V. B. Zaitsev

Molecular Oligogermanes and Related Compounds: Structure, Optical and Semiconductor Properties

The optical (UV/Vis absorbance, fluorescence in the solid state and in solution) and semiconducting properties of a number of di- and trigermanes as well as related silicon- and tin-containing germanes, 1-6 ((p-Tol)3 GeGeMe3 (1), Ph3 SnGe(SiMe3 )3 (2), (C6 F5 )3 GeGePh3 (3), (p-Tol)3 GeSiMe2 SiMe3 (4), (p-Tol)3 GeGeMe2 Ge(p-Tol)3 (5), (p-Tol)3 GeSiMe2 SiMe2 Ge(p-Tol)3 (6)) were investigated. Molecular structures of 5 and 6 were studied by X-ray diffraction analysis. All compounds displayed luminescence properties. In addition, a band gap (of about 3.3u2005eV) was measured for compoundsu20051-6 showing that those molecules display semiconductor properties.

The optoelectronic properties of nitrogen- and carbon-doped nanocrystalline titania

Carbon- and nitrogen-doped nanocrystalline titania specimens were studied by optical spectroscopy and electron paramagnetic resonance. The doping of this material was established to result in the appearance of additional absorption in the visible spectral region. The doping with admixture nitrogen was revealed to lead to the formation of nitrogen-containing paramagnetic sites, namely, N· and NO· radicals. The effect of the recharging of the detected sites under light was revealed. The obtained results could be useful for the development of photocatalytic filters on the basis of doped nanocrystalline titania.

Changes in Optical Properties of TDO BAM BCC Langmuir Films during a Phase Transition

The isotherms of water molecule adsorption and the spectra of absorption, diffusion reflection, and polarization of reflected light for hyperfine Langmuir films that were fabricated based on liquid crystals are investigated. Singularities in the reflection spectra at the temperature of the structural phase transition (∼70°C) are revealed. Some reasonable assumptions on the nature of the phase transition are made.

Changes in adsorption and optical properties near the phase transition of super thin vanadyl phthalocyanine Langmuir films

Structural transition in thin vanadyl-phtalocyanine films deposited by Langmuir technology was studied in detail with the help of the vacuum adsorption and optical spectroscopy techniques. The reversible structural transition observed only in super-thin Langmuir films is accompanied by nonreversible changes during heating. This transformation of the film having defects and amorphous regions occurs during the film transition from a metastable state to a more stable one that is characterized by a lower free energy.

The Optical Properties of Polydisperse Glass Microsphere Ensembles in the Infrared Spectral Region

Semitransparent composites with glass microspheres are promising modern materials. In particular, they contribute to the increase of the efficiency of heat-insulating coatings. An experimental study of the transmission and scattering of infrared radiation (at wavelengths from 2 to 25 μm) by a sodium borosilicate glass microsphere powder is presented. The spectra, angular-scattering patterns, and the degree of polarization of scattered radiation were studied.

Effect of the Texture of Langmuir Copolymer Films on Structural Phase Transitions

An atomic-force microscopy study has surprisingly revealed that ultrathin copolymer films fabricated according to Langmuir technology constitute a network of tangled filaments. A long-range order is absent in the samples. The observed filaments consist of several parallel-packed copolymer chains. The shape of ferroelectric domains in a film is independent of the direction of copolymer chains. Each domain includes a large number of filaments. The nature of high-temperature (ferroelectric) and low-temperature phase transitions has been discussed in terms of structural data.

Changes in the optical properties of ultrathin films of liquid crystals during phase transitions

The temperature dependences of diffuse reflection spectra and the polarization of light reflected from ultrathin Langmuir films based on liquid crystals are studied. The results are compared to the experimental data obtained on thicker liquid films. The dependences of the electric capacity of metal-film-metal structures on temperature are measured. The maximum for ultrathin films lies near 75°C, indicating the occurrence of a ferroelectric phase transition. Features in the intensity and polarization of the reflected light are registered at the phase transition temperature. It is concluded that the generality of the results obtained using samples of both types indicates the existence of a mesomorphic phase in Langmuir films. The observed differences could be associated with either dimensional effects or differences in the structures of the films.

Changes in the optical and electrophysical properties of langmuir films of liquid crystals upon a ferroelectric phase transition

The adsorption isotherms of water molecules, spectra of diffuse reflection and of reflected-light polarization, and electrophysical properties of hyperfine films fabricated on the basis of liquid crystals have been studied. A structural phase transition was detected at a temperature of about 70°C; near the transition, features of light polarization, of the reflection coefficient’s behavior, and of the temperature dependence of the sample capacitance have been found. Hypotheses regarding the nature of the phase transition are proposed.

Changes in adsorption and optical properties of liquid crystal langmuir films at structural phase transition

The adsorption isotherms of water molecules, absorption spectra, and spectra of diffuse scattering and polarization of reflected light are studied for ultrathin Langmuir films prepared based on liquid crystals. A structural phase transition near 70°C is detected. Some specific features of the reflection spectra at the phase transition temperature are found. Suggestions are made regarding the nature of the phase transition.

Dimerization of Fluorescent Molecular Probes on a Polystyrene Surface

Fluorescent spectroscopy is used to demonstrate the effect of vitrification of the surface layer of polystryene on the mobility and dimerization of probe molecules in the layer. The results of this work agree well with the data obtained earlier using an independent technique.