Chemphyschem最新文献

Bismuth vanadate (BiVO₄) is regarded as a promising photoanode candidate for photoelectrochemical (PEC) water splitting, but is limited by low efficiency of charge carrier transport and short carrier diffusion length. In this work, we report a strategy comprised of the gradient doping of W and back-to-back stacking of transparent photoelectrodes, where the 3-2 wt.% W gradient doping enhances charge carrier transport by optimizing the band bending degree and back-to-back stack configuration shortens carrier diffusion length without much sacrifice of photons. As a result, the photocurrent density of 3-2 % W:BiVO₄ photoanode reaches 2.20 mA cm^-2 at 1.23 V vs. hydrogen electrode (RHE) with a charge transport efficiency of 76.1 % under AM 1.5 G illumination, and the back-to-back stacked 3-2 % W:BiVO₄ photoanodes achieves a photocurrent of 4.63 mA cm^-2 after loading Co-Pi catalyst and anti-reflective coating under AM 1.5 G illumination, with long-term stability of 10 hours.

This comprehensive review aims to provide an overview of recent progress in utilizing plant-based biochar for supercapacitors. It specifically focuses on biochar derived from plant biomass such as agricultural residues, weeds and aquatic plants, examining their potential in energy storage applications. It explores various synthesis methods like pyrolysis and hydrothermal carbonization and evaluates their impact on biochar's structure and electrochemical properties. Additionally, it examines the electrochemical performance of biochar-based supercapacitors, focusing on parameters such as capacitance, cycling stability, and rate capability. Strategies to enhance biochar's electrochemical performance, such as surface modification and composite fabrication, are also discussed. Furthermore, it addresses existing challenges and prospects in harnessing plant-based biochar for supercapacitor applications, highlighting its potential as a sustainable and efficient electrode material for next-generation energy storage devices.

Cyclopentanone is a potential bio-fuel which can be produced from bio-mass. Its gas phase dissociation chemistry has attracted several experimental and theoretical investigations. In the photochemical and thermal decomposition studies of cyclopentanone, ethylene and carbon monoxide were found to be dominant reaction products along with several other compounds in smaller quantities. For the formation of ethylene and carbon monoxide, a concerted mechanism has been proposed as the primary reaction pathway. In addition, a step-wise mechanism involving ring-opened radical intermediate has also been considered. The present work reports gas phase thermal decomposition of cyclopentanone at high temperatures investigated using electronic structure theory methods, Rice-Ramsperger-Kassel-Marcus (RRKM) rate constant calculations, and Born-Oppenheimer direct classical trajectory simulations. The trajectory calculations were performed on density functional PBE96/6-31+G* potential energy surface using initial conditions selected from fixed energy normal mode distributions. Simulations showed that ethylene and carbon monoxide formed primarily via the concerted mechanism confirming the earlier predictions. In addition, step-wise pathways were also observed for the same products in lower fraction of trajectories. Furthermore, several other reaction products in smaller quantities and new mechanistic pathways were observed. The computed RRKM rate constants and simulation data are in agreement with experimental results and detailed atomic level dissociation mechanisms presented.

In the drive towards increased lithium based battery capacity, germanium is an attractive material due to its very high lithium storage capacity, second only to silicon. The persistent down-side is the considerable embrittlement accompanying its remarkable volume expansion of close to 300 %. A proven method to accommodate for this lattice expansion is the reduction of the size towards the nanoscale at which the fracturing is prevented by "breathing". In this work we employed a novel magnetron sputtering gas aggregation nanoparticle generator to create unprecedented layers of well-defined germanium nanoparticles with sizes below 20 nm. The electrochemical lithium intercalation was monitored by a suite of techniques under which Raman spectroscopy, which provided clear evidence of the presence of lithium inside the germanium nanoparticles. Moreover, the degree of lattice order was measured and correlated to the initial phases of the lithium-germanium alloy. This was corroborated by electron diffraction and optical absorption spectroscopy, of which the latter provided a strong dielectric change upon lithium intercalation. This study of low lithium concentrations inside layers of well-defined and very small germanium nanoparticles, forms a new avenue towards significantly increasing the lithium battery capacity.

Cr²⁺ and Cr³⁺ ions are shown to mediate the formation, morphology, and organization of arachidic acid (AA) Langmuir-Blodgett (LB) monolayers. This finding, based on cyclic voltammetry (CV), linear sweep voltammetry (LSV) and fluorescence recovery after photobleaching (FRAP) measurements, show that Langmuir monolayer formation depends on subphase pH and metal ion concentration. Following monolayer deposition on indium tin oxide (ITO), the LB monolayer organization can be modified reversibly through control of the Cr oxidation state, which has not been shown before by other monolayers formed with other divalent metal ions. The dynamics and the mobility of a chromophore (perylene) incorporated into the monolayer sense changes in Cr oxidation state-dependent organization of the LB monolayer. Demonstrating reversible changes in monolayer organization provides an opportunity to control chemical and electron access to the interface support.

It is shown, by examining the variations in off-nucleus isotropic magnetic shielding around a molecule, that thiophene which is aromatic in its electronic ground state (S₀) becomes antiaromatic in its lowest triplet state (T₁) and then reverts to being aromatic in T₂. Geometry relaxation has an opposite effect on the aromaticities of the ππ* vertical T₁ and T₂: The antiaromaticity of T₁ is reduced whereas the aromaticity of T₂ is enhanced. The shielding picture around T₂ is found to closely resemble those around certain second singlet ππ* excited states (S₂), for example, those of benzene and cyclooctatetraene, thought to be "strongly aromatic" because of their very negative nucleus-independent chemical shift (NICS) values. It is argued that while NICS values correctly follow the changes in aromaticity along the potential energy surface of a single electronic state, the use of NICS values for the purpose of quantitative comparisons between the aromaticities of different electronic states cannot be justified theoretically and should be avoided. "Strongly aromatic" S₂ and T₂ states should be referred to simply as "aromatic" because detailed comparisons between the properties of these states and those of the corresponding S₀ states do not suggest higher levels of aromaticity.

Quinoline represents a promising scaffold for developing potential drugs because of the wide range of biological and pharmacological activities that it exhibits. In the present study, quinoline derivatives obtained from CADMA-Chem docking protocol were investigated in the mean of molecular dynamics simulations as potential inhibitors of acetylcholinesterase enzyme. The examined species can be partitioned between neutral, dq815 (2,3 dihydroxyl-quinoline-4-carbaldehyde), dq829 (2,3 dihydroxyl-quinoline-8-carboxylic acid methane ester), dq1356 (3,4 dihydroxyl-quinoline-6-carbaldehyde), dq1368 (3,4 dihydroxyl-quinoline-8-carboxylic acid methane ester) and dq2357 (5,6 dihydroxyl-quinoline-8-carboxylic acid methane ester), and deprotonated, dq815_dep, dq829_dep, dq1356_dep and dq2357_dep. Twelve molecular dynamics simulations were performed including those of natural acetylcholine, of the well-known donepezil inhibitor and of the founder quinoline chosen as reference. Key intermolecular interactions were detected and discussed to describe the different dynamic behavior of all the considered species. Binding energies calculation from MMPBSA well accounts for the dynamic behavior observed in the simulation time proposing dq1368 as promising candidate for the inhibition of acetylcholinesterase. Retrosynthetic route for the production of the investigated compounds is also proposed.

Catalytic reactions occurring in an adsorbed overlayer on metallic alloy nanoparticles are of high interest in the context of applications in the chemical industry. The understanding of the corresponding kinetics is, however, still limited. One of the reasons of this state of the art is the interplay between adsorption and adsorbate-influenced segregation of metal atoms inside alloy nanoparticles. I scrutinize this interplay by using a generic field model of segregation and the mean-field approximation in order to describe adsorption, desorption, and elementary catalytic reactions. Under steady-state conditions, the segregation is demonstrated to be manifested in the change of the dependence of the activation energies of desorption or elementary reactions on coverage, and the sign of this change is positive. The effect of this change on the apparent reaction orders is briefly discussed as well.

Light patternable colorless liquid crystalline (LC) polymers are promising materials for functional photonic devices with broad applications in optical communication, diffractive optics, and displays. This work reports photoinduced optical anisotropy in thin films of azobenzene-containing (Azo) LC block copolymer supramolecular complexes, which can be decolorized after light patterning providing colorless patterned birefringent polymer films. The supramolecular complexes are prepared via intermolecular pyridine-phenol hydrogen bonding between a low-molecular-weight Azo phenol and host LC AB diblock and ABA triblock copolymers consisted of LC phenylbenzoate (PhM) blocks and poly(vinylpyridine) units. The molecular architecture of the host polymers and the morphological pattern formed by the complexes can affect orientational behavior of Azo groups under irradiation with linearly polarized light. Photoorientation of hydrogen-bonded Azo groups is accompanied by the cooperative orientation of non-photochromic PhM units, which form individual microphases and stabilize the orientation of Azo groups. This effect is specific for block copolymer complexes and it is absent for random copolymer complex, which is used as a reference sample. Optical anisotropy induced in films of the block copolymer complexes can be amplified by heating above the glass transition temperature and subsequent rinsing with diethyl ether allows colorless birefringent polymer films to be prepared.