As previously reported, arrays of Nb2O5 nanocolumns on substrates may be synthesized by anodizing Al-on-Nb bilayers in oxalic, sulfuric, malonic, or phosphoric acids. Here, for the first time, we employed a new anodizing electrolyte - selenic acid (H2SeO4) due to a unique morphology of porous anodic alumina (PAA) formed in this electrolyte featuring extremely narrow pores and therefore, the minimal possible porosity (~3%) among the PAA films prepared in the usual solutions. Such a morphology may result in distinctive structural, physical, and chemical properties of the niobium-oxide nanoarrays complemented by the specific dielectric, optical, electro-optical, catalytic, and antibacterial properties in case the selenium species are incorporated into the column structure during the anodizing. The columns were prepared from the magnetron-sputtered Al/Nb bilayers by anodizing at 12 or 40 V, followed by re-anodizing to 80 or 120 V, respectively, and selective dissolution of the alumina overlayer. Detailed XPS characterization confirmed that selenium species is present in the column material. The fitting of the narrow-scan Se 3d spectra, complicated by overlapping with Nb 4s peaks, shows that selenium is incorporated in the form of selenate (SeO42−) and selenide (Se2−) anions, likely creating a core-shell structure. Quantitative analysis reveals that about 1.5-3.0% of O2− anions in the oxide structure are replaced by selenate or selenide anions. Further investigation is in progress to understand the formation-structure-morphology relationship and explore the functional properties of the arrays.Keywords: Anodizing, porous anodic alumina, niobium pentoxide, selenium
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