6 Materialchemie
Filtern
Erscheinungsjahr
- 2021 (134) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (134) (entfernen)
Sprache
- Englisch (133)
- Mehrsprachig (1)
Referierte Publikation
- ja (134) (entfernen)
Schlagworte
- MALDI-TOF MS (12)
- Polylactide (10)
- SAXS (10)
- Crystallization (8)
- Mechanochemistry (7)
- Nanoparticles (6)
- Electron microscopy (4)
- X-ray photoelectron spectroscopy (4)
- X-ray scattering (4)
- Density functional theory (3)
- Energetic materials (3)
- Laser-induced periodic surface structures (LIPSS) (3)
- Nanomaterials (3)
- Polycondensation (3)
- Polymerization (3)
- Synchrotron radiation (3)
- XPS (3)
- 2D Materials (2)
- AFM (2)
- API (2)
- Aging (2)
- Alkali-activated materials (2)
- Catalysis (2)
- Catalyst (2)
- Composites (2)
- DNA (2)
- Dosimetry (2)
- Electrochemistry (2)
- Electronic structure (2)
- Epoxy nanocomposites (2)
- Geant4 (2)
- Geant4-DNA (2)
- HPLC (2)
- In situ real-time monitoring (2)
- Instrumentation (2)
- Ionization (2)
- Kinetics (2)
- LEE (2)
- Low energy electrons (2)
- MIC (2)
- Mechanical properties (2)
- Metal-organic frameworks (2)
- Microbially induced corrosion (2)
- Microdosimetry (2)
- NAP-XPS (2)
- Nucleation (2)
- Phase diagrams (2)
- Quick-EXAFS (2)
- Radiation damage (2)
- Radiation protection (2)
- Raman spectroscopy (2)
- Rigid amorphous fraction (2)
- Ring-opening polymerization (2)
- SZ2080 negative photo-resist (2)
- Simvastatin (2)
- Small-angle X-ray scattering (2)
- Surface functionalization (2)
- TOPAS (2)
- TOPAS-nbio (2)
- XANES (2)
- 3D printing (1)
- ACEnano (1)
- AEMFC (1)
- AFM force spectroscopy (1)
- ASTM (1)
- AZ31 (1)
- Ab initio simulation (1)
- Absolute adsorption (1)
- Acid resistance (1)
- Additive Manufacturing (1)
- Additive manufacturing (1)
- Adhesion by mechanical interlocking (1)
- Advanced material (1)
- Advanced materials (1)
- Affinity Chromatography (1)
- Affinity Extraction (1)
- Affinity Separation (1)
- Aggregation (1)
- Alkaline earth metal coordination polymers (1)
- Alloy morphology (1)
- Alternating co-poly(ether pyridine)s (1)
- Aluminium oxide hydroxide (1)
- Amorphization (1)
- Amorphous materials (1)
- Amperometry (1)
- Amphiphilicity (1)
- Analysis (1)
- Analytical methods (1)
- Anhydrite (1)
- Annealing (1)
- Anthracene schiff base (1)
- Antibacterial (1)
- Antibody Purification (1)
- Antifouling (1)
- Aromatic (1)
- Aromatic organic compounds, (1)
- Artificial intelligence (1)
- Atomic force microscopy (1)
- Au nanoparticles (1)
- AuNP (1)
- Automated Purification (1)
- Automated image analysis (1)
- Automation (1)
- Band gap (1)
- Base damage (1)
- Base loss (1)
- Bbeverages (1)
- Benchmarking (1)
- Beta decay (1)
- Beta particle (1)
- Bimetallic alloy (1)
- Biofilm formation (1)
- Biofilms (1)
- Biogene Schwefelsäurekorrosion (1)
- Biogenic acid corrosion (1)
- Biological & biomedical applications (1)
- Biomimetic (1)
- Biosourced isosorbide (1)
- Bipyramid (1)
- Bismuth titanates (1)
- Borosilicate Glass (1)
- Boson peak (1)
- Brachytherapy (1)
- Broadband dielectric spectroscopy (1)
- CCQM (Consultative Committee for Amount of Substance) (1)
- Calcium sulfate (1)
- Cancer therapy (1)
- Cancer treatment (1)
- Carbon nanoparticles (1)
- Cassical nucleation theory (1)
- Catalysts (1)
- Cell appendages (1)
- Characterisation (1)
- Charge-to-size-ratio (1)
- Citizen Science (1)
- Clustered nanoparticles (1)
- Coating materials (1)
- Column holder (1)
- Combined techniques (1)
- Complex-shape (1)
- Composition (1)
- Concentration (1)
- Concentration step (1)
- Construction (1)
- Conversion (1)
- Copolymerization (1)
- Core-shell (1)
- Core-shell structures (1)
- Correlation (1)
- Correlative analysis (1)
- Corrosion (1)
- Corrosion protection (1)
- Cryo XPS (1)
- CuNPs (1)
- Cyclic voltammetry (1)
- Cycloparaphenylenes (1)
- D7755-11 (1)
- DFT (1)
- DFT calculations (1)
- DNA damage (1)
- DNA radiation damage (1)
- DOPO (1)
- DSM 5009 (1)
- Data curation (1)
- Diagnostic Antibodies (1)
- Differential scanning calorimetry (1)
- Diffusion/diffusivity (1)
- Dimorphs (1)
- Direct damage (1)
- Direct laser interference patterning (DLIP) (1)
- Direct laser writing (1)
- Discotic liquid crystals (1)
- Disorganized bone (1)
- Dispersive-XAS (1)
- Dissociative electron attachment (DEA) (1)
- Dissociative electron transfer (DET) (1)
- Double-strand break (DSB) (1)
- Down Stream Processing (1)
- Dry DNA (1)
- Drywood termite (1)
- Dynamic light scattering (1)
- ELISA (1)
- EXAFS (1)
- Ectoine (1)
- Elastic Crystal (1)
- Elastic membrane (1)
- Elasticity (1)
- Electrical conductivity (1)
- Electrolysis (1)
- Electrolyte membrane (1)
- Electron spectroscopy (1)
- Electron tomography (1)
- Electrophoresis (1)
- Electrospinning (1)
- Electrospun nanocomposite fiber (1)
- Element-specific spectroscopy (1)
- Energy dependent XPS (1)
- Energy deposit (1)
- Energy dispersive X-ray spectroscopy (1)
- Epitaxy (1)
- Estrogen (1)
- Eu (1)
- European Centre (1)
- Eutectic (1)
- Extended X-ray absorption fine structure (EXAFS) (1)
- F pili (1)
- FAIR (1)
- FPLC (1)
- Fabrication parameters (1)
- Fast scanning calorimetry (1)
- Fatigue (1)
- Fe-Ni oxides (1)
- Femtosecond laser (1)
- Ferroelectricity/ferroelectric materials (1)
- Filter crucible (1)
- Flame retardant (1)
- Flash DSC (1)
- Flexible (1)
- Fluorine coordination polymers (1)
- Foaming (1)
- Force-distance-curve (1)
- Fuell cells (1)
- Functional properties (1)
- Gamma ray (1)
- Gas separation membranes (1)
- Gel (1)
- Glass Support (1)
- Glass powder (1)
- Glass transition temperature (1)
- Glycolide (1)
- Gold Nanoparticles (1)
- Graphene (1)
- Graphene template (1)
- Graphene-based polyglycerol sulfates (1)
- Graphhene (1)
- Grating method (1)
- Grignard reaction (1)
- Grignard-Reaktion (1)
- HAXPES (1)
- HERFD-XAS (1)
- HKUST-1 (1)
- Halloysite nanotubes (1)
- Hard x-ray photoelectron spectroscopy (1)
- High entropy alloy (1)
- High pressure (1)
- High temperature corrosion (1)
- High-Speed Separations (1)
- High-entropy alloys (1)
- High-pressure (1)
- High-throughput computations (1)
- Highly permeably polynorbornenes (1)
- Homogenization (1)
- Host–guest systems (1)
- Human Plasma (1)
- Hybrid metrology measurement (1)
- Hydantoin (1)
- Hydrated DNA (1)
- Hydrated electron (1)
- Hydration shell (1)
- Hydrogen cryostorage (1)
- Hydrogenated nanostructures (1)
- Hydrophobic interaction chromatography (1)
- Hydrophobicity (1)
- Hydroxyl radical (1)
- Hyperbranched (1)
- ICP-OES (1)
- ISO 23173 (1)
- IgG determination (1)
- Image segmentation (1)
- Imaging AES (1)
- Imaging SIMS (1)
- Imaging XPS (1)
- Immunoassay (1)
- Impact Sensitivity (1)
- In-situ (1)
- Indirect damage (1)
- Industrial application (1)
- Industrial applications (1)
- Inelastic Neutron Scattering Spectroscopy (1)
- Influenza A virus (1)
- Inter-laboratory comparison (1)
- Interaction with atmospheres (1)
- Interfacial stability (1)
- Intermodulation AFM (1)
- Intrinsically conducting polymers (1)
- Ionic liquid (1)
- Ionic liquid crystal (1)
- Iron (1)
- K-rich Birnessite (K0.45MnO2) (1)
- L-lactide (1)
- Lacunae (1)
- Lanthanides doped coordination polymers (1)
- Laser ablation (1)
- Laser processing (1)
- Laser-induced x-ray emission (1)
- Lateral resolution (1)
- Lead-free ceramics (1)
- Lignin (1)
- Lignosulfonates (1)
- Lithium-sulfur battery (1)
- Livermore model (1)
- Localized surface plasmon resonance (1)
- Low-density polyethylene (1)
- Luminescence (1)
- MCS (1)
- MOF databases (1)
- MOFs (1)
- MOUSE (1)
- Macrocycles (1)
- Magnesium alloys (1)
- Magnetism (1)
- Martin Seah (1)
- Mass Spectrometry (1)
- Mass spectrometry (1)
- Mass-Spectral Reconstruction (1)
- Material chemistry (1)
- Material synthesis (1)
- Materials Stability (1)
- Mechanical activation (1)
- Mechanical alloying (1)
- Mechanically flexible crystals (1)
- Mechanism (1)
- Mechanochemical pictographs (1)
- Mesocrystal (1)
- Mesoporous Silica (1)
- Metal fluorides (1)
- Metal organic frameworks (1)
- Metal-organic polyhedra (1)
- Methane Oxidation (1)
- Methodology (1)
- Methoxytrimethlsilane (1)
- Methyl group rotation (1)
- Metrology (1)
- Metrology in Chemistry and Biology (1)
- MicroXRF (1)
- Microbially influenced corrosion (MIC) (1)
- Microemulsion (1)
- Microfabrication (1)
- Microplastic (1)
- Microstructure (1)
- Milling (1)
- MoO3 (1)
- Modelling (1)
- Modulus (1)
- Molecular recognition (1)
- Monoclonal Antibodies (1)
- Monolith (1)
- Monte-Carlo simulation (1)
- Morphology control (1)
- Multi-resistant bacteria (1)
- Multilayercoatings (1)
- Multiphoton lithography (1)
- Multivalency (1)
- Mussel-inspired coating (1)
- Mutual calibration (1)
- Mössbauer Spectroscopy (1)
- N-Chlorination (1)
- NEXAFS (1)
- NMR spectroscopy (1)
- NMR-Spektroskopie (1)
- NP (1)
- Naica (1)
- Nano structure (1)
- Nano-safety (1)
- Nanoalloy (1)
- Nanocomposite fibers (1)
- Nanocomposites (1)
- Nanomechanical charecteisation (1)
- Nanometrology (1)
- Nanoparticle (1)
- Nanoparticle concentration (1)
- Nanosafety (1)
- Nanostructure (1)
- Nanotechnology (1)
- Narrow line method (1)
- Near ambient pressure xray photo electron spectroscopy (1)
- Near-ambient pressure X-ray photoelectron spectroscopy (1)
- Net-ionization reaction (1)
- Neural networks (1)
- Neutron scattering (1)
- Nitrides (1)
- Nitrification (1)
- Nitrobenzene reduction (1)
- Noise in image (1)
- Nomenclature (1)
- OER (1)
- OH radical (1)
- OH radicals (1)
- Ochratoxin A (1)
- Open Science (1)
- Osteogenesis (1)
- Ovariectomy (1)
- Oxidation (1)
- Oxygen Reduction Reaction (1)
- Oxygen evolution reaction (1)
- Oxygen evolution reaction (OER) (1)
- P. Fluorescens (1)
- PES (1)
- PGM-free catalyst (1)
- PVDF-based membrane (1)
- Particle scattering (1)
- Particle size and shape distribution (1)
- Penelope model (1)
- Phonons (1)
- Phosphine oxide (1)
- Phosphorus (1)
- Plasma deposition (1)
- Plasmonic photocatalysis (1)
- Plastic bottles (1)
- Plastic pollution (1)
- Platinum (1)
- Poly(acrylic acid) (1)
- Poly(amino phosphodiester) (1)
- Polyclonal Antibodies (1)
- Polyethylene colonization (1)
- Polyethylene terephthalate (1)
- Polyglycerol (1)
- Polymer based Nanocomposites (1)
- Polymer composites (1)
- Polymer of intrisic microporosity (1)
- Polymers (1)
- Polymers of intrinsic microporosity (1)
- Polymorphism (1)
- Polyvinyl alcohol (1)
- Porous materials (1)
- Powder X-ray diffraction (1)
- Prediction relative (1)
- Prehydrated electron (1)
- Principle component analysis (1)
- Process analytical technology (1)
- Process control (1)
- Protection housing (1)
- Protein A (1)
- Protein Purification (1)
- Prozessanalytik (1)
- Prozesskontrolle (1)
- Quantitative surface chemical analysis (1)
- Quantum dots (1)
- Quantum yield (1)
- Quasi-direct damage (1)
- Quasielastic neutron scattering (1)
- Quick-XAS (1)
- ROS (1)
- RXES (1)
- Radiation therapy (1)
- Radiationtherapy (1)
- Radical (1)
- Radioactive decay (1)
- Radiolysis (1)
- Rat (1)
- Reactive oxygen species (1)
- Reference materials (1)
- Regeneration (1)
- Resolution criterion (1)
- Reverse Monte Carlo (1)
- Rigid (1)
- Ring-expansion polymerization (1)
- Robustness (1)
- SARS-CoV2 inhibitor (1)
- SEM (1)
- SEM micrography (1)
- SIMS (1)
- STEM-in-SEM (1)
- Secondary ion mass spectrometry (1)
- Sialic acid (1)
- Silicon (1)
- Silicone elastomer (1)
- Simulation (1)
- Single source precursors (1)
- Single-strand break (SSB) (1)
- Sintered Material (1)
- Sintering (1)
- Size (1)
- Size measurements (1)
- Sliding (1)
- Soft X-ray (1)
- Soil microbial community (1)
- Sol-gel synthesis (1)
- Solar concentrator (1)
- Solar energy (1)
- Solarpur (1)
- Solubility (1)
- Sorption isotherm (1)
- Sorption mechanism (1)
- Spectroscopic ellipsometry (1)
- Spectroscopic imaging ellipsometry (1)
- Spectroscopy (1)
- SrF2 (1)
- Stainless steel (1)
- Standardisation (1)
- Standardization (1)
- Steel (1)
- Straight edge method (1)
- Structural control (1)
- Structural precision (1)
- Structural sealant glazing (1)
- Structure activity relationships (1)
- Structure-property relationship (1)
- Structure–property correlation (1)
- Sulphidation (1)
- Supercritical adsorption (1)
- Supramolecular chemistry (1)
- Surface (1)
- Surface Analysis Working Group (1)
- Surface analysis (1)
- Surface properties (1)
- Surface science (1)
- Sustainable Synthesis (1)
- Synthesis (1)
- System method (1)
- TED-GC/MS (1)
- TKD (1)
- TXRF (1)
- TXRF-XAS (1)
- Therapeutic Antibodies (1)
- Thermal annealing (1)
- Thermal decomposition (1)
- Thermoplastics (1)
- Thermosets (1)
- Thickness (1)
- Thickness measurements (1)
- Thin films (1)
- Thin polymer films (1)
- Tin acetates (1)
- Titanium dioxide (1)
- ToF-SIMS (1)
- Traceability (1)
- Transition-metal doped (1)
- Transmission function (1)
- Tribochemistry (1)
- Tribology (1)
- Two-dimensional chromatography (2D-LC) (1)
- USAXS (1)
- UV/VIS (1)
- Ultra-short pulse laser processing (1)
- Ultrashort pulsed laser (1)
- Uncertainties (1)
- Uptake estimation (1)
- VRFB (1)
- Van der Waals forces (1)
- Virucidality (1)
- Virus inhibition (1)
- Water (1)
- Water electrolysis (1)
- Water splitting (1)
- Wear (1)
- White light interferometry microscopy (1)
- Wide-range (1)
- X-ray Photoelectron Spectroscopy (1)
- X-ray emission hazards (1)
- X-ray magnetic circular dichroism (XMCD) (1)
- X-ray photoelectron (1)
- X-ray tomographic (1)
- XAFS (1)
- XAS (1)
- Xpoxy resin (1)
- Xray (1)
- Xray photo electron spectrocopy (1)
- Young´s modulus (1)
- ZIF (1)
- ZIF-8 (1)
- Zeolites (1)
- ZnO films (1)
- ZnO nanorods Nanocrystalline (1)
- analytical service (1)
- nm films (1)
- wrapping (1)
Organisationseinheit der BAM
- 6 Materialchemie (134)
- 6.3 Strukturanalytik (57)
- 6.1 Oberflächen- und Dünnschichtanalyse (37)
- 6.6 Physik und chemische Analytik der Polymere (24)
- 6.0 Abteilungsleitung und andere (16)
- 6.2 Material- und Oberflächentechnologien (13)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (12)
- 1 Analytische Chemie; Referenzmaterialien (7)
- 7 Bauwerkssicherheit (6)
- 4 Material und Umwelt (4)
Paper des Monats
- ja (1)
Surface-supported metal-organic frameworks HKUST-1 (Hong Kong University of Science and Technology) were used as a model system for a development of a near ambient pressure (NAP) XPS based approach to investigate interaction with atmospheres of water, methanol or pyridine at pressures ranging from 1 to 4 mbar. The films were grown on a gold substrate functionalized with a COOH-terminated self-assembled monolayer using liquidphase epitaxy in a step-by-step fashion. Measurement protocols were developed and optimised for different gases in order to obtain spectra of similar quality in terms of signal intensity, noise and shape. Peak shapes were found to depend on the efficiency of charge compensation. Reference measurements in argon proved to be a useful strategy not only for the evaluation of the Cu(II)-fraction in pristine samples, but also to identify the contributions by the respective gas atmosphere to the C 1s and O 1s photoelectron spectra. Reduced copper was found during the exposition of HKUST-1 to water vapour and pyridine, but this effect was not observed in case of methanol. Additionally, it was established that there are no changes in relative Cu(II) percentage with increasing exposure time. This indicates that saturation was reached already at the lowest time of gas exposure. A detailed elucidation of the mechanism of Cu(II) reduction to Cu(I) in HKUST-1 mediated by water and pyridine is part of ongoing work and not in the scope of the present paper.
Search of new strategies for the inhibition of respiratory viruses is one of the urgent health challenges worldwide, as most of the current therapeutic agents and treatments are inefficient. Severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) has caused a pandemic and has taken lives of approximately two Million people to date. Even though various vaccines are currently under development, virus, and especially its spike glycoprotein can mutate, which highlights a Need for a broad-spectrum inhibitor. In this work, inhibition of SARS-CoV-2 by graphene platforms with precise dual sulfate/alkyl functionalities is investigated. A series of graphene derivatives with different lengths of aliphatic chains is synthesized and is investigated for their ability to inhibit SARS-CoV-2 and feline coronavirus.
Graphene derivatives with long alkyl chains (>C9) inhibit coronavirus replication by virtue of disrupting viral envelope. The ability of these graphene platforms to rupture viruses is visualized by atomic force microscopy and cryogenic electron microscopy. A large concentration window (10 to 100-fold) where graphene platforms display strongly antiviral activity against native SARS-CoV-2 without significant toxicity against human cells is found. In this concentration range, the synthesized graphene platforms inhibit the infection of enveloped viruses efficiently, opening new therapeutic and metaphylactic avenues against SARS-CoV-2.
The catalytic potential of tin(II)acetate, tin(IV)acetate, dibutyltin-bis-acetate and dioctyl tin-bis-acetate was compared based on polymerizations of L-lactide conducted in bulk at 160 or 130C. With SnAc2 low-Lac/Cat ratios (15/1–50/1) were studied and linear chains having one acetate and one carboxyl end group almost free of cyclics were obtained. Higher monomer/catalyst ratios and lower temperatures favored formation of cycles that reached weight average molecular weights (Mw's) between 100,000 and 2,500,000. SnAc4 yielded mixtures of cycles and linear species under all reaction conditions. Dibutyltin- and dioctyl tin bis-acetate yielded cyclic polylactides under most reaction conditions with Mw's in the range of 20,000–80,000. Ring-opening polymerizations performed with ε-caprolactone showed similar trends, but the formation of COOH-terminated linear chains was significantly more favored compared to analogous experiments with lactide. The reactivity of the acetate catalysts decreased in the following order: SnAc2> SnAc4>Bu2SnAc2 Oct2SnAc2.
Background. Post-menopausal osteoporosis is a common health problem worldwide, most commonly caused by estrogen deficiency. Most of the information regarding the skeletal effects of this disease relates to trabecular bone, while cortical bone is less studied. The purpose of this study was to evaluate the influence of estrogen deficiency on the structure and mechanical properties of cortical bone.
Methods. Eight ovariectomized (OVH) and eight intact (control) Sprague Dawley rats were used. Structural features of femoral cortical bone were studied by light microscopy, scanning electron microscopy and synchrotron-based microcomputer-tomography and their mechanical properties determined by nano-indentation.
Results. Cortical bone of both study groups contains two distinct regions: organized
circumferential lamellae and disordered bone with highly mineralized cartilaginous islands. Lacunar volume was lower in the OVH group both in the lamellar and disorganized regions (182 ± 75 µm3 vs 232 ± 106 µm3 , P < 0.001 and 195 ± 86 µm3 vs. 247 ± 106 µm3 , P < 0.001, respectively). Lacunar density was also lower in both bone regions of the OVH group (40 ± 18 ×103 lacunae/mm3 vs. 47 ± 9×103 lacunae/mm3
in the lamellar region, P = 0.003 and 63 ± 18×103 lacunae/mm3
vs. 75 ± 13×103 lacunae/mm3 in the disorganized region, P < 0.001). Vascular canal volume was lower in the disorganized region of the bone in the OVH group compared to the same Region in the control group (P < 0.001). Indentation moduli were not different between the study groups in both bone regions.
Discussion. Changes to cortical bone associated with estrogen deficiency in rats require high-resolution methods for detection. Caution is required in the application of These results to humans due to major structural differences between human and rat bone.
In this study, a multi-proxy approach combining 29Si, 27Al and 1H MAS-NMR, FEG-EPMA, XANES at the Cu K-edge and XRD analytics with hydrochemical tools such as ICP-OES analyses, oxygen-isotope signatures, and thermodynamic modelling was applied to K-silicate-activated metakaolin specimens - with and without CuSO4·5H2O addition - exposed to sulfuric acid at pH = 2 for 35 days. The results revealed a multistage deterioration mechanism governed by (i) acid diffusion, (ii) leaching of K-A-S-H, (iii) microstructural damage related to precipitation of expansive (K,Ca,Al)-sulfate-hydrate phases (iv) complete dissolution of the K-A-S-H framework, (v) and formation of silica gel in the outermost corroded regions. Copper ions were mainly located in layered spertiniite-chrysocolla-like phases in the as-cured materials. The results demonstrate an overall negative effect of Cu addition on chemical material durability, implying that the reported higher durability of Cu-doped AAM in biocorrosion environments can be best explained by bacteriostatic effects.
Polymerizations of L-lactide catalyzed either by neat SnCl2 or by SnCl2 + difunctional cocatalysts were conducted in bulk at 180, 160 and 140 °C with variation of the Lac/Cat ratio and time. With neat SnCl2 poly(L-lactide) having weight average molecular weights (uncorrected Mw’s) up to 190 000 g mol−1 were obtained mainly consisting of linear chains. Addition of salicylic acid or 1,1-bisphenol yielded a higher fraction of cyclic polylactides but lower molecular weights. Furthermore, SnCl2 was compared with Bu2SnCl2 and various other metal chlorides and the best results were obtained with SnCl2. With ethyl L-lactate as initiator SnCl2-catalyzed ROPs were performed at 120 °C and the lac/initiator ratio was varied. All these experiments were conducted under conditions allowing for comparison with ROPs catalyzed with neat Sn(II)-2-ethyhexanoate. Such a comparison was also performed with ε-caprolactone as monomer.
The thermodynamic behavior of thin PVME films including the irreversible adsorbed layer on the substrate is investigated. In a first step, the growth kinetics of the adsorbed layer was studied combining a leaching technique and atomic force microscopy. Further, it was shown that there is a critical initial film thickness for the formation of a surface-filling adsorbed layer. Additionally, spectroscopic ellipsometry measurements were carried out to investigate the influence of the adsorbed layer on the glass transition temperature of the thin films. For 30 nm films and below, the influence of the adsorbed layer percolates strongly to the bulk-like layer of the film. Finally, the molecular dynamics of the adsorbed layer was studied by broadband dielectric spectroscopy, employing nanostructured-electrode systems. One process was revealed, which was assigned either to molecular fluctuations taking place in a loosely-bounded the part of the adsorbed layer, or to the desorption/adsorption of segments at the substrate.
1:1 Copolymerizations of glycolide (GL) and L-lactide (LA) is performed in bulk at 100°C and at 160°C with four cyclic tin catalysts. The resulting copolyesters are characterized by SEC measurements, 1H and 13C NMR spectroscopy and by MALDI TOF mass spectrometry. At 160°C and longer reaction time (22 h) nearly complete conversion of both monomers is achieved, and cyclic copolymers with nearly random sequences are formed. At shorter times (0.5-3.0 h, depending on catalyst) the conversion of LA is incomplete, and only cyclics having even numbers of lactyl units are obtained. At 100°C at 22 h again cycles mainly consisting of even numbered lactyl units are formed, but with even and odd numbers of glycolyl units. Copolymerization of lactide at 160°C with small amounts of GL show that formation of high Tm crystallites (Tm > 190°C) is hindered even when only > 2% of GL is added. For polyglycolide containing a smaller amount of lactide complete solubility in hexafluoroisopropanol is only observed around and above 20 mol% of lactide.
A key application of atomic force microscopy (AFM) is the measurement of physical properties at sub-micrometer resolution. Methods such as force–distance curves (FDCs) or dynamic variants (such as intermodulation AFM (ImAFM)) are able to measure mechanical properties (such as the local stiffness, kr) of nanoscopic heterogeneous materials. For a complete structure–property correlation, these mechanical measurements are considered to lack the ability to identify the chemical structure of the materials. In this study, the measured attractive force, Fattr, acting between the AFM tip and the sample is shown to be an independent measurement for the local chemical composition and hence a complete structure–property correlation can be obtained. A proof of concept is provided by two model samples comprised of (1) epoxy/polycarbonate and (2) epoxy/boehmite. The preparation of the model samples allowed for the assignment of material phases based on AFM topography. Additional chemical characterization on the nanoscale is performed by an AFM/infrared-spectroscopy hybrid method. Mechanical properties (kr) and attractive forces (Fattr) are calculated and a structure–property correlation is obtained by a manual principle component analysis (mPCA) from a kr/Fattr diagram. A third sample comprised of (3) epoxy/polycarbonate/boehmite is measured by ImAFM. The measurement of a 2 × 2 µm cross section yields 128 × 128 force curves which are successfully evaluated by a kr/Fattr diagram and the nanoscopic heterogeneity of the sample is determined.
The choice of solvents influences crystalline solid formed during the crystallization of active pharmaceutical ingredients (API). The underlying effects are not always well understood because of the complexity of the systems. Theoretical models are often insufficient to describe this phenomenon. In this study, the crystallization behavior of the model drug paracetamol in different solvents was studied based on experimental and molecular dynamics data. The crystallization process was followed in situ using time-resolved Raman spectroscopy. Molecular dynamics with simulated annealing algorithm was used for an atomistic understanding of the underlying processes. The experimental and theoretical data indicate that paracetamol molecules adopt a particular geometry in a given solvent predefining the crystallization of certain polymorphs
Thermoplastic modified thermosets are of great interest especially due to their improved fracture toughness. Comparable enhancements have been achieved by adding different nanofillers including inorganic particles such as nanosized boehmite. Here, we present a nanomechanical study of two composite systems, the first comprising a polycarbonate (PC) layer in contact with epoxy resin (EP) and the second consisting of a PC layer containing boehmite nanoparticles (BNP) which is also in contact with an EP layer. The interaction between PC and EP monomer is tested by in situ Fourier transformed infrared (FT-IR) analysis, from which a reaction induced phase separation of the PC phase is inferred. Both systems are explored by atomic force microscopy (AFM) force spectroscopy. AFM force-distance curves (FDC) show no alteration of the mechanical properties of EP at the interface to PC. However, when a PC phase loaded with BNP is put in contact with an epoxy system during curing, a considerable mechanical improvement exceeding the rule of mixture was detected.
The trend of BNP to agglomerate preferentially around EP dominated regions and the stiffening effect of BNP on EP shown by spatial resolved measurements of Young's modulus, suggest the effective presence of BNP within the EP phase.
Mussel-inspired multifunctional coating for bacterial infection prevention and osteogenic induction
(2021)
Bacterial infection and osteogenic integration are the two main problems that cause severe complications after surgeries. In this study, the antibacterial and osteogenic properties were simultaneously introduced in biomaterials, where copper nanoparticles (CuNPs) were generated by in situ reductions of Cu ions into a mussel-inspired hyperbranched polyglycerol (MI-hPG) coating via a simple dip-coating method. This hyperbranched polyglycerol with 10 % catechol groups’ modification presents excellent antifouling property, which could effectively reduce bacteria adhesion on the surface. In this work, polycaprolactone (PCL) electrospun fiber membrane was selected as the substrate, which is commonly used in biomedical implants in bone regeneration and cardiovascular stents because of its good biocompatibility and easy post-modification. The as-fabricated CuNPs-incorporated PCL membrane [PCL-(MI-hPG)-CuNPs] was confirmed with effective antibacterial performance via in vitro antibacterial tests against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and multi-resistant E. coli. In addition, the in vitro results demonstrated that osteogenic property of PCL-(MI-hPG)-CuNPs was realized by upregulating the osteoblast-related gene expressions and protein activity. This study shows that antibacterial and osteogenic properties can be balanced in a surface coating by introducing CuNPs.
Matrix‐assisted ionization (MAI) mass spectrometry does not require voltages, a laser beam, or added heat to initiate ionization, but it is strongly dependent on the choice of matrix and the vacuum conditions. High charge state distributions of nonvolatile analyte ions produced by MAI suggest that the ionization mechanism may be similar to that of electrospray ionization (ESI), but different from matrix‐assisted laser desorption/ionization (MALDI). While significant information is available for MAI using mass spectrometers operating at atmospheric and intermediate pressure, little is known about the mechanism at high vacuum.
Eleven MAI matrices were studied on a high‐vacuum time‐of‐flight (TOF) mass spectrometer using a 266 nm pulsed laser beam under otherwise typical MALDI conditions. Detailed comparisons with the commonly used MALDI matrices and theoretical prediction were made for 3‐nitrobenzonitrile (3‐NBN), which is the only MAI matrix that works well in high vacuum when irradiated with a laser.
Screening of MAI matrices with good absorption at 266 nm but with various degrees of volatility and laser energies suggests that volatility and absorption at the laser wavelength may be necessary, but not sufficient, criteria to explain the formation of multiply charged analyte ions. 3‐NBN produces intact, highly charged ions of nonvolatile analytes in high‐vacuum TOF with the use of a laser, demonstrating that ESI‐like ions can be produced in high vacuum. Theoretical calculations and mass spectra suggest that thermally induced proton transfer, which is the major ionization mechanism in MALDI, is not important with the 3‐NBN matrix at 266 nm laser wavelength. 3‐NBN:analyte crystal morphology is, however, important in ion generation in high vacuum.
The 3‐NBN MAI matrix produces intact, highly charged ions of nonvolatile compounds in high‐vacuum TOF mass spectrometers with the aid of ablation and/or heating by laser irradiation, and shows a different ionization mechanism from that of typical MALDI matrices.