Spectral-luminescent characteristics and the duration of fluorescence were measured for a series of metal-free tetrapyrroles in solid films of polyvinylbutyral at 293 and 77 K. The results obtained evidence about the lack of the viscosity factor in the case of the fluorescence enhancement under study, i.e. for the tetrapyrroles showing the enhancement effect in liquid solutions (tetraazaporphin, substituted tetraazachlorin), duration of fluorescence in a film increases insignificantly on lowering temperatures to 77 K. Analysis of experimental data made it possible to estimate the quantum yields of internal conversion and intercombinational conversion for tetraazaporphin and tetraazachlorin, which are fundamental structures in the tetrapyrrole series.

The method of sub-Doppler fluorescence spectroscopy is proposed, which is based on the features of the narrowing with time of the velocity distribution of optically excited atoms (molecules) of a rarefied gas medium in a thin cell after exposure to a sufficiently short light pulse. Changes in the established sub-Doppler resonances with time as well as the essential dependence of these resonances on dimensions of the gas cell are analyzed.

An N-type optical resonance formed in the Ʌ-system of potassium atoms (D₁ lines) using two CW narrow-band lasers, a spectroscopic cell with a length of 1.5 cm which contains vapors of potassium atoms, and a buffer neon gas with a partial pressure of 20 Torr has been investigated. It is shown that the N-type resonance splits into three equidistant components in a longitudinal magnetic field. A comparison of the N-type resonance parameters formed in the vapors of cesium and rubidium atoms has been presented. It is found that when the N-type resonance is formed, the initial and final levels are the lower ground levels Fg = 1, 2.

The interaction of the L-cysteine solution with iron(III) compounds of FeCl₃, Fe₂(SO₄)₃, Fe(NO₃)₃ was studied in an acidic medium (pH 2). It was shown that the reaction proceeded 30 minutes with the formation of L-cystine (21–40%) as the main product. It was found that the L-cysteine reaction with FeCl₃ leads to the formation of the L-cysteine sulfinic acid in the solution as a by-product. The products of the L-cysteine reaction with Fe(III) compounds were interpreted by IR and NMR spectroscopy.

In recent years, several reports have appeared on luminescence in LiMgF₃. Important applications have also been claimed. There is no record of LiMgF3 in the ICDD database. In light of the crystallographic studies on ABF₃ compounds and especially the finding that LiMgF₃ is not formed, the reports on the LiMgF₃ based phosphors appear interesting. Our reinvestigation confirmed that LiMgF₃ does not exist. It is quite likely that the interesting properties described in the literature for LiMgF₃, in fact, belong to the frozen eutectic or two-phase system. All the same, the existence of eutectic was exploited to melt MgF₂ at much lower temperature (735°C) than the melting point of MgF₂ (1263°C). We prepared LiF-MgF₂:Eu²⁺ and LiFMgF₂:Ce³⁺ by melting at 735°C. These materials exhibited properties similar to those of MgF₂:Eu²⁺ and MgF₂:Ce³⁺ phosphors, respectively. Thus, using the lower melting point of eutectic, it might be possible to prepare various MgF₂ based phosphors at temperatures as low as 735°C, against the high melting point of 1263°C for MgF₂.

The comparative study of the spectral-luminescent properties of hydrophilic 21-thia-5,10,15,20-tetra-(4-sulfonatophenyl)-porphyrin and 5,10,15,20-tetra-(4-sulfonatophenyl)-porphyrin is carried out in solutions at 293 K. The peculiarities of the halochromic effects have been revealed for the first time, which were due to the replacement of the pyrrole ring by thiophene in the macrocycle. It is found that multicenter interactions on the periphery and in the core of the macrocycle led to the modulation of the spin-orbit interactions which became apparent in changes of the fluorescence quenching efficiency. It is shown that the fluorescence of the doubly protonated form of heteroporphyrin deceases compared to the free base whereas the double protonated form of porphyrin reveals the fluorescence enhancement.

It is shown that the method of determining the frequency of pure electronic transition from molecular diffuse vibrational spectra is applicable for the estimation of a semiconductor direct band gap. This method is used to determine the direct band gap between the valence band and the photoconductivity band from the photoconductivity spectrum.

The technologies of obtaining nanostructured silicon, including porous nanosilicon are presented. The method for the synthesis of porous nanosilicon using electrochemical etching is described. The main parameters of the generation of porous silicon with specified characteristics are given. The results of the study of nanostructured porous silicon samples using a Renishaw InVia Raman Spectrometer are described in detail. This spectrometer permits to register and identify both amorphous and crystalline phase components in the samples. According to the results of granulometric studies, the crystal structure of the samples is established. The approximation of the Raman spectra confirms the absence of amorphous silicon in the samples under study. In the Raman spectra of the samples, a shift of lines towards lower energies is observed, which is characteristic of nanoparticles with a decrease in their size. The photoluminescence spectra of the synthesized samples of porous silicon exhibit a stable intense band in the range 700–900 nm, which confirms the nanocrystalline nature of the samples. We demonstrate the efficiency and sensitivity of Raman spectroscopy, which makes it possible to register even insignificant changes in the crystalline and amorphous fractions of silicon structures.

A numerical simulation of functions of the angular distribution of the scattering intensity for dimers and thrimers of finite dielectric cylinders is made using the formalism of the volume integral equation. The function of the angular distribution of the scattering intensity dependence on the optical and geometric parameters of single finite cylinders and their mutual location is studied. It is shown that the electrodynamic interaction between the cylinders leads to a strong change of the angular distribution of intensity of the radiation scattered by this system in comparison with that for two cylinders without electrodynamic coupling.

The emission spectra of oxygen behind the front of a strong shock wave have been studied in the shock wave velocity ranges of 5.7–7.4 and 8.1–10.0 km/s at pressures before the wave front of 1.0 and 0.25 Torr. Time-integrated sweeps of radiation in a wide spectral range of 200–675 nm as well as temporal oscillograms of oxygen radiation have been obtained. An analysis of the obtained panoramic spectra shows that at low velocities of the shock wave, the system of Schumann–Runge molecular bands dominates in the emission spectrum. An increase in the shock wave velocity leads to the appearance of intense atomic lines in the emission spectrum. The peculiarities of temporal oscillograms for the most typical spectral lines, such as radiation of molecular oxygen at a wavelength of 213 nm (Schumann–Runge system) and radiation of atomic oxygen at wavelengths of 394 and 645 nm, are highlighted.

We compare the nuclear magnetic resonance (NMR) linewidths of semi-heavy water (HOD) proton peaks in 29 nonhemorrhagic jaw cysts, 8 hemorrhagic cysts, and 19 abscesses. We also investigate the dependence of linewidths on fluid content and radio frequency (RF) application angles. The mixtures used for comparisons were prepared by adding 0.05 mL of each cyst or abscess to 0.95 mL of D₂O. A series of mixtures containing varying amounts of the sample was also prepared. NMR measurements of all mixtures at 400 MHz were acquired using only a 90° RF pulse. The mean linewidths of the cystic groups were quite different (p = 0.004) from each other. However, there was a moderate difference between the mean linewidths of nonhemorrhagic cysts and abscesses (p = 0.048) and between those of hemorrhagic cysts and abscesses (p = 0.045). The linewidth increases linearly with increasing fluid content but decreases with increasing RF application angle. In conclusion, the data suggest that linewidth measurements can distinguish cysts from abscesses. The concentration dependence of the linewidth also suggests that the rapid chemical exchange of protons between free and bound HODs contributes to the broadening of the linewidth.

Fluoroquinolone antibiotics (FQAs) have broad-spectrum antibacterial activity, high potency, variable indications, and excellent pharmacokinetic profiles. Many spectrophotometric assays have been described for the determination of FQAs in their pharmaceutical formulations; however, most of these assays have limited throughput for application in quality control laboratories. This study describes the development and validation of two innovative 96-microwell-based spectrophotometric assays with high throughput for the quality control of seven FQAs. These FQAs were levofloxacin (LEV), norfloxacin (NOR), ciprofloxacin (CIP), gemifloxacin (GEM), danofloxacin (DAN), enrofloxacin (ENR), and marbofloxacin (MAR). The first assay (assay I) was developed for LEV, NOR, CIP, and GEM via the formation of red metal complexes with FeCl₃. The second assay (assay II) was developed for LEV, DAN, ENR, and MAR via the formation of red charge transfer complexes with 2,3-dich1oro-5,6-dicyano-1,4-benzoquinone (DDQ). The reactions of FQAs with both FeCl₃ and DDQ reagents were performed in transparent 96-microwell plates, and the absorbance of the colored complexes was measured at 460 nm using an absorbance microplate reader. The best reaction conditions were established for both assays, under which Beer’s law was obeyed in the range of 10–100 μg/well with good correlation coefficients (0.9943–0.9982). The limits of detection were in the range of 4.5–7.5 μg/well, and the limits of quantification were in the range of 14.9–25.0 μg/well. Both assays showed high precision, as the values of the relative standard deviations (RSD) did not exceed 3.4%. The accuracy of both assays was proven by recovery studies, as the recovery values were in the range of 98.1–102.6% (±0.9–2.7%). The assays were applied for the determination of all seven FQAs in their tablets with good accuracy and precision. The assays are simple, economical, and have the capacity for high-throughput testing; therefore, they are convenient and beneficial for the regular determination of FQAs in pharmaceutical formulations. An additional advantage of these assays is that all FQAs can be determined on a single system without modifications in the detection wavelength.

A combined approach has been developed for the identification and determination of quinolone antibiotics in pharmaceuticals using solid-phase fluorescence digital colorimetry and chemometric analysis. The eigen fluorescence of quinolones and quinolone-sensitized fluorescence of europium(III) have been studied on various matrices. The paper proposes a test-system consisting of four indicator zones. Under irradiation with ultraviolet light (365 nm) of quinolone solutions applied to the indicator zones of test systems, there are observed blue fluorescence on cellulose paper (CP) and plates for high performance thin layer chromatography (HPTLC) and pink (CP–Eu, HPTLC–Eu) fluorescence. The measurement of the fluorescence intensity on the surface of the matrices has been carried out using a smartphone. The possibility of using chemometric analysis, which makes it possible to reduce the analysis time and visualize research data, has been shown. The data array was processed by principal component methods, hierarchical cluster analysis, and the kmean method using the XLSTAT software. The identification and assessment of the quantitative content of quinolone antibiotics in tablet forms have been carried out using chemometric analysis. The calibration dependences in the РСА and k-mean methods have a logarithmic form in the ranges of the determined concentrations of 0.5–250 μg/ml (R² ≥ 0.98). A technique for the determination of fluoroquinolones in pharmaceuticals has been proposed. The relative standard deviation does not exceed 0.09.

Hyperspectral imaging technology was used to classify four types of soybean varieties. The reflectance spectra of four varieties of soybeans were extracted from hyperspectral images covering wavelengths from 400 to 1000 nm. Firstly, exploratory principal component analysis and linear discriminant analysis (LDA) were carried out to infer the separability of soybean spectral data. Secondly, the spectral data were preprocessed using multiplicative scattering correction (MSC), Savitzky–Golay (SG) smoothing, and MSC and SG smoothing together. Finally, classification models based on LDA, support vector machine (SVM), and k nearest neighbor (KNN) were established based on the full wavelengths or feature wavelengths. MSC and SG smoothing joint preprocessing of the spectral data was applied to establish the SVM classification model based on the full wavelengths, which returned a classification accuracy of 95.19%. Random forest was used to select the feature wavelengths from the full wavelengths to establish the LDA classification model, and the classification accuracy reached 82.69%. The results showed that the hyperspectral imaging technique combined with SVM, KNN, and LDA algorithms can be used to classify different soybean varieties in a fast and nondestructive way.

The spatial-energy profile characteristics of the recorded pulse energy reflected from a diffusely scattering horizontal plane under its incline illumination are studied. The values of the maximum signal, the position of the maximum and the size of the best visibility area were studied as a function of the delay distance at different ratios between the pulse durations and the signal registration times. Analytical results are obtained for rectangular-shaped pulses. The results related to real-form pulses are obtained by numerical methods.

Invention relates to laser equipment. Active medium for fiber lasers contains a structurally-activated epoxy oligomer with molecules of organic dyes and a hardener. Curing agent used is finely dispersed glass with chemically activated reactive groups on the surface with the following ratio of ingredients pts.wt.: organic dye 0.0075-01; epoxy oligomer 8.0-31.5; fine-dispersed glass with chemically activated surface 68.4925-91.9. Technical result consists in enabling adjustment of the value of the refractive index of the active fibre core.

A theoretical study of infrared and interferometric methods of gas analysis has been carried out. Circuit implementations of devices have been developed, and an experimental solution of the problem of obtaining approximately the same sensitivity of the combustible gas detector to the gas components of the mixture has also been described. For both considered gas analyzers, the problem of controlling the selectivity of the analysis of gas components in an air mixture with an error of ~10% has been solved.

The characteristics of a weak absorption spectrometer consisting of a frequency-tunable diode laser and an external analytical resonator are considered. It is shown how the resonator parameters and the frequency tuning rate affect the sensitivity of the spectrometer and the reproduction of the shape and width of the recorded line.

Attenuated total reflection Fourier transform infrared spectroscopy coupled with principal component analysis was used to investigate expensive and low-priced engine oil samples. A total of 174 oil samples of 15 commercial brands (expensive and low-priced) was successfully differentiated into five viscosity grades. The percentage of successful clustering of these oils ranged from 70.6 to 100%. The viscosity grades of oils of each commercial brand were also successfully distinguished for 10 different commercial brands. The successful clustering for this ranged from 72.5 to 100% for the 159 studied oil samples. Moreover, 15 low-priced oil samples of five commercial brands were assessed with 100% accuracy.

This study analyzed the fluorescence intensity, integrated intensity of the spectral area, and fluorescence peak of vegetable oil samples subjected to different heating conditions. The photon lifetime of the vegetable oil was then calculated using the fluorescence lifetime method, which can determine whether the sample has been repeatedly heated at high temperatures. Combining these two methods improves the accuracy of detection and can help solve the problem of false and missed detection, providing a strong basis for the detection of high-temperature heated vegetable oil.

This study deals with the structural changes occurring in a Mo-reach glass dedicated to the confinement of Mo-reach radioactive waste that contains different contents of Cs₂O oxide, ranging from 0.3 to 0.6 wt.%. The glass synthesis was carried out by the double melting method at 1380°C, followed by a stage of 2 h at 600°C. Neodymium was an actinide simulator. The glasses were characterized by their physical and microstructural properties using different spectroscopic techniques. As the experiment shows, the glass geometrical density varies between 1.96 and 2.75g/cm³. X-ray diffraction (XRD) analysis shows amorphous features, with traces of crystalline germs, identified as the CaMoO4 powellite phase, which probably formed during glass cooling. Fourier transform infra-red (FTIR) analysis reveals the main chemical bounds in the glasses: Si-O-Si and O-Si-O in SiO₄, B-O-B in BO₃, and Al-O-Al in AlO₄. The addition of Cs₂O raises the rate of polymerization in the glass network and then decreases the number of no-bridged oxygens (NBO). Raman spectroscopic analysis reveals the absorption bands of MoO₄^2– in CaMoO₄. It shows that the Mo environment is altered by the addition of increasing contents of Cs₂O in the glass. This is evidenced by the absorption bands shifts at 319, 792, and 844 cm^–1. The absorption band located at 700 cm^–1, ascribed to the elongation of SiO₄ and AlO₄, is attenuated for 0.4 and 0.6% of the Cs₂O content. It shifts to 680–900 cm^–1 due to the glass high Mo content but increases in intensity with the Cs₂O content, thus disturbing the alkali positions of Ca and Na, with Cs remaining soluble in the glass. One can conclude that a little rise in the Cs₂O content inhibits the phase separation of both Na and Ca molybdates. The glasses analyses do not show particular changes in the lanthanide valences, which are probably in a +III oxidation state. The addition of Cs₂O in this kind of glass network remains an issue with respect to the coherence of its microstructure. However, about 0.6 wt.% of Cs₂O has been incorporated in the glass network, with no Cs₂O phases segregation.

An atmospheric pressure glow discharge between solution cathode and hollow anode with miniature argon gas flow was built. The spectra of excited species (including NO, O, N₂, H, and Ar) in the plasma and the characteristic parameters of the plasma were investigated. The result shows that argon gas increases the spectral intensity of the high energy species in the cathode and anode. Additionally, the plasma image and the distribution of sound frequency are collected. As the flow rate of argon increases, the plasma volume is significantly smaller. The audio signal in the high frequency band (~10000 Hz) is weakened while the argon flow rate increases. The range of sound distribution within the low frequency band becomes wider (from ~2000–3000 to ~2000–5000 Hz). This shows that argon can affect the stability of the plasma and the collision of internal particles. We also measured the spectral parameters (including electron excited temperature, rotational temperature, and electron number density). The result shows that improvement of the argon flow rate in the near cathode region can also increase the plasma parameters. The electron excited temperature and electron number density are higher in the region near the anode.

The present work is based on the method development and validation of the UV-spectrophotometric method for the quantitative estimation of chrysin. We studied how the nature of the solvent affects chrysin solubility. The stock and diluted solutions were scanned using a UV visible spectrophotometer to obtain the λ_max. The absorbance of the samples was recorded to obtain a calibration curve, which was followed by regression using MS Excel and Sigma stat software. The method developed by this process was further validated using parameters such as linearity, precision, limit of detection, limit of quantification, accuracy, and ruggedness. The solubility of chrysin was checked at 35oC in different oils, solvents, and co-solvents. The λ_max of chrysin in methanol was found to be 367 nm. The calibration curve of the drug follows linearity (2–10 μg/mL) with a correlation coefficient of 0.991. At three different levels, i.e., 80, 100, and 120%, the method’s accuracy was checked utilizing the percent recovery (97–99.5%). The precision studies were carried out in terms of intraday and interday variations. The ruggedness of the proposed method was studied by taking two. The solubility of chrysin was found to be the maximum in methanol (216.80±0.0097 μg/mL) among the oils, solvents, and co-solvents used. Thus, based on the experiments done, the developed method was observed to be accurate, precise, and reproducible. The viscosity of the solvent and the possibility of hydrogen bonding are two crucial factors that affected the solubility of chrysin in the solvents.

Correct flight parameters are critical for obtaining high-quality unmanned aerial vehicle (UAV) remote sensing images. For the UAV, the Rikola hyperspectral load needs to set the instrument's exposure time, UAV flight mode, flight altitude, and other issues when acquiring data. Using the control variable method, UAV Rikola hyperspectral images were collected under different parameters, and the gray-scale target and image's quantitative evaluation index was used to obtain the spectral curves of gray-scale targets, ground features, signal-to-noise ratio (SNR), information entropy, and sharpness of imagery. The results of the comparative analysis show: the vegetation hyperspectral data quality was better when determining the Rikola hyperspectral exposure time using the 64% diffuse plate; UAV hover mode and cruise mode had little impact on data quality; when the flight altitude was within 100 m above ground level, the higher the flying height, the better the data quality. This study therefore provides evidence for obtaining high-quality data using UAV hyperspectral load.

A potential iron phosphate (FePO₄) catalyst was prepared using a low-temperature solid-state method for the heterogeneous Fenton-like degradation of methyl blue (MB). A variety of parameters affecting the MB removal rate, including temperature, initial pH, catalyst usage, H₂O₂ and MB concentration, was studied in detail. The prepared FePO₄ exhibited a highly efficient catalytic reaction with seven cycle performance. In addition, a free radical masking experiment revealed the existence of a hydroxyl radical (•OH) and indicated that the degradation of MB was mainly due to the oxidation caused by •OH. This work suggests FePO₄ is an efficient material, which is responsible for the catalytic degradation of the azo dye MB through a heterogeneous Fenton-like system.

The optical properties of the symmetric salamo-like chemical probe (H₂CS) of Cu²⁺ were studied in EtOH/H₂O (1:1, V/V) solution by UV-Vis and fluorescence spectroscopy. In the fluorescence spectrum, the coordination of Cu²⁺ with H₂CS results in fluorescence quenching owing to the paramagnetic nature of Cu²⁺ ions. The binding constant of Cu²⁺ to the H₂CS sensor was calculated as 1.17×10¹¹ M^–1 and LOD was obtained as 5.3×10^–8 M. When Cu²⁺ ions were added, the UV-Vis spectra changed, obviously due to the electron transfer from sensor to metal bond, and a new absorption band appeared at 372 nm. When the ethylenediaminetetraacetic acid (EDTA) solution was added to the H₂CS-Cu²⁺ solution, causing a large binding constant, with EDTA releasing the free sensor molecule and finally achieving a fluorescence shutdown phenomenon.

This study aimed to investigate the molecular mobility of crude oils using the linewidth of the free radical electron paramagnetic resonance signal (EPR) as a molecular mobility probe. For this, aromatic and paraffinic crude oil samples were analyzed by X-band EPR spectroscopy, NMR experiments in time domain (TD-NMR), and rheometry. The variations on the half height linewidth with temperature presented a similar behavior for both samples, being related to different molecular mobility regimes. EPR results were compared to the variation of viscosity with temperature obtained by rheometry and TD-NMR. The results showed changes in the decrease trend of viscosity for the paraffinic sample at a temperature close to the range in which it is observed the transition from rigid to liquid regime in the EPR analysis. EPR technique showed more detailed information about the regime transition for the oil samples studied, which is in agreement with the results obtained by rheometry and TD-NMR.

A fluorescent probe II, 6-azido-2-(2-hydroxyethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione with specific identification environment H₂S, was designed and synthesized based on 4-bromine-1,8-naphthalimide and ethanamine. We used 4-bromine-1,8-naphthimide as raw materials to synthesize a new type of reactive fluorescent probe based on the mechanism of intramolecular charge transfer. These two materials are easily obtainable, low in cost, and can be synthesized through a simple two-step reaction. 1,8-Naphthalene anhydride has a moderate fluorescent ability as it introduces an electron-donating group at position 4. A change to its conjugate system can cause a push-pull electronic effect in the molecule and result in a very strong luminous effect. The structure of probe II was characterized by IR, ESI, and NMR. The preliminary screening was under the UV lamp. We found that probe II had a certain specific recognition effect on H₂S in the DMSO solvent. After the solvent screening, DMSO was selected as a solvent to identify H₂S specifically for the probe. The fluorescence spectroscopy illustrated that probe II showed green fluorescence in the DMSO solution. With the continuous addition of H₂S, probe II showed red fluorescence at 510 nm, which produced a strong fluorescence emission peak that stood out from the rest of the spectrum. The experimental results showed that the probe had a very good sensitivity at detecting H₂S (with a minimum concentration of 1×10–7 mol/L). Meanwhile, dozens of cations and anions do not interfere with the recognition of H₂S by the probe molecule in the DMSO system. At the same time, we found that probe II could also recognize H₂S by cell imaging technology.