Possible modifications of the structure of chromophores that have nonlinear optical properties due to the addition of fluorine atoms and fluorine-containing groups to the acceptor site of the molecule are considered. Quantum chemical calculations of dipole moments and first hyperpolarizability were performed for a number of nonlinear chromophores based on N-ethyl-N-(2-hydroxyethyl)-4-phenylazoaniline and modified by the addition of fluorine atoms and fluorine-containing groups to the acceptor site. Positions of maxima in the electron absorption spectrum and the values of Mulliken charges on atoms are also found. It is shown that the addition of fluorine atoms and fluorine-containing groups to the acceptor site of the chromophore molecule leads to a change (increase) in the “efficiency parameter”, defined as the product of the dipole moment by the first hyperpolarizability. The main parameters of a waveguide modulator made of the electrooptical polymer composite with fluorine-containing chromophores embedded in it are estimated.

The acid-base properties of two new 4-hydroxytiryl dyes were studied using colorimetric and spectrophotometry methods. Corresponding ionization and hydroxylation constants were determined. It is shown that the change in the water:dimethylsulfoxide ratio causes significant changes in the light absorption spectra of dyes and in the corresponding colorimetric functions. It was found that the use of the yellowness index allows one to determine moderate water content in dimethylsulfoxide (1—30 %). Color saturation function is advisable to use for analyzing such mixtures in the entire range of possible contents because its linearity is observed in the wide concentration ranges (0—99%).

Spectral properties of an indotricarbocyanine dye upon complex formation with nanodiamonds in aqueous medium were studied. Complex formation is accompanied by the disappearance of the H*-aggregated band at 514 nm as well as by a bathochromic shift of the electronic absorption peak from 706 to 718 nm. At the same time, the emission spectrum of the dye is almost unchanged, and the fluorescence excitation peak is shifted from 706 to 710 nm. Based on the analysis of IR absorption spectra, it was found that carboxyl groups in the dye molecules play an important role in the complex formation of the dye with nanodiamonds. In the presence of human blood serum, complexes break down and dye molecules bind to serum proteins, which is confirmed by a significant increase in the lifetime and fluorescence anisotropy. The complexes obtained can be used as a basis of fluorescent biosensors.

The molecular structure and spectral-luminescent properties of free bases of 2,3,7,13,17,18- hexamethyl-8,12-di-n-butylcorrole and 7,13-dimethyl-8,12-di-n-butylcorrole in solutions in the temperature range of 288—328 K were studied by methods of luminescent and absorption spectroscopy and quantum chemistry. Absorption and fluorescence spectra of studied compounds were shown to be the superimposed spectra of two NH-tautomers. Individual tautomer spectra were identified and bands were assigned to specific transitions. NH-tautomer equilibriums in the ground S0 and lower excited S1 singlet states were characterized.

A novel fluorescent probe, 2-allyl-6-((2-((2-hydroxy-5-nitrobenzylidene)amino)ethyl)amino)-1Hbenzo[de]isoquinoline-1,3(2H)-dione (ABID), based on naphthalimide-Schiff base, has been designed and synthesized for the monitoring of Cu²⁺ ions. In solution (DMSO/ HEPES, 1:1, v/v, pH 7.4), ABID displayed fluorescence quenching towards Cu²⁺ ions over other important metal ions. A good linearity with a correlation coefficient (R²) of 0.99 validated that probe ABID could be used to detect Cu²⁺ ions in 0.5–5.0 μM concentrations. The limit of detection of ABID for Cu²⁺ could reach at 3.4×10^–7 M level, and the quenching constant (K_SV) of ABID towards Cu²⁺ was calculated to be 3.4×104 M^–1. The 2:1 stoichiometry and the binding mode between ABID and Cu²⁺ were studied by a Job plot and UV-Vis and fluorescence titration. Additionally, ABID was successfully employed to monitor Cu²⁺ in the Yellow River and tap water samples.

Chelate complexes BeL2 and ZnL2 of 2-[5[(2,4,6-trimethoxyphenyl)-1,3,4-oxadiazole-2-yl]phenol (HL) were synthesized. Their composition was confirmed by thermogravymetric and IR spectroscopy analyses. Thin films of the HL ligand and its complex with beryllium(II) were spin coated on the glass substrate. Spectral-luminescent properties of the obtained compounds in solutions, solid form and films were studied. Optimal conditions for obtaining thin films were found and their morphology was studied.

We investigate the regime of active mode synchronization in a three-mirror diode laser obtained by current modulation at the intermode beat frequency of the external laser resonator. The current modulation is achieved using electrical feedback. It is shown that under certain conditions, a stable mode-locking regime is observed, and when the length of the external resonator changes, the corresponding intermode beat frequency tuning occurs. The main conditions, for which this regime is achieved, are established. The ~300 Hz width of the intermode beats spectrum at a 300 MHz intermode frequency is obtained experimentally. The broadening of the optical spectrum at the 0.5 level is ~4 nm.

We investigate the possibilities of quantum radars the radiating antennas of which consist of two interacting quantum dipoles in coherent or thermal states. It is shown that such asymmetric antennas allow us not only to reach super-resolution but also to overcome the “Rayleigh catastrophe”. In the case of a coherent antenna, an intensity measurement is sufficient to achieve these effects. In the thermal case, it is necessary to measure the temporal correlations of the field.

The optical absorption spectra and spin-Hamiltonian parameters (g factors g||, g^ , and hyperfine structure constants A||, A^) of vanadyl in zinc phosphate glass are investigated, using the high-order perturbation formulas for a 3d1 ion in tetragonally compressed octahedra. In the calculations, the required crystal-field parameters are estimated from the superposition model, and the optical absorption bands and spinHamiltonian parameters are linked with the tetragonal distortion (characterized by ΔR = R^ – R||, where R^ and R|| denote the bond lengths perpendicular and parallel to the C4 axis). Based on the calculations, the tetragonal distortion ΔR (»1.795 Å) was obtained, and negative signs of the hyperfine structure constants A|| and A^ are suggested.

The defects and optical properties of a LiNbO₃:Mg(5.05):Fe(0.009 mol.%) crystal are studied by the methods of IR-absorption spectroscopy, Raman spectroscopy, laser conoscopy, and optical spectroscopy. It is established that the bands of absorption related to valent vibrations of OH groups shift to the highfrequency area and are narrower for this crystal compared to a nominally pure congruent crystal. It indicates a higher order in the OH groups location and the higher stiffness of O–H bonds in the structure of the LiNbO₃:Mg(5.05):Fe(0.009 mol %) crystal than in a congruent crystal.

We study the absorption and photoluminescence spectra of organic solar cells based on P3HT:PCBM and P3HT:ITIC at simultaneous monitoring the photovoltaic parameters. The characteristic changes of the optical properties of such devices, related to the degradation of their performance, are explored. A direct correlation is established between the changes in the photovoltaic parameters and the absorption and photoluminescence spectra over time.

The infrared spectra of magnesium aluminate spinel (MAS, MgAl₂O₄) ceramic are recorded in a wide range from 50 to 1000 cm^–1 (reflectivity) and 1000–5000 cm^–1 (transmittance). In addition to the MAS reflectivity spectrum, the IR reflection spectrum of a-Al₂O₃ is recorded in the range of structural bands. A comparative analysis permits to clarify the origin of the series of structural bands in the spectrum, which is composed of vibrations localized in either octahedra AlO₆ or tetrahedral MgO4 and AlO₄ cells. A comparison of the spectra is carried out for two MAS ceramics synthesized both by the hydrolysis of double Mg-Al isopropylate method and the modified Pechini method.

Reflection and transmission measurements of thin (40 µm) polyamide films implanted with Co⁺ ions at ion current density of 4µA/cm² and fluence range of 2.5 × 10¹⁶—1.5 × 10¹⁷ cm^–2 have been performed in the wave length range of λ = 200—1100 nm. Implantation leads to a significant (up to 80%) decrease in the transmission of the implanted films and an increase in the reflection of both the implanted and nonimplanted sides due to carbonization of the surface layer and the formation of cobalt inclusions in it. Within the framework of two- and three-layer models, which include one or two modified layers and an undamaged part of the film, the transmission of light when incident on the implanted and non-implanted sides was simulated and fluence dependence of the effective refractive index of the modified layer was determined. The effective refractive index was within 1.3—2.1 in the studied fluence range.

The crystalline nanoparticles of Y_0.5–xCe_0.5Tb_xF₃, doped with Tb³⁺ ions with various concentrations (x = 0, 0.005, 0.01, 0.05, 0.1, 0.15, 0.2) were synthesized via co-precipitation method. The crystal structure and chemical composition of the nanoparticles were studied using transmission electron microscopy, scanning electron microscopy, and x-ray diffractometry. The obtained nanoparticles of solid solutions had an elliptical shape with a size of 10—15 nm along the long axis and good crystallinity with the structure of a CeF₃ crystal. The spectral-kinetic properties of the obtained nanoparticles, as well as the effect of the concentration of Tb³⁺ activator ions on the energy transfer from Ce³⁺ to Tb³⁺ ions were investigated. Energy transfer from Ce³⁺ to Tb³⁺ ions in nanocrystals of the Y_0.5–xCe_0.5Tb_xF₃ solid solutions occurs mainly through the dipole-dipole interaction. The results of evaluating the efficiency of energy transfer from Ce³⁺ to Tb³⁺ ions show its increase with increasing the concentration of Tb³⁺ ions.

The Cu₂SnS₃ (CTS) thin films were produced by deposition of Sn/Cu layers by RF sputtering followed by annealing in an Ar/S atmosphere with S and Sn sources. According to XRD analyses and Raman spectroscopy, it was shown that single-phase CTS films of a monoclinic structure with traces of the CuxS phase were formed at a temperature of 520 °C. The scanning electron spectroscopy revealed a compact and homogeneous microstructure of the polycrystalline CTS layers. Photoluminescence spectra of the СTS films of monoclinic modification show one wide peak in the energy range of 0.7—1.0 eV, due to optical transitions of electrons from the conduction band to deep energy levels of acceptor-type defects.

The use of X-ray fluorescence analysis using the fundamental parameters (FP) method without the need for calibration samples is extremely desirable for some applications. The accuracy of element concentration calculations performed using the FP method with the XRS-FP software package is analysed. The possibility of performing X-ray fluorescence analysis without the need for reference samples renders this software package indispensable for the analysis of unknown samples.

In the theoretical investigation of the self-focusing of elegant Hermite-Cosh-Gaussian (EHChG) beams, the crucial role of decentred parameters has been explored thoroughly in the case of the weak relativistic and ponderomotive regime of interaction. In the present study, the cartesian coordinate system has been employed, which enables us to study the evolution of two transverse beam-width parameters simultaneously. The differential equations for the beam-width parameters are set up through the parabolic wave equation approach by following WKB and paraxial approximations.

In present work we developed and validated five spectrophotometric methods for determination of magnesium orotate dihydrate in distilled water, pH 1.2, 4.5, 6.8, and 7.4 buffer systems. These media were selected to extend the applicability of the developed methods from the development of dosage forms to regular quality control. In all media, linear correlation was observed over the concentration range of 1 to 25 μg/mL. The developed methods were found to be selective and specific to the determination of magnesium orotate dihydrate in the presence of various excipients, as well as accurate, precise, and robust (the percent relative standard deviation was found to be less than 2%, and the percent recoveries were between 98 to 102%). The developed methods were also found to be highly sensitive, since the detection and quantification limits were found to be less than 1 μg/mL. The degradation kinetic studies reveal the stability of magnesium orotate dihydrate against hydrolysis (acidic or basic), oxidation, photolysis, and thermal treatment.

The mechanisms of 2-isopropyl-5-methyl-1,4-benzoquinone (thymoquinone) action on human larynx carcinoma cells of the HEp-2 line were studied using methods of fluorescence assay and Raman spectroscopy. It was found that thymoquinone has a more pronounced toxic effect compared to 1,4-benzoquinone and 2,3,5-trimethyl-1,4-benzoquinone. A decrease of the mitochondrial potential and the release of cytochrome c from the mitochondria are observed under the action of thymoquinone, which indicates the activation of apoptosis of the tumor cells along the mitochondrial-mediated pathway. The obtained results demonstrate the prospects of using Raman spectroscopy in the study of programmed cell death.

The high-sensitivity spectrometer for emission spectral analysis based on a modified two-jet plasmatron DGP-50M and high resolution spectral equipment using a multichannel spectrum recorder is proposed. The spectrometer was tested by measuring gold concentrations using classical and scintillation spectral analysis methods. The possibility of a significant decrease of the sensitivity limits of spectral analysis when determining small gold contents by the scintillation method is shown.

The possibility to obtain the frequency of a pure-electronic transition from the spectra of circular dichroism, circularly polarized fluorescence, magnetically induced chirooptical spectra, as well as the spectra of the dissymmetry factors of dichroism is shown. Examples are presented of such determination from the experimentally measured spectra of molecular optical rotation in absorption and emission. It is shown that the frequency of a pure-electronic transition in the dissymmetry factor spectra can be indicated by their extremum. As in diffuse linear vibronic spectra, the pure-electronic transition frequencies do not correspond to the maxima of the spectra.

The excited states of mustard and related alkyl sulfides have been calculated using time dependent density functional theory. Among the seven commonly used density functionals, PBE0 exhibits the most accurate excited energy, while the Pearson-related coefficient of calculated energies and experimental peaks reaches 0.98. Boltzmann average analysis reveals that excited energies of different conformers are almost the same. The calculated excited states of mustard come to 5.56 and 6.00 eV, which are assigned as n®σ* transition by the natural transition orbital visualization. Besides, sulfur ethers with C₂ν symmetry show similar ultraviolet properties as mustard, whereas the excited states of simulated agents with the SCH₂CH₂Cl group differ from mustard.

In this study, the ¹⁴N NQR parameters of the possible isomers of borazyne were reported in the singlet and triplet states at the M062X/6-311G(d,p) level of theory. Electric field gradient tensors (q_xx, q_yy,q_zz), nuclear quadrupole coupling constants (c_zz, c_yy, c_xx), asymmetry parameter (h), and nuclear quadrupole resonance frequencies (n₊, n_–, n₀) were estimated. Relative energy, frontier orbital energy, and HOMO-LUMO gap values of these isomers were calculated. From the energetic aspect, ortho and meta(2) isomers were the most stable isomers in the singlet and triplet states, respectively. The singlet state was a more stable spin isomer compared to the triplet state between all isomers, except the meta(2) isomer. Aromaticity analysis of the studied molecules on the basis of nucleus-independent chemical shift values showed that the aromaticity of the triplet state was stronger than that of the singlet state for ortho and para isomers. For the meta (2) isomer, the aromaticity of the singlet state was stronger than that of the triplet state. To calculate the atomic charge of nitrogen atoms, natural bonding orbital method analysis was used.

Raman spectroscopy is proposed here for the study of forsterite-hydroxyapatite (FS-HA) composite coating on a stainless-steel substrate. However, in order to analyze the Raman spectrum accurately, noise and background removal is always required. A comparative study has been done for the correction of background. The wavelet-based denoising of the signal was done using level 6 decomposition with sym4 wavelet and the thresholding method used was soft thresholding. In the present work, the effectiveness of the wavelet-based denoising method has been compared with Savitsky–Golay smoothing, quadratic regression, and low pass filter method. It is found that the wavelet-based denoising method works better as compared to other methods as it is able to smooth the signal and to increase the SNR while maintaining the peak intensity undistorted. Peaks are calculated for the different composition of the HA-FS composite. The variation of peak location in the processed Raman spectra suggests that the variation in concentration of FS and HA in the coating can be studied by using Raman spectroscopy.

Due to special mining technology, ionic rare earth mines easily change the surrounding surface soil properties and cause damage to the ecosystem, which leads to difficulties in vegetation ecological restoration. In this paper, tung trees, bamboo willow, and slash pine were selected as reclamation vegetation, and their spectral characteristics under ecological environmental stress were compared. In addition, by analyzing the correlation between their chlorophyll contents and spectral parameters, a theoretical basis for hyperspectral remote sensing for monitoring rare earth reclaimed vegetation growth is provided. The results show that the reflectance of the visible bands in the three vegetation types is less than 0.15, and there are different degrees of “redshifting” in the green peaks and red valleys; correlation analysis was carried out between the chlorophyll contents of the three vegetation types and the original spectra and derivative spectra. The optimal band in the original spectra was concentrated near the red valley. The first-order derivative spectra are more dispersed than the original spectra; the tung tree signal is concentrated in the red edge region, the slash pine signal is located in the near-infrared band, and the bamboo willow signal is located near the green peak and the red edge band. The three vegetation types have some of the same but also different chlorophyll-sensitive parameters. Among them, REP is the maximum parameter for the tung tree, Dr is the maximum parameter for slash pine, and SD_r – SD_b/SD_b + SD_r is the maximum parameter for bamboo willow, which can provide a reference for the construction of inversion models of different vegetation chlorophyll contents.

The main objective of the present study is a quantitative determination of menthol using a simple, sensitive, and reproducible method of reacting menthol with an aromatic aldehyde (salicylaldehyde) in an acidic medium. A linear response was observed between the concentration and the absorbance in the range 0.02–3 mg/5mL possessing a correlation coefficient greater than 0.999 and exhibiting good recovery values (99.54–100.40%). The wavelength of the maximum absorbance (λmax) was measured at 498 nm immediately after the reaction and subsequently within 1 h. The proposed method was validated according to the ICH guidelines for parameters including linearity, precision, accuracy, range, stability, and robustness. Hence the developed method can be used in the analysis of menthol in drug formulations.

A novel spectrophotometric method is described, including multivariate regression/model updating, for the analysis of a quaternary mixture of clopidogrel, atorvastatin, aspirin, and its degradation product salicylic acid. The multivariate algorithms adopted are partial least squares with and without using a “Genetic Algorithm” for selecting variables. Upon updating both models, they could be effectively applied to determine the studied drugs in their pharmaceutical formulations. Similarly, clopidogrel and aspirin in their combined pharmaceutical preparations could be readily determined. Moreover, the proposed method could be extended to the determination of spiked salicylic acid as a minor component in aspirin raw material and dosage forms. The accuracy and precision of the proposed methods were approved through statistical comparison with the reported methods.