Methods for determining the oxidant/antioxidant activity of free radicals, antioxidant compounds, and free radical oxidation products in biological fluids are discussed. General approaches toward the analysis of the antioxidant potential of complex natural objects using differential spectroscopy are presented.

The radiation parameters are calculated: Einstein coefficients, oscillator strengths, Frank-Condon factors, wavenumbers of electronic-vibrational transitions in the system of bands A2П1/2–X 2 ∑+  of the molecule CsXe (0 ≤ v′ ≤ 15, 0 ≤ v′′ ≤ 14). The calculations are conducted on the basis of Hulbert–Hirschfelder potential curves. The vibrational energies and corresponding wave functions necessary for the calculation of radiation parameters are found as a result of numerical solution of the radial Schrodinger equation.

Chromatographic, chromatographic-mass-spectroscopic and IR-spectroscopic studies of oil samples from natural bitumen were carried out and their radiation resistance was estimated in the range of absorbed dose D = 45–230 kGy at a dose rate P = 0.52 Gy/s (gamma radiation). It was established that the high concentration of tar and asphaltenes in bituminous rocks increases their radiation resistance.

We investigated the aromaticity in the lowest triplet T₁ state of NH-tautomers of the free base corroles with a different architecture of peripheral substitution using the quantum chemistry methods. It is established that the dominating π-conjugation pathways differ for NH-tautomers, but the dominating π-conjugation pathways in the ground singlet S₀ and excited triplet Т₁ states for each of two tautomers are the same. It is found that the aromaticity degree of the macrocycle in the triplet Т₁ state distinctly decreases compared to the ground S₀ state. It is shown that the macrocycle of the free base corroles in the triplet Т₁ state should be considered as antiaromatic. Relationships of the aromaticity degree with the macrocycle conformation and electronic effects of peripheral substituents are discussed.

The luminescence spectra of several polarity indicators at temperatures of 20 and 120°C, including previously studied at room temperature Coumarin 153 and coronene and also Nile Red and Pigment Red 179 are registered in solutions of liquid stationary phases of different polarity. The effect of temperature on the spectral parameters sensitive to the polarity of the stationary phases is estimated for the indicators. The prospects for estimating the polarity of stationary liquid phases using luminescent methods at high temperatures are demonstrated.

The electroluminescent characteristics of powerful AlInGaN LEDs in the regime of high-pulsed current are investigated. The current dependencies of power and emission spectra of blue-green LEDs are established in their relationship with the efficiency of active medium Ti:Sapphire pumping. The reached values of the optical pumping power density using LEDs are estimated.

Using in situ Raman spectroscopy, the chemical mechanism of gadolinium oxide dissolution in the GdCl₃-KCl melt is established. The changes in the normalized intensities of the vibrational bands is used to determine the kinetic parameters of the ongoing chemical reaction. It is established that the concentration of the reagent — gadolinium oxide — decreases with time according to an exponential law, the order of the reaction with respect to Gd₂O₃ is the first. It is shown that the introduction of gadolinium oxide into the melt in an amount exceeding its solubility leads to the formation of a solid phase of gadolinium oxychloride GdOCl.

The morphology of track membranes based on polyethylene terephthalate and polypropylene with different track diameters and their surface densities were studied by UV, IR, Raman spectroscopy, and scanning electron microscopy (SEM). The SEM method was used to plot the distribution curves of the number of tracks depending on their average size (diameter). Similar distribution curves were obtained using UV and IR spectroscopy. Good agreement was found between the data of independent methods of optical spectroscopy and SEM. It is shown that with an increase in the surface density of tracks, the background elastic scattering in the Raman spectra increases linearly. It is proposed to use the observed effect in the Raman spectra to estimate the surface track density of polymer track membranes.

The paper is devoted to gyrotropic characteristics of a non-ideal 1D photonic crystal with an arbitrary number of sublattices (of which one is the optically active potassium dithionate K₂S₂O₆) and to their variation due to a random layer substitution in the K₂S₂O₆ sublattice by modeling impurity layers of an orientationally disordered molecular crystal. We adopt a microscopic approach to study the specific (per unit volume) light polarization plane rotation angle in the exciton spectrum region and perform the numerical calculation of the superlattice optical activity dependence on concentrations of impurity layers and of point-like defects (orientationally disordered molecules) which the latter contain.

An analysis of theoretical model studies of photochromic systems with reversible fluorescence modulation based on polymer nanospheres containing CdSe/ZnS semiconductor quantum dots (QDs), and photochromic diarylethene DAE2 molecules is presented. Based on the known relations of the theory of Förster resonance energy transfer (FRET), a model is constructed for the efficiency of modulation of QD fluorescence E(r) caused by photochromic transformations of DAE2 molecules located near them due to the FRET mechanism. The boundaries of the optimal values of the parameters that affect the efficiency of the fluorescence modulation due to FRET are determined. The efficiency of FRET E(r) is given for some boundary values of the influencing factors. It is shown that E(r) ~ 0.7 can be achieved at distances between donors and acceptors r = 4.5 nm, if one QD with a fluorescence quantum yield Q = 0.4 accounts for at least n = 16 DAE2 molecules (or at Q = 0.8 and n = 8), as well as at distances r = 3 nm (Q = 0.1 and n = 6; Q = 0.4 and n = 2; Q = 0.8 and n = 1). The results obtained can be used to optimize the structure and technology for the synthesis of photochromic luminescent nanospheres.

A simple, accurate, novel, safe, and precise method was developed for the estimation of erlotinib hydrochloride in tablet dosage form using a mixture of methanol and acetonitrile (50:50% V/V). The maximum and subsidiary peak absorption of erlotinib hydrochloride were noted at 247 and 333 nm, respectively. Erlotinib hydrochloride follows Beer’s law in the concentration range of 5–30 μg/mL (r² = 0.9992). In the proposed method, the subsidiary peak absorption wavelength of 333 nm was used to estimate the concentration of erlotinib hydrochloride in tablets. The linear regression equation was found to be y = 0.0461x + 0.0164. The developed method was validated according to the International Conference on Harmonization (ICH) guidelines, and the values of accuracy, precision, and other statistical variables were found to be in accordance with the prescribed values.

Amitriptyline hydrochloride (AMH) is a first-generation tricyclic antidepressant drug. Higher doses of AMH may lead to undesirable clinical conditions such as cardiac arrhythmia, anxiety (sleep disturbances), tachycardia, convulsion, and hyperglycemia. Hence, the accurate analytical method for the quantification of AMH is crucial. The reported AMH quantification methods are less sensitive and require chromogenic reactions. A newly developed spectrophotometric method for the quantification of AMH in the aqueous medium (greener) without using chromogenic conditions is reported. The λ_max of AMH is found to be 239 nm, and the method has been validated according to the International Conference on Harmonization Q2A guidelines. The linearity of the developed method is within the range 0.5–2.5 µg/mL with the correlation coefficient (r²) of 0.9949, which indicates the higher sensitivity of the detection compared with the reported spectrophotometric methods. The percentage recovery (98–102%), precision, limit of detection (0.0266 µg/mL), and limit of quantification (0.0806 µg/mL) data also ensure the method efficiency. The forced degradation studies under the influence of various external factors also suggested the validity of the proposed method for routine analysis. The method was extended for the quantification of AMH present in marketed formulations.

This study showed the synthesis of polyethylene glycol-chitosan-nano Ag (PEG-Chi-Ag) composites to improve the homogeneous distribution of nano Ag and their antibacterial properties. In particular, various concentration ratios of nano Ag to PEG-Chi were adjusted to control the microstructure of the composites. Chitosan was used as a reducing and stabilizing agent. All the composites showed a rough microstructure with a homogeneous distribution of nano Ag on the matrix. In addition, the homogeneous distribution of nano Ag on the PEG-Chi-Ag composites resulted in antibacterial activities. These results indicated that PEG-Chi-Ag composites had great potential application in antibacterial treatment and nanomedicine.

A new fluorescent “turn-on” sensor for Hg2+, N-allyl-4-(ethylenediamine-5-methylsalicylidene)-1,8-naphthalimide (HL) has been designed by combining a 1,8-naphthalimide moiety as a fluorophore and  a Schiff base as a recognition group. As expected, HL displays high selectivity for Hg2+ over other ions (Na+, K+, Ca2+, Mg2+, Al3+, Pb2+, Fe3+, Ni2+, Zn2+, Hg2+, Ag+, Co2+, Cr3+, Mn2+, and Cd2+) with obvious fluorescence enhancement in solution (DMF/tris–HCl buffer, 1:1, v/v, pH 7.2). Moreover, the fluorescence intensity of HL has shown good linearity with a correlation coefficient (R2) of 0.99, confirming that HL could be applied to quantitatively detect mercury ions in the range of 0.5–4.0 μM, whereby the detection limit reaches 0.26 µM. Meanwhile, the association constant (Ka) between Hg2+ and HL achieves 7.35×1011 M–1. Based on the fluorescence titration and Job’s plot analysis, the formation of a complex between HL and Hg2+ is by 2:1 complex ratio.

The article is devoted to the latest optical correlation methods for the analysis of gas mixtures with a quasi-periodic spectrum structure. The developed design of the device is presented to demonstrate the possibility of using the Fabry-Perot interferometer as a correlation mask. A specific example of using an interferometer in a remote methane analyzer is also described.

The dependences of the intensity of sonoluminescence of cesium, lithium and sodium in aqueous solutions of their salts with a concentration of 400—600 g⁄L on the frequency and intensity of ultrasound have been studied. Techniques for the sonoluminescence determination of cesium, lithium and sodium in highly concentrated solutions have been developed on the example of aqueous solutions of nuclear power plants (NPP) salt heat carrier and brines. It is shown that the value of the relative standard deviation of the results of the determination of cesium, lithium and sodium in highly mineralized solutions of their salts decreases with an increase in the frequency of ultrasound initiating sonoluminescence to an ultrasound frequency of 10—12 MHz at an intensity of 20 W⁄cm². A technique of determining the content of the main substance in solutions of NPP salt heat carrier and brines has been developed. The correctness of the obtained results has been checked by the method of additions, as well as by the analysis of the same samples by alternative methods, namely, gravimetric and atomic absorption spectrometry. The obtained results do not contain significant systematic errors. The possibility of analyzing hot NPP heat carriers up to a temperature of 150 °C has also been shown.

The possibility to determine the direct and indirect band gap from photoconductivity spectrum is shown. Using various structures as an example, it is shown, that the band gap determined from the photoconductivity spectrum differs from the one determined from the edge optical spectrum. By this method in composite structures it is possible to indicate impurity band gaps.

The possibility of controlling the chemical purity of the surface of optical elements by the ellipsometric method has been analyzed. The rationale of the possibility of measuring the parameters of contaminating films on the optical surface of elements by the ellipsometric method has been given simplification has been shown of the process of determining the thickness of the contaminating film while expanding the possibility of its measurement on an optical element made of different materials. Ellipsometric studies of freshly polished and used metal mirrors made of copper and copper alloy (zirconium bronze), aluminum and its alloys AMG-6, AL-9, AL-24 have been carried out. Research has also been conducted on elements made of K-8 and K-108 (State Standard 3514-94) optical glasses, which are the most typical materials used for manufacture of optical parts for laser technique of visible and near IR-range, from single crystals of NaCl, BaF₂ and sapphire (Al₂O₃). Parameters of contaminating films on the surface of these elements have been measured. It has been concluded that it is advisable to use the ellipsometry method during the input (before carrying out physicochemical cleaning) and during the output (after cleaning) control of the optical element to assess the contamination of the optical surface and also for the quantitative analysis of the concentration of contaminants on the optical surface of the elements while working off the technology of their physicochemical cleaning.

Using the method of spectrophotometry and scanning probe microscopy, the influence of the heating procedure and temperature of annealing in air on the transmission spectra and morphology of linear-chain carbon films synthesized by the ion-plasma method is herein studied. When the film is heated to a temperature 360–400^oC with a rate of 5°C/min and then annealed in air for 10 min, the effect of a significant increase in the transmittance in the wavelength range 350–500 nm is found. It is shown that when holding at the indicated temperatures in a preheated oven for 10 min, the film transmittance does not change, but the film delamination from the substrate is observed. The discovered phenomena can be explained by the peculiarities of intercalation of oxygen atoms of air into the film.

Coloration of polyvinyl alcohol–phosphotungstic acid (PVA–PTA) films by gamma radiation was studied at different concentrations of PTA. It was found that at a minimum concentration (1%), the coloration of the films occurs as a result of radiation-induced reduction of heteropolyanion by two electrons, while at high concentrations (≥20%), one-electron reduction takes place. In the intermediate range of concentrations, the fraction of PTA heteropolyanions reduced by two electrons decreases with a simultaneous increase in the fraction of one-electron reduced anions.

Photogalvanic cells have been studied with respect to the photostability of the brilliant cresyl blue (ВСВ) dye sensitizer Fructose reductant sodium lauryl sulfate surfactant NaOH alkali electrolyte solution and the consequent electrical output over a long time period. It is observed that ВСВ dye photosensitizer molecules undergo photodecay, but despite this decay, the cell, even with the photodecayed electrolyte, has a promising capacity to produce power with storage. The observed characteristics (spectral and electrical data) of the electrolyte are quite indicative of the stability of the ВСВ dye photosensitizer-based photogalvanic cell.

Sr₃B₂O₆:Dy³⁺,Eu^{3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum, energy transfer mechanism, and color brightness of the samples are studied using scanning electron microscopy, X-ray diffraction, fluorescence spectrophotometry, and color coordinate (CIE) calculations. Furthermore, the effects of the synthesis temperature, holding time, rare-earth element doping amount, and charge compensation agent on the luminescence intensity of the samples are investigated. Results show that the luminescent effect of the sample containing Na+ as the charge compensator is better than that of the sample containing K+. When the concentrations of Dy3+ and Eu3+ are 2 and 3%, respectively, the calcination temperature is 700°C, and the holding time is 3 h, the samples exhibit the best luminescence performance and the color coordinates are in the white-light region, indicating a good white-light luminescent material.}

Biological signals such as magnetic resonance spectroscopy (MRS) signals are susceptible to noise and artifacts. The information obtained from these signals is significant in analyzing human physiological conditions. MRS, a non-ionizing and non-invasive method, presents an effective alternative method to biopsy for diagnosis and analysis from generated signals that are rich in chemical information of the tissues in the region of interest. A persisting problem of this method is the presence of noise and artifacts causing misinterpretation and subsequent incorrect diagnosis. The present research proposes a denoising strategy using the rational-dilation wavelet transform-based signal decomposition and a thresholding criterion designed using the L_pq norm-based sparsity measure of the decomposition levels of the signal. Compared with the standard state-of-the-art methods, which are effective in denoising but can cause distortion of the signal at discontinuities, the proposed method can remove artifacts such as spurious echoes present in the magnetic resonance signals and improve the signal-to-noise ratio without distorting the signal.

The grafting of specific functional groups has been drawing attention later as a simple and effective way to modify materials surfaces to induce a particular response without significant changes in bulk properties and even very small impact in some surface properties. In the case of anionic group grafting, colorimetry analyses using complexed cationic stains are a fast way to determine the grafting density. This technique is especially interesting for the quantification of grafted species such as sulfonates or carboxylate groups. Although simple, this method involves a certain number of crucial parameters and small deviations could lead to unreliable quantification and consequently lead to a performance below the expected. To evaluate how the parameter choice, or errors, could influence the final quantification, poly ε-caprolactone samples were grafted with poly(sodium 4-styrene sulfonate) and stained with toluidine blue O in different conditions of pH, incubation, and decomplexation time, and light exposure. All four studied parameters have shown a stronger influence on the final measured grafting density value.

Forsythoside E is one of the major secondary metabolites in Forsythia suspensa. The interactions between forsythoside E and two types of cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) were investigated in PBS buffer (pH 7.40) by using multispectroscopic techniques. Forsythoside E increased the fluorescence intensity of AChE but quenched the fluorescence of BChE. Synchronous fluorescence studies showed that forsythoside E mainly acts on tyrosine residues of AChE and tryptophan residues of BChE. It was also proved that the complex between the compound and cholinesterases formed spontaneously at a stoichiometric ratio of 1:1 via multispectral technology. Finally, forsythoside E inhibited the activities of cholinesterases with similar IC₅₀ values of 1.08 mM for AChE and 0.92 mM for BChE. The results illuminate the details of the interaction between forsythoside E and cholinesterases.

A new, green, simple, and validated ultrasound-assisted dispersive microsolid-phase extraction method applying unprecedented adsorbent-modified multiwalled carbon nanotubes was achieved for preconcentration and separation of trace cobalt (Co(II)) and nickel (Ni(II)) ions in diverse ecological samples before determination by flame atomic absorption spectrometry. The suggested approach uses a novel chelating agent named 3-(2,4-dihydroxyphen-1-ylazo)-1,2,4-triazole, which is chelated with Co(II) or Ni(II) ions as efficient and selective sorbent at pH 8.0. The impact of many parameters has been studied and optimized. Under ideal conditions, the calibration curves were linear within 1.0–200 and 2.0–300 μg/L ranges, with limits of detection equaling 0.30 and 0.60 μg/L for Co(II) and Ni(II) ions, respectively. The preconcentration factor attained 200, while the highest sorption capacities of Co(II) and Ni(II) are around 300 and 380 mg/g, respectively. The relative standard deviation (%RSD) regarding repeatability for Co(II) and Ni(II) upon calculation was 1.30 and 1.70% for intraday, and 1.750 and 1.95% for interday. To ensure the correctness of the suggested preconcentration approach, certified reference materials (SRM 1570A spinach leaves and TMDA-52.3 enriched water) were employed. The proposed approach was applied to determine the concentration of Co(II) and Ni(II) ions in a range of genuine water, juice, and food samples, and the findings were excellent.

Mislabeling and adulteration are problems in the food industry. Considering the frequent occurrence of safety affairs in agricultural products, it is necessary to establish a traceability system for the quality and safety of agricultural products. The aim of the present study was to establish a rapid detection method for distinguishing rice samples from ten different products of geographical indication in China using laser-induced breakdown spectroscopy (LIBS). A support vector machine (SVM) is used to calculate the recognition rate of single spectral lines and multi-spectral lines of the geographic origins of rice. The adjusting spectral weighting of the multi-spectral line composition of mineral metal elements is higher, which can effectively improve the identification rate of the origin of the rice. The results show that the classification accuracies of single spectral line recognition and multi-spectral line recognition are 90.8 and 94.6%, respectively. It can be concluded that the LIBS technique combined with SVM should be a promising tool for rapidly distinguishing different geographic origins of rice.

A multi-ion chromogenic sensor based on a terpyridine moiety was developed for the semiquantitative, visual, and sensitive speciation analysis of Fe^{2+ and Co2+ ions in water. Each metal ion exhibited a different color, and significant color evolution was observed by the naked eye, resulting in semiquantitative visual detection. A smartphone was used for visual detection by identifying the RGB values of the probe solutions. The application of smartphones shortened the detection time dramatically and reduced the detection cost. This method provides a new strategy for the semiquantitative detection of heavy metal ions in water samples.}

A variety of pictures in hyperspectral fields requires a reduction in dimensionality, which often needs unique algorithms such as principal component analysis and minimum noise fraction (MNF). This article investigates the improved method of non-negative sparse matrix transformation based on the maximum likelihood covariance estimation and the Frobenius norm to better achieve dimensionality reduction. Non-negativity is presented based on the sparse matrix, which reduces the calculation time and improves efficiency. In order to verify the non-negative sparse matrix transforms (n-SMT) algorithm, samples eroded by disease were selected in the experiment and classified to identify the different parts of leaves after dimension reduction. Besides the n-SMT method, the MNF algorithm is also applied to all the samples. This article compares the two algorithms’ operating time and verifies the accuracy of classification after the n-SMT algorithm.

Mesogenic 4-pentyl-4′-cyanobiphenyl (5CB) is a commonly used dielectric material for display devices and liquid crystal biosensors. A small concentration of ZnO nanoparticles was dispersed in 5CB nematic liquid crystals by the chemical precipitation method. The phase changes, phase retardation, and transition temperature of the prepared samples were studied by polarizing optical microscopy (POM) and differential scanning calorimetry analysis. The dielectric properties were measured by dielectric spectroscopy, which was performed within the frequency range from 1 Hz to 10 MHz. A novel phase was identified and confirmed by the dielectric parameters in dispersed ZnO 5CB (N5CB). Specifically, the temperature dependence of relaxation times was estimated for both the samples, which strengthen the POM studies and the influence of nanoparticles on the lattice arrangement. The temperature dependence and the dispersion effect of ZnO nanoparticles on the dielectric constant and dielectric losses were also studied. The sensitivity of mesogenic phases to external forces was confirmed through the present work. From all these results, it has been concluded that N5CB finds potential application in the preparation of fast switching devices.