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A silicon-based photodetector containing two identical n+–p-photodiodes is described. One of the photodiodes had a wide spectral response with high sensitivity in the ultraviolet region. The sensitivity of the second was reduced in the short-wavelength part of the spectrum by creating additional recombination centers in the near-surface region by implanting As ions. The spectral sensitivity of the differential signal obtained by subtracting photocurrents had a pronounced short-wavelength characteristic. The long-wavelength limit of the spectral range in terms of the λ0.5 level, depending on the doping dose, was in the range of 0.37–0.47 μm. The sensitivity maximum corresponded to λmax = 0.32–0.37 μm. The electrical and noise characteristics of the photodetector are given. The possibility of using differential photodetectors as two-color ones is shown. [ABSTRACT FROM AUTHOR]

Crosslinked polysiloxanes with boron bis(dibenzoylmethanate) complexes used as crosslink junctions of polymer networks are first synthesized, and their physicochemical, mechanical, thermal, and fluorescent properties are studied. It is shown that the polymers under study feature the elastic behavior, possess high thermal and thermo-oxidative stability, and exhibit intense fluorescence in a wide wavelength range (400‒700 nm). [ABSTRACT FROM AUTHOR]

The photophysical properties of functional distyryl derivatives of dipyrrometheneboron difluoride (BODIPY) in various solvents have been studied. It was shown that in all solvents, the studied compounds have similar absorption and fluorescence spectra, which are characteristic of the distyryl derivatives of BODIPY. Small bathochromic shifts of the spectra with increasing solvent polarity, as well as insignificant changes in the rate constants of radiative and nonradiative processes, provide evidence that the S1 states are of the (π,π*) type. These dyes can be used to visualize processes in living systems. [ABSTRACT FROM AUTHOR]

An herbal formulation of a multiphytoadaptogen (MPA) developed at the N. N. Blokhin Cancer Center and containing phytocomponents from Oplopanax elatus Nakai has been studied in preclinical and clinical trials for preventive oncology. Secondary metabolites were identified in the extract of rhizomes and roots of O. elatus and in the MPA pharmaceutical composition using high performance liquid chromatography-mass spectrometry (HPLC-MS/MS). Compounds identical to ginsenosides Rd and Re (tetracyclic triterpene saponins from Panax ginseng) and araloside C and stipuleanoside R2 (pentacyclic triterpene saponins, oleanolic acid derivatives, from Aralia mandshurica) were identified in the MPA and in the extract of rhizomes and roots of O. elatus. The spectra of biological activity of ginsenosides Rd and Re, araloside C, and stipuleanoside R2 were analyzed in silico using the PASS computer program. According to published data and in silico analysis, the activities of ginsenosides Rd and Re, araloside C, and stipuleanoside R2 correspond to properties previously confirmed in the MPA studies for preventive oncology. [ABSTRACT FROM AUTHOR]

Long-lived delayed fluorescence of dispersions of microcrystals of naphthalene–β-cyclodextrin–cyclohexane ternary complexes has been studied. It has been established that the delayed fluorescence is due to the T–T annihilation process. The kinetics of delayed fluorescence has a nonexponential character; the average lifetime is 0.68 s. The shape of the decay rate curves of delayed fluorescence does not depend on the intensity of excitation light. The nonexponential nature of the delayed fluorescence is presumably associated with the presence in the crystals of paired naphthalene molecules with different mutual positions and pair formation energies. [ABSTRACT FROM AUTHOR]

The major bioactive constituents in extracts from roots of Eleutherococcus senticosus (Rupr. & Maxim) (Araliaceae) and in a multi-adaptogen herbal formulation (Multiphytoadaptogen) were analyzed using high-performance liquid chromatography (HPLC) in combination with tandem mass spectrometry. Chromatography was performed on an ACQUITY UPLC BEH C18 column in gradient mode. A TSQ Vantage triple quadrupole mass spectrometer with electrospray ionization was used for the analysis. Eleutherosides B (syringin, a phenylpropanoid) and E (syringaresinol diglucoside, a lignan) were identified in both the multi-adaptogen herbal formulation and E. senticosus root extract. The results could be used for standardization and quality testing of herbal formulations including eleutherosides B and E and for justification of the biological action of Multiphytoadaptogen and studies of its new properties considering the identified bioactive constituents. The probable mechanisms of the antitumor and additive/synergistic effects of eleutherosides B and E were established by in silico analysis of their biological activity profiles. [ABSTRACT FROM AUTHOR]

Tandem mass spectrometry (HPLC-MS/MS) was used to analyze biologically active compounds in extracts of the tuber and roots of Rhodiola rosea (family Crassulaceae) and in the pharmaceutical formulation Multiphytoadaptogen (MPA). Chromatography was run on Acquity UPLC BEH C18 columns with gradient elution. A TSQ Vantage ternary quadrupole mass spectrometer with electrospray ionization was used. MPA, like the Rhodiola rosea tuber/root extract, was found to contain salidroside, rosavin, rosarin, rosiridin, and rhodionin. These results can be used for standardization, identification, and quality control of phytocomplexes containing these Rhodiola rosea compounds to identify grounds for the mechanisms of the biological actions of MPA and studying its novel properties, taking account of the components identified. The PASS computer program was used for in silico evaluation of the spectra of the antitumor activities of these compounds. Antitumor effects were predicted with high probability for all five phytocomponents; the specific characteristic of the actions of individual compounds suggested that combinations might be used for treating a wide spectrum of malignant neoplasms. [ABSTRACT FROM AUTHOR]

This review considers the main stages in the development of fluorescent chemosensor materials performed at the Photochemistry Center of the Russian Academy of Sciences over the past 15 years. Systems based on original acridine dyes synthesized at the Photochemistry Center and well-known fluorescent dyes and fluorophores of the family of boron difluoride diketonates are described. Polymer films and microparticles and silica micro- and nanoparticles have been studied as solid-state matrices for chemosensors. [ABSTRACT FROM AUTHOR]

The luminescent chemosensor properties of Eu(III) dibenzoylmethanate with caproic acid have been revealed. It has been shown that the interaction of the Eu(III) chelate with ammonia vapor leads to an increase in the luminescence intensity of the complex. The experimentally determined limit of detection for ammonia was 3 ppm. The reversibility of the optical response has been established. The resulting chemosensor composition with the luminescence switching effect under the action of the analyte is promising for environmental monitoring. [ABSTRACT FROM AUTHOR]

The priority direction of the pharmaceutical composition Phytoladaptogene (PLA) development based on the prediction of biological activity spectra for several secondary metabolites of medicinal plants using the PASS computer program and validation in vitro of the prediction result was determined. PLA is a complex of structurally diverse small organic compounds including biologically active substances of phytoadaptogenes (ginsenosides from Panax ginseng, rhodionin from Rhodiola rosea and others) compiled considering previously developed pharmaceutical compositions. Two variants of the pharmaceutical composition were studied—major (22 compounds) and minor (13 compounds) ones. The probability of activity exceeds the probability of inactivity for 1400 out of 1945 pharmacological effects and mechanisms predicted by PASS for the major version of PLA. The wide range of predicted activities is mainly due to the compounds' low structural similarity to each other. An in silico prediction indicates the possibilities of antitumor properties against bladder, stomach, colon, ovarian and cervical cancers both for minor and major PLA compositions. It was found that the highest probability values of activity are predicted for three mechanisms: Apoptosis agonist, Caspase 3 stimulant, and Transcription factor NF kappa B inhibitor. According to the PharmaExpert program, they are associated with the antitumor effect against bladder cancer. Experimental validation was performed in vitro on the human bladder cancer cell line RT-112. As a result of the MTT test the cytotoxicity of the PLA major variant was found to be higher than that of the minor one. In the in vitro experiments using two methods—double staining with annexin V and propidium iodide as well as detection of active caspase 3 in cells—the death of bladder cancer cells by the apoptosis mechanism was also confirmed. The data obtained correspond to the results of the prediction and indicate the major PLA composition advantages. Phytoladaptogene can become the basis for the development of a drug with antitumor activity against bladder cancer. Antitumor activity predicted by PASS for other cancers may be the subject of further studies. [ABSTRACT FROM AUTHOR]

The basic photophysical characteristics and the hydrolytic stability and photostability of dibenzoylmethanatoboron complexes containing various substituents at the boron atom have been studied. It has been found that the hydrolytic stability of these complexes increases in the order DBMBO < DBMBF2 < DBMB(C6F5)2. The rate constants of the hydrolysis reaction and the energy (EA), enthalpy (ΔH≠), and entropy (ΔS≠) of activation have been calculated from the data obtained. The study of the photostability of boron complexes of dibenzoylmethane showed that the photodegradation of these compounds in acetonitrile increases in the order DBMBF2 < DBMBO < DBMB(C6F5)2 and correlates with the change in ΔH≠ of hydrolysis. [ABSTRACT FROM AUTHOR]

Phytochemical analysis of cloudberry leaves isolated one new (1) and four well-known compounds (2-5) and established their structures. Compounds 1 (4-O-α-L-arabinofuranosylellagic acid) and 2 [(–)-epicatechin] belonged to the tannin class. The rest of the isolated compounds were the flavonoid glucuronic glycosides quercetin 3-O-β-D-glucuronide (3), quercetin 3-O-β-D-2′′-galloylglucuronide (4), and kaempferol 3-O-β-D-glucuronide (5). Compounds 4 and 5 were isolated from Rubus chamaemorus L. for the first time. Predictions of the biological activity spectra for isolated 1-5 using the PASS program provided insights regarding the most promising directions for studying their biological activity. [ABSTRACT FROM AUTHOR]

An investigation has been performed of 1.55-μm vertical-cavity surface-emitting lasers based on heterostructures with a buried tunnel junction (BTJ) with a height difference of 15 nm. The devices are obtained by wafer fusion of heterostructures grown by molecular beam epitaxy and provide single-mode lasing at a BTJ diameter of up to 8 μm. A decrease in the BTJ size leads to a sharp increase in the threshold current, the output optical power, and the resonance frequency at the lasing threshold. Stable single-mode lasing takes place due to the smoothed boundary of the buried surface relief, which induces a gradual change in the profile of the effective refractive index in the lateral direction with the effective current confinement retained. This makes it possible to reduce significantly the transverse optical confinement factor for the higher-order modes even at a large BTJ size. However, at a small BTJ size, it leads to the formation of a saturable absorber in unpumped parts of the active region. [ABSTRACT FROM AUTHOR]

The results are presented of a study and optimization of the conditions under which heterointerfaces of the GaAs–InGaAsP type are formed via the direct intermolecular wafer bonding (fusion) of a heterostructure of an active region on an InP substrate and distributed Bragg reflectors on GaAs substrates upon the fabrication of hybrid heterostructures for long-wavelength vertical-cavity surface-emitting lasers (VCSELs). The heterostructures are grown by solid-source molecular-beam epitaxy. It is shown that, in the case of the incomplete removal of oxide films during preparation of the wafers before fusion and/or in the presence of adsorbed water on the wafer surfaces, the fused interface contains a large number of amorphous inclusions, which are most likely oxides of Group-III elements. Optimization of the conditions in which a buried tunnel junction is formed on the surface of the heterostructure on an InP wafer made it possible to reduce the surface roughness to 1 nm and to ensure that the thickness of the GaAs–InGaAsP fused interface does not exceed 5 nm, with no dislocations or other extended defects found at the fused heterointerfaces. The 1.55-μm VCSELs fabricated from the hybrid heterostructures created using the developed technology demonstrate efficient lasing under continuous-wave pumping in a wide temperature range, which is indicative of the high optical quality of the fused heterointerfaces in the VCSEL structure. [ABSTRACT FROM AUTHOR]

A design of a tunnel junction (TJ) based on n++-InGaAs/p++-InGaAs/p++-InAlGaAs layers for vertical-cavity surface-emission lasers (VCSELs) for the 1.55-μm spectral range fabricated by wafer fusion of an InAlGaAsP/InP optical cavity and wafers with AlGaAs/GaAs distributed Bragg reflectors has been suggested and tested. The presence of the oxidation-resistant InGaAs layers makes it possible to employ the molecular-beam epitaxy in all stages of the fabrication technology of VCSELs, including the overgrowth of the surface profile in the TJ layer. Owing to the Burstein–Moss effect and to the thickness minimization of the p++-InGaAs layer, it was possible to avoid a buildup of the internal optical loss. As a result, the characteristics of the thus fabricated devices are comparable with those of VCSELs having an n++-/p++-InAlGaAs TJ and a similar level of the mirror losses. [ABSTRACT FROM AUTHOR]

Studies of the characteristics of ohmic contacts to epitaxial and ion-doped gallium-nitride layers, based on the Cr/Pt/Au metallization system, are reported. The possibility of forming low-resistance contacts without the application of high-temperature treatment is shown. It is demonstrated, for AlGaN/GaN-based heterostructures, that the characteristics of Ti/Al/Ni/Au ohmic contacts are improved upon using ion implantation through a silicon-dioxide mask. [ABSTRACT FROM AUTHOR]

An experimental complex is described for conducting high-performance screening of the functional characteristics of photoluminescent chemosensor materials (CSMs) intended for determining volatile organic compounds in the gas phase and optimizing the characteristics of matrix sensors based on CSMs in multicomponent vapor-gas mixtures. The complex combines a system for the continuous generation of multicomponent gas-vapor mixtures, which allows automated control of the composition of the mixture and the concentration of its components in the range from 0.01 mg/m3 to saturated vapors, and a system for exciting and recording the photoluminescence spectra of samples. The experimental data obtained in the study of fluorescent responses of a set of CSM based on boron dibenzoylmethanatoboron difluoride (DBMBF2) in mixtures of aromatic substances. [ABSTRACT FROM AUTHOR]

An active area based on InGaAs/InGaAlAs superlattice for laser diodes operating in the spectral range between 1535 and 1565 nm is proposed and realized practically. It is demonstrated that using a superlattice increases the mode gain at the same values of the pump-diode current density relative to a typical active-area design based on an array of InGaAs quantum wells. [ABSTRACT FROM AUTHOR]

Phosphor polymers that exhibit luminescence in the blue region of the spectrum are produced by impregnating thermoplastic polymers with neodymium(III) acetylacetonate in a supercritical carbon dioxide medium. The spectral characteristics of the prepared systems are studied, and an interpretation of the observed change in the nature of luminescence is proposed. [ABSTRACT FROM AUTHOR]

The results of studying the dynamic characteristics of 1.55-μm single-mode vertical-cavity surface-emitting lasers (VCSELs) formed by the fusion of wafers of high-quality Bragg reflectors and an active region based on thin highly strained InGaAs/InAlGaAs quantum wells are presented. It is found that the proposed design of the active region and optical microcavity of the laser make it possible in principle to attain a high level of differential laser gain in the temperature range of 20°C–85°C, but weak electron localization leads to an increase in gain compression at elevated temperatures. Due to this fact, the VCSEL modulation bandwidth at 20°C can be increased from 9.2 to 11.5 GHz due to an increase in output optical losses, while the modulation bandwidth at 85°C does not exceed 8.5 GHz, depends weakly on the output optical losses, and is mainly limited by the optical-gain saturation. [ABSTRACT FROM AUTHOR]

Molecular beam epitaxy techniques were used to grow a quantum-cascade laser (QCL) heterostructure based on an In0.53Ga0.47As/Al0.48In0.52As heteropair lattice-matched with an InP substrate. InP layers were used to form an optical waveguide. The obtained QCL heterostructure ensured room-temperature lasing in the 8-μm wavelength range at a maximum output optical power of 0.45 W from one facet in a standard ridge geometry of the Fabry–Pérot cavities formed by cleaved facets. [ABSTRACT FROM AUTHOR]

The results of a study of internal optical losses and current injection efficiency in vertical-emitting lasers of a spectral range of 1.55 µm obtained by sintering plates of high-q Bragg reflectors and the active region on the basis of thin strained InGaAs/InAlGaAs quantum wells have been presented. It has been shown that the proposed design of the laser provides a record low level of internal optical losses (less than 6.5 cm–1) and high efficiency of current injection (more than 90%) at room temperature, which allows the realization of submilliampere threshold currents. As the temperature rises to 85°C, the current injection efficiency drops to 70% due to the thermal emission of charge carriers from the active region, accompanied by an increase in internal optical losses to 9.1 cm–1 because of an increase in absorption on free carriers and/or intersubband absorption in the valence band. [ABSTRACT FROM AUTHOR]

Abstract: It has been shown that the introduction of electron-donating or electron-withdrawing groups in the para-position of dibenzoylmethanatoboron difluoride (DBMBF2) makes it possible to control the fluorescenсe characteristics of fluorophore exciplexes with methylbenzenes (MB). The fluorescent properties of DBMBF2/MB exciplexes at the gas-solid interface have been studied using the example of DBMBF2 adsorbed on the surface of trimethylsilylated aerosil. [ABSTRACT FROM AUTHOR]

Results of investigation of 1550 nm range stripe semiconductor lasers fabricated from heterostructures with different designs of the gain medium are presented. It is shown that the proposed designs of the gain medium allow obtaining the effective lasing at high level of total optical losses, comparable with the typical optical losses in the vertical-cavity surface-emitting lasers. The evaluation of modal gain in different types of the gain mediummade it possible to estimate the possible frequencies of the small-signal modulation of vertically emitting lasers and proposed the ways to increase them up to 20 GHz or more. [ABSTRACT FROM AUTHOR]

The results of studies on fabrication of vertical-cavity surface-emitting 1.55-µm lasers by fusing AlGaAs/GaAs distributed-Bragg-reflector wafers and an active region based on thin In0.74Ga0.26As quantum wells grown by molecular-beam epitaxy are presented. Lasers with a current aperture diameter of 8 µm exhibit continuous lasing with a threshold current below 1.5 mA, an output optical power of 6 mW, and an efficiency of approximately 22%. Single-mode lasing with a side-mode suppression ratio of 40-45 dB is observed in the entire operating current range. The effective modulation frequency of these lasers is as high as 9 GHz and is limited by the low parasitic cutoff frequency and self-heating. [ABSTRACT FROM AUTHOR]

Silica nanoparticles (SNPs) with a diameter of 100 nm and surface-modified by covalently linked dibenzoylmethanatoboron difluoride have been synthesized and characterized. Suspensions of SNPs in dichloroethane are used as ink suitable for the microvalve ink-jet printing of sensing layers. It is demonstrated that SNP-based thin films are sensitive for methylbenzene vapors and could be a good candidate as a printed sensor. Responses of sensing films to methylbenzene vapors are analyzed using multivariate nonlinear regression. [ABSTRACT FROM AUTHOR]

Single-mode lasing at room temperature in quantum-cascade lasers (QCLs) with arched cavity design has been demonstrated. The output optical power in single-mode lasing regime at ~7.7-μm lasing wavelength was above 6 mW with a side-mode suppression ratio of up to 25 dB. The QCL heterostructure for the arched cavities was grown by molecular-beam epitaxy (MBE) based on a heterojunction of In0.53Ga0.47As/Al0.48In0.52As solid alloys, lattice-matched with InP substrate, and InP layers performing the function of waveguide claddings. [ABSTRACT FROM AUTHOR]

It has been shown that fluorescence quenching of 2,7-dimethyl- N,N-di- p-tolylacridine-9-amine (9-DTAA) solutions in hexane and acetone by tetrabromomethane (TBM) was dynamic in nature with the quenching rate constants of 1.5 × 10 and 0.6 × 10 Ms, respectively. The difference in the constants was explained by the possibility of competition between the processes of the formation of solvation shell around the excited singlet 9-DTAA* molecule and the formation of the 9-DTAA*/TBM encounter complex. [ABSTRACT FROM AUTHOR]

10.1134/S0030400X18080143 [ABSTRACT FROM AUTHOR]

The name of the seventh author should read L. Ya. Karachinsky. [ABSTRACT FROM AUTHOR]