The formation of porous alumina by galvanostatic anodization in selenic acid has been investigated. The influence of the electrolyte concentration on the morphological features and the self-ordering behavior of the porous oxide film has been studied. The best pore arrangement is obtained upon anodization in 0.5 M H₂SeO₄. Using chronopotentiometry, gravimetric analysis and FESEM it is shown that the highest degree of pore ordering is caused by an optimal combination of the two mechanisms that lead to pore initiation: mechanical instability and field-assisted dissolution. In addition, by means of Raman spectroscopy it is found that the optical properties of porous alumina anodized in selenic acid do not exhibit parasite effects due to electrolyte incorporation during anodization. Hence, these templates are of great interest to fabricate and investigate functional nanostructures for optoelectronics.

Applicability of porous anodic alumina formed in selenic acid based electrolyte as the matrix for formation and Raman characterization of nanomaterials is investigated. For that, Raman spectra of nanostructured CdS layers deposited on top of porous alumina matrices are obtained. These spectra were compared with the ones, registered for the composites prepared using the commonly used matrix formed in oxalic acid solution. It is shown that application of porous alumina matrix formed in selenic acid electrolyte afford to detect the peaks corresponding to the CdS layers even at small amounts of CdS. It happens due to the absence of luminescence background in such matrix, which exists in matrices produced in organic acid electrolytes, for example, in oxalic acid.

Porous anodic alumina films were formed in various acidic electrolytes. The features of its Raman spectra determined by the electrolyte nature are observed. As the thermal treatment could make the different impact on the chemical structure and optical properties of porous Al 2 O 3 formed in the different electrolytes, the porous alumina samples were annealed at different temperatures up to 500°C and the effect of the annealing on the Raman spectra is analyzed. It is shown that the choice of the annealing temperature can affect significant changes in the Raman scattering of porous alumina matrix. Depending on the electrolyte, these changes could concern both intensity and the shape of the Raman spectra. PAA fabricated in the selenic acid solution demonstrate the weakest dependence of the Raman response on the annealing temperature. Thus it is good candidate for PAA application as the matrices for the formation and Raman investigation of nanocomposites when the processes of nanostructures synthesis require heat-treatment procedures.

We report a comprehensive study on the effect of H₂SeO₄ electrolyte temperature on the composition, defect, morphological, and luminescent properties of porous anodic aluminum oxide (AAO). An increase in the synthesis temperature led to a decrease in the AAO cell diameter from 85–115 nm to 38–58 nm (depending on the electrolyte concentration) and enhanced the etching of the AAO walls, which even resulted in the disintegration of the AAO into individual fibers at 40 °C. The selenium concentration in the samples formed in 0.5–1.5 M H₂SeO₄ in the temperature range of 5–40 °C did not exceed 2 at.% and fell below the detection limit at 40 °C. The formation of a nanocrystalline Al₂O₃ phase was observed in the H₂SeO₄ electrolyte at 40 °C. The samples exhibited weak photoluminescence. We identified three types of paramagnetic centers in AAO formed in H₂SeO₄: F⁺ centers (N_sF = 8.2 × 10¹⁵ g⁻¹), newly discovered centers with an unpaired electron localized on an oxygen atom (N_sO = 10¹⁷ g⁻¹), and centers associated with selenate radicals (N_sS = 6 × 10¹⁸ g⁻¹). By comparing the photoluminescence spectra and defect concentrations, we conclude that the luminescence of AAO formed in selenic acid is exclusively due to F⁺ centers, while other paramagnetic centers do not contribute.

The complex study of the influence of the H2SeO4 electrolyte temperature on the porous anodic aluminum oxide (AAO) composition and defects, morphological, luminescent properties is performed. The synthesis temperature increasing leads to decrease of AAO cell diameter from 85-115 nm to 38-58 nm (depending on the electrolyte concentration) and increases AAO walls etching that can even lead to AAO etching to individual fibers at 40°C. Selenium concentration in the samples formed in 0.5-1.5 M H₂SeO₄ at 5-40°C does not exceed 2 at.% and becomes undetectable at 40°C. It is established that the formation of the nanocrystalline phase Al₂O₃ in H₂SeO₄ electrolyte is observed at 40°C. The samples exhibit very weak photoluminescence. It was shown that in AAO formed in H2SeO4 there are 3 types of paramagnetic centers: F⁺ centers (NₛF=8.2·1015 g^-1), newly discovered centers in which the unpaired electron belongs to an oxygen atom (NₛO=1017 g^-1), and paramagnetic centers associated with selenate radicals (NₛS=6·1018 g^-1). By comparison of the photoluminescence spectra and defect concentrations, it is assumed that the luminescent properties of AAO obtained in selenic acid are exclusively determined by F⁺ centers. The centers associated with other reaction products do not contribute to the AAO luminescent properties.