Derivatives of octahydroacridino[4,3-c]acridin-1,9(2H,5H)dione are synthesized using the condensation of diazomethines (N ¹,N ⁵-di-R-benzylidenenaphthalen-1,5-diamines) with dimedone in butanol. The structure of the prepared compounds is confirmed by the methods of nuclear magnetic resonance and IRspectroscopy. The spectral and luminescent properties of the synthesized compounds are studied in ethanol and DMF as solvents at 293 and 77 K. It is found that the absorption spectra are formed by three S_n←S₀ (n = 1-3) electronic transitions and the frequencies of 0-0 transitions from singlet (S₁) and triplet (T₁) states are equal to 24400 and 20800 cm^{- 1} , respectively. The fluorescence quenching by ethanol is due to the formation of the complex with the hydrogen bonds; the lifetime of this complex is less than 10^{- 9} s. Phosphorescence in the studied compounds is caused by the existence of a naphthalenic fragment in the molecule.

In this paper, we investigate the spectral and kinetic features of the fluorescence quenching of rhodamine 6G molecules in a heterogeneous system of macroporous silica (C-80) and water caused by the combined influence of the outer heavy atom (KI) and resonance-excited surface plasmons on citrate hydrosol silver nanoparticles. It is shown that surface plasmon quenching occurs when the donor-acceptor interaction of iodine and silver nanoparticles complexes takes place. It is found that the activation energy of rhodamine 6G fluorescence quenching in a heterogeneous medium has a minimum that is associated with diffusive deceleration during the formation of silver nanoparticles clusters.

In this paper, we theoretically investigate the light absorption and the nonradiative exchange of the energy of electronic excitation between the metal circular-section nanowire and luminophore molecules. For the case of no interactive molecules, we calculated the energy transfer rate from a single excited molecule to the nanowire and the kinetics of the decay of the luminophor excited state. The energy transfer rate from the coaxial J-aggregate monolayer to the nanowire is calculated for the case of the molecules combined in the J-aggregates. The possibility of the hybrid exciton-plasmon state in this system is shown. The significant influence of the geometric characteristics of these systems on the rate of the transformation of the electronic excitation energy is established.

This study provides a new approach to the classification of textile fibers by using principal component analysis (PCA), based on UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). Different natural and synthetic fibers such as cotton, wool, silk, linen, viscose, and polyester were used. The spectrum of each kind of fiber was scanned by a spectrometer equipped with an integrating sphere. The characteristics of their UV-Vis diffuse reflectance spectra were analyzed. PCA revealed that the first three components represented 99.17% of the total variability in the ultraviolet region. Principal component score scatter plot (PC1×PC2) of each fiber indicated the accuracy of this classification for these six varieties of fibers. Therefore, it was demonstrated that UV diffuse reflectance spectroscopy can be used as a novel approach to rapid, real-time, fiber identification.

A numerical simulation of the scattering phase function (PF) for dimers of finite dielectric cylinders is made using the formalism of the volume integral equation. The PF 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 photoacoustic signal generated by laser-induced nanobubbles (PA-LINB) proved to be a sensitive tool to monitor the aggregation of gold nanoparticles. Here, a simple and label-free photoacoustic method for the rapid detection of Pb²⁺ in the aqueous phase was developed. Due to the high affinity of Pb²⁺ ions to glutathione, the presence of Pb²⁺ led to the aggregation of glutathione-conjugated gold nanoparticles (GSH-GNPs). Hence, by measuring the variation of the PA-LINB signal after the aggregation of GSH-GNPs, Pb²⁺ can be quantified. A low detection limit for Pb²⁺ (42 nM) and a wide linear working range (~42-1000 nM) were achieved. Furthermore, the proposed method showed good selectivity against other metal ions.

Self-assembly of thiolated polyethylene glycol (PEG)-modified Au nanoparticles (NPs) into a closely packed particle film at a water-air interface for the production of reproducible, highly active surface-enhanced Raman scattering (SERS) was developed. Upon modification with thiolated PEG, the Au NPs can sustain severe conditions (e.g., 3 M NaCl solution), and after separation from colloids and drying, they can be redispersed into water, forming colloids again. We found that the thiolated PEG-modified Au NPs, from their concentrated colloids, can spontaneously self assemble into a two-dimensional (2D) closely packed particle film at the water-air interface. With abundant hot spots created and exposed, the 2D particle film produces large, reproducible SERS signal for 4-mercaptobenzoic acid (probe molecule), reaching a detection limit of 1´10^-11 M. These results offer a useful way for the storage of Au NPs and the fabrication of highly reproducible and active SERS substrate.

In this paper, we invstigated the features of photoacoustic phenomena induced by the second harmonic of YAG:Nd³⁺ laser pulses in a methylene blue solution in a water/glycerol (1:1) mixture containing titanium dioxide nanoparticles as a light-scattering impure. Using stationary spectroscopy, we found that the dimerization degree of methylene blue is substantially lower for this solvent comparing with water. The dependencies of the signal amplitude normalized to the pulse energy density and the effective signal rise constant on the methylene blue and titanium dioxide nanoparticles concentrations were obtained. It is shown that the signal rise constant depends linearly on the concentration of titanium dioxide nanoparticles, while the amplitude is almost independent. A method is suggested for simultaneous photoacoustic determination of concentrations of both components. For testing samples, the uncertainty of the determination of the components concentration is less than 5% for methylene blue and less than 37% for titanium dioxide.

We investigated the influence of temperature (in the range 20-40 °С) on the main vibrational-rotational bands (ν₁, ν₂, ν₃, 2ν₂, and 2ν₄) of the methane Raman spectrum. It is demonstrated that if the temperature rises, the Raman shifts of the Q-branches of these bands increases in different ways, and the relative intensities of the 2ν₂ and 2ν₄, overtones, being in the Fermi resonance with ν₁, decreases. A method is proposed for the determination of the temperature of methane-containing gaseous media. An estimation is given for the impact of temperature fluctuations on the results of Raman analysis of the natural gas composition.

A simple, fast, and sensitive spectrophotometric method is reported for the determination of heparin concentration in human plasma samples. The assay is based on enhancing the extinction intensity of CTAB-capped gold nanoparticles in the presence of heparin molecules. The strong electrostatic interaction of the positively-charged gold nanoparticles with the negatively-charged heparin molecules induces a marked increase in size of gold nanoparticles, which results in a dramatic rise in the extinction spectrum of gold nanoparticles. Since the enhanced extinction intensity at 528 nm is proportional to the concentration of heparin, quantitative determination of heparin is possible. Under optimum conditions, the enhanced extinction intensity is linearly correlated with the concentration of heparin in the range 0.18-11.98 U/mL with limit of detection 0.08 U/mL.

The reaction mechanism of cefonicid sodium with bovine serum albumin was investigated by traditional fluorescence spectroscopy and synchronous fluorescence spectroscopy. The results demonstrated that cefonicid sodium caused a strong fluorescence quenching of bovine serum albumin through a static quenching mechanism, during which the electrostatic force played the dominant role in this system, and the number of binding sites in the system was close to 1. It also showed that the primary binding site for cefonicid sodium was closer to tryptophan residues located in sub-hydrophobic domain IIA. Moreover, circular dichroism spectroscopy showed that the secondary structure of bovine serum albumin changed. The donor-to-acceptor distance r < 8 nm indicated that the static fluorescence quenching of bovine serum albumin was a non-radiation energy transfer process. The data obtained from Δl = 60 nm and l_ex= 295 nm indicated that synchronous fluorescence spectroscopy had higher sensitivity and accuracy compared to traditional fluorescence spectroscopy.

A new technology has been developed to improve the visibility of blood vessels on the images of biological tissues based on the relation between image color components, scattering properties of the tissue and hemoglobin content in it. A statistical operator was presented to convert a three-color image of tissue into the parametric map objectively characterizing the concentration of hemoglobin in the tissue regardless of the illumination and shooting conditions. An algorithm for obtaining the conversion parameters for imaging systems with known spectral characteristics was presented. An image of a multilayer multiple-scattering medium modeling bronchial tissue was synthesized, and the efficiency of the proposed conversion was evaluated on its basis. It was shown that the conversion makes it possible to increase the contrast of blood vessels by almost two orders and significantly improve the clarity of the display of their borders, to almost completely eliminate the influence of background and non-uniform illumination of the medium in comparison with the original image.

We studied the effect of therapeutic doses of optical radiation on hematological parameters of blood irradiated in vivo: hemoglobin concentration, hematocrit and the number of erythrocytes in the peripheral blood of patients during courses of extracorporeal, overvein and intravenous blood irradiation and after their completion. It was shown that reversible changes during the procedures differed from those received after the course completion. At the end of the course the hematological parameters changed in different directions and became both higher and lower than the initial parameters depending on the initial values and photoinduced changes in blood oxygenation. It was demonstrated the regulatory effect of photohemotherapy on oxygen-depended processes changing the inflow of oxygen into the cells as well as the generation of reactive oxygen species and their inhibition by antioxidant systems.

The dynamic and static quenching of 6-(2',7'-dimethoxy-4',5'-dichloro)carboxyfluorescein (JOE) by nucleosides (deoxyadenosine, deoxycytidine, deoxyguanosine, thymidine, and deoxycyridine) in the tris-acetate buffer solution was analyzed using the Stern-Volmer equation. Only one of the five nucleosides - deoxyguanosine - was found to exhibit predominantly static quenching. The quantum yields of the fluorescence of 5- and 6-carboxyfluorescein (FAM), as well as of 5- and 6-JOE, covalently bound by a rigid (4-transaminocyclohexanol) linker to the oligonucleotide, is greater than for their analogues with flexible (6-aminohexanol) linker. It is shown that quenching of fluorescence in systems with a flexible linker takes place mainly with the van der Waals contact of the fluorophore with guanine. An increase in the number of consecutively located guanines at the 5'-end linked to the dye in the composition of oligonucleotides and their duplexes results in a decrease in the quantum yield of fluorescence. Quantum-chemical calculations show a shift of the absorption and fluorescence spectra of 5-FAM and 5-JOE isomers to the low-frequency region compared to 6-isomers

Carbendazim is among the most popular benzimidazole bactericides that are widely used to boost food production, and its residue poses a great threat to human health and the environment. In this paper, we presented a colorimetric sensor based on gold nanoparticles (Au-NPs) for the detection of carbendazim residues. The Au-NPs were stabilized by citric acid synthesized by chloroauric acid and sodium citrate with a diameter of about 13 nm. Upon reaction with carbendazim, the sensor gave a clear color change that could be distinguished with the naked eye. Thus we elaborated a new method for rapid determination of this benzimidazole bactericide. After optimization of the detection conditions, the sensor showed a very good linear relationship with the carbendazim concentrations varying from 10 to 600 ppb with a detection limit down to 3.4 ppb (S/N=3). These preliminary results demonstrate that the presented sensor is promising for fast carbendazim analysis.

It was found with the help of spectrophotometry, IR spectroscopy, X-ray phase analysis, and thermogravimetry, that new supramolecular structures in the β-cyclodextrin-β-resorcylic acid system are generated as a result of the spontaneous exothermic process. It was proved that the inclusion complexes of the host-guest type with 1:1 ratio between β-cyclodextrin and molecular form of β-resorcylic acid (or its monovalent anion) are formed through the van der Waals interactions of the aromatic ring of β-resorcylic acid with the inner hydrophobic cavity of β-cyclodextrin. It was shown that there are the partial displacement of water molecules from the inner cavity of the cyclic oligosaccharide and the complete immersion of β-resorcylic acid molecule inside it; the thermal stability of β-resorcylic acid increases.

The feasibility of the compositional analysis of drugs by calibration-free laser-induced breakdown spectroscopy (LIBS) was investigated using multivitamin tablets as a sample material. The plasma was produced by a frequency-quadrupled Nd:YAG laser delivering UV pulses with a duration of 5 ns and an energy of 12 mJ, operated at a repetition rate of 10 Hz. The relative fractions of the elements composing the multivitamin drug were determined by comparing the emission spectrum of the laser-produced plume with the spectral radiance computed for a plasma in a local thermodynamic equilibrium. Fair agreement of the measured fractions with those given by the manufacturer was observed for all elements mentioned in the leaflet of the drug. Additional elements such as Ca, Na, Sr, Al, Li, K, and Si were detected and quantified. The present investigations demonstrate that laser-induced breakdown spectroscopy is a viable technique for the quality control of drugs.

A novel multi-pass cell laser absorption spectrometer to measure δ¹³C diluted with nitrogen using a 1.658 μm near-infrared distributed-feedback laser was developed. The system temperature and pressure were measured with an accuracy of ±11 mK and ±3.2 Pa, respectively. The spectrometer is small, reliable, and compact. To minimize the temperature effect in absorbance ratio measurements, we used two appropriate absorption line pairs with nearly the same temperature dependences. The absorption spectrometer demonstrated high precision (a repetitive precision (reproducibility) of ~0.9‰ (1s) is obtained at 300 ppmv methane concentrations). This concentration ratio is adequate for most CH₄ source characterization studies.

A statistical model is proposed to approximate experimental data on the FTIR spectroscopy of paint samples from paintings of different ages. The model is based on random variations of several parameters (initial rates of ageing and moments and degrees of the ageing rate changing). The parameters that characterize the scatter of the paint compositions and storage conditions are determined. The numerical results are in qualitative agreement with the experimental data. In the framework of the model, variations in the initial composition of paint and variety of storage conditions almost equally contribute to the observed dispersion of the experimental data.

The effects of water temperature on the characteristics of ZnO nanoparticles produced by laser ablation method in water were investigated experimentally. The nanoparticles were prepared by pulsed laser ablation of a zinc metal target in distilled water at different temperatures. The synthesized ZnO nanoparticles were characterized using X-ray diffraction analysis and transmission electron microscopy. The results show that the produced samples are crystalline with a hexagonal wurtzite phase. Transmission electron microscopy has revealed that the ZnO nanoparticles are spherical. The strain and the crystallite size of the nanoparticles were investigated by X-ray peak broadening. The mean crystallite size of the ZnO nanoparticles estimated from the TEM images is in good agreement with three models of the Williamson-Hall method. According to the results, the size distribution of the produced ZnO nanoparticles depends strongly on the temperature of the ablation environment.

Low-resolution (LR) spectra of trans- and gosh- conformations of the ethyl alcohol molecule (СН₃СН₂ОН) and the trans-conformation of the deuterated-isopropyl alcohol ((СD₃)₂CDOH) molecule were calculated in the range 0-2 THz using the method of additive modeling of LR spectra by high-resolution microwave spectra. The frequency bands of the spectra of LR were found where the absorption by both molecules is maximal: 660-680 and 1120-1160 GHz for gosh- and trans-conformations of the ethyl alcohol molecule and 480-500 GHz for the trans-conformation of the deuterium-substituted isopropyl alcohol molecule. A comparative analysis of spectral regions in which the maximum absorption occurs was carried out for the molecules of ethanol, n-propanol, isopropanol and deuterated isopropanol. It is concluded that, when going to heavier compounds, the LR spectra maxima shift toward lower frequencies. That is very important for their spectral identification for the purpose of environmental monitoring and production quality control.

The FTIR reflection spectra of ZnSe ceramics prepared by hot pressing (HP), physical vapor deposition (PVD), and PVD combined with isostatic hot pressing (HIP) are presented. The optical constants of polished and dry-ground specimens were taken for comparison. The grinding treatment simulated the erosion of faces of optical elements made of zinc selenide under hard dust particles and weathering. In polished spectra, the residual stresses manifested themselves in the IR reflection spectra of the ZnSe^PVD and ZnSe^HIP ceramics characterized by the pronounced orientation of grains but were lacking in the spectra of the ZnSe^HIP ceramics due to a cancellation effect in randomly oriented grains of the latter material. The stresses detected by shifts of the absorption bands calculated by the Kramers-Kronig method increased significantly after the abrasive treatment of the specimens. In addition, the absorption bands caused by anharmonicity of the distorted lattice increased several times. The latter effect was dependent on the processing pre-history of the ceramics.

The full spectral complex of optical functions of the 6H-SiC polytype was determined in the energy range from 0 to 35 eV. The spectra of ε₂(E), - Imε^-1, - Im(1+ε)^-1 were decomposed into 15 simple bands. Main parameters of the bands were established including the maximum energy and oscillator strengths. The calculations were performed on the basis of the experimental reflectivity spectrum using the Kramers-Kronig relation and an improved nonparameteric method of the Argand diagrams.

The feasibility of using three-dimensional fluorescence spectroscopy to monitor nitrogen content in algal bio-oil was investigated. The experimental results suggested that all the bio-oil samples studied exhibited strong fluorescence. Three fluorescence peaks were observed at l_ex/l_em = 240/375 nm (peak A), 290/380 nm (peak B), and 330/395 nm (peak C). The blue-shift in the fluorescence emission wavelength of peak C after upgrading indicated that the fluorescence molecules may lose some functional groups during the upgrading process. Further studies showed that there was a strong linear relationship between the fluorescence intensity ratio of peak C to peak B and the nitrogen content. This work suggests that the use of three-dimensional fluorescence spectroscopy could provide a sensitive, low cost, intuitive and rapid tool for monitoring the nitrogen content in algal bio-oil.

The implementation of logical operations on sets represented in the form of images is considered using a stimulated echo hologram. It is shown that the stimulated echo hologram can be used to implement the logical operation of the set intersection.

Based on a study of 153 kinds of commercial vodka products, the possibility of identifying counterfeit samples is shown by introducing a unified additive with the concentration that is minimum acceptable for the instrumental detection and multivariate analysis of UV-Vis transmission spectra. The 100% probability of detection of counterfeit products is achieved through the use of hierarchical clustering analysis or C-means method in two-dimensional space of principal components.

The glasses were prepared by a melt quenching technique and characterized by X-ray diffraction (XRD), optical absorption, and luminescence spectral studies. The XRD analysis indicates that the prepared samples are of fully amorphous nature. Optical absorption spectra have been investigated using the Judd-Ofelt theory. Radiative parameters such as transition probabilities, branching ratios, radiative lifetime, and stimulated emission cross section have been evaluated using Judd-Ofelt intensity parameters. The luminescence spectra of both of Dy³⁺ as well of Sm³⁺ doped glasses were recorded with the 476 nm line of an Ar⁺ laser. Based on the values of stimulated emission cross section, radiative transition rate, and branching ratio of the emission transition⁴F_9/2®⁶H_13/2 of Dy³⁺ , it is suggested that 2 mol.% of Dy³⁺ LiCaB glass is a promising luminescent material for lasing applications.

A total of 130 topsoil samples collected from Guoyang County, Anhui Province, China, were used to establish a Vis-NIR model for the prediction of organic matter content (OMC) in lime concretion black soils. Different spectral pretreatments were applied for minimizing the irrelevant and useless information of the spectra and increasing the spectra correlation with the measured values. Subsequently, the Kennard-Stone (KS) method and sample set partitioning based on joint x-y distances (SPXY) were used to select the training set. Successive projection algorithm (SPA) and genetic algorithm (GA) were then applied for wavelength optimization. Finally, the principal component regression (PCR) model was constructed, in which the optimal number of principal components was determined using the leave-one-out cross validation technique. The results show that the combination of the Savitzky-Golay (SG) filter for smoothing and multiplicative scatter correction (MSC) can eliminate the effect of noise and baseline drift; the SPXY method is preferable to KS in the sample selection; both the SPA and the GA can significantly reduce the number of wavelength variables and favorably increase the accuracy, especially GA, which greatly improved the prediction accuracy of soil OMC with R_cc, RMSEP, and RPD up to 0.9316, 0.2142, and 2.3195, respectively.

During slaughtering and further processing, chicken carcasses are inevitably contaminated by microbial pathogen contaminants. Due to food safety concerns, many countries implement a zero-tolerance policy that forbids the placement of visibly contaminated carcasses in ice-water chiller tanks during processing. Manual detection of contaminants is labor consuming and imprecise. Here, a successive projections algorithm (SPA)-multivariable linear regression (MLR) classifier based on an optimal performance threshold was developed for automatic detection of contaminants on chicken carcasses. Hyperspectral images were obtained using a hyperspectral imaging system. A regression model of the classifier was established by MLR based on twelve characteristic wavelengths (505, 537, 561, 562, 564, 575, 604, 627, 656, 665, 670, and 689 nm) selected by SPA, and the optimal threshold T = 1 was obtained from the receiver operating characteristic (ROC) analysis. The SPA-MLR classifier provided the best detection results when compared with the SPA-partial least squares (PLS) regression classifier and the SPA-least squares supported vector machine (LS-SVM) classifier. The true positive rate (TPR) of 100% and the false positive rate (FPR) of 0.392% indicate that the SPA-MLR classifier can utilize spatial and spectral information to effectively detect contaminants on chicken carcasses.