Refine
Has Fulltext
- no (155)
Year of publication
- 2016 (155) (remove)
Document Type
- Article (155) (remove)
Language
- English (155) (remove)
Is part of the Bibliography
- yes (155)
Keywords
- Ion mobility spectrometry (3)
- X-ray structure (3)
- biomaterials (3)
- crystallization (3)
- Density functional calculations (2)
- IR-MALDI (2)
- Janus emulsions (2)
- Kinetics (2)
- Laser (2)
- Microemulsions (2)
- NMR spectroscopy (2)
- Nanoparticles (2)
- Oligo(epsilon-caprolactone) (2)
- Palladium (2)
- Theoretical calculations (2)
- configuration (2)
- conformation (2)
- copper(II) (2)
- crystal structure (2)
- electron paramagnetic resonance (2)
- fluorescent probes (2)
- microwave irradiation (2)
- nanoparticles (2)
- tetrabromidocuprate(II) (2)
- 1,2-dithiosquarate (1)
- 1,2-dithiosquaratometalate (1)
- 1D structures (1)
- 3-color fret (1)
- 3D structure (1)
- 4D NOESY (1)
- 8-oxohobartine (1)
- Adsorption (1)
- Adsorption of uremic toxins (1)
- AgAu alloy nanoparticles (1)
- Alkenes (1)
- Amides (1)
- Amines (1)
- Amino acids (1)
- Anisotropic gold nanoplatelets (1)
- Anserine (1)
- Aristotelia chilensis (1)
- Au nanoarrays (1)
- BBTP (1)
- Benzazepine (1)
- Biaryls (1)
- Bioelectrocatalysis (1)
- Biomass (1)
- Biomaterial (1)
- Biopolymers (1)
- Block copolymers (1)
- Bound states (1)
- Bragg coherent x-ray diffractive imaging (1)
- C-C coupling (1)
- CAL-72 osteoblasts (1)
- CC2 calculations (1)
- Calcium phosphates (1)
- Carbene ligands (1)
- Charge transfer (1)
- Chemical shift assignment (1)
- Chromophores (1)
- Chronic kidney disease (CKD) (1)
- Claisen rearrangement (1)
- Click chemistry (1)
- Collagen-binding peptide (1)
- Conformational analysis (1)
- Cross-coupling (1)
- Crystal packing (1)
- Crystal structure (1)
- DNA complexation (1)
- DNA origami (1)
- DNA origami nanostructures (1)
- DNA radiation damage (1)
- Decontamination (1)
- Depth profiling (1)
- Diastereoselectivity (1)
- Direct electron transfer (1)
- Discrete variable representation (1)
- Doping (1)
- Drop profile analysis tensiometry (1)
- Drug design (1)
- Dual scale factors (1)
- EPR spectroscopy (1)
- Electrochemistry (1)
- Electrospray ionization (1)
- Enantioselectivity (1)
- Energy transfer (1)
- Enzymatic degradation (1)
- Enzymatic polymer degradation (1)
- Equilibrium (1)
- Escherichia coli (1)
- External mass transfer (1)
- Extraction (1)
- FRET (1)
- FhuA (1)
- Fluorescence (1)
- Fluorescence spectroscopy (1)
- Fusarium proliferatum (1)
- Gelatin-chitosan composites (1)
- Gelatin-chitosan scaffolds (1)
- Generalized Langevin oscillator model (1)
- Grafting-from polymerization (1)
- HPLC (1)
- Heck reaction (1)
- High-harmonic generation (1)
- Homogeneous catalysis (1)
- Human sulfite oxidase (1)
- Hyaluronic acid (1)
- Hybrid materials (1)
- Hydrogels (1)
- Hydrogenation (1)
- Hydrophobin (1)
- Hypoosmotic stress (1)
- ICSS (1)
- IFT (1)
- Imaging (1)
- InP nanowires (1)
- Interfacial tension (1)
- Kinetic analysis (1)
- L-929 fibroblasts (1)
- LC composites (1)
- LCST (1)
- Lactams (1)
- Langmuir monolayer (1)
- Langmuir monolayer degradation technique (1)
- Langmuir technique (1)
- Laponite (1)
- Laser induced desorption (1)
- Light scattering (1)
- Liquid chromatography (1)
- Local density friction approximation (1)
- Maltose-modified poly(ethyleneimine) (1)
- Mass transfer (1)
- Matrix IR spectrum (1)
- Mechanical properties (1)
- Mesoporous materials (1)
- Modified Mannich reaction (1)
- Molecular dynamics simulations (1)
- Molecular dynamics with friction (1)
- Monolayer (1)
- Morphology (1)
- Multiblock copolymer (1)
- N ligands (1)
- NIPAAm (1)
- Na+ homeostasis (1)
- Nano-bioextractant (1)
- Nanocrystal growth (1)
- Nanotriangle stacking and welding (1)
- Nauclea diderrichii (1)
- Non-adiabatic transitions (1)
- Nuclear magnetic resonance (NMR) (1)
- Nucleophilic addition (1)
- Numerical propagation (1)
- Oligo(omega-pentadecalactone) (1)
- P ligands (1)
- Pendant drop tensiometry (1)
- Penicillium digitatum (1)
- Pesticides (1)
- Phase morphology (1)
- Pleurotus ostreatus (1)
- Poly-epsilon-caprolactone (1)
- Polyampholytes (1)
- Polyethyleneimine (1)
- Polymer architecture (1)
- Polyplexes (1)
- Porous scaffold (1)
- Porphyrins (1)
- Protein (1)
- Protein voltammetry (1)
- Protein-polymer conjugate (1)
- Push-pull effect (1)
- Quantum dynamics (1)
- RAFT polymerization (1)
- Reactive foaming (1)
- Reduction (1)
- Respiration (1)
- Rheology (1)
- Ring method (1)
- Rotational barriers (1)
- Ruthenium (1)
- SANS (1)
- SAXS (1)
- SDS inverse micelle (1)
- SQM-FF (1)
- Schrodinger equation (1)
- Selenium (1)
- Self-assembly (1)
- Shadowgraphy (1)
- Silanes (1)
- Sodium transport (1)
- Spectroscopy (1)
- Spiro compounds (1)
- Staphylococcus aureus (1)
- Stereochemistry (1)
- Strontium (1)
- Structure elucidation (1)
- Sulfonamides (1)
- Surface chemistry (1)
- Surface removal (1)
- Synchrotron radiation XPS (1)
- Synthesis and processing (1)
- Synthetic methods (1)
- TSNMRS (1)
- Tautomerism (1)
- Temperature-memory effect (1)
- Tetrapyrroles (1)
- Thermomechanical history (1)
- Thermosensitivity (1)
- Thienopyridine (1)
- Transmembrane protein (1)
- Tubular network structure (1)
- Twisted double bonds (1)
- Two-dimensional separations (1)
- Vibrio cholerae (1)
- WAXS (1)
- Water (1)
- X-ray (1)
- X-ray scattering (1)
- Y-aromaticity (1)
- ab initio calculations (1)
- acids (1)
- activated urethane derivatives (1)
- actuation (1)
- adsorption (1)
- adsorption kinetics (1)
- aldehydes (1)
- alkyl nitrates (1)
- allyl alcohols (1)
- arenes (1)
- arsenious acid (1)
- assemblies (1)
- atomic force microscopy (1)
- atomic force microscopy (AFM) (1)
- azobenzene (1)
- bending stiffness (1)
- bio-inspired (1)
- biodegradable polymers (1)
- biodiversity (1)
- biomineralization (1)
- block copolymers (1)
- bone tissue engineering (1)
- bottom-up (1)
- cadmium (1)
- carbohydrate derivatives (1)
- carbohydrate derivatives (1)
- carboxyanhydrides (1)
- cardiovascular disease (1)
- cardiovascular implant (1)
- cellular uptake (1)
- chain mobility (1)
- cholesteric phase (1)
- chromenes (1)
- chromophores (1)
- chronic kidney disease (CKD) (1)
- click triazoles (1)
- colloidal aggregation (1)
- common species (1)
- cononsolvency (1)
- copolymers (1)
- coumarins (1)
- crown compounds (1)
- crystal structures (1)
- cyclooligomers (1)
- cytotoxicity (1)
- density functional calculations (1)
- dienes (1)
- differential scanning calorimetry (DSC) (1)
- dissociative electron attachment (1)
- drug carrier system (1)
- ecosystem function (1)
- effect of alkyl side chains (1)
- electrospinning (1)
- electrostatics (1)
- elimination (1)
- ellipsometric mapping (1)
- enzyme catalysis (1)
- explosives (1)
- fludarabine (1)
- fluorescence (1)
- fluorescence anisotropy (1)
- fluorescence correlation spectroscopy (1)
- fluorescent dyemonomers (1)
- fronts (1)
- g-quadruplex (1)
- gas permeation (1)
- glass transition temperature (1)
- graphene (1)
- hemocompatibility (1)
- hole array (1)
- human monocytic (THP-1) cells (1)
- hydrogel (1)
- hydrophobic uremic toxins (1)
- identity hypothesis (1)
- impedance spectroscopy (1)
- in situ fluorescence microscopy (1)
- indole alkaloids (1)
- interaction potential (1)
- intracellular pH indicator (1)
- inverse micelles (1)
- ion mobility spectrometry (1)
- ionic liquids (1)
- ketones (1)
- land use (1)
- linear assemblies (1)
- liquid crystal (1)
- liquid crystal polymer (1)
- liquid crystalline polymer (1)
- lithography (1)
- lower critical solution temperature (1)
- luminescence (1)
- macrocyclic compounds (1)
- mass spectrometry (1)
- medicinal mushrooms (1)
- melt (1)
- melt-recrystallization (1)
- metal-organic frameworks (1)
- microgel (1)
- microgels (1)
- microparticles (1)
- molecular thermometers (1)
- mu CT imaging (1)
- multiblock copolymer (1)
- multiphoton processes (1)
- multitrophic (1)
- nanoimprint (1)
- nanoreactor (1)
- nanostructures (1)
- naphthalimide (1)
- olefination (1)
- organic-inorganic composite material (1)
- pH-sensitive liposome (1)
- paper (1)
- phenols (1)
- phosgene-free synthesis (1)
- photofragmentation (1)
- photoionization (1)
- photonic wires (1)
- photophysics (1)
- phototunable optical properties (1)
- pi-Electron delocalization (1)
- platelet activation (1)
- platelet adhesion (1)
- platelets (1)
- poly(2-ethyl-2oxazoline) (1)
- poly(N-vinylcaprolactam) (1)
- poly(dimethylsiloxane) (1)
- poly(ether imide) (1)
- poly(ether imide) microparticles (1)
- poly(ethylene glycol) (1)
- polyester (1)
- polymer crystallization (1)
- polymer solutions (1)
- polymeric sensors (1)
- polypeptides (1)
- polypeptoids (1)
- polystyrene-block-poly(4-vinylpyridine) (1)
- potassium (1)
- protecting groups (1)
- protein adsorption (1)
- quantum dots (1)
- reactive oxygen species (ROS) (1)
- recognition (1)
- recombinant protein (1)
- regioselectivity (1)
- resonance energy-transfer (1)
- ring closing metathesis (1)
- ring-opening polymerization (1)
- root mean square roughness (1)
- rotational diffusion (1)
- ruthenium (1)
- scale (1)
- scanning tunneling microscopy (1)
- selective drug release (1)
- selective light reflection (1)
- self-assembled micelles (1)
- self-assembled monolayers (1)
- self-organization (1)
- sensitivity (1)
- sensor (1)
- shape analysis (1)
- shape-memory effect (1)
- shape-persistent macrocycles (1)
- sodium (1)
- soft-templating (1)
- solvatochromism (1)
- spectroscopic ellipsometry (1)
- spider silk (1)
- steric hindrance (1)
- stimuli-sensitive polymers (1)
- strain field (1)
- strand breakage (1)
- strong field (1)
- substituent effects (1)
- surface plasmon resonance (1)
- systems (1)
- tandem reaction (1)
- temperature (1)
- thermo-responsive polymers (1)
- thermoresponsive (1)
- thermoresponsive polymers (1)
- thin films (1)
- thiophenes (1)
- thrombogenicity (1)
- time-dependent configuration interaction (1)
- time-resolved fluorescence spectroscopy (1)
- tin-rich ITO (1)
- translational diffusion (1)
- uremia (1)
- xanthenes (1)
- ylides (1)
- yolk@shell materials (1)
Institute
- Institut für Chemie (155) (remove)
The performance of non-empirically tuned long-range corrected hybrid functionals for the prediction of vertical ionization potentials (IPs) and electron affinities (EAs) is assessed for a set of 24 organic acceptor molecules. Basis set extrapolated coupled cluster singles, doubles, and perturbative triples [CCSD(T)] calculations serve as a reference for this study. Compared to standard exchange-correlation functionals, tuned long-range corrected hybrid functionals produce highly reliable results for vertical IPs and EAs, yielding mean absolute errors on par with computationally more demanding GW calculations. In particular, it is demonstrated that long-range corrected hybrid functionals serve as ideal starting points for non-self-consistent GW calculations.
We report on an extension of the previously established concept of oligospiroketal (OSK) rods by replacing a part or all ketal moieties by thioketals leading to oligospirothioketal (OSTK) rods. In this way, some crucial problems arising from the reversible formation of ketals are circumvented. Furthermore, the stability of the rods toward hydrolysis is considerably improved. To successfully implement this concept, we first developed a number of new oligothiol building blocks and improved the synthetic accessibility of known oligothiols, respectively. Another advantage of thioacetals is that terephthalaldehyde (TAA) sleeves, which are too flexible in the case of acetals can be used in OSTK rods. The viability of the OSTK approach was demonstrated by the successful preparation of some OSTK rods with a length of some nanometers.
Block copolypeptoids comprising a thermosensitive, crystallizable poly(N-(n-propyl)glycine) block and a watersoluble poly(N-methylglycine) block, P70My (y = 23, 42, 76, 153, and 290), were synthesized bY ring-opening polymerization of the corresponding N-alkylglycine N-carboxyanhydrides (NCAs) and examined according to their thermo-induced aggregation and crystallization in water by turbidimetty, micro-differential scanning calorimetry (micro-DSC); cryogenic scanning electron microscopy (cryo-SEM), analytical ultracentrifugation (AUC), and static light scattering (SLS). At a temperature above the cloud point temperature, the initially formed micellar aggregates started to crystallize and grow into larger complex assemblies of about 100-500 nm, exhibiting flower-like (P70M23), ellipsoidal (P70M42 and P70M72) or irregular shapes (P70M153 and.P70M290).
Different approaches have been proposed to treat cancer cells using gold nanoparticles (AuNPs) in combination with radiation ranging from infrared lasers to high-energy ion beams. Here we study the decomposition of the DNA/RNA nucleobases thymine (T) and uracil (U) and the well-known radiosensitizer 5-bromouracil (BrU) in close vicinity to AuNPs, which are irradiated with a nanosecond pulsed laser (532 nm) matching the surface plasmon resonance of the AuNPs. The induced damage of nucleobases is analyzed by UV-vis absorption spectroscopy and surface-enhanced Raman scattering (SERS). A clear DNA damage is observed upon laser irradiation. SERS spectra indicate the fragmentation of the aromatic ring system of T and U as the dominant form of damage, whereas with BrU mainly the cleavage of the Br-C bond and formation of Br- ions is observed. This is accompanied by a partial transformation of BrU into U. The observed damage is at least partly ascribed to the intermediate formation of low energy electrons from the laser-excited AuNPs and subsequent dissociative electron attachment to T, U, and BrU. These reactions represent basic DNA damage pathways occurring on the one hand in plasmon-assisted cancer therapy and on the other hand in conventional cancer radiation therapy using AuNPs as sensitizing agents.
Synchrotron-radiation XPS analysis of ultra-thin silane films: Specifying the organic silicon
(2016)
The analysis of chemical and elemental in-depth variations in ultra-thin organic layers with thicknesses below 5 nm is very challenging. Energy- and angle-resolved XPS (ER/AR-XPS) opens up the possibility for non-destructive chemical ultra-shallow depth profiling of the outermost surface layer of ultra-thin organic films due to its exceptional surface sensitivity. For common organic materials a reliable chemical in-depth analysis with a lower limit of the XPS information depth z(95) of about 1 nm can be performed. As a proof-of-principle example with relevance for industrial applications the ER/AR-XPS analysis of different organic monolayers made of amino- or benzamidosilane molecules on silicon oxide surfaces is presented. It is demonstrated how to use the Si 2p core-level region to non-destructively depth-profile the organic (silane monolayer) - inorganic (SiO2/Si) interface and how to quantify Si species, ranging from elemental silicon over native silicon oxide to the silane itself. The main advantage of the applied ER/AR-XPS method is the improved specification of organic from inorganic silicon components in Si 2p core-level spectra with exceptional low uncertainties compared to conventional laboratory XPS. (C) 2015 Elsevier B.V. All rights reserved.
We demonstrate that a single-layer graphene replicates the shape of DNA origami nanostructures very well. It can be employed as a protective layer for the enhancement of structural stability of DNA origami nanostructures. Using the AFM based manipulation, we show that the normal force required to damage graphene encapsulated DNA origami nanostructures is over an order of magnitude greater than for the unprotected ones. In addition, we show that graphene encapsulation offers protection to the DNA origami nanostructures against prolonged exposure to deionized water, and multiple immersions. Through these results we demonstrate that graphene encapsulated DNA origami nanostructures are strong enough to sustain various solution phase processing, lithography and transfer steps, thus extending the limits of DNA-mediated bottom-up fabrication.
The aggregation kinetics of thermoresponsive core-shell micelles with a poly(N-isopropyl acrylamide) shell in pure water or in mixtures of water with the cosolvents methanol or ethanol at mole fractions of 5% is investigated during a temperature jump across the respective cloud point. Characteristically, these mixtures give rise to cononsolvency behavior. At the cloud point, aggregates are formed, and their growth is followed with time-resolved small-angle neutron scattering. Using the reversible association model, the interaction potential between the aggregates is determined from their growth rate in dependence on the cosolvents. The effect of the cosolvent is attributed to the interaction potential on the structured layer of hydration water around the aggregates. It is surmised that the latter is perturbed by the cosolvent and thus the residual repulsive hydration force between the aggregates is reduced. The larger the molar volume of the cosolvent, the more pronounced is the effect. This framework provides a molecular-level understanding of solvent-mediated effective interactions in polymer solutions and new opportunities for the rational control of self-assembly in complex soft matter systems.
The authors report on the fabrication of a thermoresponsive biosensor for the amperometric detection of glucose. Screen printed electrodes with heatable gold working electrodes were modified by a thermoresponsive statistical copolymer [polymer I: poly(omega-ethoxytriethylenglycol methacrylate-omega-3-(N,N-dimethyl-N-2-methacryloyloxyethyl ammonio) propanesulfonate-co-omega-butoxydiethylenglycol methacrylate-co-2-(4-benzoyl-phenoxy)ethyl methacrylate)] with a lower critical solution temperature of around 28 degrees C in aqueous solution via electrochemically induced codeposition with a pH-responsive redox-polymer [polymer II: poly(glycidyl methacrylate-co-allyl methacrylate-co-poly(ethylene glycol) methacrylate-co-butyl acrylate-co-2-(dimethylamino) ethyl methacrylate)-[Os(bpy)(2)(4-(((2-(2-(2-aminoethoxy) ethoxy) ethyl) amino) methyl)-N,N-dimethylpicolinamide)](2+)] and pyrroloquinoline quinone-soluble glucose dehydrogenase acting as biological recognition element. Polymer II bears covalently bound Os-complexes that act as redox mediators for shuttling electrons between the enzyme and the electrode surface. Polymer I acts as a temperature triggered immobilization matrix. Probing the catalytic current as a function of the working electrode temperature shows that the activity of the biosensor is dramatically reduced above the phase transition temperature of polymer I. Thus, the local modulation of the temperature at the interphase between the electrode and the bioactive layer allows switching the biosensor from an on-to an off-state without heating of the surrounding analyte solution. (C) 2015 American Vacuum Society.
In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([C(n)C(1)im](+)[NTf2](-) and [C(4)C(1)im](+)[I](-)). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra.
The spatial magnetic properties (Through Space NMR Shieldings - TSNMRS) of a number of Y-shaped structures possessing 4n+2 pi-electrons (i.a. the trimethylenemethane ions TMM2+, TMM2-, the guanidinium cation, substituted and hetero analogues) have been computed, visualized as Isochemical Shielding Surfaces (ICSS) of various size and direction, were examined subject to present Y-aromaticity and the results compared with energetic and geometric criteria obtained already. (C) 2016 Elsevier Ltd. All rights reserved.
Poly(2-alkyl-2-oxazoline)s (PAOx) exhibit different crystallization behavior depending on the length of the alkyl side chain. PAOx having methyl, ethyl, or propyl side chains do not show any bulk crystallization. Crystallization in the heating cycle, that is, cold crystallization, is observed for PAOx with butyl and pentyl side chains. For PAOx with longer alkyl side chains crystallization occurs in the cooling cycle. The different crystallization behavior is attributed to the different polymer chain mobility in line with the glass transition temperature (T-g) dependency on alkyl side chain length. The decrease in chain mobility with decreasing alkyl side chain length hinders the relaxation of the polymer backbone to the thermodynamic equilibrium crystalline structure. Double melting behavior is observed for PButOx and PiPropOx which is explained by the melt-recrystallization mechanism. Isothermal crystallization experiments of PButOx between 60 and 90 degrees C and PiPropOx between 90 and 150 degrees C show that PAOx can crystallize in bulk when enough time is given. The decrease of Tg and the corresponding increase in chain mobility at T > T-g with increasing alkyl side chain length can be attributed to an increasing distance between the polymer backbones and thus decreasing average strength of amide dipole interactions. (C) 2015 Wiley Periodicals, Inc.
For Vibrio cholerae, the coordinated import and export of Na+ is crucial for adaptation to habitats with different osmolarities. We investigated the Na+-extruding branch of the sodium cycle in this human pathogen by in vivo Na-23-NMR spectroscopy. The Na+ extrusion activity of cells was monitored after adding glucose which stimulated respiration via the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR). In a V. cholerae deletion mutant devoid of the Na+-NQR encoding genes (nqrA-F), rates of respiratory Na+ extrusion were decreased by a factor of four, but the cytoplasmic Na+ concentration was essentially unchanged. Furthermore, the mutant was impaired in formation of transmembrane voltage (Delta psi, inside negative) and did not grow under hypoosmotic conditions at pH 8.2 or above. This growth defect could be complemented by transformation with the plasmid encoded nqr operon. In an alkaline environment, Na+/H+ antiporters acidify the cytoplasm at the expense of the transmembrane voltage. It is proposed that, at alkaline pH and limiting Na+ concentrations, the Na+-NQR is crucial for generation of a transmembrane voltage to drive the import of H+ by electrogenic Na+/H+ antiporters. Our study provides the basis to understand the role of the Na+-NQR in pathogenicity of V. cholerae and other pathogens relying on this primary Na+ pump for respiration. (C) 2015 Elsevier B.V. All rights reserved.
Janus emulsions, formed by mixing two oil components (i.e., olive oil (OO) and silicone oil (SiO)) with water in the presence of two surface active biopolymers, i.e., gelatin and chitosan, are investigated in more detail. The stability of Janus droplets formed strongly depends on the polymer components used. The mixture of both biopolymers represents an extraordinary effect which can be related to the complex formation of gelatin and chitosan. Taken into account that under the given pH conditions, in the acidic pH range between 4 and 6, below the isoelectric point of gelatin, both polymers are polycations, one can conclude that non-Coulombic interactions are of relevance for the enhanced surface activity of the complexes. Dynamic interfacial tension (gamma) measurements by using the drop profile analysis tensiometry (PAT) indicate a strong adsorption of the polymer complexes at the olive oil/water interface in contrast to the silicone/water interface. In a first step, the polymer complexes are adsorbed at the interface, and in a second step, a more rigid skin-like polymer layer is formed. This first example of a polymer-stabilized Janus emulsion opens new perspectives for the application, e.g., in food emulsions or for making scaffold materials.
We dissect the sources of error leading to inaccuracies in the description of the geometry and optical excitation energies of pi-conjugated polymers. While the ground-state bond length alternation is shown to be badly reproduced by standard functionals, the recently adapted functionals PBEh* and omega PBE* as well as the double hybrid functional XYGJ-OS manage to replicate results obtained at the CCSD(T) level. By analysis of the bond length alternation in the excited state, a sensitive dependence of the exciton localization on the long-range behavior of the functional and the amount of Hartree-Fock exchange present is shown. Introducing thermal disorder through molecular dynamics simulations allows the consideration of a range of thermally accessible configurations of each oligomer, including trans to cis rotations, which break the conjugation of the backbone. Thermal disorder has a considerable effect when combined with functionals that overestimate the delocalization of the excitation, such as B3LYP. For functionals with a larger amount of exact exchange such as our PBEh* and omega PBE*, however, the effect is small, as excitations are often localized enough to fit between twists in the chain.
A series of new fluorescent dye bearing monomers, including glycomonomers, based on maleamide and maleic esteramide was synthesized. The dye monomers were incorporated by radical copolymerization into thermo-responsive poly(N‑vinyl-caprolactam) that displays a lower critical solution temperature (LCST) in aqueous solution. The effects of the local molecular environment on the polymers’ luminescence, in particular on the fluorescence intensity and the extent of solvatochromism, were investigated below as well as above the phase transition. By attaching substituents of varying size and polarity in the close vicinity of the fluorophore, and by varying the spacer groups connecting the dyes to the polymer backbone, we explored the underlying structure–property relationships, in order to establish rules for successful sensor designs, e.g., for molecular thermometers. Most importantly, spacer groups of sufficient length separating the fluorophore from the polymer backbone proved to be crucial for obtaining pronounced temperature regulated fluorescence responses. View Full-Text
Metal-containing ionic liquids (ILs) are of interest for a variety of technical applications, e.g., particle synthesis and materials with magnetic or thermochromic properties. In this paper we report the synthesis of, and two structures for, some new tetrabromidocuprates(II) with several "onium" cations in comparison to the results of electron paramagnetic resonance (EPR) spectroscopic analyses. The sterically demanding cations were used to separate the paramagnetic Cu(II) ions for EPR measurements. The EPR hyperfine structure in the spectra of these new compounds is not resolved, due to the line broadening resulting from magnetic exchange between the still-incomplete separated paramagnetic Cu(II) centres. For the majority of compounds, the principal g values (g|| and g(perpendicular to)) of the tensors could be determined and information on the structural changes in the [CuBr4](2-) anions can be obtained. The complexes have high potential, e.g., as ionic liquids, as precursors for the synthesis of copper bromide particles, as catalytically active or paramagnetic ionic liquids.
Polyelectrolyte multilayers (PEMs) with stratification of the internal structure were assembled from statistical amphiphilic copolyelectrolytes of opposite charges. These polyelectrolytes organize in aqueous solutions into micellar structures with fluoroalkyl and aromatic nanodomains, respectively, that were also preserved after deposition as thin films via layer-by-layer (LbL) electrostatic self-assembly. The unimolecular micelles, formed due to statistical compositions of amphiphilic polyelectrolytes used, were shown to suppress chain interdiffusion between adjacent layers in resulting micellar PEMs, as evidenced by spectroscopic ellipsometry, atomic force microscopy (AFM), and neutron reflectometry (NR) measurements. Additionally, hydrophobic cores of the micelles were used as hosts for photoactive molecules, namely, ferrocene and perfluorinated magnesium phthalocyanine. Stratified micellar multilayers were then deposited as hollow capsules using CaCO3 microparticles as templates. Photoinduced electron transfer (PET) between ferrocene and phthalocyanine solubilized in the polymer micelles was demonstrated to occur efficiently inside the stratified, polyelectrolyte walls of the capsules, due to the polarity gradient created by the incompatible aromatic and fluoroalkyl domains. The obtained results present a new approach to construct well-organized, self-assembled nanostructured materials for solar energy conversion.
Here we apply and expand the knowledge developed in the case of the H atom to describe high-harmonic generation (HHG) for the H-2 molecule by using time-dependent configuration interaction with single excitations. The implications of using a finite atomic orbital basis set and the impact of a heuristic lifetime model which addresses ionisation losses are discussed. We also examine the influence of the angular momentum of the basis on the computed HHG spectra. Moreover, we discuss the impact of adding diffuse functions and ghost atoms in different geometrical configurations around the molecule. The effects of these additional centres on the HHG spectra are correlated with the physical interpretation of this nonlinear optical phenomenon as given by the three-step model, relating the maximal radial extent of the electron as predicted by the model to the radial extent of the Gaussian basis sets. [GRAPHICS] .
para-Substituted aryl prenyl ethers undergo a deprenylation reaction upon microwave irradiation. This offers the opportunity to use a prenyl ether as a thermolabile protecting group in the synthesis of natural products with a chromone structure, which proceeds via a tandem deprenylation/6-endo-cyclization sequence.
Nowadays, the encapsulation of therapeutic compounds in so-called carrier systems is a very smart method to achieve protection as well as an improvement of their temporal and spatial distribution. After the successful transport to the point of care, the delivery has to be released under controlled conditions. To monitor the triggered release from the carrier, we investigated different fluorescent probes regarding their response to the pH-induced collapse of pH-sensitive liposomes (pHSLip), which occurs when the environmental pH falls below a critical value. Depending on the probe, the fluorescence decay time as well as fluorescence anisotropy can be used equally as key parameters for monitoring the collapse. Especially the application of a fluorescein labeled fatty acid (fPA) enabled the monitoring of the pHSLips collapse and the pH of its microenvironment simultaneously without interference. Varying the pH in the range of 3 < pH < 9, anisotropy data revealed the critical pH value at which the collapse of the pHSLips occurs. Complementary methods, e.g., fluorescence correlation spectroscopy and dynamic light scattering, supported the analysis based on the decay time and anisotropy. Additional experiments with varying incubation times yielded information on the kinetics of the liposomal collapse.