The photophysical properties of indotricarbocyanine dyes upon complexation with serum albumin have been studied, and the technique for controlling their formation using electrophoresis has been optimized. In connection with the degradation of dye molecules under the action of acids, the search for the area of localization of the dye under study on the surface of the gel plate was carried out by recording the fluorescence spectra of the dye before protein fixation and visualization followed by the completion of the protocol for obtaining electrophoregrams. To minimize the possible influence of the luminescence of the gel components, the excitation was carried out by the radiation of a semiconductor laser with a wavelength of 684 nm, which initiates the fluorescence of the studied dyes. It was established that the position of the maxima and the half-width of the fluorescence spectra of dyes with an orthophenylene bridge in the conjugation chain in the regions of the electropherogram corresponding to the localization of albumin coincide with the characteristics of the emission of dyes in initial solutions with albumin, which makes it possible to reveal the formation of covalently bound complexes of dye molecules with albumin.

The regularities of composition changes of silicon/germanium alloy thin films formed on a monocrystalline silicon substrate by electrochemical deposition of germanium into a porous silicon matrix with subsequent rapid thermal annealing (RTA) at a temperature of 750–950°C are studied. An analysis of the samples by Raman spectroscopy showed that an increase of RTA temperature leads to a decrease in the germanium concentration in the formed film. A decrease of the RTA duration at a given temperature makes it possible to obtain films with a higher concentration of germanium and to control the composition of thin silicon/germanium alloy films formed by changing the temperature and duration of RTA. The obtained results on controlling the composition of silicon/germanium alloy films can be used to create functional electronic devices, thermoelectric power converters, and optoelectronic devices.

Operating regimes of an optical system consisted of compact pulsed master diode-pumped Q-switched Nd:YAG laser and triple-crystal (KTP) ring cell of the optical parametric oscillator have been investigated. It has been experimentally shown that frequency-selective properties of a passive Q-switched unit in the “natural mode selection” are enhanced by creating a polarization interference filter Lyot with the phase plate in the form of a laser active element with the thermally induced birefringence and a polarizer. Such filter Lyot appears in the Nd:YAG laser cavity during operation at relatively high energy and repetition rate of radiation pulses (60–100 mJ, 20 Hz). The combined action of the “natural mode selection” process and the Lyot filter ensures the stable operation of a passive Q-switched Nd:YAG laser in the single frequency lasing mode (the lasing bandwidth is less than 57 MHz). The master single frequency pulsed Nd:YAG laser (λ = 1.06 μm) allows reducing the energy of pulses applied to the input of the optical parametric oscillator by more than 1.5 times while maintaining the specified energy level of the output pulses (30 mJ, λ = 1.57 μm). An additional increase in the efficiency of the optical parametric oscillator conversion is achieved by introducing a two-lens 1.3^x telescope into the master laser cavity.

The optical properties of doped oxoselenides of rare-earth elements of optical purity RE₂O₂Se:RE' (RE = Gd, Y; RE' = Sm, Tb) are studied. Photoluminescent properties of oxoselenides of rare earth elements of optical purity in the form of powders and thin films demonstrate the fundamental possibility of using them as a scintillation material for detectors of ultraviolet or ionizing radiation.

The first results on the study of photoluminescence and lasers radiation spectra of a CdHgTe solid solution-based quantum well structure with microdisk cavities of different diameters are demonstrated. It is shown that the presence of cavities contributes to an increase in the maximum operating temperature of generation compared to the unprocessed structure.

The results of an IR spectroscopic study of the content of water and hydrogen defects in hydrothermal and pegmatite quartz from quartz-vein occurrences in Karelia (North-West Russia), considered as a promising source of high-purity quartz raw materials, are presented. It is shown that the main amount of water in the analyzed quartz is in molecular form, and OH groups associated with aluminum, lithium, and boron trace elements in the quartz lattice are also identified. Granular quartz with the lowest content of molecular water and OH-groups is the most preferred for use as a high-purity quartz raw material.

Large-block crystals of FeIn₂S₄, MnIn₂S₄ ternary compounds and MnxFe_1–xIn₂S₄ solid solutions are grown by the method of directional crystallization (horizontal Bridgman method). The structure of the obtained crystals is determined by X-ray diffraction analysis. It is shown that both the starting compounds and solid solutions based on them crystallize in the cubic spinel structure. The IR reflection spectra in the frequency range 50–500 cm^–1 of crystals of ternary compounds FeIn₂S₄, MnIn₂S₄ and solid solutions MnxFe_1–xIn₂S₄ are studied. The frequencies of transverse (ω_TO) and longitudinal (ω_LO) optical phonons are determined. The concentration dependences of these parameters are plotted and the nature of their behavior is established

The crystal structure and electronic properties of the rhenium disulfide of a triclinic crystal system within density functional theory and pseudopotential theory are investigated. It is shown that calculated primitive cell parameters and angles within local density approximation are in good agreement with experimental data. It is established that the observed direct-gap character of rhenium disulfide is related to the interband transitions at point X. The electrons energy spectrum is characterized by a large number of the valley, the electronic structure is mainly formed by the 3p- and 5d-states of sulfur and rhenium ions, respectively, and during the transition from the valence band to the conductance band the role of 5d-states increases and the role of 3p-states decreases. The observed structure is due to the low-symmetry primitive cell and a large number of nonequivalent positions of its constituent ions.

Nanostructured thin films on a silicon substrate have been obtained by the method of high-frequency repetitively pulsed (f~10–15 kHz) laser action with a wavelength of 1.064 μm and a power density q = 54 MW/cm²  on La_0.4Ba_0.6CoO₃ ceramics at a pressure in the vacuum chamber p = 2.2 Pa. The morphology of the obtained films was studied using atomic force microscopy. The features of the transmission spectra in the visible, near, and mid-IR regions are revealed. An analysis of the electrical properties of the La_0.4Ba_0.6CoO₃ structure was carried out.

In the context of development of LED luminaries with antibacterial effect but without harmful effects on human health, the characteristics of an LED lighting system consisting of a commercial violet LED and a green phosphor based on CsPbBr₃ nanocrystals are studied. Internal efficiency of the nanocrystalline phosphor in a silicone compound was found to exceed 40% falling down noticeably because of heating for electric current of the order of 0.1 A (excitation intensity of the order of 0.1 W/mm²). This nondesirable feature can be diminished using remote phosphor design of luminaries as well as by rising thermal stability of nanocrystals with chemical techniques.

X-ray fluorescence analysis procedure for determining a mass absorption coefficient in two-layer Co/Cr thin-film systems on polycor substrates has been proposed. Easy-to-make thin-film layers of sputtered cobalt on a polymer film substrate were used. Correction coefficients have been calculated that take into account the attenuation of the primary radiation of the X-ray tube and the absorption intensity of the analytical line of a bottom layer element in a top layer.

Combining deep machine learning with silver nanoparticle (Ag NP)-based surface-enhanced Raman spectroscopy (SERS), we have developed a novel method for whole blood analysis for cancer detection applications. The whole blood was collected from two groups: one group of patients (n = 26) with lung cancer and another group of healthy volunteers (n = 45). The logistic regression (LR), k-nearest neighbor (KNN), decision tree (DT), and random forest (RF) algorithms were employed to develop a diagnostic model using the same spectral data. The results show that the diagnostic accuracy of LR, KNN, DT, and RF models was 87, 66, 77, and 83%, respectively. LR is superior to other algorithms in the SERS spectra classification of whole blood. We therefore believe that this proposed strategy will have great clinical potential for SERS technology combined with LR and act as a complementary method for the detection of lung cancer.

A kinetic spectrophotometric method that is sensitive and simple has been developed for the quantification of the venlafaxine hydrochloride in bulk as well as in pharmaceutical preparations. In this technique, venlafaxine is oxidized in the presence of alkaline potassium permanganate as an oxidizing agent and sodium hydroxide as a basic medium, and the reaction is carried out at room temperature. Due to the production of a manganate ion, the spectrophotometric measurement was performed at 610 nm. A fixed-time-based approach (15 min) was used to plot calibration graphs. The proposed method was optimized for all the conditions of reaction, whereby the linearity range was found to be 5–30 µg/mL with a limit of detection of 0.07 µg/mL. For the quantification of venlafaxine hydrochloride in a dosage form, the developed method was successfully applied and the percentage recovery was 98.87–100.22%. Statistical comparison was done for the obtained results with those of an official method and no significant differences regarding precision and accuracy were found.

An ultraviolet-visible (UV-Vis) spectrophotometric method was developed for the simultaneous determination of isoniazid (INH) and rifampicin (RIF) using Vierordt’s method. In this method, along with methanol, two other solvents such as phosphate buffer pH 7.4 and citro-phosphate buffer pH 5.0 were also selected, the former of which is simulated with the pH of lung epithelial lining fluid and the latter is simulated with the phagolysosomal environment. A 1:1.5 ratio of pure INH:RIF was selected and scanned, which showed similar absorption maxima at three solvents, and on that basis absorption maxima at 263 and 335 nm of INH and RIF, respectively, were selected. A calibration curve within the concentration ranges between 4 and 24 µg/mL of INH and 6–36 µg/mL of RIF follows the Beer–Lambert law. It was validated with respect to linearity, sensitivity, precision, and accuracy according to International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use guidelines.

Magnetic resonance spectroscopy was used to determine local metabolic changes in the structure of a brain tumor and to assess the significance in differentiating the histological result and the likelihood of tumor recurrence. The observed decrease in the spectrogram of the characteristic marker of neurons – N-acetylaspartate and the appearance of choline, lactate indicate the absence of signs of tumor recurrence.

The process of adrenaline autoxidation in an alkaline medium (pH=10.65) in the presence of sulfite was experimentally studied by UV-Vis spectroscopy. The absorption spectra of the final product of autoxidation (λ_m = 290–300 nm, ε_m = 8400 M^–1 · cm^–1), the intermediate adduct of adrenochrome with sulfite (λ_m =343 nm, ε_m = 68000 M^–1 · cm^–1), and the reactive an intermediate product, presumably adrenolutin (λ_m = 311, ε_m = =140000 M^–1 · cm^–1 and λ_m=373 nm, ε_m =129000 M^–1 · cm^–1) were determined with experimental data processing. The estimated equilibrium constant for the formation of adrenochrome adduct with sulfite 5000 M^-1 agrees with the literature data for carbonyl compounds. The results obtained explain the contradictions in the results of various authors concerning the oxidation and autoxidation of adrenaline in an alkaline medium.

It is shown that for reliable operation of laser diode matrices, it is important to ensure the maximum allowable, but not leading to their destruction, current input and output rate. Some of the solutions used in the design of laser diode drivers are listed in order to limit the increase in the rate of current input and output. A method for controlling the rate of rise of the laser emitter current is proposed, the essence of which is to form the leading and trailing edges of the output current of the laser driver so that its first and, at least, the second derivative are continuous, in order to avoid triggering internal mechanisms that lead to degradation of the emitter structure.

Тhe development of a photoelectrical hydrogen sensor without sensor element heating is presented. For the sensitive element of the hydrogen sensor the Pd/n-InP (Schottkie diode) and Pd/oxide/InP (met-alinsulator-semiconductor) structures were developed and investigations of the photovoltage and the photocurrent of the structures depending on the hydrogen concentration in the range 0.1–100 vol.% in a nitrogen– hydrogen gas mixture were carried out. It is shown that the photovoltage and photocurrent decay rate and the hydrogen concentration are exponentially related to each other. The laboratory samples of sensor for hydrogen determination in the range 100–30000 ppm which able to operate at room temperature with response rate of 1–2 s are developed.

Plasmonic effects can be used in high sensitivity sensors, which have attracted widespread attention. However, most of the previously reported refractive index sensors can no longer be adjusted once fabricated, and their figure of merit (FOM) is undesirable. Concerning this, we propose a refractive index sensor consisting of a graphene waveguide and a graphene elliptical cavity working in the mid-infrared range. Its performance can be adjusted in real time by applying a bias voltage to the graphene patterns. The sensitivity of the proposed sensor can reach 2850/refractive index unit and FOM up to 633, respectively. Owing to its excellent sensing properties of high sensitivity and high FOM, the proposed sensor can be applied in gas sensing.

An integrated approach based on the use of data mining methods has been proposed to improve the efficiency of the analysis of photon counting histograms in the study of the molecular composition of a substance by the method of fluorescence fluctuation spectroscopy. The method of principal components is used to test the hypothesis about the cluster separability of multidimensional experimental data. The reason for the compression of a point cloud into a characteristic nonlinearity, or so-called arc-shaped cloud, in the space of first two principal components is investigated. Examples of simulated data sets on some selected molecular systems of various brightness and concentration are considered. Nonlinear effects complicate interpretation and subsequent quantitative analysis of data. It has been established that the arching of the data cloud is a consequence of the presence of a significant variation in one or more physical parameters. In particular, it is the result of a significant increase in the variation in the parameters of the brightness or concentration of molecules. These parameters can be as additional measure in assessing the quality of the experiments if only one type of molecule is studied, and also can be used for characterizing the system under study in the case of a mixture of molecules of different types. It is proposed to apply the locally weighted scatterplot smoothing normalization to eliminate the nonlinear effects in the space of principal components.

Pr³⁺-doped MSr₄(BO₃)₃ (M = Li, Na) were synthesized and determined by a combustion method and by X-ray powder diffraction analysis. The photoluminescence (PL) behavior of the borates that were prepared was investigated by using a fluorescence spectrometer. The emission peaks of the Pr³⁺-doped MSr₄(BO₃)₃ (M = Li, Na) were observed at 609 and 606 nm, respectively. Finally, the PL spectra of LiSr₄(BO₃)₃:Pr³⁺ and NaSr₄(BO3)₃:Pr³⁺ with different Pr³⁺ doping concentrations were analyzed in detail.

Aluminum alloys are irreplaceable in key lightweight components of automobiles, aircraft, aerospace vehicles, and ships. The main raw material of aluminum alloys is bauxite, and so the high-precision sorting and identification of bauxite is very important in guaranteeing the performance of aluminum alloys. This article describes a convolutional neural network (CNN) structure that, combined with principal component analysis-assisted laser-induced breakdown spectroscopy, can identify different types of bauxite samples. First, the data collected by a spectrometer are normalized to eliminate the influence of different dimensions on the excitation intensities of each spectral line. The feature dimensionality of the normalized samples is then reduced through principal component analysis. The features of the input data are extracted multiple times through convolution and pooling operations in the CNN. Experimental results show that the classification accuracy under a single convolution and pooling structure reaches 97.4%, whereas that under multiple convolution and pooling structures can reach 99.6%. To evaluate the performance of the proposed model, models based on k-nearest neighbors, random forest, support vector machine, and full-spectrum feature inputs are constructed. The results show that CNNs have great potential in the field of bauxite identification and classification, and provide a reliable data processing method that enables laser-induced breakdown spectroscopy to classify materials with similar chemical properties.

Two-dimensional (2D) and 3D Raman spectroscopic imaging of Spirulina platensis was carried out to investigate its applicability in studying the chemical distribution and morphology of algal cells. The Spirulina trichome was easily damaged by laser illumination unless the laser parameters were properly adjusted. Raman spectra exhibited an evident sign of fluorescence, which changed during cumulative laser illumination on the same spot. Six peaks were selected from the spectra for chemical mapping, which showed distinct cellular features, including the central and peripheral parts of the cytoplasm, cell wall, sheath, and medium residues. Possible chemicals/organelles in these parts and mechanisms were discussed.

Eggs are nutritious food that can decompose to emit hydrogen sulfide (H₂S) gas when stored for a long time. We designed a surface-enhanced Raman scattering (SERS) sensor based on self-assembled silver nanoparticles (Ag NPs) to detect endogenous H₂S generated in rotten eggs. The Ag NPs were prepared using a reduction method to enhance the Raman signal of the probe molecule, 4-mercaptobenzoic acid. The prepared Ag-NP substrate exhibited an excellent Raman strength enhancement effect, good uniformity, and long-term stability. To explore the possibility of using a SERS platform in H₂S gas detection, a quantitative analysis with different H₂S concentrations was performed. The results showed a good linear relationship between the Raman intensity at 1073 cm^–1 and various H₂S concentrations, and the H₂S detection limit was as low as 0.03 μM.

Visible light reflectance spectra were taken from signatures inscribed with five different inks of five different ball-point pens by a modular portable Vis-NIR spectrophotometer with PC. The ink-analysis procedure was nondestructive, consisting of visible reflectance spectra acquisition from multiple designated sampling spots of each signature, using a customized reflection probe holder and a tungsten white light source. Sampling spots were preselected to partly cover the signature ink-line on the white background (paper). The repeatable reflectance spectra (R%), recorded and plotted for each ink, which is subject of this study, appeared with typical spectral features (extrema) for each tested ink. To determine another characteristic spectral feature for ink discrimination, such as inflexion points specific to the absorption edges, a numerical derivative of the first order was calculated for the average R% spectrum of each ink. The wavelengths at which the typical features appear were used for Vis-NIR codification of each ink for discrimination purposes. A different code could be assigned for each ink, using the description of the “general feature,” the extrema, and the inflexion points from the reflectance spectrum. This method can be used as a nondestructive tool for ink identification for forensic purposes.

A method was reported regarding a novel surface-enhanced Raman scattering probe to detect and quantify Hg²⁺ with reasonable specificity and selectivity. Highly selective and sensitive detection of Hg²⁺ in traditional Chinese medicine preparations was achieved by using silver nanoparticles as Raman substrate and 4,4'-dipyridine (Dpy) as the signal probe with the assistance of the polymerizing agent sodium chloride. Here, the 4,4'-dipyridine molecule was adsorbed on the surface of silver nanoparticles through Ag-N. Then, sodium chloride was supplemented to induce aggregation of silver nanoparticles, resulting in a significant enhancement of its signal. The presence of Hg²⁺ could make the 4,4'-dipyridine fall off from the surface of silver nanoparticles and reduce the signal. It showed an enviable detection speed with 10 ng/mL sensitivity. A good linear relationship between Raman spectral signal and Hg²⁺ concentration 50–1000 ng/mL (R² = 0.9884) was observed. The recoveries ranged from 97.47 to 100.07% for the detection of Qingkailing injection. The results indicated that the surface-enhanced Raman scattering-based 4,4'-Dipyridine probe method for detecting heavy metals could eliminate the interference of other small molecules in the complex system and perform significantly higher detection sensitivity than the pharmacopeia standard

A highly sensitive fluorescence-enhanced aptasensor was designed to detect silver ions (Ag⁺) using metal-enhanced fluorescence. Interaction of Ag⁺ with cytosine nucleobases was used to achieve a low detection limit. Aptamer-modified gold nanoparticles (Au NPs) were mixed with 6-carboxyfluorescein (FAM)-labeled DNA to prepare the sensor. In a solution without Ag⁺, aptamer and FAM-labeled DNA strands remained free because of repulsion between cytosine. In the presence of Ag⁺, pairs of aptamer and FAM-labeled DNA strands formed double helices through cytosine–Ag⁺–cytosine interactions. These interactions brought FAM close to the Au NPs. The number of adenines repeats in the aptamer was altered to adjust the distance between the Au NPs and FAM, and provide controllable localized surface plasmon resonance. With the optimum number of adenine repeats (n = 24), the linear range for detection of Ag⁺ was 0.694 to 6.94 nmol/L and the detection limit was 0.694 nmol/L. The aptasensor showed excellent specificity and gave a strong detection signal for Ag⁺ present at trace concentrations to overcome issues associated with the detection of weak signals.

Flexible surface-enhanced Raman spectroscopy (SERS) substrates were produced by in situ chemical reduction of Ag⁺ on poly(vinyl alcohol)/chitosan (PVA/CS) nanofibers. PVA/CS nanofibers (which have a large number of amino and hydroxyl functional groups) were prepared by electrospinning, which can provide more sites for adsorbing Ag⁺ than pure PVA. The Ag nanoparticles were evenly distributed on the PVA/CS nanofibers. The SERS substrate also exhibited excellent water stability, sensitivity, and uniformity. The detection limit of probe molecule rhodamine 6G was 10⁻⁷ M and the relative standard deviation was 5%. In addition, the Ag-PVA/CS nanofibers substrate was effective for recognition and detection of norfloxacin, a well-known antibiotic that is pertinent to food safety and animal/human health.

Laser-induced breakdown spectroscopy (LIBS) technology has been applied to many fields, so it is crucial for quantitative analyses of LIBS spectra. However, there is a problem in the field of LIBS spectra. Even in the same experimental setting, the same sample exhibits different spectra with different instruments, which is mainly reflected in the intensity, wavelength shift, and peak width differences. These differences cause standardization problems in LIBS spectroscopy and serious interference in quantitative analyses. The aim of this study is to correct the difference by applying the extreme learning machine method and the deep extreme learning machine method to two different spectral datasets. The first dataset is the ChemCam calibration target sample set, which contains two spectral datasets produced by using ChemCam on instruments on the Curiosity rover and at the Mars Science Laboratory (MSL). The other dataset comprises spectra obtained from calibration target samples produced by the ChemCam team at MSL. The performance of the two algorithms is tested, and the results show that our calibration transfer methods are stable predictive methods that provide significantly lower prediction error compared with linear transfer and the piecewise direct standardization method. The model established by the partial least square method is used for quantitative analyses of the transferred spectra, and the transmitted spectra showed improved quantitative accuracy.