Himiâ vysokih ènergij

The photophysical properties of biphotochromic dyads DoX and D10 containing two identical photochromes, 2-[2-(pyrene-1-yl)ethenyl]-quinoline (PEQ), linked by bridge groups of different lengths, as well as the corresponding dipyrenylcyclobutanes CBoX and CB10 formed from the dyads in the [2+2] photocycloaddition reaction (PCA) have been investigated by time-resolved emission spectroscopy (TRES). On the basis of TRES, the number of emitters was determined, their emission spectra, excited state lifetimes, and rate constants of competitive physical and chemical processes (emission, energy transfer, and reactions) were calculated. In dyads, the formation of excimers, possible intermediates of the PCA reaction, was detected by the appearance of emitters with lifetimes significantly increased compared to the model PEQ-photochrome. In cyclobutanes, a decrease in the lifetime of pyrene substituents as compared to 1-methylpyrene shows the energy transfer from substituents to the cyclobutane ring, which, according to the predissociation mechanism, initiates the ring-opening reaction (retro-PCA). In addition, CBoX shows the presence of non-emitting conformers. Quantum chemical calculations by DFT method confirmed the possibility of formation of different conformers of cyclobutane CBoX, differing in the relative position of pyrenyl substituents and the degree of their interaction with each other.

The use of ultraviolet irradiation in the practice of AOPs (Advanced Oxidation Processes) for the treatment of wastewater of various origins has been the subject of many studies. In recent years, the possibilities of using AOPs based on sulfate radicals, the main source of which is peroxodisulfuric acid, have been actively considered. In this paper, the effect of peroxydisulfuric acid additives on the process of photodegradation of fuchsin, bromocresol green and methyl red was studied. It was proven that the combination of UV radiation and H₂S₂O₈ has a synergistic effect and makes it possible to significantly increase the efficiency and rate of oxidation of dyes in comparison with individual photo- and reagent treatment. The maximum oxidation efficiency was 99.9% for bromocresol green, 93% for fuchsin and 76% for methyl red.

The spectral and kinetic characteristics of the dye Sbt ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]thiazol-3-ium iodide) and its homodimers Dbt-5, Dbt-10 in chloroform and its binary mixtures with solvents of different polarity were studied. It was found that with an increase in the proportion of hexane in chloroform solutions of the studied dyes, non-fluorescent H-aggregates are formed. It was found that the spectral and photophysical parameters of the studied dyes depend on the polarity and viscosity of the solvents. Quantum-chemical calculations of the charge distribution and potential energy in the ground and excited states for the molecules of the studied compounds were carried out. Sbt and Dbt-10 dyes are characterized by higher values of quantum yields and lifetime of the excited state in a viscous medium, which is associated with the formation of the TICT (twisted intramolecular charge transfer) state. The transition of molecules to this state leads to effective quenching of fluorescence.

The radiolysis of the extractant N¹,N³-dimethyl-N¹,N³-dibutyltetradecylmalonamide and its 30% solution in n-tridecane under the action of 3 MeV electrons was studied. The key radiolytic processes are fragmentation of the extractant molecules. The decomposition is predominant along the bonds located in the β-position relative to the carbonyl group: N-Me, N-Bu, C-C₁₄H₂₉ and C-C(O). The C-C(O) bond is the weakest – its cleavage gives more than half of all the extractant degradation products. The observed yield of extractant degradation in solution is almost one and a half times higher than in the undiluted state. At the same time, a decrease in the yield of diluent degradation is observed in the solution. The observed effects indicate partial physical and chemical protection of the diluent by the dissolved extractant.

The crosslinking of polyethylene of pipe grades via 900 keV electrons at an absorbed dose of 50 to 400 kGy in the presence of antioxidants and a crosslinking agent was studied. The degree of crosslinking of polyethylene was measured by the content of the gel fraction, determined by its extraction in xylene. It was shown that in all cases the 60% degree of cross-linking is achieved at a dose of about 100 kGy. It is advisable to combine the standard method for determining the gel fraction with visual inspection of samples to identify the conditions for the formation of an excessively low-melting material. It has been shown that ±7% crosslinking degree non-uniformity can be achieved with dose non-uniformity of up to ±50%.

In this work, tetrafluoroethylene telomers were synthesized in carbon tetrachloride. The resulting telomers were then irradiated in air with ⁶⁰Co γ-rays at doses in the range of 18–1020 kGy. When studying the IR spectra of the irradiation products, it was found that the intensity of the absorption band (AB) at 850 cm^–1, which can be associated with the –CCl₃ terminal groups, decreases with increasing irradiation dose. At the same time, a new AB appears in the IR spectrum at ~1775 cm^–1, caused by the carboxyl group, the intensity of which increases with increasing irradiation dose. Studying the dependence of the intensity of the noted AB on the dose allowed us to conclude that the removal or transformation of the terminal –CCl₃ groups and the formation of –COOH groups are independent processes.

Five samples of tetrafluoroethylene (TFE) telomers with different monomer concentrations (С_i) in carbon tetrachloride were obtained by radiation telomerization. It was found that the IR spectra of the obtained telomers differ from the IR spectrum of polytetrafluoroethylene mainly by the presence of an absorption band of terminal CCl₃ groups at 850 cm^–1, the intensity of which (I₈₅₀) increases with decreasing С_i. It was shown that the dependence of I₈₅₀ on С_i is well described by a fractional rational function. Then, dry telomers were treated with ⁶⁰Co γ-rays with a total dose of 1020 kGy both in air and vacuum. A detailed analysis of the IR spectra of the irradiated samples showed that in vacuum, transformation or detachment of terminal CCl₃ groups occurs. When telomeres are irradiated in air, in addition to this, the formation of carboxyl (-COOH) groups is observed. If the stability of the telomere is associated with the formation of -COOH groups, then for the studied series of telomeres, the stability increases with the growth of С_i.

The paper presents the results of PVDF film polarization in glow, barrier and corona discharges. Measurements of the piezoelectric coefficient d33 showed that the highest polarization efficiency under the selected process conditions is observed in the corona discharge. The study of samples by X-ray phase analysis and ATR-FTIR spectroscopy showed that after polarization, the proportion of piezoactive β-phase increases in the polymer, the highest content of which is observed after treatment in a corona discharge. It is noted that treatment in a discharge leads to a change in the wettability of the sample surface.

In this work, for the first time, the plasma-enhanced chemical vapor deposition (PECVD) method was used to obtain thin films of InGaZnO (IGZO) composition of various stoichiometry, morphology and phase composition. The films were synthesized using the setup described in detail in our works [1–5]. The initial substances were elementary high-purity In, Ga and Zn, the carrier gases were Ar and H₂, and a mixture of (Ar–H₂–O₂) was used as a plasma-forming gas. The process of plasma-enhanced chemical synthesis was studied by the method of optical emission diagnostics. The mechanisms of the plasma-enhanced process were proposed. The chemical composition of the samples was determined by energy-dispersive X-ray microanalysis. The obtained samples were also examined by scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical profilometry. The electrical properties of the obtained films – type, mobility and concentration of carriers – were determined by Hall effect measurements.