Himiâ vysokih ènergij

The dynamics of differential absorption spectra of Mn²⁺ : Zn_0.48Cd_0.52S/ZnS quantum dots (QDs) after excitation with a femtosecond (fs) pulse of 360 nm in aprotonic nonpolar cyclohexane and polar propylene carbonate solvents in comparison with the protonic polar solvent water has been studied by femtosecond laser spectroscopy method. The absorption and luminescence spectra of QDs in water revealed bands related to trapped states. The fading band related to the edge exciton of QD attenuates significantly faster in water than in aprotonic solvents, which suggests rapid electron transfer from the 1Se level to trap states in competition with electron transfer to manganese. Apparently, the competition of these processes is the reason for the decrease in the quantum yield of manganese luminescence in Mn²⁺ : Zn_0.48Cd_0.52S/ZnS when passing from aprotonic solvents to water.

The process of quenching of long-lived phosphorescence of ternary complexes naphthalene-β-cyclodextrin-cyclohexane, localized in the matrix of double complexes β-cyclodextrin-cyclohexane, in aqueous suspension of crystalline hydrates and powder formed by drying of crystalline hydrates has been studied. In the suspension, the phosphorescence kinetics are monoexponential and the quenching is dynamic; the bimolecular quenching constant is equal k_q = 0.87 × 10⁵ s^–1M^–1. In the powder, the phosphorescence kinetics are not monoexponential, which is apparently due to the different surrounding structure of the naphthalene molecules. The inhomogeneity of the environment is expressed in the presence of a distribution of the rate constants of radiation-free processes and a decrease in the availability of naphthalene molecules for interaction with oxygen.

The properties of dipyrenylcyclobutanes CB10 and CBoX, which are products of the [2+2]-photocycloaddition reaction (PCA) of the corresponding biphotochromic dyads D10 and DoX, have been studied. The absorption and fluorescence spectra of cyclobutane CBoX revealed the presence of different types of pyrene substituents, with strong and weak interactions in the ground S₀ and excited S₁ states. In both cyclobutanes, energy transfer (ET) from the pyrenyl substituents to the cyclobutane rings is observed, initiating the cyclobutane opening reaction (retro-PCA), which occurs via a predissociation mechanism. The photochromic pair “D10-CB10” is an example of a new type of photochrome operating by the mechanism of the PCA reaction and can function as a two-channel color-correlated fluorescent photoswitch.

A CO catalyst based on TiO₂ was synthesized with additions of 10 wt % TiC_0.2N_0.8 and 10 wt % Pd. The catalyst was tested by TEM, X-ray photoelectron spectroscopyand X-ray patterns. The effect of UV radiation on catalytic properties was investigated and long-term tests were carried out for 100 days. UV radiation was found to increase the rate of the CO oxidation reaction, decrease the activation energy of the reaction rate constant, and increase the long-term stability of the catalytic properties. The activation energy of the reaction rate constant is determined in the temperature range from 288 to 308 K, which is equal to 23 ± 1 kJ/mol under UV illumination of the catalyst. The catalyst has good prospects for use in photocatalytic air cleaners.

The article deals with the photochemical oxidation of nitrofural and tetracycline in the presence of oxygen-containing additives (hydrogen peroxide, peroxydisulfuric acid, potassium persulfate). It was found that the addition of oxygen-containing additives significantly increases the efficiency and rate of APS degradation. The highest degradation efficiency is achieved using hydrogen peroxide, but the high cost of the reagent allows us to consider peroxydisulfuric acid and potassium persulfate as potential alternatives.

Telomeres are formed under the action of gamma rays from a ⁶⁰Co source at room temperature in solutions of tetrafluoroethylene in propylene oxide with concentrations of 0.08–4.2 mol/L; telomer chain length depends on the monomer content in the solution. Monomer consumption during irradiation was controlled calorimetrically and gravimetrically; its complete conversion is observed at irradiation doses of 10–15 kGy. Molecular-mass characteristics of radiolysis products were determined by thermogravimetry. The telomeres with chain length less than 6 form true solutions. At the degree of monomer polymerization 6–15 colloidal solutions are formed, at more than 15 – dense gels. In the structure of propylene oxide fluorotelomer, the end functional epoxy group is retained. The morphology of the coating layers was investigated by atomic force microscopy.