ИСТИНА

The formation of nanotube arrays of anodic titania and anodic auminium oxide occurred by electrochemical oxidation of Al- and Ti-foil. Various electrolytes based on ammonium fluoride, sulfuric, oxalic and selenic acid were used for preparation. During the synthesis process, the current density, anodization time, and annealing temperature were varied. Spin centers were studied on a Bruker ELEXSYS-E500 EPR spectrometer (X-band). Photoluminescence spectra were studied using an LS-55 Perkin Elmer luminescence spectrograph. In the EPR spectra of a series of titania nanotubes annealed in air in the temperature range 250-500 C, a signal from dangling carbon bonds (g=2.0027±0.0003) is recorded.The concentration of these spin centers decreased with increasing annealing temperature. For this series of samples, we also measured the photoluminescence spectra. It was found that there is a correlation between the concentration of defects and the intensity of photoluminescence, which indicates that in titania nanotubes the radiative recombination of photoexcited electrons and holes occurs at the dangling carbon bonds. It has been established that by annealing titania nanotubes in air at different temperatures (250-500 0C), it is possible to control the concentration of spin centers and the intensity of photoluminescence. A series of auminium oxide nanotubes prepared in electrolytes based on various acids - sulfuric (A1), oxalic (A2) and selenic (A3) - were studied by EPR and photoluminescence methods. It was found that all samples contain oxygen vacancies with an unpaired electron (g=2.0022±0.0003); their concentration is maximum in the samples A2. In addition, O2- radicals (g1=2.023±0.0003, g2=2.008±0.0003, g3=2.0035±0.0003) were detected in samples A1 and A3. It was found that the photoluminescence intensity correlates with the concentration of oxygen vacancies. Therefore, it can be assumed that photoluminescence in auminium oxide nanotubes is due to radiative recombination of electrons and holes at oxygen vacancies. By controlling the photoluminescence intensity by varying the concentration of spin centers during the synthesis process, it is possible to obtain nanoporous auminium oxide with low photoluminescence intensity for subsequent use as an optical sensing platform for detecting various biological analytes with high sensitivity and selectivity using various optical methods.Thus, the results obtained have important implications for practice. The experiments were performed using the facilities of the Collective Use Center at the Moscow State University.