonds. This approach allows for an efficient and qualitatively accurate estimation of Vibrational Densities of States (VDOS) as well as IR and VSF spectra, which are then tested against experimental spectra from our collaborators.
In order to extend previous work on unimolecularly dissociated water on α-Al 2 O 3 , we then considered a different system, namely, a fully hydroxylated (0001) surface, which results from the reconstruction of the UHV-stable Al-terminated surface at high water contents. This model is then further extended by considering a hydroxylated surface with additional water molecules, forming a two-dimensional layer which serves as a potential template to simulate an aqueous interface in environmental conditions. Again, employing finite-temperature AIMD trajectories at the PBE+D2 level, we investigated the behaviour of both hydroxylated surface (HS) and the water-covered structure derived from it (known as HS+2ML). A full range of spectra, from VDOS to IR and VSF, is then calculated using the same methodology, as described above. This is the main focus of the second project, reported in Chapter 5. In this case, comparison between theoretical spectra and experimental data is definitely good. In particular, we underline the nature of high-frequency resonances observed above 3700 cm −1 in VSF experiments to be associated with surface OH-groups, known as “aluminols” which are a key fingerprint of the fully hydroxylated surface.
In the third and last project, which is presented in Chapter 6, the extension of VSF spectroscopy experiments to the time-resolved regime offered us the opportunity to investigate vibrational energy relaxation at the α-alumina / water interface. Specifically, using again DFT-based AIMD simulations, we simulated vibrational lifetimes for surface aluminols as experimentally detected via pump-probe VSF. We considered the water-covered HS model as a potential candidate to address this problem. The vibrational (IR) excitation and subsequent relaxation is performed by means of a non-equilibrium molecular dynamics scheme. In such a scheme, we specifically looked at the O-H stretching mode of surface aluminols. Afterwards, the analysis of non-equilibrium trajectories allows for an estimation of relaxation times in the order of 2-4 ps which are in overall agreement with measured ones.
The aim of this work has been to provide, within a consistent theoretical framework, a better understanding of vibrational spectroscopy and dynamics for water on the α-alumina(0001) surface,ranging from very low water coverage (similar to the UHV case) up to medium-high coverages, resembling the hydroxylated oxide in environmental moist conditions.