Russian Journal of Physical Chemistry A最新文献

Microbial rhodopsin KR2 is a transmembrane photoactive protein that transports sodium ions across the membrane using light energy. KR2 is a promising tool for optogenetics, enabling optical control of neuronal activity. Here we explore the possibility of two-photon S₀ → S₁ excitation of KR2 and its red-shifted double mutant KR2 P219T/S254A with entangled and classical photon pairs. By using molecular dynamics simulations, a high-level XMCQDPT2-based QM/MM approach, and the sum-over-states formalism for calculating two-photon absorption (TPA) strengths, we show that the microbial rhodopsins intrinsically exhibit large classical TPA cross-sections due to a pronounced electron density redistribution upon the S₀ → S₁ transition. The nonclassical contribution turns out to be considerably larger than the classical counterpart in both KR2 and its double mutant, and the quantum entanglement of photon pairs further increases their transition strengths by one order of magnitude. Our calculations reproduce the experimental red shift in the absorption of the double mutant of KR2 and, while revealing only a slight increase in the classical TPA cross-section in KR2 P219T/S254A, show that its entangled TPA strength decreases. These variations, induced by alterations in the local electric field of the protein caused by the two amino acid replacements, can be attributed to changes in the permanent dipole moments between the ground and excited states. Our results demonstrate high tunability of the nonlinear photophysical properties of microbial rhodopsins, which can be used for the rational design of more efficient optogenetic tools upon two-photon excitation.

Catalysts based on nickel, cobalt, and platinum deposited on coal and silica gel are synthesized and investigated. Energy dispersive X-ray analysis (EDX) is performed to determine the distribution of metals in the bulk phase. The atomic ratio in subsurface layers is measured via X-ray photoelectron spectroscopy (XPS). It is shown that the concentration of metal on a surface can differ significantly from its content in the bulk phase. Profiles of the distribution of metal from the surface to the depth of a catalyst granule are constructed. Textural characteristics of the studied catalysts are obtained. A way of determining the number of active sites on a catalyst’s surface is proposed based on EDX, XPS, and the textural characteristics of a sample. The calculated numbers of metal atoms are compared to the amount of reactive hydrogen adsorbed on active centers. Results allow determination of the effect synthesis has on the content of active sites on the surface of a catalyst.

The possibility of using UHF energy in the synthesis of ZSM-5 type zeolite with a reduced content of Na⁺ ions intended for the catalytic pyrolysis of biomass is investigated to find solutions for enhancing energy efficiency (shortening the period of crystallization) while preserving the morphological features of specimens, along with their textural and catalytic characteristics. The research subject was ZSM-5 type high-silica zeolite with a modulus of 50.0. The objects of study are the physico-chemical patterns that occur while microwaving a mixture of initial components and their subsequent hydrothermal crystallization. X-ray phase analysis and IR spectroscopy are used to determine the optimum time of exposure to microwaves for a mixture of initial ingredients and their subsequent crystallization, while keeping the content of the crystalline phase at a level of 80% or more. The results in this work are of interest from a fundamental viewpoint and can be used in optimizing existing industrial technologies.

In this study, electron paramagnetic resonance (EPR) hyperfine coupling constants (hfccs) of fluorinated nitrobenzene and nitrophenol radical anions were calculated using Density Functional Theory (DFT) with B3LYP functional at 6-31+G(d), 6-31++G(d,p), LanL2DZ, LanL2MB, EPR-II, and EPR-III basis sets. The obtained results were evaluated based on their agreement with the experimental data. The LanL2DZ was identified as the optimal basis set. Using this set, the EPR and Natural Bond Orbital (NBO) analysis of all the radical anions were performed. The simulated EPR spectra, generated using the calculated hfccs, were found to be in good agreement with the experimental spectra. A theoretical equation for the hfcc of fluorine atom was proposed and validated against multiple experimental datasets with high accuracy.

Iodine-131 is frequently used in nuclear medicine for both diagnosis and treatment of thyroid conditions. Given that it’s radioactive and potentially linked to thyroid cancer, patients usually undergo monitoring for a week to avoid harm from the radioactive iodine. Graphene oxide’s electrical and mechanical traits have led to its widespread study in biomedicine. Its adsorption process utilizes its large surface area, porous structure, and functional groups that enable attractants to bind. This research employed the modified Hammer method to synthesize and characterize graphene oxide, utilizing it to remove iodine both in the laboratory and in living subjects. Results showed the produced graphene oxide structures were nanoscale, thus increasing the surface available for adsorption. The lab tests on adsorption showed they followed the Langmuir model, with optimal adsorption at 50 mg graphene oxide, pH 7.4, 37°C, and a 35-min contact time. Moreover, the results revealed graphene oxide did not negatively affect the rabbits’ liver or kidney functions, and the clearance rate observed in the living subjects was 71.95%.

The results of our study of the sorption of the anionic dye methylene orange (MO) and hexavalent chromium oxy ions from aqueous solutions using mono-, bi-, and three-component systems Al₂O₃ (A), ZrO₂ (Z), xAl₂O₃−ZrO₂ (xAZ), and xAl₂O₃−[ZrYb]O₂ (xAZYb) with different heat treatments after sol-gel synthesis are presented. The influence of the sorbent composition and heat treatment temperature of 180, 500, and 800°C on the extraction of sorbate anions was determined based on the parameters of sorption isotherms and adsorption kinetics at 25°C. The Henry constants of sorption of the methyl orange dye (L/m²) on the samples calcinated at 500°C decrease linearly with the increasing content of A. The xAZYb samples showed better dye and dichromate ion sorption characteristics than xAZ. The studied systems, which are precursors of alumina–zirconia ceramics, can be used in the adsorption removal of pollutant anions from the aquatic environment.

Silver nanoparticles (AgNPs) are most often used as surface-enhanced Raman scattering (SERS) substrates thanks to their surface plasmon resonance, but conventional chemical reduction methods suffer from particle aggregation, poor controllability, and pollution. In this work, we have employed graphene/Cu as a platform for the precision assembly of AgNPs to create AgNPs/graphene/Cu (AgNPs/Gr/Cu), leveraging electron localization and interfacial engineering to promote the controlled reduction of Ag⁺ and subsequent Ag deposition. The formation kinetics of AgNPs were systematically investigated and modulated via adjusting solvent polarity, precursor concentration, reaction time and temperature, to establish the correlation between AgNPs morphology and synthesis parameters. Specifically, the hexagonal lattice of graphene facilitated the epitaxial growth of Ag (111), thereby favoring the formation of hexagonal AgNPs. Additionally, the electron transfer between Ag and graphene altered the charge distribution on Ag surface, affecting the deposition/arrangement of Ag atoms and effectively preventing the oxidation/aggregation of AgNPs. The fabricated AgNPs/Gr/Cu manifested superior performance in SERS.

CuO–Mn₂CuO₄ composite materials for tailored hydrogen evolution were successfully synthesized using a simple method. The synthesis process used Cu(NO₃)₂⋅3H₂O and MnCO₃ as precursors. The resulting composites were comprehensively characterized using a suite of analytical techniques, including scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X‑ray diffraction. The electrochemical performance of the CuO–Mn₂CuO₄ composites was systematically evaluated through cyclic voltammetry and linear sweep voltammetry, while electrochemical impedance spectroscopy was used to investigate the hydrogen evolution reaction at the electrode interface. The composite demonstrated a 0.31 V reduction in overpotential compared to the bare glassy carbon electrode, with a hydrogen evolution rate of approximately 0.76 mL min^–1 cm^–2, with a current density of 100 mA cm^–2, which was approximately three times that of the GCE.

In this research, the performance of polyethylene glycol (PEG) as a nanocarrier for the targeted drug delivery of cyclophosphamide (CLP) was investigated by density functional theory, infra-red, frontier molecular orbital and natural bonding orbital computations. The achieved results showed the interaction of CLP with PEG is experimentally feasible. The calculated thermodynamic parameters showed CLP adsorption process is spontaneous, exothermic and two sided. The impact of temperature and solvent on the interactions was also checked out and the results showed the presence of water as the solvent does not affect the interactions. Besides, by increasing of temperature CLP interactions with adsorbent become weaker indicating PEG can be employed as a temperature sensitive drug carrier. The increasing of dipole moment and also the decline of chemical hardness and bandgap showed when CLP adsorbs on the surface of PEG its chemical reactivity and bioavailibity improves substantially. The natural bonding orbital results demonstrated CLP interaction with PEG has a physisorption nature.

Abstract—In continuation of previous published works on the synthesis and crystallographic characterization of dioxouranium complexes with symmetrical NNOO tetradentate Schiff bases, we report herein deep investigations of the supramolecular features, and electrochemical properties of the studied crystal. This includes 3D molecular Hirshfeld surface analysis and visualization of the resulting three-dimensional supramolecular network. The analysis identifies H⋅⋅⋅C/C⋅⋅⋅H contacts as the main contributors to crystal packing, accounting for 34.7%. The 3D supramolecular network of LUO₂ is formed through the overlap of chains, resulting in a porous structure along the (Oa) direction. The pores are uniform, non-circular, and approximately 9 Å in size along the shorter diagonal. In addition, the electrochemical properties of the uranyl complex, studied via cyclic voltammetry, revealed a quasi-reversible U(VI)/U(V) redox process with a half-wave potential (E_1/2) of –1126 mV vs. SCE in DMF. Measurements using a glassy carbon electrode indicated diffusion-controlled redox behavior. Thermal studies indicate that the complex is non-volatile and a high thermal stability.