In this paper, CaGa2S4:3%Nd,5%Yb; CaGa2S4:5%Yb; CaGa2S4:3%Nd compounds were synthesized, and their photoluminescence (PL) spectra, PL excitation (PLE) spectra and PL decay properties were studied at room temperature under one-photon and multi-photon excitation in a wide range of excitation intensities. The synthesis of the CaGa2S4 compound was carried out by a solid-phase reaction of a stoichiometric mixture of CaS and Ga2S3 powders in a quartz ampoule. Yb and Nd doping was carried out during the synthesis process using YbF3 and NdF3. PLE spectra were studied in the wavelength range from 250 to 850 nm, and PL spectra in the range of 400-1500 nm. It has been shown that after introducing Yb3+ ions into thiogallate crystals with Nd3+ ions, a new band near 488 nm is formed and the PL intensity increases by 1-2 orders of magnitude. The anti-Stokes PL spectra of CaGa2S4: Nd, Yb crystals in the visible region of the spectrum (400-700 nm) were studied when excited by continuous wave laser radiation with a wavelength of 975 nm. The kinetics of PL decay of all types of compounds at different wavelengths of single- and multi-photon excitation were determined. Depending on the PLE conditions, wavelength and intensity of the exciting radiation, monoexponential and non-monoexponential decay kinetics were observed with decay times in the range of 20-90 mu s. Possible mechanisms of PLE and PL of CaGa2S4 crystals doped with neodymium and ytterbium ions are discussed.

Spectral luminescence, kinetic and energetic properties of hexachlorosubphthalocyaninatoboron(III) chloride and its azaanalogue containing fused pyrazine fragments instead of benzene rings were studied at 298 and 77 K. Weak phosphorescence of complexes was detected and characterized in near-infrared region of spectrum, its parameters depend substantially on the presence of methyl iodide due to its external effect of heavy atom in solutions. Quantum yields of photosensitized formation of singlet oxygen were determined by the relative luminescence method.

The luminescent and photophysical properties of the etioporphyrin-I complex with indium(III) chloride, InCl-EtioP-I were experimentally studied at room and liquid nitrogen temperatures in pure and mixed toluene solutions. At 77 K, in a 1:2 mixture of toluene with diethyl ether, the quantum yield of phosphorescence reaches 10.2%, while the duration of phosphorescence is 17 ms. At these conditions, the ratio of phosphorescence-to-fluorescence integral intensities is equal to 26.1, which is the highest for complexes of this type. At 298 K, the quantum yield of the singlet oxygen generation is maximal in pure toluene (81%). Quantum-chemical calculations of absorption and fluorescence spectra at temperatures of 77 K and 298 K qualitatively coincide with the experimental data. The InCl-EtioP-I compound will further be used as a photoresponsive material in thin-film optoelectronic devices.

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

Luminescence spectra of several polarity indicators, including Coumarin 153 and coronene that were previously studied at room temperature and Nile Red and Pigment Red 179, were recorded at 20 and 120°C in solutions of liquid stationary phases of various polarities. The effect of temperature on the spectral parameters sensitive to the stationary phase polarity was estimated for these indicators. The prospects for estimating the polarity of stationary liquid phases using luminescent methods at high temperatures was demonstrated.

The estimation of the applicability and the choice of the scale of quantitative one-parameter evaluation of the polarity of stationary liquid phases were carried out for gas-liquid chromatography. The absorption and luminescence spectra of five indicators including coumarin 153, coumarin 314, coronene, 4-dicyanomethylene-2-methyl-6-[4-(di-methylamino)-styryl]-4H-pyran (DCM), 3-aminophthalimide have been obtainned in solvents of different polarity at room temperature. The dependence of the wavelength of the fluorescence and absorption maxima on the polarity of the medium was evaluated. Various spectroscopic polarity scales are compared. The fluorescent coronene scale has been shown to be the most appropriate. This scale was used to assess the polarity of some widespread phases (squalane, polydimethylsiloxane liquid PMS-100, 3,3'-oxydipropionitrile, 2-ethyl-hexylsebacinate, etc.) for gas-liquid chromatography. This approach has been shown to be promising for preliminary selection of chromatographic stationary phases.

The applicability of stationary liquid phases for gas–liquid chromatography was evaluated. The scale for quantitative one-parameter estimation of their polarity was chosen. Absorption and luminescence spectra of the five indicators coumarin 153, coumarin 314, coronene, 4-dicyanomethylene-2-methyl-6-[4-(dimethylamino)styryl]-4H-pyran (DCM), and 3-aminophthalimide in solvents of different polarity were obtained at room temperature. The dependence of the fluorescence and absorption maxima wavelengths on the medium polarity was evaluated. Various spectroscopic polarity scales were compared to show that the coronene fluorescence scale was most appropriate. This scale was used to assess the polarity of some widespread phases (squalane, polydimethylsiloxane PMS-100, 3,3′-oxydipropionitrile, 2-ethylhexylsebacate, etc.) for gas-liquid chromatography. This approach was shown to be promising for preliminary selection of chromatographic stationary phases.

Методами квантовой химии исследованы спектрально-люминесцентные свойства заряженных (анионной и катионной) форм трех замещенных бензальдегидов, проявляющих биологическую активность: o-анисового (2-метоксибензальдегид) и сиреневого (3,5-диметокси-4-гидроксибензальдегид) бензальдегидов и ванилина (3-метокси-4-гидроксибензальдегид). Расчеты показали, что в случае заряженных форм исследуемых молекул состояние S1 в отличие от нейтральных форм является состоянием ππ*-типа и по своей локализации аналогично S2 (ππ*)-состоянию нейтральных молекул (анисового альдегида и ванилина) или S3 (ππ*)-состоянию сиреневого бензальдегида. По результатам расчета показано, что в области спектра 240-420 nm нет новых электронных переходов, формирующих полосы поглощения в спектре, отличающиеся по природе и локализации от электронных переходов нейтральных молекул. Рассчитанные характеристики флуоресценции заряженных форм исследованных молекул показали, что в отличие от нейтральных форм эффективность радиационного распада заряженных форм много выше, что связано с изменением орбитальной природы состояния S1 при переходе от нейтральной к заряженной форме. Согласно анализу расчетных и экспериментальных данных флуоресценции исследуемых замещенных бензальдегидов в спиртовых растворах, флуоресценция на 410 nm принадлежит катионным формам. В ванилине и сиреневом альдегиде также имеется возможность слабой флуоресценции анионных форм этих соединений. Ключевые слова: замещенные бензальдегиды, спектрально-люминесцентные свойства, методы квантовой химии.

The phosphorescence of three new palladium and three platinum complexes of benzo-fused hydroporphyrazines—analogues of phthalocyanine, in which molecule one or two isoindole fragments are replaced by a hydrogenated pyrrole ring which gives macrocycles of the type of chlorin, bacteriochlorin, and isobacteriochlorin—analogues of photosynthetic pigments, is studied in the near-IR range under stationary lamp excitation. The phosphorescence spectra of the complexes of trans-dibenzotetrahydroporphyrazines are recorded for the first time (for both platinum and palladium) which could not be found for a long time because of the unprecedented remoteness of the 0–0 bands from the visible region (1.67, 1.52 µm for Pd, Pt) as well as because of the low quantum yield of phosphorescence. The fluorescence of these complexes in the near-IR range is found as well. The approximate additivity of the action of the structural factors—hydrogenation of the pyrrole rings, aza-substitution, and benzo-substitution—on the energy of the lowest triplet state T1 is shown based on the comparison of the experimental results with the own and published data for palladium complexes of the tetrapyrrole series. The obtained information is substantial for the targeted creation of emitters in the near-IR range (1.0–1.7 µm).

Phosphorescence in the near-IR range under stationary lamp excitation was studied of three palladium and three platinum complexes of benzocondensed hydroporphyrazine phthalocyanine analogues in which molecule one or two isoindole fragments are replaced by a hydrogenated pyrrole ring, giving macrocycles of photosynthetic pigments analogues of chlorin, bacteriochlorin and isobacteriochlorin types. For the first time, the phosphorescence spectra of trans-dibenzotetrahydroporphyrazines (for both platinum and palladium) have been registered, which detection failed during long time due to the record removal of 0-0 bands from the visible area (1.67 and 1.52 µm for Pd and Pt), and also because of the small quantum yield of phosphorescence. The fluorescence of these complexes was also detected.in the near-IR range. On the basis of comparison of experimental results with own and literature data for palladium complexes of a number of tetrapyrroles is shown the approximate additivity of the influence of structural factors — hydrogenation of pyrrole rings, aza- and benzo substitution — on the energy of the lower triplet state T1. The information obtained is essential for targeted creation of emitters in the near-IR range (1.0-1.7 µm).

The spectral-luminescent properties of the charged (anionic and cationic) forms of three biologically active substituted benzaldehydes, namely, o-anisaldehyde (2-methoxybenzaldehyde), syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde), and vanillin (3-methoxy-4-hydroxybenzaldehyde), are studied by quantum-chemical methods. Calculations show that the S1 state of the charged forms of the studied molecules, in contrast to the neutral forms, is of the ππ* type, and its localization is similar to the localization of the S2 (ππ*) state of the neutral molecules (anisaldehyde and vanillin) or of the S3 (ππ*) state of syringaldehyde. According to the calculation results, the spectral range of 240–420 nm contains no new absorption bands corresponding to electronic transitions differing in nature and localization from the electronic transition of the neutral molecules. The calculated fluorescence characteristics of the charged forms of the studied molecules show that the radiative decay rate of the charged forms is considerably higher than that of the neutral forms, which is related to the different orbital nature of the S1 state in the neutral and charged forms. Analysis of the calculated and experimental data on the fluorescence of the studied substituted benzaldehydes in alcohol solutions reveals that the fluorescence at 410 nm belongs to the cationic forms. Vanillin and syringaldehyde may also exhibit weak fluorescence of their anionic forms.

Substituted benzaldehydes, which are widespread in nature, exhibit antibacterial, anti-inflammatory, antiviral, and anticarcinogenic activity with low toxicity, which makes them promising in medicine. The results of an experimental and theoretical study of the spectral-luminescent properties of four neutral forms of hydroxy- and methoxy-substituted benzaldehydes are presented. The absorption spectra of the studied compounds in hexane and ethanol were obtained. The spectra of fluorescence and fluorescence excitation of the substances in ethanol solutions were measured. Based on quantum chemical calculations, the orbital nature of electronic transitions, the features of the electron density distribution upon excitation, and changes in the structure of the compound are determined and the rate constants of photophysical processes are estimated. According to calculations, in all the compounds studied, the S 1 state is formed by the n π* transition and the intensity of the long-wavelength bands in these compounds is formed by one or two ππ* transitions. The fluorescence quantum yield is estimated from experimental and theoretical data. The results of analysis and comparison of experimental data with the results of quantum chemical calculations allow a conclusion that the neutral forms of the studied substituted benzaldehydes are not responsible for the fluorescence observed in experiments with ethanol solutions.

Fluorescent silver nanoclusters immobilized on a plastic substrate are obtained by photoinduced template synthesis using polyacrylic acid chemically grafted to the substrate surface as a template. The electronic absorption and fluorescence spectra of nanoclusters are studied depending on the polyacrylic acid grafting density. It is found that the optical absorption and fluorescence intensities of nanoclusters monotonically increase with increasing grafting density. The position and shape of the absorption and emission spectra almost do not change. The higher the polymer template grafting density, the higher the fluorescence stability of samples during storage at room temperature.

New high efficiency luminescence films that convert UV radiation in a wavelength range of 220–410 nm into the europium ion luminescence are first obtained using a supramolecular diamond-containing complex of europium(III) with bathophenanthroline. The films allow the degree of radiation monochromaticity to be tuned at the main band of Eu3+ ions, centered at 615 nm. The excitation spectrum profile, as well as the half-width of the main emission band at 615 nm (a 5D0–7F2 transition) and the quantum yield values (in a range of ~0.3–0.8), is found to depend on the type of matrix material. The optical materials presented in the present work are promising candidates for the design of various light-emitting devices, such as screens, indicators, solar concentrators, organic LEDs, and laser media.

AbstractFluorescent silver nanoclusters immobilized on a plastic substrate are obtained by photoinduced template synthesis using polyacrylic acid chemically grafted to the substrate surface as a template. The electronic absorption and fluorescence spectra of nanoclusters are studied depending on the polyacrylic acid grafting density. It is found that the optical absorption and fluorescence intensities of nanoclusters monotonically increase with increasing grafting density. The position and shape of the absorption and emission spectra almost do not change. The higher the polymer template grafting density, the higher the fluorescence stability of samples during storage at room temperature.

Substituted benzaldehydes widely distributed in nature exhibit antibacterial, anti-inflammatory, antiviral, anti-carcinogenic activity with low toxicity, which make their promising in medicine. The results of an experimental and theoretical study of the spectral-luminescent properties of four neutral forms of hydroxy- and methoxy-substituted benzaldehydes are presented. The absorption spectra of the studied compounds were obtained in hexane and ethanol. Measurements of fluorescence spectra and fluorescence excitation of solutions were carried out in ethanol. Based on quantum chemical calculations, the orbital nature of electronic transitions, the features of the electron density distribution upon excitation and changes in the structure of the compound are determined and the rate constants of photophysical processes are estimated. According to calculations, for all compounds studied, the S1 state is formed by the nπ-type transition, and the intensity of the long-wavelength bands in these compounds is formed by one or two ππ-transitions. The fluorescence quantum yield values are estimated from experimental and theoretical data. As a result of the analysis and comparison of experimental data and the results of quantum chemical calculations it was concluded that the neutral forms of the studied substituted benzaldehydes are not responsible for the observed fluorescence in experiments with ethanol solutions.

For the first time, using the supramolecular diamond-containing europium (III) complex with bathophenanthroline, new luminescent films were obtained, converting UV radiation in the wavelength range of 220–410 nm with high efficiency to luminescence of europium ions, with the ability to control the degree of monochromaticity of radiation in the main emission band of Eu3+ ions with maximum of 615 nm. It was found that the shape of the excitation spectra, the half-width of the main emission band of 615 nm (transition 5D0–7F2), the values of quantum yields (within ~ 0.3–0.8) depend on the type of matrix material. The proposed optical materials can be used in the development of various light-emitting devices: screens, indicators, solar concentrators, organic light-emitting diodes, laser media.

Model studies on Coumarin 343–detonation nanodiamond complexes are described. The complexation of coumarin molecules with diamond nanoparticles due to covalent bonding leads to a considerable change in their spectral-luminescence properties, which makes it possible to distinguish between the behaviors of a free dye and a bound luminophore in the studied objects, in particular, in cell cultures. Experiments with an acute monocytic human leukemia culture show that the studied diamond nanocomplexes are easily captured by the cells and visualized in them; therefore, these complexes can be used to transport photocontrolled reagents and, ultimately, new drugs.

The possibility of formation of radiation defects with new luminescent properties is investigated in sodium and magnesium fluorides nanosized crystals. Nanocrystals obtained by mechanical fragmentation of the single crystals have been irradiated by gamma-rays at 77 K or electron beams at room temperature. Their TEM images have been received. Luminescence, luminescence excitation and absorption spectra of nanocrystals have been measured immediately after.-irradiation without samples defrosting and after termination of the defects aggregation processes at room temperature. The formation of radiation color centers with previously unknown optical characteristics has been discovered in nanocrystals. Numbers of anion vacancies and electrons entering into these centers composition were established in sodium fluoride. The structure transformation of the centers, containing two anion vacancies and an electron, was revealed after sodium fluoride samples defrosting. For sodium fluoride the data on the Huang-Rhys parameters and lifetimes of the photoluminescence for here studied and previously known centers of the same composition are determined and compared. The results obtained show that near-clusters color centers can be formed in crystals with different structures and atomic compositions.