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Now showing items 1 - 16 of 117744

  • Energy transfer from TPD to CdSe/CdS/ZnS colloidal nanocrystals

    Kurochkin, N. S.   Katsaba, A. V.   Ambrozevich, S. A.   Vitukhnovsky, A. G.   Vashchenko, A. A.   Tananaev, P. N.  

    The efficiency of electronic-excitation energy transfer from organic semiconductor TPD to CdSe/CdS/ZnS nanocrystals passivated with different organic ligands is investigated. It is shown that the rate of energy transfer from TPD to nanocrystals decreases with increasing thickness of the passivation coating. It is suggested that the Forster mechanism is responsible for the excitation transfer.
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  • Nonlinear optical response of planar and spherical CdSe nanocrystals

    Selyukov, A. S.   Isaev, A. A.   Vitukhnovsky, A. G.   Litvak, V. L.   Katsaba, A. V.   Korshunov, V. M.   Vasiliev, R. B.  

    The nonlinear optical response of a colloidal solution of planar CdSe semiconductor nanocrystals (nanoplatelets) is studied for the first time. The nonlinear optical response of these nanoparticles is compared to that of spherical CdSe nanocrystals (quantum dots). The photoinduced nonlinearity is attributed to the optical generation of long-lived charge carriers in the nanoobjects under study. It is shown that, upon the exposure of a cell with the solution of nanoparticles to focused continuous-wave (cw) laser radiation with a wavelength of 473 nm, the nonlinear optical responses of CdSe nanoplatelets and quantum dots are somewhat different at identical optical densities at the above-indicated wavelength. The differences are supposedly associated with a higher diffusion rate of spherical nanoparticles in the solution because of their smaller size compared to that of nanoplatelets.
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  • Hybrid organic–inorganic light emitting diodes

    Vitukhnovsky, A. G.   Vashchenko, A. A.   Vasiliev, R. B.  

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  • Picosecond time of spontaneous emission in plasmonic patch nanoantennas

    Eliseev, S. P.   Vitukhnovsky, A. G.   Chubich, D. A.   Kurochkin, N. S.   Sychev, V. V.   Marchenko, A. A.  

    A significant (to 12 ps) decrease in the lifetime of excited states of quantum emitters in the form of three-layer colloidal quantum dots (CdSe/CdS/ZnS) placed in an aluminum-triangular silver nanoprism cavity (patch nanoantenna) has been experimentally demonstrated. The decrease in the time of spontaneous emission of quantum dots has been explained by the Purcell effect. The Purcell coefficient for an emitter in the resonator has been found to be 625. Such a significant increase in the rate of spontaneous emission in the patch nanoantenna is due to an increase in the local density of photon states in the plasmonic cavity.
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  • Effect of Bonding Scandium(III) ion to 1,3-Diketones on Their Luminescent Properties

    Vitukhnovsky, A. G.   Ambrozevich, S. A.   Korshunov, V. M.   Taydakov, I. V.   Metlin, M. T.   Selyukov, A. S.  

    We study the influence of bonding Sc(III) ion with 1,3-diketonate ligands on luminescent properties of 1,3-diketones in two complexes by means of optical spectroscopy. We show that the sensitization of the ligand luminescence of the complexes obtained increases from 0.8% for neat ligands and to 4% for the synthesized compounds; this fact is confirmed by the quantum yield measurements.
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  • Effect of Bonding Scandium(III) ion to 1,3-Diketones on Their Luminescent Properties

    Vitukhnovsky, A. G.   Ambrozevich, S. A.   Korshunov, V. M.   Taydakov, I. V.   Metlin, M. T.   Selyukov, A. S.  

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  • Surface states effect on photoluminescence of CdS colloidal nanocrystals

    Katsaba, A. V.   Ambrozevich, S. A.   Vitukhnovsky, A. G.   Fedyanin, V. V.   Lobanov, A. N.   Krivobok, V. S.   Vasiliev, R. B.   Samatov, G.  

    CdS colloidal nanocrystals with an average size of 4.5 nm and oleic acid as surfactant were studied using photoluminescence spectroscopy and time-correlated single photon counting technique at different temperatures. Observed spectra revealed three thermally activated luminescence bands at 2.15, 1.76, and 1.37 eV in addition to conventional band edge recombination of the nanocrystals. We present a kinetic model based on concept of single emitters which quantitatively describes the luminescence of the ensemble of the nanocrystals in the temperature range 10-300 K. We determined activation energies (18.2 and 8.6 meV) for transitions responsible for the luminescence. The 1.76 eV band most probably emerges from the intrinsic defects on the surface of CdS, whereas bands at 2.15 and 1.37 eV result from the influence of oleic acid bonded to the surface of the nanocrystals. (C) 2013 AIP Publishing LLC.
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  • Electrical conductivity and luminescence of metal-organic nanocomposites

    Chubich, D. A.   Fedorovich, R. D.   Vitukhnovsky, A. G.  

    We presented the results of experimental study of electrical and luminescence properties of planar nanocomposites based on gold island films and layers of efficient organic luminophores - aluminum (III) 8-hydroxyquinolinate (Alq(3)) and europium beta-diketonates [Eu(DBM)(3) bath, Eu(DBM)(3) phen, and Eu(DBM)(3)]. The mechanisms of electroluminescence of such hybrid systems are discussed and the processes of luminescence excitation in the organic component of nanocomposites are considered in detail. It is shown that the spectral characteristics of europium beta-diketonates are controlled by the Eu3+ ion fluorescence. The proposed mechanisms of nanocomposite electroluminescence are confirmed by the results of measurements of cathodoluminescence spectra of organic luminophores.
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  • Two-Wave Laser Stereolithography for Fabrication of IR Sensors for Surface-Enhanced Spectroscopy

    Vitukhnovsky, A. G.   Zvagelsky, R. D.   Kolymagin, D. A.   Pisarenko, A. V.   Chubich, D. A.  

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  • Absorption properties of the composite silver/dye nanoparticles in colloidal solutions

    Lebedev, V. S.   Vitukhnovsky, A. G.   Yoshida, A.   Kometani, N.   Yonezawa, Y.  

    The results of the experimental and theoretical studies of the optical absorption properties of the composite metal/organic nanoparticles in colloidal solutions are reported. The nanoparticles consist of Ag-core coated with the J-aggregate of 3,3 '-disulfopropyl-5,5 '-dichlorothiacyanine sodium salt (TC). The absorption spectrum of the composite Ag/TC nanoparticles exhibits two peaks at lambda = 395 and 480 nm, which originally come from the localized surface plasmon resonance of Ag nanoparticles and the electronic excitation of TC-dye, respectively. To explain the results obtained we calculate the extinction cross-section of such composite material on the basis of a model for the polarizability of two concentric spheres by taking into account complex frequency-dependent dielectric functions of Ag and the TC-dye and size-dependent effects. The model provides a good description of the main features in the measured absorbance. It is shown that for the core-shell nanoparticles under investigation the peak positions and their intensities are strongly dependent on their geometrical size and the thickness of the J-aggregate coating. This opens a possibility to controllable driving of the absorption properties of such composite materials. (c) 2008 Elsevier B.V. All rights reserved.
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  • ABSORPTION SPECTRA SIMULATION OF PERSISTENCE-TYPE CYANINE DYE AGGREGATES IN LB FILMS

    VITUKHNOVSKY, A. G.   LOBANOV, A. N.   PIMENOV, A. V.   YONEZAWA, Y.   KOMETANI, N.  

    Simulation of the absorption spectra of the 2D persistence-type molecular aggregates consisting of the combination of oxacyanine dye (S9) and thiacyanine dye (S11) is being considered. These aggregates are modeled by square matrix structure in the extended dipole approximation. The simulation takes into account the vector properties of the transitional dipole moment, its orientation, diagonal disorder and the composition of the aggregate. Good fit with the experiment is obtained for dipole tilt angle thetas=40deg, dipole moment mu=8.1 D and the disorder parameter of 450 cm -1 for various molar fractions of dyes
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  • Luminescence and electronic structure of Nd3+ complex with pyrazole-substituted 1,3-diketone and 1,10-phenanthroline

    Metlina, D. A.   Metlin, M. T.   Ambrozevich, S. A.   Taydakov, I., V   Lyssenko, K. A.   Vitukhnovsky, A. G.   Selyukov, A. S.   Krivobok, V. S.   Aminev, D. F.   Tobokhova, A. S.  

    We studied luminescent properties of two Nd3+ complexes with two different ligands. The first one was 1,3-diketone bearing a pyrazole fragment and the second ligand was either 1,10-phenanthroline or RIM. For the ligand environment composed of 1,3-diketone and 1,10-phenanthroline the position of the hybrid triplet level was as low as 18200 cm(-1). The spectral features specific to Nd3+ emission observed in the photoluminescence spectra of the complexes under optical excitation provided the evidence for ion-centered luminescence. Radiative transitions were identified using the obtained spectroscopic data. Corresponding diagram of the energy levels of the complex with 1,10-phenanthroline ligand was developed. Possible energy transfer pathways were discussed.
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  • Synthesis,structure,and luminescent properties of Pr-III complexes with pyrazole-derived 1,3-diketone and 1,10-phenanthroline

    Metlin, M. T.   Ambrozevich, S. A.   Krasnosel'sky, S. S.   Vitukhnovsky, A. G.   Nefedov, S. E.   Taidakov, I. V.  

    The interaction of PrCl3 with 1,3-bis(1,3-dimethy1-1H-pyrazol -4-yl)-1,3-propanedione in aqueous ethanol in the presence of a base and 1,10-phenanthroline was studied. It was shown that the composition of the products was dependent on the reaction conditions. The solvate [Pr(L)(3)(Phen)]center dot 3Pr(i)OH crystallizes in a monoclinic crystal system (P2(1)/c space group, a =3D 12.2239(12) angstrom, b =3D 20.3403(19) angstrom, c =3D 26.134(3) angstrom, beta =3D 102.380(2)degrees at 150 K). Absorption spectra of the complex in solution, as well as the spectra and the kinetic parameters of photo- luminescence were investigated.
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  • Luminescent Properties of a Composite of Acrylic Polymers Doped with Eu(III) Complex for Ink-Jet Printing Applications

    Taydakov, I. V.   Ambrozevich, S. A.   Varaksina, E. A.   Vitukhnovsky, A. G.   Tyutyunov, A. A.   Melnik, O. A.  

    We present a composite material based on polymer matrices doped with a new europium(III) complex exhibiting high quantum yield. The Eu(III) complex was introduced into two types of polymer matrices. We investigate the concentration influence of the complex embedded into polymers on luminescent properties of the composite material. This Eu(III) complex proved to be highly dispersible in polymers and compatible with ink-jet technology.
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  • Luminescence properties of hybrid associates of colloidal CdS quantum dots with J-aggregates of thiatrimethine cyanine dye

    Smirnov, M. S.   Ovchinnikov, O. V.   Dedikova, A. O.   Shapiro, B. I.   Vitukhnovsky, A. G.   Shatskikh, T. S.  

    Luminescence properties of water-soluble hybrid associates of semiconductor colloidal CdS quantum dots (QDs) with average size of 2.5 nm, 3.2 nm, 4.2 nm and J-aggregates of 3,3'-di-(gamma-sulfopropyl)-4,4',5,5'-dibenzo-9-ethylthiacarbocyanine betaine pyridinium salt (Dye) in gelatin were investigated using the methods of absorption, steady-state and time-resolved luminescence spectroscopy. The decrease in luminescence intensity of CdS QDs and increase in luminescence intensity of Dye J-aggregates were detected with increasing of Dye concentration. It was shown that curves of luminescence decay of CdS QDs are non-exponential. The decreasing of luminescence lifetime of CdS QDs with increasing of Dye J-aggregates concentration was observed. It was concluded that dynamic quenching due to non-radiative resonance energy transfer takes place. It was shown that overlap integral between luminescence spectra of CdS QDs and absorption spectra of Dye J-aggregates increases with the increase of average diameter of CdS QDs and luminescence decay of CdS QDs is accelerated. Energy transfer efficiency for all three sizes of QDs was more than 31%. (C) 2016 Elsevier B.V. All rights reserved.
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  • Optimization of carrier mobility in luminescence layers based on europium beta-diketonates in hybrid light-emitting structures

    Bochkov, M. A.   Vitukhnovsky, A. G.   Taidakov, I. V.   Vashchenko, A. A.   Katsaba, A. V.   Ambrozevich, S. A.   Brunkov, P. N.  

    The hole conductivity in films of three compounds, complexes based on europium beta-diketonates, deposited by vacuum evaporation is studied by the time-of-flight technique. It is shown that no carrier photogeneration is observed in films under pulsed excitation with 337 nm light. The introduction of pentacene-based photogeneration layers into the samples made it possible to observe transient-current curves. It was found that a dispersive component of the transient current, associated with hole transport, is observed in a complex of europium with an auxiliary ligand based on bathophenanthroline. These data were used to determine the hole mobility. No dispersive component of the transient current was observed in complexes with an auxiliary ligand based on phenanthroline. A conclusion is made that the latter is due to the low mobility in compounds of this kind. This is attributed to a decrease in the degree of conjugation of the aromatic system, which occurs on passing from bathophenanthroline to phenanthroline.
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