A. A. Chuiko

Laser-Induced Electron-Transfer Processes in a Pyrene–β-Cyclodextrin Complex in Titanosilicate Systems

We have used fluorescent spectroscopy and laser flash photolysis to investigate the photonics of pyrene molecules in a pyrene–β-cyclodextrin inclusion complex in various media. We have observed a protective effect of β-cyclodextrin relative to solubilized pyrene molecules during quenching of fluorescence by Ti ions (or titanium dioxide particles) in mixed colloids. In the presence of a precursor of silica (a TEOS solution), the pyrene molecules react with the colloidal silica particles formed, and the reaction is accompanied by decomposition of the pyrene–β-cyclodextrin inclusion complex and efficient photoionization of pyrene.

Fluorescent properties of pyrene-β-cyclodextrin inclusion complexes in titanium-silica sols

Fluorescence of pyrene-β-cyclodextrin inclusion complexes in silica and titanium-silica stable sols is studied. It is revealed that high fluorescence ability of pyrene in the aforementioned systems is retained due to the binding with β-cyclodextrin. The study of the influence of N,N-dimethylaniline on the fluorescence of complexes shows that, varying the ratio between cyclodextrin and molecules capable of penetrating into its hydrophobic cavity, one may both efficiently encapsulate these molecules or replace some of them with others in titanium-silica sols.

Matrix Synthesis of N-Containing Carbon Nanotubes

N-Containing carbon nanotubes were prepared by the pyrolysis of acetonitrile in an alumina matrix. Nanotubes were obtained with given diameter and length. Amorphous carbon is also formed on the alumina surface in the acetonitrile pyrolysis.

Photophysics of pyrene adsorbed on aerosil

The spectral luminescence properties of pyrene adsorbed on the surface of aerosil have been investigated at different thermal activation temperatures (453, 773, and 1073°K) and different degrees of surface coverage (0.01–10% of monolayer). The differences from the properties of pyrene adsorbed on silica gel are dictated by the high polarity of the aerosil surface, the less significant rearrangement of its hydroxyl coverage in thermal treatment, and its pronounced energetic discrete homogeneity at low degrees of coverage.

Photonics of perylene on the surface of SiO2

Stationary and kinetic spectrofluorometry and diffuse reflection spectroscopy have been used to study the photophysics and photochemistry of perylene, adsorbed on the surface of porous (silica gel) and nonporous (aerosil) silica after thermal activation in air (at 453, 773, and 1073 K) as function of the degree of surface coverage.

Kinetics of Pyrene Fluorescence Quenching in the Presence of N,N-Dimethylaniline on the Surface of Titania Silica Colloids

A study was carried out on pyrene (Py) fluorescence quenching in the presence of N,N-dimethylaniline (DMA) on the surface of titania–silica colloids. Py fluorescence quenching is a function of the TiO2 content in the binary colloids. The coadsorption of DMA molecules is accompanied by an increase in the Py fluorescence intensity due to the competitive adsorption of amine on the surface. Calculation of the formal kinetics of Py fluorescence quenching indicates the existence of two groups of sites differing in adsorption activity within each group.

ELECTRONIC DONOR-ACCEPTOR INTERACTIONS OF ANTHRACENE WITH A DEHYDROXYLATED SURFACE OF SILICA GEL AND AEROSIL

The ability of a dehydroxylated surface of silica gel and aerosil to enter into donor-acceptor interactions with poly-acenes was demonstrated by methods of steadystate and kinetic spectrofluorometry. The anthracene molecule forms EDA complexes with electron-acceptor sites of silica gel and aerosil in the ground state (charge-transfer complex, CTC) and the excited state (exciplex). At a degree of coverage of the silica gel and aerosil surfaces by polyacene molecules of 10−1–10−3% of a monolayer, energetic and structural inhomogeneity of the OH groups of silica gel appears. Silica gel possesses stronger electron acceptor sites; the electron-acceptor sites of aerosil are more accessible to EDA interactions and more monotypic. Vacancy defects of the SiO2 matrix are suggested as accepting sites.

Spectroscopic kinetic characteristics of the fluorescence of anthracene sorbed on silica gel

The spectroscopic kinetic characteristics of the fluorescence of anthracene adsorbed on silica gel have been investigated. The formation of charge-transfer (CT) complexes between the anthracene molecules and acceptor sites on silica gel which had been heat-treated in a vacuum has been discovered. Along with the emission of the CT complexes, the luminescence of an excited CT complex, i.e., an exciplex, has been detected. Hypotheses regarding the nature of the electron-acceptor sites on silica gel have been advanced.