The spectral-luminescent properties of the 21-thia-5,10,15,20-tetraphenylporphyrin and 21,23-dithia-5,10,15,20-tetraphenylporphyrin were studied in solutions at 293 K. The origin of the spectral shifts upon heterosubstitution was discussed on the basis of the Gouterman four-orbital model. It was shown that the quenching of the fluorescence of heteroporphyrins is due to the effect of the internal heavy atom, the role of which plays heteroatom of the thiophene ring.
The article presents the results of a study of luminescent glow of silicon dioxide during of its reactive ion-plasma etching, which has the highest intensity in the plasma of fluorinated gases. It is established that this luminescence is accompanied by the phenomenon of interference. Probable mechanisms of this phenomenon are considered. The possibility of using luminescence to control the etching of the SiO2 film, as well as layers of other materials lying on it, is shown.
Volume and surface photoluminescence of congruent and stoichiometric lithium niobate crystals obtained with different technologies was studied. It was found that luminescence intensity in stoichiometric crystal was lower than in congruent one. Luminescence in the crystal volume is mainly caused by NbLi defects, while for the near-surface layer, luminescence quenching is observed in the long-wave ( ˃ 500 nm) region of the spectrum due to energy scattering on the crystal lattice vibrations and an increase in the luminescence intensity of the NbNb4+-O–-pair. It is shown that the luminescence bands with maxima at 426 and 446 nm are caused by the complex defects in the form of electron-hole pairs NbNb4+-O–, in which the niobium atom is bound to the oxygen atoms by a covalent and electrostatic bond. An increase in the Li/Nb ratio leads to a shift of the luminescence bands to the short-wave spectral region and to a change of the fundamental absorption edge of the studied crystals.
Efficiency dependence of the steady-state resonance SRS on parameters of pump radiation and scattering medium centers was investigated theoretically. It was shown, that this efficiency cannot be significant due to the high absorption of pump radiation and the Stokes component.
A new integro-functional equation for the four-dimensional Fourier transform of the four-point coherence function of a laser beam in a turbulent medium is derived and two families of exact analytical solutions of this equation are obtained. These solutions are valid for any level of air refractive index fluctuations. Exact analytical representations for integral characteristics of the fourth-order mutual coherence function are obtained on the basis of these solutions. In particular, the truncated spectrum characteristics of the spatial correlation function of intensities were sound. These representations can be used to test the asymptotical, numerical and other methods of finding this function and its integral properties.
Photovoltaic and photoconductive properties of styrene-nonylmethacrylate copolymer film composites, poly-n-epoxypropylcarbazole doped with the tetranuclear metal complex Cu4L4(OCH3)4 (L– = N, N'-dibenzyl-N"-trichloroacetyltryes), and sensitizer - an organic compound with intramolecular charge transfer, was investigated. It was found that in the visible spectral range these composites have a hole type photoconductivity, and the internal photoelectric effect is determined by the photogeneration of charge carriers from the metal complex molecules and the sensitizer. The kinetics of formation and relaxation of photogenerated charge carriers was studied by the ESR method. It was concluded that the molecules of the metal complex in the polymer composite increase the efficiency of photogeneration of non-equilibrium charge carriers, and thereby affect the photovoltaic properties of the composites.
Mn1.5AgIn8.0S14 single crystals were grown by the Bridgman directed melt crystallization method. Crystals composition and structure were determined. It was found that these single crystals crystallize in a cubic spinel structure with a lattice constant a = 10.765 ± 0.005 Å. The width of the band gap of Mn1.5AgIn8.0S14 single crystals was estimated from the transmission spectra in the region of the edge of its intrinsic absorption in the temperature range of 10—320 K. The band gap width decreases with the temperature increasing and a functional approximation of this dependence was obtained.
We investigated the optical properties of nanoparticles of the core-metal shell type and the composites based on them in the classical approximation. The frequency dependences of the real and imaginary parts of the dielectric permeability of bilayer particles, as well as the absorption coefficient of the composites based on them, are calculated. We established the existence of small-scale oscillations of the real and imaginary parts of the dielectric permeability and absorption coefficient in the low-frequency region of the spectrum. The behavior of the dielectric function of bilayer nanoparticles for the limiting cases of thin and thick shells is analyzed. The influence of the effective mean free path of electrons on the optical characteristics of bilayer nanoparticles is considered. The presence of two maxima of the absorption coefficient of the composite due to the hybridization of polar modes is demonstrated.
Flexible SERS substrates were obtained by the photo-activated synthesis of silver nanoparticles in a thin (10—170 nm) layer of poly(acrylic acid) chemically grafted to the surface of a polypropylene film. The plasmonic absorption and the SERS activity of the substrates were studied depending on the thickness of the grafted layer for a fixed time of nanoparticle synthesis. The results indicate dense three-dimensional packing of plasmonic nanoparticles in the grafted polymer layer. The substrates have a storage-stable and surface-uniform SERS activity.
We experimentally studied the luminescence of a continuous electric discharge in cytosine vapors. The luminescence spectra of the discharge in the wavelength range 200—500 nm were obtained. More than 25 spectral bands were found in the luminescence spectrum. A method of identification for more intensive molecular bands was proposed.
In this paper, a new spectral variables selection method, induced mutation genetic algorithm (IMGA), is proposed for near-infrared (NIR) spectroscopy. Based on the idea of genetic algorithm (GA), the IMGA greatly simplifies the process of biological evolution, which not only inherits the advantages of global optimization of the GA, but also effectively improves the convergence speed. In this study, the IMGA is applied to the selection of characteristic spectral variables for green tea origin identification. After five times of genetic evolutions, 11 characteristic spectral variables are selected from 156 spectral variables. Based on the 11 characteristic spectral variables, the classification model is built by partial least squares (PLS), and both the sensitivity and specificity of classification model are raised to 1 for prediction set. The overall results indicate that the IMGA can be well applied to the selection of characteristic spectral variables and effectively improve the prediction accuracy and calculation speed of the near-infrared model.
We studied the composition of phosphomolybdic acids (PMA) formed during the interaction of molybdenum oxide and phosphoric acid with a Mo/P = 12 molar ratio using 31P NMR. The molybdenum oxide conversion degree grows with the dilution of the reaction mixture. The main product of the reaction for the whole region is H7PMo11O39 acid. The maximum concentration of H3PMo12O40 acid is observed at a H2O:MoO3 mass ratio of 10, which is optimal for the preparative synthesis of PMA (84% yield).
We established the structures of the products of reactions of 2,2-di (4-nitrophenyl)-1-chloroethene and 2,2-di (4-nitrophenyl)-1,1-dichloroethene with sodium nitride and their ratio by 1H NMR and IR spectroscopy, chromatography-mass spectrometry, data from balance experiments, and high performance liquid chromatography. It is shown that in the reaction of 2,2-di (4-nitrophenyl)-1-chloroethene with a nitrite ion in dimethylformamide, 4,4'-dinitrobenzophenone, oxime of 4,4'-dinitrobenzophenone, and 4,4'-dinitrobenzanilide are formed at a ratio of 50, 30, and 20%, respectively. The reaction products of 2,2-di (4-nitrophenyl)-1,1-dichloroethene with NaNO2 in DMF are 4,4'-dinitrobenzophenone (95–97%) and oxime of 4,4′-dinitrobenzophenone (2.5-3.0%).
In this study, a hydrogen peroxide-based chemical bleaching technique was applied on two different types of renal stones. The characterization was achieved after the bleaching process. They were identified as calcium phosphate and calcium oxalate monohydrate. The samples were analyzed using dispersive Raman spectroscopy with a 532 nm excitation laser. To compare the results, the samples were measured using both FT-IR and FT-Raman spectroscopy. Consequently, the mineral/matrix ratio of Raman bands changed for both samples, but without any noticeable frequency shifts in the Raman spectra.
A rapid and sensitive spectrophotometric method has been developed for the quantitative analysis of three antiviral, anti-parkinsonism drugs, namely amantadine (AMA), memantine (MET), and rimantadine (RIM). The method is based on the usage of 1,3-indandione (IDO) as a chromogenic reagent to form charge transfer complexes with the studied drugs and produce colored reaction products with an absorbance maximum at 522 nm, allowing quantitative analysis of these drugs. In addition, the study was validated according to the official guidelines that permits usage in quality control laboratories. Many factors (reagent volume, diluting solvent, temperature, reaction and stability time) influencing the reactions were studied and optimized. The results showed that this method is able to detect AMA, MET, or RIM over a linear range between 10–140 µg/mL with high selectivity and robustness. Furthermore, the study results were applied to analyze the drugs in their pharmaceutical preparations with acceptable accuracy and precision.
A hyperspectral imaging system (400–800 nm) combined with multivariate analyses was investigated to discriminate between beef, pork, and mutton species based on the feature wavelengths of intact and minced samples. The performances of classification models constructed by combining linear discriminant analysis (LDA), partial least squares discriminant analysis (PLS-DA), or a support vector machine (SVM) with a variable selection method, such as a successive projection algorithm (SPA), regression coefficient analysis (RCA), or random frog (RF), were compared. The results clearly showed that the linear classifier was preferred to the nonlinear classifier in the identification of red meat species. Furthermore, instead of selecting different sets of feature wavelengths for different types of meat samples, only a set of optimum wavelengths including five wavebands (567, 579, 595, 624, and 732 nm) were identified as universal feature wavelengths by a comprehensive comparison of three schemes, namely, variable fusion, data merging, and cross modeling. A simplified LDA model was then established based on these important wavelengths, yielding classification accuracies of 94.20 and 98.36% in the validation set for the intact meat and minced samples, respectively. The overall results showed that the integration of hyperspectral imaging and multivariate analyses has great potential for rapid and nondestructive differentiation of common red meat species.
The possibility of using magnetic nanoparticles as an adsorbent for the effective removal of anionic dyes from aqueous solutions was investigated. The binding of eosin, tartrazine, and fast green with superparamagnetic Fe3O4 nanoparticles was studied using Vis spectroscopy. The binding parameters (constant and binding site) were obtained from spectrophotometric titration data using the Langmuir model for equilibrium binding. High values of binding constants (~105 M–1) indicate the promise of using magnetic nanoparticles to remove anionic dyes from polluted waters.
Based on deep learning, a desertification grassland classification (DGC) and three-dimensional convolution neural network (3D-CNN) model is established. The F-norm2 paradigm is used to reduce the data; the data volume was effectively reduced while ensuring the integrity of the spatial information. Through structure and parameter optimization, the accuracy of the model is further improved by 9.8%, with an overall recognition accuracy of the optimized model greater than 96.16%. Accordingly, high-precision classification of desert grassland features is achieved, informing continued grassland remote sensing research.
The methodological aspects of determining the total content of chlorine nitrate (ClONO2) from groundbased measurements of solar radiation spectra using a Bruker 125HR Fourier spectrometer at the St. Petersburg station (59.88° N, 29.82° E, 20 m above sea level) of the international observational network NDACC are considered. The developed technique was applied to the spectra measured in the period from 2009 to 2019, and the results were compared with the calculations by the EMAC chemistry-climate model. A good qualitative and quantitative agreement of the experimental data with the results of numerical modeling was obtained. For the period 2009—2017, the average mismatch between the model and experimental ensembles was 3%, the standard deviation was 43%, and the correlation coefficient was 0.79 ± 0.02, which indicates an adequate description of the variability of the total ClONO2 content by the model. The assessment of the linear trend of the total ClONO2 content showed a significant decrease in the total chlorine nitrate content in the atmosphere over St. Petersburg both according to ground-based measurements (–2.3 ± 1.9% per year) and modeling results (–1.2 ± 0.4% per year).
A method for the determination of scandium (Sc) in aluminum alloy samples by inductively coupled plasma optical emission spectrometry was developed. The method was optimized by the Box–Behnken design, which evaluated the operational conditions (radio frequency power, nebulizer gas flow rate, and sample flow rate). The optimum conditions were established as a radio frequency power of 1300 W, a nebulizer gas flow rate of 0.83 L/min, and a sample flow rate of 0.9 mL/min. Satisfactory performance characteristics (background equivalent concentration, limits of detection and quantification) were obtained under the optimum conditions. The method proposed using the optimum conditions allowed Sc determination with limits of detection and quantification of 0.15 and 0.48 μg/L, respectively. The accuracy of the proposed method was confirmed by analyzing an aluminum alloy certified reference material and performing a standard addition method. The standard addition experiments resulted in recoveries between 96.5% and 105%. The method developed has been applied to the Sc determination in aluminum alloy samples from the Beijing Institute of Aeronautical Materials, and the recovery study results ranged between 98.0 and 100.5%.
A method for processing big datasets of the kinetic curves of fluorescence decay using data mining algorithms is proposed to determine the parameters of biophysical and optical processes that occur in molecular systems. The idea of the developed method is in partitioning the initial fluorescence dataset into clusters according to the degree of likeness to some measure of similarity, finding cluster medoids, using a data reduction method and visualizing experimental data in twoor three-dimensional space, analyzing the fluorescence curves of the medoids by analytical or simulation models. The applicability of the method is considered by the example of the analysis of datasets representing systems of fluorophores. The developed method uses substantially less time and computation of the analytical approximation function, though the accuracy of the estimated parameters is higher than in the classical approach.
A simple algorithm for calculating the electron-vibrational energy levels of a polyatomic molecule, suitable for mass practical use, is proposed. The approach is based on using natural coordinates and averaging the matrix of kinematic coefficients in the kinetic energy operator. This allows us to exclude from this operator the non-differential term, which greatly complicates the mathematical procedure.
The results of a theoretical study of the dependence of the diffraction efficiency of a transmission hologram formed in a sample of a Bi12SiO20 photorefractive crystal on the orientation angle, specific rotation of the crystal, and its thickness are presented. The theoretical model takes into account linear electrooptical, inverse piezoelectric and photoelastic effects. It is shown that with a change in the sign of the specific rotation of the crystal, there can be a shift of the maximums of diffraction efficiency relative to the orientation angle.
ABSTRACTS ENGLISH-LANGUAGE ARTICLES 
This article reports a simple, convenient, and very sensitive method for the determination of 6-thioguanine (6-TG). The basic phenomenon in the proposed method is fluorescence resonance energy transfer, where acridine orange (AO) act as a donor and citrate-stabilized silver nanoparticles (AgNPs) as an acceptor. A noncovalent bond between the surfaces of AgNPs and AO was found, and the effect of fluorescence quenching was observed. The fluorescence spectra of AO recovered after further addition of 6-TG are responsible for the aggregation of AgNPs. Under ideal conditions, the linear relationship of 6-TG in the concentration range of 0.005 to 0.04 μM was displayed, and the limit of detection of 6-TG was obtained as 5.3 nM. Under ideal conditions, the linear relationship of 6-TG was displayed in the concentration range of 0.005 to 0.04 μM, and the limit of detection of 6-TG was obtained as 5.3 nM. The proposed method offers a rapid analysis to determine 6-TG in human serum, blood, and urine samples.
Maturity is not only an important factor affecting the internal quality of the Nanguo pear, but also an important theoretical basis for grading online fruit. Based on the hyperspectral imaging technology, in this paper, back-propagation neural network and support vector machine models are established to identify Nanguo pear maturity by information fusion of spectral features and image features. The results show that the identification results of the support vector machine based on information fusion of spectral features and image features are the best, and the recognition rate is above 95%. Among them, the recognition rates of immature and mature samples reach 100%.
An innovative approach was developed to determine benzotriazole (BTA) in aqueous solutions. This method was based on surface plasmon resonance (SPR) property of gold nanoparticles (AuNPs). The reaction between gold nanoparticles and benzotriazole was occurred. Then, benzotriazole was determined by spectrophotometry. Also, transmission electron microscopy (TEM) was used to show aggregation of gold nanoparticles in the presence of BTA. The effect of various parameters such as pH, contact time, concentration of gold nanoparticles, amount of buffer, and different surfactant was investigated. The proposed method is capable of determining BTA in the range of 10–100 µg/L with a limit of detection (LOD) 5 µg/L and limit of quantification (LOQ) 16 µg/L. In addition, the relative standard deviation (RSD) of this method was 2.5 and 1%. Also, benzotriazole was measured in real water samples.
In the present work a method was proposed for the direct determination of Ca, Fe, K, and Mg and qualitative analysis of anthropized and cabruca soil samples from different depths (0–20 and 20–40 cm) by laser-induced breakdown spectroscopy (LIBS). The LIBS instrumental parameters were evaluated using a central composite design with a central point. The variables evaluated were as follows: delay time in five levels (0.5, 0.7, 1.2, 1.7, and 1.9 µs) and fluence at five levels (1448, 1811, 2659, 3514, and 3820 J·cm–2). The best results obtained were with a delay time of 1.2 μs and fluence of 2659 J·cm–2. The proposed calibration model for Ca, Fe, K, and Mg obtained using LIBS data presented a good correlation with the reference values obtained by inductively coupled plasma atomic emission spectrometry (ICP OES). In addition, multivariate data analysis from LIBS spectra in the region of 186–1042 nm was performed using principal component analysis (PCA). From the LIBS spectra it was possible to discriminate the different analyzed samples, showing that the combination of LIBS with PCA is an excellent option for the discrimination of soils.
We studied the characteristics of laser-induced air plasma optical radiation and jamming the imaging CCD detector. Optical emission spectra of the air plasma ranged from 400 to 700 nm are composed of individual spectral lines superposing on continuous radiation, while the continuum radiation is mainly due to bremsstrahlung and recombination radiation. The jamming threshold of the CCD imaging detector jammed by optical radiation of the laser-induced air plasma is 3.98 · 10 10 W/cm2. With increasing laser intensity, the plasma expansion volume and spectral intensity will increase, the image quality of the CCD detector will deteriorate, and the jamming area on the CCD detector will become larger. The experimental results indicate that the jamming effect of laser-induced plasma radiation on CCD detectors can overcome the shortcomings of a single-wavelength laser use, which is important for improving the optoelectronic jamming effect.
Based on the characteristics of space target components, this paper proposes a spectral in-degree distribution curve-matching algorithm. Simulation experiments showed the average accuracy of the proposed algorithm is improved in comparison with the Harsanyi–Farrand–Chang and HySime algorithms. The simulation experiments were performed for a case in which the number of mixed spectral bands was reasonably small. The results showed the number of endmembers could be estimated accurately when the number of endmembers was three to eight. The algorithm proposed in this paper is suitable for estimating the number of endmembers of a space target.
