articles+ search results

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Alcanol, Alkanol, Alcool, Alcohol, Aliment, Food, Alimento, Catalyseur, Catalyst, Catalizador, Cinétique, Kinetics, Cinética, Corrélation, Correlation, Correlación, Effet solvant, Solvent effect, Efecto solvente, Epoxydation, Epoxidation, Epoxidación, Etat transition, Transition state, Estado transitorio, Ethanol, Etanol, Isomère, Isomer, Isómero, Liaison hydrogène, Hydrogen bond, Enlace hidrógeno, Mécanisme, Mechanism, Mecanismo, Méthode fonctionnelle densité, Density functional method, Oxyde, Oxides, Óxido, Peroxyde d'hydrogène, Hydrogen peroxide, Peróxido de hydrogeno, Réactivité chimique, Chemical reactivity, Reactividad química, Solvant organique, Organic solvent, Solvente orgánico, Stabilisation, Stabilization, Estabilización, density functional calculations, epoxidation, hydrogen bonds, kinetics, and solvent effects

In our attempt to synthesize β-caryophyllene oxide in food-compatible conditions, we observed the uncatalyzed and highly selective epoxidation of β-caryophyllene, a strained bicyclic sesquiterpene, in ethanol with aqueous H2O2 under radical-suppressing conditions without the addition of a catalyst. The unusual reactivity of β-caryophyllene allowed us to use it as a probe for the mechanism of the solvent-assisted epoxidation in a wide range of organic solvents. A kinetic study was performed to investigate the epoxidation mechanism; an excellent correlation was found between the observed epoxidation rates in different solvents and the Abraham's hydrogen bond formation parameters of these solvents. By means of computational analysis, it was found that the main role of the solvent consists of the stabilization of the elongated O―O bond of H2O2 in the transition state through hydrogen-bond donation to the leaving OH moiety of H2O2. α-Humulene was found to possess similar reactivity as β-caryophyllene whereas isocaryophyllene—the unstrained isomer of β-caryophyllene—was unreactive.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines classiques de la physique (y compris les applications), Fundamental areas of phenomenology (including applications), Optique, Optics, Formation des images et traitement optique, Imaging and optical processing, Fluorescence, Fonction étalement point, Point spread functions, Imagerie, Imagery, Imaginería, Microscopie fluorescence, Fluorescence microscopy, Microscopía fluorescencia, Moment dipolaire, Dipole moments, Moment transition, Transition moments, Orientation moléculaire, Molecular orientation, Superrésolution, Superresolution, Superresolución, Limite diffraction, Diffraction limit, Molécule individuelle, Single molecules, fluorescence microscopy, molecular orientation, rotational mobility, single-molecule studies, and super-resolution imaging

Numerous methods for determining the orientation of single-molecule transition dipole moments from microscopic images of the molecular fluorescence have been developed in recent years. At the same time, techniques that rely on nanometer-level accuracy in the determination of molecular position, such as single-molecule super-resolution imaging, have proven immensely successful in their ability to access unprecedented levels of detail and resolution previously hidden by the optical diffraction limit. However, the level of accuracy in the determination of position is threatened by insufficient treatment of molecular orientation. Here we review a number of methods for measuring molecular orientation using fluorescence microscopy, focusing on approaches that are most compatible with position estimation and single-molecule super-resolution imaging. We highlight recent methods based on quadrated pupil imaging and on double-helix point spread function microscopy and apply them to the study of fluorophore mobility on immunolabeled microtubules.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Chimie minerale et origine de la vie, Inorganic chemistry and origins of life, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Dioxyde de soufre, Sulfur dioxide, Dióxido sulfúrico, Fonctionnelle densité, Density functional, Funciónal densidad, Oxydation, Oxidation, Oxidación, Phase gazeuse, Gas phase, Fase gaseosa, Spectrométrie masse, Mass spectrometry, Espectrometría masa, Transfert oxygène, Oxygen transfer, Transferencia oxígeno, density functionals, gas-phase chemistry, ion-molecule reactions, mass spectrometry, and sulfur dioxide oxidation

The oxidation of SO2 by nonmetal oxoanions in the gas phase is investigated in an experimental and theoretical study of the structure of the species involved and the reaction kinetics and mechanism. SO3, SO3·- and SO4·- are efficiently produced by reaction of OnXC- anions (X = Cl, Br, and I; n = 0 and 1) with SO2; XO- ions mainly react to give SO3 by oxygen-atom transfer, whereas OXO- ions mainly give SO3·- by oxygen-anion transfer. On descending the halogen group from chlorine to iodine, the SO3/SO3·- ratio decreases and increases for reactions involving XO- and OXO- anions, respectively, whereas the formation of SO4·- is particularly significant with OIO-. Kinetic factors play a major role in the reactions of OnXO-, depending on the halogen atom and its oxidation state.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Force, Fuerza, Gaz à l'eau, Water gas, Gas con agua, Interaction hydrophobe, Hydrophobic interaction, Interface, Interfase, Microscopie force atomique, Atomic force microscopy, Microscopía fuerza atómica, Nanobulle, Nanobubble, AFM probe, hydrophobic interactions, nanobubbles, peakforce quantitative nanomechanics, and snap-in

The long-range attractive force or snap-in is an important phenomenon usually occurring when a solid particle interacts with a water/gas interface. By using PeakForce quantitative nanomechanics the origin of snap-in in the force curve between the atomic force microscopy (AFM) probe and the water/gas interface of nanobubbles has been investigated. The snap-in frequently happened when the probe was preserved for a certain time or after being used for imaging solid surfaces under atmospheric conditions. In contrast, imaging in liquids rarely induced a snap-in. After a series of control experiments, it was found that the snap-in can be attributed to hydrophobic interactions between the water/gas interface and the AFM probe, which was either modified or contaminated with hydrophobic material. The hydrophobic contamination could be efficiently removed by a conventional plasma-cleaning treatment, which prevents the occurring of the snap-in. In addition, the adsorption of sodium dodecyl sulfate onto the nanobubble surface changed the water/gas interface into hydrophilic, which also eliminated the snap-in phenomenon.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Physique atomique et moleculaire, Atomic and molecular physics, Structure électronique des atomes, des molécules et de leurs ions: théorie, Electronic structure of atoms, molecules and their ions: theory, Surfaces d'énergie potentielle, Potential energy surfaces, Propriétés moléculaires et interactions avec les photons, Molecular properties and interactions with photons, Spectres photoélectroniques, Photoelectron spectra, Composé organique, Organic compounds, Conversion interne, Internal conversion, Dynamique moléculaire, Molecular dynamics, Dinámica molecular, Energie transition, Transition energy, Energía transición, Espace phase, Phase space, Etat excité, Excited states, Etat électronique excité, Electronically excited state, Estado electrónico excitado, Interaction vibronique, Vibronic interaction, Interacción vibrónica, Peptide, Peptides, Processus ultrarapide, Ultrafast process, Proceso ultrarrápido, Quantité mouvement, Momentum, Réaction chimique, Chemical reactions, Spectre photoélectron, Photoelectron spectra, Structure électronique, Electronic structure, Surface énergie potentielle, Potential energy surfaces, electronic structure, energy localization, internal conversion, molecular dynamics, and potential energy surfaces

The absorption of light by molecules can induce ultrafast dynamics and coupling of electronic and nuclear vibrational motion. The ultrafast nature in many cases rests on the importance of several potential energy surfaces in guiding the nuclear motion—a concept of central importance in many aspects of chemical reaction dynamics. This Minireview focuses on the non-ergodic nature of internal conversion, that is, on the concept that the nuclear dynamics only sample a reduced phase space, potentially resulting in localization of the dynamics in real space. A series of results that highlight the nonstatistical nature of the excited-state deactivation process is presented. The examples are categorized into four groups. 1) Localization of the energy in one degree of freedom in S2→S1, transitions, in which the transition is either determined by the time spent in the S2→S1 coupling region or by the time it takes to reach it. 2) Localization of energy into a single reactive mode, which is dictated by the internal conversion process. 3) Initiation of the internal conversion by activation of a single complex motion, which then specifically couples to a reactive mode. 4) Nonstatistical internal conversion as a tool to accomplish biomolecular stability. Herein, the discussion on nonstatistical internal conversion in DNA as a mechanism to eliminate electronic excitation energy is extended to include molecules with an S—S bond as a model of the disulfide bridge in peptides. All of these examples are summed up in Kasha's rule. For systems with multiple degrees of freedom it will be possible to locate an appropriate motion somewhere in phase space that will take the wavepacket to the coupling region and facilitate an ultrafast transition to S1. Once at S1, the momentum of the wavepacket is lost and the only options left are the statistical processes of reaction or light emission.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Structure des liquides et des solides; cristallographie, Structure of solids and liquids; crystallography, Cristaux liquides, Liquid crystals, Cristal liquide, Liquid crystals, Etat nématique, Nematic state, Estado nemático, Oxadiazole, Oxadiazoles, Propriété physique, Physical properties, bent-core motecules, liquid crystal, nematic phases, oxadiazoles, and physical properties

Over the last ten years, the nematic phases of liquid crystals formed from bent-core structures have provoked considerable research because of their remarkable properties. This Minireview summarises some recent measurements of the physical properties of these systems, as well as describing some new data. We concentrate on oxadiazole-based materials as exemplars of this class of nematogens, but also describe some other bent-core systems. The influence of molecular structure on the stability of the nematic phase is described, together with progress in reducing the nematic transition temperatures by modifications to the molecular structure. The physical properties of bent-core nematic materials have proven difficult to study, but patterns are emerging regarding their optical and dielectric properties. Recent breakthroughs in understanding the elastic and flexoelectric behaviour are summarised. Finally, some exemplars of unusual electric field behaviour are described.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Carbone, Carbon, Carbono, Carbyne, Carbino, Composé polyynique, Polyynic compound, Compuesto poliínico, Cumulène, Cumulene, Cumuleno, Longueur liaison, Bond length, Longitud enlace, Méthode fonctionnelle densité, Density functional method, bond-length alternation, carbynes, cumulenes, density functional calculations, and polyynes

A question of both fundamental as well as practical importance is the nature of one-dimensional carbon, in particular whether a one-dimensional carbon allotrope is polyynic or cumulenic, that is, whether bond-length alternation occurs or not. By combining the concept of aromaticity and antiaromaticity with the rule of Peierls distortion, the occurrence and magnitude of bond-length alternation in carbon chains with periodic boundary conditions and corresponding carbon rings as a function of the chain or ring length can be explained. The electronic properties of one-dimensional carbon depend crucially on the bond-length alternation. Whereas it is generally accepted that carbon chains in the limit of infinite length have a polyynic structure at the minimum of the potential energy surface with bond-length alternation, we show here that zero-point vibrations lead to an effective equalization of all carbon-carbon bond lengths and thus to a cumulenic structure.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Physique atomique et moleculaire, Atomic and molecular physics, Structure électronique des atomes, des molécules et de leurs ions: théorie, Electronic structure of atoms, molecules and their ions: theory, Calculs et techniques mathématiques en physique atomique et moléculaire (sauf les calculs de corrélation électronique), Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations), Théorie de la fonctionnelle de densité, Density-functional theory, Energie cinétique, Kinetic energy, Etude théorique, Theoretical study, Liaison carbone carbone, Carbon carbon bond, Enlace carbono carbono, Méthode fonctionnelle densité, Density functional method, Structure électronique, Electronic structure, 3115E, bond theory, charge-shift bonding, covalent bonding, local kinetic energy, and quantum chemical topology

Analysis of the kinetic energy density within a molecule identifies patterns in its electronic structure that are linked to the concept of charge-shift bonding. This is illustrated in a detailed study of twelve molecules, possessing carbon-carbon covalent as well as carbon-carbon charge-shift bonds in various degrees of orders, including propellanes and heteropropellanes. Regions of slow electrons are fundamental for such a correlation, and a RoSE (region of slow electrons) indicator ν±, based on the positive definite kinetic energy density τ, is employed to characterize classes of charge-shift bonds in terms of its full topology of all critical points of rank three.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Generalites, General, Instruments, appareillage, composants et techniques communs à plusieurs branches de la physique et de l'astronomie, Instruments, apparatus, components and techniques common to several branches of physics and astronomy, Instrumentation, équipement et techniques optiques, Optical instruments, equipment and techniques, Microscopes optiques conventionnels, Conventional optical microscopes, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Théorie des réactions, cinétique générale, Theory of reactions, general kinetics, Etude théorique, Theoretical study, Maximum vraisemblance, Maximum likelihood, Maxima verosimilitud, Microscopie optique, Optical microscopy, Méthode analytique, Analytical method, Método analítico, Superrésolution, Superresolution, Superresolución, 0760P, Molécule individuelle, Single molecules, localisation molécule, analytical approximations, localization microscopy, maximum likelihood estimation, single-molecule studies, and super-resolution light microscopy

A study of the uncertainty of localizing single-molecule emitters for super-resolution light microscopy is presented. Maximum likelihood estimation (MLE) is found to be superior to least-squares fitting for low background levels, but the performance difference between the two methods decreases to a few percent for practical background levels. It is shown that the performance limit of MLE, the Cramér―Rao lower bound, is well described by a concise analytical formula with only spot width and signal and background photon count as input parameters. These predictions for the lateral localization uncertainty are compared with the localization error obtained from repeated localizations of the same single-molecule emitter. Agreement within a few percent is found, thus verifying the validity of the fitting model and the concise analytical approximation. The analysis is extended by novel analytical results for the dependence of the axial localization uncertainty on background level for the astigmatic, bifocal, and double-helix methods.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Matériaux particuliers, Specific materials, Fullerènes et matériaux apparentés; diamants, graphite, Fullerenes and related materials; diamonds, graphite, Sciences appliquees, Applied sciences, Energie, Energy, Combustibles, Fuels, Combustibles de remplacement. Production et utilisation, Alternative fuels. Production and utilization, Hydrogène, Hydrogen, Carbone, Carbon, Carbono, Fullerènes, Fullerenes, Graphène, Graphene, Oxygène, Oxygen, Oxígeno, Réduction chimique, Chemical reduction, Reducción química, Stockage hydrogène, Hydrogen storage, Support, Soporte, carbon, fullerene, graphene, hydrogen storage, and oxygen reduction reaction

N-doped graphene has become an important support for Pd in both hydrogen storage and catalytic reactions. The molecular orbitals of carbon materials (including graphene, fullerene, and small carbon clusters) and those of the supported Pd species will hybrid much stronger as N dopants are introduced, owing to the increased electrostatic attraction at the interface. This enhances the carbon substrates' catching force for the sup ported Pd, preventing its leaching and aggregation in many practical applications. The better dispersion and stabilization of Pd nanoparticles, which are induced by various carbon supports with N-doping, are pleasing to us and could increase their efficiency and facilitate their recycling during various reaction processes in several fields.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Etat colloïdal et états dispersés, Colloidal state and disperse state, Etudes physiques et chimiques. Granulométrie. Phénomènes électrocinétiques, Physical and chemical studies. Granulometry. Electrokinetic phenomena, Métal transition, Transition metal, Metal transición, Agrégat ionique, Ionic cluster, Agregado iónico, Argent, Silver, Plata, Dissociation, Disociación, Energie, Energy, Energía, Isomère, Isomer, Isómero, Méthode fonctionnelle densité, Density functional method, Méthode optimisation, Optimization method, Método optimización, Photon, Fotón, Silicium, Silicon, Silicio, Spectrométrie IR, Infrared spectrometry, Espectrometría IR, Structure, Estructura, IR spectroscopy, cluster compounds, density functional calculations, silicon, and silver

Cationic silver-doped silicon clusters, SinAg+ (n=6-15), are studied using infrared multiple photon dissociation in combination with density functional theory computations. Candidate structures are identified using a basin-hopping global optimizations method. Based on the comparison of experimental and calculated IR spectra for the identified low-energy isomers, structures are assigned. It is found that all investigated clusters have exohedral structures, that is, the Ag atom is located at the surface. This is a surprising result because many transition-metal dopant atoms have been shown to induce the formation of endohedral silicon clusters. The silicon framework of SinAg+ (n=7-9) has a pentagonal bipyramidal building block, whereas the larger SinAg+ (n=10-12, 14, 15) clusters have trigonal prism-based structures. On comparing the structures of SinAg+ with those of SinCu+ (for n=6-11) it is found that both Cu and Ag adsorb on a surface site of bare Sin+ clusters. However, the Ag dopant atom takes a lower coordinated site and is more weakly bound to the Sin+ framework than the Cu dopant atom.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Etat colloïdal et états dispersés, Colloidal state and disperse state, Membranes, Cholestérol, Cholesterol, Colesterol, Couche bimoléculaire, Bilayer, Capa bimolecular, Dynamique moléculaire, Molecular dynamics, Dinámica molecular, Lipide, Lipids, Lípido, Membrane, Membrana, Résonance magnétique nucléaire, Nuclear magnetic resonance, Resonancia magnética nuclear, Vésicule, Vesicle, Vesícula, NMR spectroscopy, cholesterol effect, fast field-cycling NMR, lipid bilayers, and molecular dynamics

The general applicability of fast field-cycling nuclear magnetic resonance relaxometry in the study of dynamics in lipid bilayers is demonstrated through analysis of binary unilamellar liposomes composed of 1,2-dioleoyl-sn-glycero-3-posphocholine (DOPC) and cholesterol. We extend an evidence-based method to simulating the NMR relaxation response, previously validated for single-component membranes, to evaluate the effect of the sterol molecule on local ordering and dynamics over multiple timescales. The relaxometric results are found to be most consistent with the partitioning of the lipid molecules into affected and unaffected portions, rather than a single averaged phase. Our analysis suggests that up to 25 mol%, each cholesterol molecule orders three DOPC molecules, providing experimental backup to the findings of many molecular dynamics studies. A methodology is established for studying dynamics on multiple timescales in unilamellar membranes of more complex compositions.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Sciences appliquees, Applied sciences, Energie, Energy, Combustibles, Fuels, Combustibles de remplacement. Production et utilisation, Alternative fuels. Production and utilization, Hydrogène, Hydrogen, Alliage, Alloys, Aleación, Hydroborate, Hydroborates, Hidroborato, Oxydation, Oxidation, Oxidación, Stockage hydrogène, Hydrogen storage, alloys, borohydride oxidation reaction, galvanic displacements, hydrogen storage, and metal hydrides

This work provides insights into the processes involved in the borohydride oxidation reaction (BOR) in alkaline media on metal hydride alloys formed by LaNi4.7Sn0.2Cu0.1 and LaNi4.78Al0.22 with and without deposited Pt, Pd, and Au. The results confirm the occurrence of hydrolysis of the borohydride ions when the materials are exposed to BH4- and a continuous hydriding of the alloys during BH4- oxidation measurements at low current densities. The activity for the direct BOR is low in both bare metal hydride alloys, but the rate of the BH4- hydrolysis and the hydrogen-storage capacity are higher, while the rate of H diffusion is slower for bare LaNi4.78Al0.22. The addition of Pt and Pd to both alloys results in an increase of the BH4- hydrolysis, but the H2 formed is rapidly oxidized at the Pt-modified catalysts. In the case of Au modification, a small increase in the BH4- hydrolysis is observed as compared to the bare alloys. The presence of Au and Pd also leads to a reduction of the rates of alloy hydriding/de-hydriding.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie organique, Organic chemistry, Benzoquinodiméthane-7,7,8,8-tétracarbonitrile, 7,7,8,8-Tetracyanoquinodimethane, Complexe de bore, Boron complex, Boro complejo, Complexe de gallium, Gallium complex, Galio complejo, Composé aromatique, Aromatic compound, Compuesto aromático, Conductivité électrique, Electrical conductivity, Conductividad eléctrica, Diffraction RX, X ray diffraction, Difracción RX, Energie activation, Activation energy, Energía activación, Guanidine, Monocristal, Single crystal, Réduction chimique, Chemical reduction, Reducción química, Semiconducteur, Semiconductor materials, Semiconductor(material), Structure cristalline, Crystalline structure, Estructura cristalina, boron, donor-acceptor systems, gallium, guanidines, and tetracyanoquinodimethane

In this work, we report on the reduction of tetracyanoquinodimethane (TCNQ) with dicationic complexes of guanidinyl-functionalized aromatic (GFA) electron donors. In contrast to reduction with free GFAs, milder reduction conditions were achieved, and this led to semiconducting materials with extended TCNQ π stacking. The charge on the TCNQ units was estimated from the structural data obtained by single-crystal X-ray diffraction analysis and from IR spectroscopic data. The electrical conductivity was studied and the activation energy of the semiconducting materials was estimated from the temperature dependence of the conductivity.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Etude des interfaces, Study of interfaces, Capacité électrique, Capacitance, Capacitancia, Dynamique moléculaire, Molecular dynamics, Dinámica molecular, Effet température, Temperature effect, Efecto temperatura, Electrode, Electrodes, Electrodo, Graphite, Grafito, Liquide ionique, Ionic liquid, Líquido iónico, Simulation, Simulación, Composé de l'imidazolium, Imidazolium compound, Imidazolium(1-butyl-3-méthyl) hexafluorophosphate, differential capacitance, electric double layer, ionic liquids, molecular dynamics, and temperature effects

Temperature-dependent electric double layer (EDL) and differential capacitance-potential (Cd-U) curves of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM+ /PF6-) were studied on a graphite electrode by molecular dynamics simulations. It was found that all Cd-U curves were asymmetric camel-shaped with higher Cd at negative polarization, attributed to the specific adsorption of BMIM+. In addition, the maxima of Cd at the negative polarization decrease monotonically with temperature due to the thicker EDL, whereas at the positive polarization they gradually increase from 450 to 550 K and decrease at 600 K. Such temperature effects at positive polarization may be understood in terms of the competition between two aspects: the weakening specific adsorption of BMIM+ allows more effective screening to the positive charge and overall increasing EDL thickness. Although the former dominates from 450 to 550 K, the latter becomes dominant at 600 K.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Adsorption, Adsorción, Charpente organométallique, Metal organic framework, Armazòn organometálico, Solution solide, Solid solution, Solución sólida, Sorption, Sorción, breathing effect, gas adsorption, host-guest systems, metal-organic frameworks, and solid solutions

Metal―organic frameworks are promising materials for manifold applications. This Minireview highlights approaches for the fine-tuning of specific sorption properties (e.g. capacity, selectivity, and breathing behavior) of this interesting class of materials. Central aspects covered are the control over the crystal morphology, the targeted tuning of sorption properties by judicious choice of metal centers and linkers, and the preparation of host-guest systems. We want to introduce the reader to these topics on the basis of the manipulation of a handful of outstanding prototypical metal-organic frameworks.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Structure des liquides et des solides; cristallographie, Structure of solids and liquids; crystallography, Cristaux liquides, Liquid crystals, Couche intermédiaire, Interlayers, Cristal liquide, Liquid crystals, Modèle phénoménologique, Phenomenological model, Modelo fenomenológico, Structure, Estructura, antiferroelectric liquid crystal, bent-core liquid crystal, complex structures, phenomenological models, and polar smectics

Complex structures in polar smectic systems can be studied within framework of discrete phenomenological models. Considered interactions are usually described by nonlinear trigonometric functions that do not allow for a straightforward search for solutions. The review or tnree methods reported in the literature are presented and their appropriateness, advantages and disadvantages are discussed. Examples are given as an illustration for each method.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Structure des liquides et des solides; cristallographie, Structure of solids and liquids; crystallography, Cristaux liquides, Liquid crystals, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Nanomatériaux et nanostructures : fabrication et caractèrisation, Nanoscale materials and structures: fabrication and characterization, Divers, Other topics in nanoscale materials and structures, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Etat colloïdal et états dispersés, Colloidal state and disperse state, Etudes physiques et chimiques. Granulométrie. Phénomènes électrocinétiques, Physical and chemical studies. Granulometry. Electrokinetic phenomena, Cristal liquide, Liquid crystals, Cristal líquido, Dispersion, Dispersión, Electrooptique, Electrooptics, Electroóptica, Etat nématique, Nematic state, Estado nemático, Nanomatériau, Nanostructured materials, Nanoparticule, Nanoparticle, Nanopartícula, Or, Gold, Oro, Silane, Silano, Synthèse, Synthesis, Síntesis, 8270D, dispersions, electro-optics, functional silanes, liquid crystals, and nanoparticles

Chemically and thermally robust liquid crystal silane-functionalized gold nanoparticles (i.e. AuNP1-AuNP3) were synthesized through silane conjugation. Colloidal dispersions of these particles with mesogenic ligands that are structurally identical (as in AuNP1, AuNP2) or compatible (as in AuNP3) with molecules of the nematic liquid crystal (N-LC) host showed superior colloidal stability and dispersibility. The thermal, optical, and electro-optic behaviors of the N-LC composites at different concentrations of each gold nanoparticle were investigated. All dispersions showed lower values for the rotational viscosity and elastic constant, but only AuNP3 with a dissimilar structure between the nanoparticle ligand and the host displayed the most drastic thermal effects and overall strongest impact on the electro-optic properties of the host. The observed results were explained considering both the structure and the density of the surface ligands of each gold nanoparticle.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie des réactions induites par rayonnements, particules et ultrasons, Physical chemistry of induced reactions (with radiations, particles and ultrasonics), Photochimie, Photochemistry, Electrochimie, Electrochemistry, Etude des interfaces, Study of interfaces, Dépôt électrolytique, Electrodeposition, Photoélectrochimie. Electrochimiluminescence, Photoelectrochemistry. Electrochemiluminescence, Décomposition, Decomposition, Descomposición, Dépôt électrolytique, Electrodeposition, Depósito electrolítico, Nanocomposite, Nanocompuesto, Nanomatériau, Nanostructured materials, Or, Gold, Oro, Oxyde, Oxides, Óxido, Photocatalyse, Photocatalysis, Fotocatálisis, Photoélectrochimie, Photoelectrochemistry, Fotoelectroquímica, Remplacement, Replacement, Reemplazo, Semiconducteur, Semiconductor materials, Semiconductor(material), Synthèse, Synthesis, Síntesis, BiVO4, Bismuth?Vanadate, Dissociation de l'eau, Water splitting, electrosynthesis, nanomaterials, oxide semiconductors, photoelectrochemistry, and water splitting

A Au-BiVO4 nanocomposite is synthesized by a two-step strategy involving anodic electrodeposition combined with in situ galvanic replacement. First, a BiVO4 layer is prepared by the anodic oxidation of pre-electrodeposited Bi film in a VO43- containing electrolyte. Thus-prepared BiVO4 film contains excess metallic Bi, which is then galvanically replaced with Au from an aqueous HAuCl4 solution, resulting in the Au-BiVO4 composite in the second step. Optical, photoelectrochemical and photocatalytic properties are investigated by using X-ray diffraction, energy-dispersive X-ray analysis, diffuse reflectance spectrometry, and photoelectrochemical analyses. The visible-light photocatalytic activity of the Au-BiVO4 composite is evaluated using the decomposition of methyl orange dye and is superior to the bare BiVO4 film counterpart.

Biochemistry, molecular biology, biophysics, Biochimie, biologie moléculaire, biophysique, General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Atomic molecular physics, Physique atomique et moléculaire, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Etat colloïdal et états dispersés, Colloidal state and disperse state, Etudes physiques et chimiques. Granulométrie. Phénomènes électrocinétiques, Physical and chemical studies. Granulometry. Electrokinetic phenomena, Emulsions. Microémulsions. Mousses, Emulsions. Microemulsions. Foams, Métal transition, Transition metal, Metal transición, Ammoniac, Ammonia, Amoníaco, Electrocatalyse, Electrocatalysis, Electrocatálisis, Emulsion eau huile, Water oil emulsion, Emulsión agua aceite, Forme, Shape, Forma, Microémulsion eau huile, Water oil microemulsion, Microemulsión agua aceite, Nanoparticule, Nanoparticle, Nanopartícula, Platine, Platinum, Platino, Synthèse, Synthesis, Síntesis, ammonia, electrocatalysis, nanoparticles, platinum, and shape

The increasing number of applications for shape-controlled metal nanoparticles (NPs) has led to the need for easy, cheap, and scalable methodologies. We report the synthesis of (100) preferentially oriented Pt NPs, with a particle size of 9 nm, by using a water-in-oil microemulsion method. The specific surface structure of the NPs is induced by the presence of H2SO4 in the water phase of the microemulsion. Interestingly, the results reported herein show how increasing amounts of H2SO4 lead to the formation of Pt NPs containing a larger amount of (100) sites on their surface. This preferential surface orientation is confirmed electrochemically by using the so-called hydrogen adsorption/desorption process. In addition, transmission electron microscopy measurements confirm the presence of cubic-like Pt NPs. Finally, the electrocatalytic properties of the Pt NPs are evaluated towards ammonia and CO electro-oxidations, which are (100) structure-sensitive reactions.