Russian Journal of Physical Chemistry A最新文献

A rheological study of solvation of algal cellulose and nanocellulose in dimethylacetamide with a lithium chloride addition as one of priority direct solvents has been performed. It was established that algal cellulose in solution can form spatial structures—cationic complexes with dimethylacetamide stabilized by chlorine anions. The activation energy of this process is 29.4–42.8 kJ/mol. The concentration dependence of viscosity indicates the presence of association interactions, which are most pronounced at a cellulose/nanocellulose concentration of >1.5% in solution. It was determined by rotational viscometry that 2.0% algal cellulose/nanocellulose solutions have pseudoplastic properties. The solutions are promising raw materials for the production of nonwoven materials and hydro/aerogels for biomedical use.

Aqueous solutions of nonionic surfactants behave differently than those of ionic surfactants. Micellar properties and structural characterization of Polysorbate 80 (commonly known as Tween 80) were investigated in the presence of different additives at different temperatures (303–323 K) by using cloud point (CP), densitometry, and viscometry techniques. Nonionic surfactant shows the optimum effect when used near their CP, as the presence of additives strongly influences them. The compounds or additives that break the structure of water will increase the CP, while those that help to build the water structure show a decrease in the CP. Adding ester, urea, and carbohydrates decreases the CP of Polysorbate 80, while alcohol and thiourea show the opposite trend. Density and viscosity measurements of Polysorbate 80 in the presence of monovalent salts (NaX, X = Cl^–, Br^–, ({text{NO}}_{3}^{ - }), and salicylate) confirmed the change in molecular structure.

Quantum and molecular mechanics (QM/MM) potentials are used to calculate molecular dynamics trajectories for the EYFP protein of the green fluorescent protein family. Machine learning models are constructed to establish the relationship between the geometric parameters of the chromophore in the frame of its trajectory and the properties of its electronic excitation. It is shown that it is not enough to use only bridging bonds between the phenyl and imidazolidone fragments of the chromophore as a geometric parameter, and at least two more neighboring bonds must be added to the model. The proposed models allow determination of the dipole moment variation upon excitation with an average error of 0.11 a.u.

Thermophysical properties like densities, refractive indices, and static dielectric constants have been measured for the binary mixtures of glycerol (GY) with N,N-dimethylformamide (DMF), ethylene glycol (ELG) and formamide (FMD) over entire concentration range at 293.15 K. From experimental data various related and excess properties were determined and reported for the binary systems. The results show that, the dielectric constant decreases for GY + DMF, GY + ELG and increases for GY + FMD mixtures. The densities and refractive indices of the studied systems decrease over the entire mole fraction range at the studied temperature. From results of related and excess properties various molecular interactions, hydrogen bonding, structural effects and other possible interactions between unlike and like molecules of the binary systems were discussed.

The authors explore the electrokinetic properties and electrophoretic deposition (EPD) of non-aqueous suspensions of samarium-doped cerium dioxide Ce_0.8Sm_0.2O_1.9 (SDC) with added molecular iodine at concentrations of 0 to 1 g/L. The study reveals an inversion of zeta potential in the SDC suspension as the concentration of iodine rises. Notable cathodic deposition is observed under EPD conditions in a suspension with 10 g/L of SDC and 1 g/L of added iodine at voltages above the threshold value (6 V), despite a negative zeta potential of −5.9 mV measured electroacoustically. Findings suggest a potential interpretation related to overcompensating for the charge in the suspension, due to high concentrations of co-ions and counterions within a double electric layer (DEL).

The Gibbs energies of the transfer of the silver(I) ion from methanol (MeOH) to dimethyl sulfoxide (DMSO) and from ethanol (EtOH) to N,N-dimethylformamide (DMF) were determined by potentio-metry. Our own and literature data on the thermodynamic characteristics of the transfer of Ag⁺ from alcohols (S₁) to aprotic (S₂) solvents were summarized and analyzed. It has been established that the replacement of amphoteric solvents with aprotic ones leads to significantly increased solvation of the silver(I) ion. The enthalpy contribution to the Gibbs energy of ion transfer in the case of the replacement (S₁ → S₂) is dominant. The strengthening of solvate complexes of Ag⁺ with solvent in the case of the replacement of S₁ by S₂ is caused mainly by an increase in the electron donor-acceptor (EDA) interactions due to a decrease in the acidity of solvents.

Single phase ceramic samples of new compositions (1 − x)NaNbO₃ – хLiNbO₃ (x = 0; 0.05; 0.10; 0.15), modified with a LiF additive, are prepared through solid state reactions, and their crystal structure, microstructure and dielectric and nonlinear optical properties are studied. A drop from 108.1 to 42.8 nm of the volume-weighted crystallite size distribution function corresponding to coherent scattering regions is observed. A rise in the temperature of phase transitions and a weakening of nonlinear optical properties are revealed as the concentration of Li cations grows.

In this work, we use molecular dynamics (MD) method to calculate the monomeric and competitive absorption behavior of six nuclear-industrial elemental gases: H₂, N₂, I₂, Ar, Kr, Xe in the lanthanide-based MOF (Nd-MOF: {[Ln₂(IDA)₃]⋅(H₂O)₂}_n (Ln = Nd; H₂IDA = iminodiacetic acid). Subsequently, the density functional theory (DFT) is employed to calculate the electronic density difference of MOF systems for different gases and adsorption sites. Furthermore, the thermodynamic stability of MOF materials is analyzed by integrating DFT combined MD. The result shows that the MOF system has a higher absorptive selectivity to the inert elemental gases, while the absorptions of I₂ are very weak, due to molecular sieve effect. The channel structure of Nd-MOF exhibits different characteristics depending on the composition of the adsorption sites, and both types of channels have deeper adsorption potential wells for inert gases. Moreover, we note that the lattice remains stable under working conditions (250–400 K), and is prone to thermal decomposition at 700 K with the saturation of heat capacity. The Nd-MOF system is expected for the adsorption and separation of mixed-elemental gases and the purification of I₂.

Aromatic hydrocarbons (benzene, toluene, xylene) are valuable intermediates in the chemical and petrochemical industries, so the conversion of butane into aromatics is an important catalytic process from both scientific and industrial viewpoints. In addition to the production of aromatic compounds, the production of hydrogen during aromatization of lower alkanes is also of interest. This review describes industrial processes and presents the main achievements in the field of scientific research into butane aromatization on heterogeneous catalysts over the past 15 years. Current problems and possible directions of studies on the development of catalysts for aromatization of C₄ hydrocarbons are also discussed.

Expressions for the thermodynamic potentials (TPs) of small systems are traditionally used in thermodynamics by analogy with TPs of ordinary macro-phases. This form of introducing TPs for small systems eliminates their specificity consisting in the presence of dimensional dependences for TP values and all other thermodynamic functions. To take into account the sizes of small systems in the traditional method of introducing TPs, it is necessary to explicitly reflect the presence of an interface and the associated heterogeneity of the internal local properties of a small system. The general case is discussed when dimensional dependences of TPs of small systems in limited volumes are introduced, with macroscopic concepts of the phase and the interface non-autonomy being preserved. Options are considered to introduce size dependences into TPs of small droplets and separated fluid phases inside pores.