R. Yu. Smyslov

Photophysical and electrical properties of polyphenylquinolines containing carbazole or indolo[3,2-b]carbazole fragments as new optoelectronic materials

Photophysical and electrical properties of new synthesized 2,6-polyphenylquinolines (PPQs) containing an oxygen or phenylamine bridging group between quinoline cycles and, as an arylene radical, alkylated derivatives of carbazole or indolo[3,2-b]carbazole are studied. It is shown that the photosensitivity for new PPQs is 104–105 cm2/J and the photogeneration quantum yield of free carriers is as high as 0.15. Photophysical parameters increase with the phenylamine bridging group in place of the oxygen one and when using indolocarbazole instead of carbazole. It is found that a film of polyphenylquinoline containing an oxygen bridging group and an alkylcarbazole fragment in the polymer repeat unit exhibits “white” luminescence. Both electron and hole transport with a mobility of ∼10−6 cm2/(V s) are detected in films of all studied polymers. The conductivity value and type can be controlled by varying the chemical structure of the (oxygen or phenylamine) bridging group between PPQ cycles and by choosing carbazole or indolo[3,2-b]carbazole derivatives as an arylene radical.

Determination of the size and phase composition of silver nanoparticles in a gel film of bacterial cellulose by small-angle X-ray scattering, electron diffraction, and electron microscopy

The nanoscale structural features in a composite (gel film of Acetobacter Xylinum cellulose with adsorbed silver nanoparticles, stabilized by N-polyvinylpyrrolidone) have been investigated by small-angle X-ray scattering. The size distributions of inhomogeneities in the porous structure of the cellulose matrix and the size distributions of silver nanoparticles in the composite have been determined. It is shown that the sizes of synthesized nanoparticles correlate with the sizes of inhomogeneities in the gel film. Particles of larger size (with radii up to 100 nm) have also been found. Electron microscopy of thin cross sections of a dried composite layer showed that large particles are located on the cellulose layer surface. Electron diffraction revealed a crystal structure of silver nanoparticles in the composite.

Specifics of structural organization and properties of lysine dendrimers of different generations and related supramolecular structures

Lysine dendrimers of different generations containing covalently attached anthracene-based luminescent labels (one label per six dendrimer molecules) and fifth-generation heterodendrimers containing various amino acid units located between lysine fragments were synthesized. Homodendrimers were studied by means of the polarized luminescence technique. It was found that the packing density of lysine fragments in macromolecules increases with an increase in the generation number. Their capability of forming supramolecular structures changes in this case; the number of polymacromolecular associates produced in the solution and on the polymer matrix in interpolymer complexes decreases and their complexing power in the reaction with low-molecular-mass compounds increases. It was found that dendrite molecules acquire a looser structure on passing to heterodendrimers and their complexing ability varies in the corresponding manner; the number of polymacromolecular associates in the solution and on the polymer matrix in the interpolymer complexes increases and binding of low-molecular-mass compounds is reduced.

Structural and dynamic characteristics of a star-shaped calixarene-containing polymer in aqueous solutions: the formation of mixed-shell micelles in the presence of poly(methacrylic acid)

Structural and dynamic characteristics of a star-shaped polymer with a central tert-butylcalix[8]arene core and poly(N-isobutyryl ethylenimine)-ω-piperazine arms in aqueous solutions were studied via the polarized-luminescence method. To conduct investigations, a luminescent label of the anthracene structure was attached to the polymer. It has been shown that polymer macromolecules are in an aggregate state in water. The aggregate comprises about 5 macromolecules. During mixing of the star-shaped polymer with macromolecules of un-ionized poly(methacrylic acid), a mixed-shell micelle in which poly(methacrylic acid) units interact with both poly(N-isobutyryl ethylenimine)-ω-piperazine moieties and isobutyl fragments incorporated into the core of the micelle is formed.

Formation of a composite from Se0 nanoparticles stabilized with polyvinylpyrrolidone and Acetobacter xylinum cellulose gel films

Formation of a composite from Se0 nanoparticles stabilized with polyvinylpyrrolidone and Acetobacter xylinum cellulose gel films was studied. The optimal sorption parameters at which the amorphous form of the selenium complex is preserved in the composite were suggested.

Synthesis and photo- and electroluminescent properties of copolyfluorenes with nile red fragments in side chains

New copolyfluorenes containing units of 4,7-dibromo-2,1,3-benzothiadiazole (green luminophore) and 3,6- or 2,7-dibromocarbazole derivatives with side-chain fragments of green (4-pyrrolidinyl-1,8-naphthalimide) and red (Nile red) luminophores and additional carbazole or diphenyloxadiazole groups are synthesized via the Suzuki copolycondensation reaction. The structure of the polymers is modified via insertion of triphenylamine, aryloxadiazole, and quinoxaline units in the backbone of copolyfluorenes and via introduction of triphenylamine, fluorene, and benzene terminal groups. The molecular-weight characteristics of the polycondensation products and the specific features of the transfer of polyfluorene emission energy to the indicated luminophores in solutions and films are studied. Coating the emissive copolyfluorene layer with electron-conducting and hole-blocking layers of poly[9,9-bis(6′-diethoxyphosphorylhexyl)fluorene] makes it possible to increase the brightness of light-emitting diodes (to 2380–3900 cd/m2) and their current and luminance efficiencies.

Carbazole-containing polyphenylquinolines as a basis for optoelectronic materials with white luminescence

The photophysical properties of poly-2,2′-(1-dodecyl carbazole-4,7-yl)-6,6′-(oxy)-bis-(4-phenylquinoline) in a solution, as a film, and in a poly(methyl methacrylate) or poly-N-vinylcarbazole host matrix have been studied. Considerable positive solvatochromism in the photoluminescence spectra, compared with solvatochromism in the absorption spectra, indicates that the dipole moment of the donor-acceptor complex increases in the excited state. Calculations show that the dipole moments of the complex in the ground and excited states differ by more than an order of magnitude. Upon transition to films, photoluminescence is observed in the entire visible spectral range (white luminescence). The intensity of the white luminescence grows by an order of magnitude when the polymer is dispersed in a poly(methyl methacrylate) matrix. The integrated photosensitivity and parameters of the photogeneration process (quantum yield of carrier photogeneration, quantum yield of free carrier formation, and thermalization radii) have been determined.

Luminescence of Ln3+ lanthanide complexes in polymer matrices

The photoluminescence properties of Tb3+ and Eu3+ complexes with polymer ligands containing various kinds of complexing groups—namely, carboxyl (5–20 mol %), pyridylquinoline (5 mol %), or pyridylnaphthyl (5 and 10 mol %) groups—in solution and block are considered. The chemical structure of a neutral comonomer (methyl methacrylate; styrene; isopropyl-, phenyl-, or benzylmethacrylamide; and N-vinylamides) in polymer ligands is varied. The intensity of photoluminescence is dependent not only on the chemical nature of a complexing group but also the chemical nature of a neutral comonomer and a spacer. Variation in the nature of a comonomer and a ligand makes it possible to prepare complexes in which a high luminescence of a low-molecular-mass complex is preserved and advantages inherent in a polymer complex are acquired. The effect of the nature of the polymer matrix (photoactive and photoinert) on the efficiency of electronic-excitation energy transfer is ascertained. The data on the photoluminescence of metal-polymer complexes that are based on polymer ligands containing vinylcarbozole units and that possess hole conductivity make it possible to regard them as materials for electroluminescence. The intensity of photoluminescence of these complexes is related to the competition of oppositely directed photophysical processes in a macromolecule: formation of excimers and migration of electronic excitation energy. An analysis of the published data and of the results of the authors shows that detailed studies of these polymer systems in solution and in matrices are needed to gain insight into the relationship between photo- and electroluminescence properties of metal-polymer complexes, because the matrix plays different roles in photoluminescence and electroluminescence (inner filter or conduction); as a consequence, the emission spectra may differ appreciably. It is shown that the efficiency of electroluminescence may be improved if the transfer of energy from the lanthanide ligand in a complex to the conducting matrix is decreased.

Investigation of nanocomposites based on hydrated calcium phosphates and cellulose Acetobacter xylinum

Composites based on two biocompatible compounds, namely, inorganic hydrated calcium phosphates and organic microfibrillar ribbons of cellulose Acetobacter xylinum, are prepared by aggregation in an aqueous suspension. The influence of the structural organization of the hydroxyapatite and temperature-time conditions on the formation of the composite materials of different compositions is investigated. It is revealed that the composite materials are textured and retain the crystal structure of cellulose and the structure of initial hydrated calcium phosphates. The analysis of the crystal structures allows us to propose a model of the interaction between the mineral and organic components of the composite material. In the framework of the model, the interaction is provided through the formation of hydrogen bonds with the participation of hydroxyl groups and oxygen atoms of the phosphor group of the hydroxyapatite and primary OH groups located at the (−110) and (110) faces of cellulose nanocrystals.

Interaction of Se0 nanoparticles stabilized by poly(vinylpyrrolidone) with gel films of cellulose Acetobacter xylinum

The sorption and desorption of poly(vinylpyrrolidone)-Se0 (PVP-Se0) nanoparticles on gel films of cellulose Acetobacter xylinum (CAX) are investigated. It is revealed that the hydrodynamic radius Rh of PVP-Se0 nanoparticles decreases from 57 nm in the initial solution (without CAX gel films) to 25 nm after the sorption of nanostructures on gel films and then increases to approximately 100 nm after the desorption of nanoparticles with water from dry samples of the CAX gel film-PVP-Se0 nanocomposite. It is found that selenium atoms do not penetrate into crystallites of the cellulose nanofibrils and replace water molecules sorbed by the primary hydroxyl groups of their walls. Poly(vinylpyrrolidone)-Se0 nanoclusters differ in the number and size upon their sorption inside the cellulose gel film and on the film surface.