Внеуниверситетские публикации ученых БНТУ: Recent submissions

Now showing items 2761-2780 of 4615

    • Resonant Raman Scattering of ZnS, ZnO, and ZnS/ZnO Core/shell quantum dots 

      Milekhin, A. G.; Yeryukov, N. A.; Sveshnikova, L. L.; Duda, T. A.; Himcinschi, C.; Zenkevich, E. I.; Zahn, D. R. T. (2012)
      Resonant Raman scattering by optical phonon modes as well as their overtones was investigated in ZnS and ZnO quantum dots grown by the Langmuir–Blodgett technique. The in situ formation of ZnS/ZnO core/shell quantum dots was monitored by Raman spectroscopy during laser illumination.
      2017-05-27

    • Influence of Single Dye Molecules on Temperature and Time Dependent Optical Properties of CdSe/ZnS Quantum Dots: Ensemble and Single Nanoassembly Detection 

      Zenkevich, E. I.; Stupak, A. P.; Kowerko, D.; Borczyskowski, C. von (2012)
      Optical spectroscopy on ensembles and single CdSe/ZnS semiconductor quantum dots (QDs) demonstrates a competition of trap and near band edge photoluminescence (PL). This competition can be markedly influenced by a few surface attached pyridyl functionalized dye molecules (porphyrins or perylene diimides) forming nanoassemblies with well defined geometries. Temperature variation ...
      2017-05-27

    • Formation Principles and Ligand Dynamics for Nanoassemblies of CdSe Quantum Dots and Functionalized Dye Molecules 

      Blaudeck, T.; Zenkevich, E.; Abdel-Mottaleb, M.; Szwaykowska, K.; Kowerko, D.; Cichos, F.; Borczyskowski, C. von (2012)
      Functional dye molecules, such as porphyrins, attached to CdSe quantum dots (QDs) through anchoring meso-pyridyl substituents, form quasi-stable nanoassemblies. This fact results in photoluminescence (PL) quenching of the QDs both due to Förster resonance energy transfer (FRET) and the formation of non-radiative surface states under conditions of quantum confinement (non-FRET). ...
      2017-05-27

    • Size-Dependent Non-FRET Photoluminescence Quenching in Nanocomposites Based on Semiconductor Quantum Dots CdSe/ZnS and Functionalized Porphyrin Ligands 

      Zenkevich, E. I.; Blaudeck, T.; Milekhin, A.; Borczyskowski, C. von (2011)
      We review recent experimental work to utilize the size dependence of the luminescence quenching of colloidal semiconductor quantum dots induced by functionalized porphyrin molecules attached to the surface to describe a photoluminescence (PL) quenching process which is different from usual models of charge transfer (CT) or Foerster resonant energy transfer (FRET). Steady-state ...
      2017-05-27

    • Assembly principles and relaxation processes in nanosized heterogeneous complexes: Multiporphyrin structures and CdSе/ZnS nanocrystals 

      Zenkevich, E. I.; Borczyskowski, C. von (2009)
      Based on the extra-ligand addition effect, the principles of targeted self-assembly of nanosized multiporphyrin complexes of various types with controllable geometry and composition (up to 8 tetrapyrroles) and heterogeneous composites based on trioctylphosphine oxide-stabilized CdSe/ZnS semiconductor nanocrystals and organic compounds were developed. The dynamics and mechanisms ...
      2017-05-27

    • Photoinduced relaxation processes in self-assembled nanostructures: multiporphyrin complexes and composites "CdSе/ZnS quantum dot-porphyrin" 

      Zenkevich, E. I.; Borczyskowski, C. von (2009)
      Here, we discuss self-assembled multicomponent organic/inorganic nanostructures. Self-assembled multiporphyrin triads were formed via non-covalent interactions of meso-phenyl bridged ZnOEP chemical dimer, (ZnOEP)₂Ph, with dipyridyl substituted tetrapyrrole extra-ligand. In tetrads, the dimer (ZnOEP)₂Ph is covalently linked via 5-mesoposition to additional electron acceptors ...
      2017-05-27

    • Laser confocal and spatially-resolved fluorescence spectroscopy of porphyrin distribution on plasma deposited polymer films 

      Zenkevich, E. I.; Martin, J.; Borczyskowski, C. von; Ageeva, T. A.; Titov, V. A.; Knyukshto, V. N. (2008)
      Laser confocal microscopy and spatially-resolved fluorescence spectroscopy have been used for the study of the interaction of di(p-aminophenyl)etioporphyrin (DAPEP) and tetra(p-aminophenyl)porphyrin (TAPP) molecules with the surface of thin (7-15 μm) polypropylene films treated by 0.5 M KCl solution and activated by air non-equilibrium plasma at the normal atmospheric pressure. ...
      2017-05-27

    • Time resolved photoluminescence anisotropy of CdSe/ZnS nanoparticles in toluene at 300 K 

      Petrov, E. P.; Cichos, F.; Zenkevich, E.; Starukhin, D.; Borczyskowski, C. von (2005)
      For CdSe nanoparticles it has been theoretically and experimentally shown that at low temperatures the photoluminescence is circularly polarized in accordance with a wurtzite structure and the corresponding allowed optical transitions. In the present Letter, we report on related investigations on CdSe/ZnS colloids in toluene solution. From time resolved photoluminescence anisotropy ...
      2017-05-27

    • Resonant Raman studies of compositional and size dispersion of CdS₁₋ₓSeₓ nanocrystals in a glass matrix 

      Azhniuk, Yu. M; Milekhin, A. G.; Gomonnai, A. V.; Lopushansky, V. V.; Yukhymchuk, V. O.; Schulze, S.; Zenkevich, E. I.; Zahn, D. R. T. (2004)
      Resonant Raman scattering spectra of glass-embedded CdS₁₋ₓSeₓ nanocrystals are measured and complemented with TEM and optical absorption as well as photoluminescence data. The selectivity of the resonant Raman process not only for the size, but also for the composition of nanocrystals within the ensemble, is directly observed in the dependence of phonon band frequency, linewidth ...
      2017-05-27

    • Ab initio Study of Exciton Transfer Dynamics from a Core-Shell Semiconductor Quantum-Dot to a Porphyrin-Sensitizer 

      Kilin, D. S.; Tsemekhman, K.; Prezhdo, O. V.; Zenkevich, E. I.; Borczyskowski, C. von (2007)
      The observed resonance energy transfer in nanoassemblies of CdSe/ZnS quantum dots and pyridyl-substituted free-base porphyrin molecules [Zenkevich et al., J. Phys. Chem. B 109 (2005) 8679] is studied computationally by ab initio electronic structure and quantum dynamics approaches. The system harvests light in a broad energy range and can transfer the excitation from the dot ...
      2017-05-27

    • Identification and assignment of porphyrin-CdSe Hetero-nanoassemblies 

      Zenkevich, E. I.; Blaudeck, T.; Shulga, A. M.; Cichos, F.; Borczyskowski, C. von (2007)
      Hetero-nanoassemblies in toluene solution are formed via anchoring pyridyl substituted free base porphyrin molecules on the colloidal core-shell semiconductor nanocrystals CdSe/ZnS. The formation can be identified via quenching of semiconductor photoluminescence and followed via spectral changes of porphyrin spectral properties such as fluorescence, fluorescence decay and absorption. ...
      2017-05-27

    • Multistep photoinduced electron transfer in self-organised nano-scale porphyrin triads 

      Zenkevich, E. I.; Shulga, A. M.; Borczyskowski, C. von (2002)
      Well-defined structurally organised porphyrin triads of a controlled geometry andnanoscale size have been formed in liquid solutions using the combination of a covalent approach and non-covalent self-assembly. The triads contain zinc-octaethylporphyrin chemical dimer, (ZnOEP)₂Ph, with covalently linked electron acceptors (p-benzoquinone, Q or pyromellitimide, Pim), and additional ...
      2017-05-26

    • Self-assembled nanoscale photomimetic models: structure and related dynamics 

      Zenkevich, E. I.; Borczyskowski, C. von; Shulga, A. M.; Bachilo, S. M.; Rempel, U.; Willert, A. (2002)
      Using static and time-resolved measurements, dynamics of non-radiative relaxation processes have been studied in self-assembled porphyrin triads of various geometry, containing the main biomimetic components, Zn–porphyrin dimers, free-base extra-ligands (porphyrin, chlorin or tetrahydroporphyrin), and electron acceptors A (quinone or pyromellitimide). The strong quenching of the ...
      2017-05-26

    • Interaction of multiporphyrin systems with molecular oxygen in liquid solutions: Extra-ligation and screening effects 

      Sagun, E. I.; Zenkevich, E. I.; Knyukshto, V. N.; Shulga, A. M.; Starukhin, D. A.; Borczyskowski, C. von (2002)
      Steady-state and time-resolved studies indicate that for a sequence of porphyrin or chlorin chemical dimers Zn-cyclodimer → (ZnOEP)₂Ph → (ZnOEP)₂ → (ZnHTPP)₂ → (ZnOEChl)₂ with relative lowering of excited S₁- and T₁-states, the extra-ligation by pyridine (PYR) does not influence essentially on fluorescence parameters but leads to an increase of T₁-states non-radiative decay (the ...
      2017-05-26

    • Competition between electron transfer and energy migration in self-assembled porphyrin triads 

      Zenkevich, E. I.; Willert, A.; Bachilo, S. M.; Rempel, U.; Kilin, D. S.; Shulga, A. M.; Borczyskowski, C. von (2001)
      The photoinduced electron transfer (ET) and the energy migration (EM) processes have been studied in liquid solutions and polymeric (PMMA) films for the triads consisting of the Zn-octaethylporphyrin chemical dimer (the energy and electron donor, D) and dipyridyl substituted tetrapyrrole extra-ligands (porphyrins, chlorin, tetrahydroporphyrin) as the acceptors, A. On the basis ...
      2017-05-26

    • Steric interactions influence on electron transfer efficiency in meso-nitrophenylporphyrins and their chemical dimers 

      Knyukshto, V. N.; Zenkevich, E. I.; Sagun, E. I.; Shulga, A. M.; Starukhin, D. A.; Bachilo, S. M. (2001)
      Steric interactions upon mono- and di-meso-phenyl substitution in octaethylporphyrins (OEP) and their chemical dimers with the phenyl spacer manifests itself in the dramatical T₁-state lifetimes shortening at 293 K (from ms down to μs in degassed toluene solutions) without any influence on spectral-kinetic parameters of S₀- and S₁-states. This effect is explained by non-planar ...
      2017-05-26

    • Photoinduced electron transfer dynamics for self-assembled porphyrin arrays in solutions and films 

      Zenkevich, E. I.; Kilin, D. S.; Willert, A.; Bachilo, S. M.; Shulga, A. M.; Rempel, U.; Borczyskowski, C. von (2001)
      Electronic excitation energy deactivation in self-assembled porphyrin triads has been studied by the time correlated single photon counting technique as a function of the solvent polarity (toluene-acetone mixtures), temperature (77-350 K), and mutual spatial arrangement of the donor and acceptor subunits. The donor (Zn-octaethylporphyrin chemical dimer) fluorescence quenching ...
      2017-05-26

    • Manifestation of nonplanarity effects and charge-transfer interactions in spectral and kinetic properties of triplet states of sterically strained octaethylporphyrins 

      Knyukshto, V. N.; Sagun, E. I.; Shulga, A. M.; Starukhin, D. A.; Bachilo, S. M.; Zenkevich, E. I. (2001)
      Properties of the triplet states of octaethylporphyrins with the steric hindrance (free bases and Pd complexes) are studied by the methods of stationary and kinetic spectroscopy in the temperature range from 77 to 293 K. The mono-mesophenyl substitution results in a decrease in the quantum yield and shortening of the phosphorescence lifetime of Pd complexes by 250–3500 times in ...
      2017-05-26

    • Pathways for photoinduced electron transfer in meso-nitro-phenyl-octaethylporphyrins and their chemical dimers 

      Knyukshto, V.; Zenkevich, E.; Sagun, E.; Shulga, A.; Bachilo, S. (1999)
      The photophysical properties of meso-nitro-phenyl-octaethylporphyrins and their dimers with electron-accepting NO₂ groups in the para-, meta- and ortho-positions of the phenyl ring were studied. For the ortho-NO₂ case in deaerated toluene at 295 K, strong fluorescence quenching is caused by the intramolecular electron transfer from the porphyrin S₁ state in the absence of phenyl ...
      2017-05-25

    • Unusual dynamic relaxation of triplet-excited meso-phenyl-substituted porphyrins and their chemical dimers at room temperatures 

      Knyukshto, V.; Zenkevich, E.; Sagun, E.; Shulga, A.; Bachilo, S. (1998)
      It has been found that for mono- and di-meso-phenyl-substituted octaethylporphyrin (OEPs), etioporphyrins, corresponding Zn complexes and OEP chemical dimers (with a meso-phenyl spacer) a drastic shortening of triplet lifetimes from a ms to μs timescale in deaerated toluene solutions at 295K takes place without any changes of the spectral-kinetic parameters of the S₀ and S₁ states. ...
      2017-05-25