Comparative analysis of the absorption and fluorescence spectra and fluorescence excitation spectra of thioflavin T (ThT) in various solvents and in the composition of amyloid fibrils has shown that ThT, when excited in the region of the long-wavelength absorption band, fluoresces in the spectral region with a maximum at 478-484 nm. The appearance in aqueous and alcohol solutions of a fluorescence band with a maximum near 440 nm has been attributed to the presence in the composition of the ThT preparations of an impurity with an absorption band in the 340-350-nm range. The literature data showing that in glycerol ThT has a wide fluorescence spectrum with two maxima are due to the artifact connected with the use of a high concentration of the dye. It has been suggested that the cause of the low quantum yield of ThT aqueous and alcohol solutions is the breakage of the system of conjugated bonds due to the reorientation of the benzothiozole and benzaminic rings of ThT in the excited state with respect to one another. The main factor determining the high quantum yield of fluorescence of ThT incorporated in fibrils is the steric restriction of the rotation of the rings about one another under these conditions. The suggestions made have been verified by the quantumchemical calculation of the ThT molecule geometry in the ground and excited states.

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The spectral-luminescent properties of symmetrical indotricarbocyanine dyes with the same cation and different anions (Br − , BF 4 − ) in cancerous HeLa cells, an isotonic solution of NaCl, and organic solvents have been investigated. It is shown that when these dyes are present in cells in nontoxic concentrations, they are in a monomeric state, they are localized in the region with a low dielectric permeability, bonded to biological macromolecules, and do not make contact with an aqueous medium. It has been established for the first time that the molecules of the polymeric dyes are present in cells predominantly in the form of contact ion pairs, and in a dye with the Br − anion the presence of free cations or solvately separated ionic pairs is revealed. It is shown that the shift of the ion equilibrium toward contact ion pairs for the dyes in the cells (as compared to the low-polarity organic solvents) can be due to the fairly high concentration of salts in the biosystem.

We present the results of a study of the spectral luminescence properties of three groups of indotricarbocyanine dyes, each of which is formed from compounds with the same cation and different anions. In high-polarity solvents, in the absorption and emission spectra of the dyes we see one type of center; in low-polarity solvents, due to the presence of different ionic forms of the dyes (free ions, contact ion pairs), we observe either one type or two types of centers. By analysis of the luminescence of molecular oxygen in the 1.27 µm spectral region, we determined the efficiency of photosensitization of 1 O 2 formation by dyes in deuterated solvents. We have shown that in low-polarity solvents, the yield for singlet oxygen generation is higher for indotricarbocyanine dyes which are found in the contact ion pair state and which also contain a heavy atom (I) in the anion. We have observed that an increase in the fraction of contact ion pairs in solution as the dye concentration increases or when an additional salt is introduced leads to an increase in the quantum yield for generation of singlet oxygen. In polar deuterated acetonitrile, the counterion has no effect on the efficiency of photosensitization of oxygen by the dyes.Introduction. Most polymethine dyes are salts whose molecules in solutions can be found in the form of an equilibrium mixture of several types of ionic forms (free ions, contact and solvent-separated ion pairs) [1]. The equilibrium between these forms is shifted toward an increase in the fraction of one form when the temperature and the nature of the solvent are varied, when the anion is substituted, and when ionic and solvating additives are added to the solution. The state of the ionic equilibrium in solutions has an effect on the processes of dissipation of the electronic excitation energy in the polymethine dye molecules. The fluorescence quantum yield and the fluorescence lifetime of the polymethine dye molecules decrease symbatically with strengthening of the anion-cation interactions [2, 3]. In the ion pairs, the probabilities of torsional vibrations in the polymethine chain are higher and the yield for photoisomerization of the molecules is higher; the degree of vibronic interactions and the probabilities of rotation about bonds are higher as more stable ion pairs are formed [4][5][6].Despite the significant number of publications devoted to study of the photophysical properties of polymethine dyes in different types of solvents, due attention has not been paid to the effect of the state of ionic equilibria on the efficiency of singlet oxygen generation by polymethine dyes. At the same time, such a study is important from both a scientific and an applied viewpoint. The applied importance is due to prospects for using these dyes for photochemotherapy of cancer and as biological fluorescent labels [7][8][9], and also because in biological structures, their molecules are mainly found in the form of contact ion pairs [10]. In this case, the efficiency of polymethine dyes as photosensitizers...

681.785.554We have designed and built a multi-object spectrometer with micromirror array as a reconfigurable entrance aperture. In interactive mode, the instrument makes it possible to record both the hyperspectrum of the studied region as a whole and also sets of spectra of arbitrarily specified fragments. In this case, a spectral resolution of 0.8 nm or better is provided in the subranges 400-670 nm and 650-900 nm, aperture ratio of the spectroscopic channel at least 1:5. The analytical characteristics of the instrument make it possible to use it to solve a broad range of problems in modern multi-object spectroscopy and hyperspectroscopy.Introduction. In recent decades, in applied spectroscopy the objects of investigation increasingly often are extended regions of space: fragments of the Earth's surface, a stellar cloud, human tissue, etc. Methods allowing us to obtain the optical spectrum for a large number of small fragments of the studied region with a certain spatial and spectral resolution have acquired the name "multi-object" methods (if the full spatial and spectral image I(x, y, λ) is recorded, "hyperspectral" methods). Multi-object spectroscopy and hyperspectroscopy are used in medical diagnostics, for remote (aerospace-based) monitoring of the Earth's surface, in forensics, spectroscopy of single quantum objects, and in astronomy studies [1][2][3][4][5].Today, hyperspectral images (HSI) are most often obtained by scanning the entrance slit of a dispersive spectrometer over the analyte image (or scanning the image over the slit) or by recording the image through sequentially switched narrow-band spectral filters. The major disadvantages of the first approach are the connection between the spatial resolution and the spectral resolution (both are determined by the slit width), use of mechanical scanning systems, and the relatively long time period required for acquisition of hyperspectral images with sufficient spectral and spatial resolution [6][7][8][9][10][11][12]. In the second approach, when using a set of mechanically switched filters, the spectral resolution is usually low, and the use of tunable filters (optoacoustic, electro-optic, interference polarization) does not provide fast response and lets us work only with small aperture angles [13].Development is underway for alternative approaches potentially promising gains in aperture and HSI acquisition time as a result of a multiplex approach and based on the principles of Fourier transform spectroscopy [14,15]. However, at this time the instrumentation cannot compete with traditional types of hyperspectrometers.The use of modern spatial light modulators (SLMs), permitting real-time control of the configuration of the entrance aperture of the imaging spectrometer, is promising for development of new types of hyperspectrometers [16]. The indicated approach has advantages such as the possibility of fast readjustment for operation in different modes, simple realization of the mode with electronically controllable scanning of the entrance slit formed ...