A review of researches that both initiated and provided development of a hybrid IR laser system based on conversion of Q-switched radio-frequency discharge slab CO and CO₂ lasers in various nonlinear crystals is presented. The broadband laser system developed operates in the spectral range from ~2 to ~20 μm due to generation of emission on difference and sum frequencies in these crystals.

For two free base corroles with different architecture of peripheral substitution, the solvatochromic shifts of absorption bands in a series of solvents of different nature are herein determined, and the nature  of the solvatochromic effects is analyzed by the Valentine method. It is found that the solvatochromism of the free bases of corroles originates due to universal nonspecific interactions, and the short-wavelength T2 tautomer experiences stronger solvation. It is shown that in polar aprotic solvents (acetone, acetonitrile, dimethylformamide, and dimethylsulfoxide), specific acid-base interactions occur simultaneously, leading to the formation of the deprotonated form. It is found that both deprotonated and protonated forms of corroles also show nonspecific solvation, leading to solvatochromic shifts, the magnitude of which exceeds that for free base corroles. It is proposed that this feature is due to an excess (negative or positive) electronic charge  of the macrocycle. 

The Mn/Fe ratio, which serves as a marker of the content of rare earth elements and the platinum group elements in ferromanganese nodules, was determined in samples taken during expeditions to the Kara Sea and the Laptev Sea, as well as in a set of certified reference materials (ОOPE 601—604). The analysis was carried out by calibration-free laser-induced breakdown spectroscopy, based on the use of plasma parameters and intensities of analytical lines of manganese and iron (Mn I 542.04 nm and Fe I 539.71 nm). Boltzmann plot was used to determine the plasma temperature and Stark broadening of Fe I line 538.34 nm was used to determine electron density. We have shown the possibility of determining the Mn/Fe ratio in range from 0.2 to 4.2 in ferromanganese nodules of various geographic origin. A high coefficient of linear determination (R² = 0.938) and proportionality between the results of calibration-free laser-induced breakdown spectroscopy and inductively coupled plasma atomic emission spectrometry (1:0.99) were achieved.

The dependences of the efficiency factors of radiation absorption by spherical hybrid nanoparticles  of the core-shell system, respectively, with gold-quartz and quartz-gold materials with core radii r₀ = 40, 50, 60, 70 nm and shell thicknesses Δr₁ = 10, 20, 30 nm in the wavelength range of 300–3000 nm at temperatures of particles and surrounding quartz T = 300, 1173 K are theoretically calculated and studied. Essential change of radiation absorption by a nanoparticle is established with an increase of temperatures of nanoparticles and environment. The change of optical properties of nanoparticles significantly influences the efficiency of energy absorption of solar or optical radiation by nanoparticles, heating temperature of nanoparticles and environment and further thermal processes. The results are interesting for purposes of creation of high-temperature solid nanostructured absorbers of solar radiation containing absorbing radiation  of a nanoparticle and also for creation of new materials for high-temperature nanophotonics. 

The methods of infrared (IR) spectroscopy and Raman spectroscopy (RS) are herein used to characterize the features of the surface state of Ti₃C₂T_x (T = OH^–, O^2–, F^–) layered materials obtained in the form of powder and two-dimensional (2D) particles forming a stable colloidal solution. A powdered sample of Ti₃C₂Т_х is obtained by removing aluminum from Ti₃AlC₂ by treatment in an HF solution, 2D Ti₃C₂Т_х particles are obtained by treating Ti₃AlC₂ in an HCl+LiF solution followed by sonication. The phase composition and morphology of the samples are studied by X-ray diffraction and electron microscopy. The IR and Raman spectroscopy methods permitted to differentiate the presence of terminal groups (O^2–, OH^–, F^–) of various nature with a quantitative predominance of the OH form in the Ti₃C₂T_x powder sample and OH and fluoride ions in 2D Ti₃C₂T_x particles, and also detect the presence of TiO_x impurities.

Nitrogen-doped Zn₂GeO₄ (ZGO:N) phosphors were synthesized using a chemical hydrothermal approach. The influence of nitrogen doping on the structural and optical properties of ZGO phosphors was investigated. Results indicated that N ions substituted for O ions successfully and N doping expanded throughout the unit cell of the crystal host lattice. We observed a slight blue-shift in bandgap energy, which signified the weak quantum confinement of the prepared ZGO nanoparticles. At a 260-nm excitation wavelength, compared with the photoluminescence (PL) spectrum of the ZGO phosphors, the peak position of emission  of the N-doped ZGO phosphors blue shifted. In the vibrational modes of ZGO owing to N incorporation,  H substituted at the O site, subsequently causing passivation in ZGO:N nanoparticles. The concentration  of N ions in ZGO:N played important roles in the evolution of PL intensity and quality of nanocrystals. This result contributed to the optimization of nitrogen-doped phosphors with 5 mol% content. The possible luminescence mechanism of ZGO:N phosphors was also discussed.

Cement-based materials sometimes encounter sulfate attack and ammonium salt environments during service, which can severely affect the long-term durability of these materials. In cement-based materials, the formation of thaumasite usually requires five conditions: sulfate, silicate, carbonate, and sufficient water and low temperature (15C). However, under other conditions, thaumasite can also form. To study the changing trend of thaumasite in an ammonium salt solution at ambient temperature (25C), the formation process of thaumasite was studied by laser Raman spectroscopy and thermodynamic analysis. The reaction was accelerated in the presence of NH₄⁺ ions at ambient temperature, and the presence of SO₄²⁻ anions enhanced this trend; this enhancement was even greater than that at low temperature. The change in the Gibbs free energy of formation of thaumasite in the presence versus absence of NH₄⁺ ions was studied using thermodynamic methods, and the acceleration mechanism of the formation of thaumasite in the presence of NH₄⁺ ions was explained.

We studied the behavior of nitrogen in silicon dioxide films on single-crystal silicon substrates by the attenuated total reflection (ATR) method and time-of-flight secondary ion mass spectrometry. Nitrogen was introduced into a dielectric formed by pyrogenic oxidation at a temperature of 850 ºС in an atmosphere of wet oxygen by implantation of N+ ions with an energy of 40 keV at doses of 2.5·1014 and 1.0·1015 cm–2, followed by rapid thermal annealing at a temperature of 1000 or 1050 ºС with a duration of 15 s in air. Nitridization of some of the samples was carried out during thermal annealing in a nitrogen atmosphere with the addition of a small amount of oxygen at a temperature of 1200 ºС for 120 minutes. It is established that during heat treatments, the majority of nitrogen atoms diffuse to the SiО2/Si interface and accumulate in the near-boundary region of the oxide. The ATR spectra show an absorption band with maxima at ~2320 and 2360 cm–1, which is probably due to vibrations of double cumulative bonds of the O=Si=N– type. The formation of these bonds is due to the interaction of nitrogen with dangling bonds at the silicon-dielectric interface, as a result of which uncompensated or strained bonds are replaced by more stable ones. The resulting stronger chemical bonds prevent charge accumulation on the surface of the SiО2/Si interface. Keywords: gate dielectric, heat treatment, ion implantation, attenuated total reflection.

 We study the spectra of excitation and photoluminescence of CaAl₂O₄:Eu³⁺ nanoluminophores in a wide interval of temperatures and laser excitation levels from 40 to 2.3 · 10³ kW/cm². The photoluminescence spectra of CaAl₂O₄:Eu³⁺ have the shape of narrow lines and are located in the region 550–750 nm of the visible spectrum. An extremely high stability of the position and shape of the photoluminescence spectra of  nanopowders under investigation is established at high levels of laser excitation up to 2.3 · 10³ kW/cm²  at a constant luminescence efficiency up to 60 kW/cm². A further increase in the excitation level leads to  a reversible drop in the photoluminescence efficiency. The threshold of an irreversible drop in the luminescence efficiency has not been reached.

Periodic Si/SiO₂/Si₃N₄/Si structures with an insular surface layer were formed by selective laser annealing. The study by infrared Fourier spectrometry showed a decrease in the transmittance of the island structure formed by selective laser annealing compared to the structure without annealing in range 2–25 microns. It is shown that the decrease in the transmittance value may be due to the presence of highly alloyed regions of recrystallized silicon in the surface layer. Analysis of dispersion curves obtained by FDTD modeling showed that plasma-like oscillations were detected in the range of 5–20 THz, which can support in layers of periodic high-alloyed silicon islands in a layer of unalloyed silicon. The results of the study are interpreted considering the assumption of the occurrence of “spoof” surface plasmons in a structure with an insular surface layer.

We study the interaction of the bisbenzimodazole compound Hoechst 33258 with bovine serum albumin and calf thymus DNA by the fluorescence spectroscopy method. The fluorescence spectra of the complexes are obtained. Based on their maxima, the dependence curves of the fluorescence intensities of complexes of this ligand with protein and DNA on the ratio r = macromolecule/ligand are constructed. It is shown that the dependence curve in the case of albumin decreases at low protein concentrations and increases at its high concentrations. In the case of DNA, this curve increases significantly. This fact is due to the binding of the ligand to both DNA and albumin.

We carry out the spectral analysis of enamel, enamel-dentin junction, and dentin of human teeth at the stage of connective tissue dysplasia and without it. It is established that in the case of connective tissue dysplasia in the hard tissues of teeth there is a clear heterogeneity of spectra. In the group with connective tissue dysplasia the maximum changes of IR spectra are observed in collagen and non-collagen proteins of the organic matrix of enamel and dentin. For the group without connective tissue dysplasia the greater uniformity is observed in dentin. The biochemical abnormalities detected in the dentin of the lower “wisdom” teeth can be explained by dysplastic collagen formation disorders in the dental hard tissues, which leads to marked shifts in the enamel layer under the aggressive action of the oral fluid. In the group without connective tissue dysplasia the imbalance in the structure of the protein matrix of tooth enamel is related only to the mineralizing effect of the oral fluid on it.

The thermodynamic stability constants of coordination compounds of calcium(II) and magnesium(II) ions with amino acids in aqueous solutions at 298 K were calculated by spectrophotometry using the mathematical processing of experimental data. The main principles and approaches of mathematical processing are shown. Differences of calcium(II) and magnesium(II) ions as complexing amino acids as ligands are indicated, a regularity in the complex formation of amino acids of various structures is established.

Quantitative analyses of the nitrogen concentration in compound fertilizer were performed using laserinduced breakdown spectroscopy (LIBS). Thirty-two samples were used as a calibration set, and eight samples were used as a validation set. To eliminate the matrix effect, partial least-squares regression (PLSR) and least-squares support vector regression (LS-SVR) were used to establish models. For the partial leastsquares regression model, the correlation coefficients for the calibration and prediction sets were 0.837 and 0.794, respectively. While using the LS-SVR method, the correlation coefficients for the calibration and prediction sets were improved to 0.994 and 0.993, respectively. Therefore, the LS-SVR method improved the analysis accuracy. The prediction mean absolute error was 0.023%. The results indicate that LIBS coupled with  LS-SVR is a reliable and accurate method for determining the nitrogen concentration in compound fertilizer.

Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the PLS model were compared and analyzed. The results show that the PLS quantitative model has the best effect when using 11-point smoothing combined with standard normal variables (SNVs) as the preprocessing method. The coefficients of determination  (R_c², R_p²) of the model training set and prediction set are 0.9900 and 0.9996, respectively. The root means square errors (RMSECV, RMSEP) are 11.7 and 5.23, respectively, and the average relative error of prediction is only 2.96%, which indicates a high prediction accuracy rate and accuracy. This work demonstrates that LIBS technology has broad application prospects for the quantitative detection of specific ingredients  in flour products and provides a basis for the real-time monitoring and evaluation of food safety. 

The process of coal mining generates high amounts of coal gangue. Accordingly, coal-gangue separation is a key problem limiting coal production and quality. Terahertz time-domain spectroscopy was combined with multivariate statistical analyses to identify different kinds of coal and gangue. First, the terahertz spectrum and power spectrum of the sample were measured, and the refractive index and absorption coefficient of the sample were calculated from the terahertz time-domain spectrum of the sample. Significant differences in the power spectrum, refractive index, and absorption coefficient were found between different kinds of coal and gangue. After combining multivariate statistical methods – cluster analysis (CA) and principal component analysis (PCA) – a model based on THz parameters and different types of coal and gangue was established. During cluster analysis, the Euclidean distance of two types of samples and the score of the first principal component in the principal component analysis could reflect the similarity and dissimilarity between coal and gangue samples, and consistent results were obtained for CA and PCA. The experimental results showed that the combination of terahertz technology and multivariate statistical methods yielded an accurate approach to distinguishing between coal and gangue.

The possibility of implementing logical operations for images using accumulated echo-hologram with or without phase difference between pairs of exciting pulses is considered. The possibility for performing  a number of logical operations with images in a nano-time domain (union of sets, difference of sets, intersection of sets, symmetric difference) is show, which leads to appropriate filtering and image processing.

The possibilities of thermal imaging and spectral technology in organization of the control of laser technological processes of high-temperature modification of structural materials are analyzed. It is shown that the application of thermal imaging technology is reasonable when adjusting these processes. For continuous control it is more perspective to apply small spectral technique. Solutions are proposed that allow continuous monitoring on the basis of determination of two parameters: the effective heating temperature T_e of the treated surface in the area of influence of laser radiation and parameter a associated with the effective heating area. It is shown that introduction of small-sized spectral devices for continuous monitoring into the feedback loop of the control system for laser set-ups is promising. 

The choice of the generation modes of quantum cascade lasers for optical-acoustic sensors of methane and ammonia is substantiated and the tuning and output characteristics of these lasers depending on the current and temperature are given. The results of experiments on studying the concentration sensitivity of working samples of devices developed on the basis of these lasers and ready for testing are presented. It is shown that the linear dynamic range of methane concentration measurement using the optoacoustic gas analyzer under study was approximately four decades: from ~0.3 to ~2000–3000 ppm CH₄.

On homogeneous monocrystals of solid solutions (FeIn₂S₄)_х·(In₂S₃)_1–х, grown by the method of directional melt crystallization (vertical Bridgman method), IR reflection spectra in the frequency range of  50—450 cm^–1 were studied. The frequencies of transverse (ω_TO) and longitudinal (ω_LO) optical phonons, as well as their damping coefficients, were determined. The concentration dependences of the mentioned parameters were constructed and the nature of their behavior was established.

A hierarchical convolutional neural network (CNN) model for mixed gas concentration inversion  is proposed. In our experiment, mixtures of SO₂, NO₂, and NH₃ were analyzed. SO₂ and NO₂ were the detected gases, while NH₃ was the interfering gas. For the simulation samples, the average absolute errors were 0.5 and 0.9 ppm for SO₂ and NO₂, respectively. For the experimental samples, the model performed well when the absorption intensities of components differed by no more than one order of magnitude. Compared with the single-module CNN model without a hierarchical structure, the results demonstrate that  the hierarchical structure reduces cross-interference and improves the prediction accuracy to a great extent. We believe that our model will have a promising application in the field of gas detection.

Using hydrolyzed olive leaves as a carbon source and thiourea as a dopant, nitrogen-sulfur co-doped carbon quantum dots (NS-CQDs) were synthesized in the present work. The as-prepared NS-CQDs exhibited quasispherical morphology with an average particle size of 2–5 nm. Functional groups such as carboxyl and hydroxyl groups distributed on the surface of NS-CQDs were suggested to contribute to the good water solubility, biocompatibility, and strong fluorescence. Amphotericin B (AMB) was found to enhance the fluorescence intensity of NS-CQDs, whereas Fe(III) quenched the fluorescence of NS-CQDs. Taking advantage  of such fluorescent characteristics, we established herein a quantitative method of measuring the content  of AMB and Fe³⁺ in water, with detection limits of 10.0 and 7.4 M, respectively.

A sensitive, reproducible, and cost-effective spectrofluorimetric method was developed for the quantification of solifenacin succinate in bulk and its tablet formulation. The method was validated in accordance with the International Conference on Harmonization guidelines with respect to linearity, accuracy, precision, limit of detection, limit of quantification, and robustness. Excellent linearity was noted in the concentration range of 15.0–95.0 μg/mL with a correlation coefficient (r²) of 0.9961. The limits of detection and quantitation for the proposed method were found to be 1.19 and 3.62 μg/mL, respectively. Excellent recovery  of the drug was obtained from its marketed tablet formulation with the proposed method.

The ZnO, MgO, NiO, and AlO nanoparticles and Zn-Al and Mg-Ni composite oxides were synthesized by the green method from the Prunus persica leaves extract. The synthesized nanoparticles were characterized through FTIR, XRD, SEM, and TEM. The FTIR study was carried out to find out the presence of various functional groups in nanoparticles. Their size was studied by the XRD method which exposed that the nanoparticles were in the range of 19–29 nm, and the size and morphology were studied by SEM, which was further confirmed by TEM. The synthesized nanoparticles were tested for antibacterial activity. In particular, ZnO showed a good inhibitory effect with 22.31 mm of inhibition against Pseudomonas aeruginosa.

The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown spectroscopy (LIBS). Aiming to preserve the surfaces of coins, the LIBS technique can perform real-time analysis of latent fingerprints of samples. The study is important as it has been observed that there are specific differences in the elemental compositions of coins that are not mentioned by the RBI. The study could also be used as a reference document for identifying and avoiding the circulation of counterfeit coins. Concentrations of constituents present in these coins have been determined by the calibration-free LIBS method. Furthermore, the current report employs appropriate statistical methods like principal component analysis and partial least square regression for the interpretation of complex data obtained from LIBS experiments, both qualitatively and quantitatively. These methods yield remarkable accuracy and are proven to be sufficiently robust.

We combined Raman spectroscopy with machine learning for the classification of 11 plastic samples.  A confocal Raman system with an excitation wavelength of 532 nm was used to collect the Raman spectral data of plastic samples and principal component analysis was used for feature extraction. The prediction models of plastic classification based on three machine learning algorithms are compared. The results show that all three machine learning algorithms are able to classify 11 plastics well. This indicates that the combination of Raman spectroscopy and machine learning has great potential in the rapid and nondestructive classification of plastics. 

Dy³⁺-doped Ba₂Be₂B₂O₇ was prepared and characterized using a combustion method and X-ray diffraction analysis. The photoluminescence (PL) properties of the synthesized borates were analyzed using a fluorescence spectrometer. Dy³⁺-doped Ba₂Be₂B₂O₇ emits 483, 575, and 667 nm light in response to the UV excitation of 351 nm. Subsequently, different mole ratios of Dy³⁺-doped Ba₂Be₂B₂O₇ were prepared, and their PL properties were studied in detail. Finally, the optimal concentration of Dy³⁺ ions in Ba₂Be₂B₂O₇ was found to be 0.05 mole.

Tb³⁺-doped Zn-Al (ZnAlTb) hydrotalcites with tunable blue-green emission synthesized by coprecipitation. The compositions and properties of the samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and photoluminescence. XRD and FTIR results indicate that the samples were in a pure hydrotalcite-like phase. The fluorescence spectra indicate that the ZnAl hydrotalcite exhibited blue fluorescence at 350–450 nm. Under an excitation wavelength of 231 nm, ZnAlTb hydrotalcite exhibited the characteristic green emission of ⁵D₀–⁷F_J of Tb³⁺, and the fluorescence lifetime of the sample was 0.8442 ms. At different excitation wavelengths, ZnAlTb hydrotalcites can exhibit emission from green to blue wavelengths, which indicates that ZnAlTb hydrotalcites are potential multicolor functional materials.

Three simple, sensitive, precise, and rapid spectrophotometric methods are developed and optimized for the assay of vardenafil in pharmaceutical formulations. The procedures are ascertained on the oxidation  of vardenafil with a slight excess of N-bromosuccinimide (NBS), and the unreacted oxidant is estimated by evaluating the amount of the unconsumed NBS by reacting with a fixed amount of safranin (method A), crystal violet (method B), and aniline blue (method C) in an acidic medium by measuring the absorbance at 530, 600, and 610 nm, respectively. In all the methods, the amount of NBS consumed corresponds to the amount of the drug. Beer’s law range, Sandell’s sensitivity, and the corresponding molar absorptivity values  of 1.1104×10⁴, 1.0305×10⁴, and 6.217×10³ L/mol cm for methods A, B, and C are calculated. The limits of detection and quantification are evaluated. The methods are also evaluated statistically by means of Student’s t-test and F-test. The results show excellent agreement and insignificant difference between the proposed methods and the reference method. The developed methods are successfully applied to the assay of Vardenafil in pure and dosage forms, and no interference is observed from common excipients present  in pharmaceutical formulations.