Browsing by Author "Zenkevich, E. I."

Now showing items 1-20 of 35

    • 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

    • 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

    • 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

    • Complexation and interchromophoric interactions in self-organized porphyrin and chlorin triads 

      Chernook, A. V.; Shulga, A. M.; Zenkevich, E. I.; Rempel, U.; Borczyskowski, C. von (1996)
      Spectral properties and equilibrium constants of multimolecular complexes (triads) formed by 2-fold coordination of dipyridyl-substituted free bases of porphyrin, chlorin, or tetrahydroporphyrin with Zn-porphyrin and Zn-chlorin dimers bridged by either of two different spacers between the monomeric entities have been studied in methylcyclohexane at room temperature. The ability ...
      2017-05-18

    • Concentration effects in pigment solutions 

      Gurinovich, G. P.; Losev, A. P.; Zenkevich, E. I. (1978)
      Gurinovich, G. P. Concentration effects in pigment solutions / G. P. Gurinovich, A. P. Losev, E. I. Zenkevich // Spectroscopy Letters. – 1978. – Vol. 11, № 7. – P. 493-511.
      2017-05-18

    • Deactivation of excited states in nanostructures containing cu-porphyrin subunit 

      Zenkevich, E. I. (Ивановский государственный химико-технологический университет, 2016)
      Here, we present a semi-review of mutual Belarussian-German collaboration in the field of supramolecular chemistry and photophysics of tetrapyrrole compounds of various types: porphyrin chemical dimers, self-organized multiporphyrin complexes, ordered aggregates of photosynthetic pigments and nanoassemblies based on semiconductor CdSe/ZnS quantum dots and porphyrins. A special ...
      2020-11-11

    • Directed energy transfer due to orientational broadenning of energy levels in photosynthetic pigment solutions 

      Rubinov, A. N.; Zenkevich, E. I.; Nemkovich, N. A.; Tomin, V. I. (1982)
      The directed non-radiative energy transfer through monomeric molecules of chlorophyll “a” and pheophytin “a” at high concentrations (c ~ 10⁻²) in a rigid matrix of polyvinylbutyral has been found by using the nanosecond laser spectrofluorimeter. The phenomenon is caused by orientational broadening of pigment molecular spectra owing to its interaction with a solvent. The observed ...
      2017-05-18

    • Electron transfer in porphyrin multimolecular self-organized nanostructures 

      Zenkevich, E. I.; Bachilo, S. M.; Shulga, A. M.; Rempel, U.; Willert, A.; Borczyskowski, C. von (1998)
      On the base of of covalent and non-covalent bonds nanoscale self-assembling multiporphyrin arrays with well-defined geometry, the controllable number of interacting components and their spectral and photophysical properties were formed. The deactivation of excited singlet and triplet states was studied using steady-state, time-resolved picosecond fluorescence (∆½≈30 ps) and ...
      2017-05-25

    • Energy transfer in ethane-bisporphyrins studied by fluorescence line narrowing and spectral hole burning 

      Mauring, K.; Suisalu, A.; Kikas, J.; Zenkevich, E. I.; Chernook, A. V.; Shulga, A. M.; Gurinovich, G. P. (1995)
      The quasi-line fluorescence excitation spectrum of 1,2-bis (2,3,7,8,12,13,17,18-octaethyl-21H,23 H-porphino) ethane at 4.8 K consists of two subbands with the splitting mean value of 51cm⁻¹, that are ascribed to the donor and the acceptor half of the homodimer. The donor's fluorescence is quenched by an efficient energy transfer to the acceptor. The energy transfer rate of 10¹¹ ...
      2017-05-18

    • Fluorescence line narrowing study of cyclopentaneporphyrin chemical dimers at 4.2 K 

      Starukhin, A.; Zenkevich, E. I.; Shulga, A.; Chernook, A. (1996)
      The monomers of Zn-cyclopentanporphyrins (ZnOEP-cycle and ZnOEP-cycle=CH2) and their chemical dimers covalently linked via isocycles (Zn-cyclodimers) have been studied by the method of fluorescence line narrowing (FLN) in tetrahydrofurane-toluene (3:1) glassy matrixes at 4.2 K. Well-resolved fluorescence spectra upon laser excitation into the S₀→S₁ absorption band have been ...
      2017-05-18

    • Formation and optical properties of self-organized pentameric porphyrin arrays 

      Chernook, A. V.; Rempel, U.; Borczyskowski, C. von; Zenkevich, E. I.; Shulga, A. (1996)
      Principles of formation, electronic absorption and fluorescence spectra are reported for self-organized pentameric arrays of tetrapyrrolic macrocycles. In these arrays two molecules of Zn-porphyrin dimers, Zn(II)l,4-bis[5-(10,15,20-tri-p-hexylphenylporphyrinyl)]-benzene ((ZnHTPP)₂) are bound via one molecule of a tetrapyridyl-substituted free base of porphyrin or tetrahydroporphyrin. ...
      2017-05-25

    • 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

    • 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

    • 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

    • Investigations of Chl α aggregates cross-linked by dioxane in 3-methylpentane 

      Oksanen, J. A. I.; Zenkevich, E. I.; Knyukshto, V. N.; Pakalnis, S.; Hynninen, P. H.; Korrpi-Tommola, J. E. I. (1997)
      In this work, dioxane-bound aggregates of chlorophyll a are prepared in 3-methylpentane. The properties of the aggregates are studied by using steady-state and time-resolved spectroscopies. The Qy-region absorption spectrum of the chlorophyll α-dioxane aggregate shows four clearly resolvable narrow bands with comparable intensities. The band maxima are located at 683, 689, 698 ...
      2017-05-25

    • 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

    • Ligand dynamics and temperature effects upon formation of nanocomposites based on semiconductor CdSе/ZnS quantum dots and porphyrins: ensemble and single object measurements 

      Zenkevich, E. I.; Blaudeck, T.; Kowerko, D.; Stupak, A. P.; Cichos, F.; Borczyskowski, C. von (2012)
      Dye molecules with pyridyl side substituents (porphyrins and heterocyclic perylene diimides) coordinatively attached to semiconductor CdSe/ZnS quantum dots (QDs) surface form quasi-stable “QD-Dye” nanocomposites of various geometry in the competition with capping molecules (tri-n-octyl phosphine oxide or long chain amines) exchange. This results in photoluminescence (PL) quenching ...
      2017-05-27

    • 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

    • 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

    • NH-tautomerism and visible absorption spectra of porphyrins with nonsymmetrical substitution: oscillator model and mo calculations 

      Zenkevich, E. I.; Shulga, A. M.; Filatov, I. V.; Chernook, A. V.; Gurinovich, G. P. (1985)
      On the basis or experiments Ihe oscillator model has been established for individual NH tautomers or porphyrins with asymmetrical substitution. CNDO/2 calculations explain the inversion of Q ₓ (O.O) and Q y (O.O) electronic transition intensities in NH tautomers as a consequence of the inversion of LUMO coefficients c₁ and c₂ for fixed x and y molecular oscillators.
      2017-05-18