Dual Functional Ta-Doped Electrospun TiO₂ Nanofibers with Enhanced Photocatalysis and SERS Detection for Organic...

There is a growing interest in multifunctional nanomaterials for the detection as well as degradation of organic contaminants in the water. In this work, we report on the development of dual functional TiO₂ nanofibers (TNF) with different tantalum (Ta) doping (1-10 mol %) by a simple electrospinning technique. As-prepared TNF show mesoporous dominant structure, which are favorable for photocatalytic activity due to the presence of catalytic spots. Ta doping decreases the crystalline size within TiO₂ matrix because of the incorporation of Ta⁵⁺ ions and restricts the phase transformation from anatase to rutile. Ta doping slightly enhances the visible light absorption because of the Ti³⁺ defects sites created upon Ta⁵⁺ doping. The effect of Ta doping within TiO₂ matrix was systematically studied for the degradation of methylene blue (MB) dye under ultraviolet (UV) and solar light irradiation. The 5% Ta-doped TNF were found to be optimal and showed 5.1 and 2.2 times higher photocatalytic activity as compared to TNF under UV and solar light irradiation, respectively. The effect of Ta doping for the detection of MB molecules was also studied by surface enhanced Raman scattering (SERS). It was observed that 5% Ta-doped TNF exhibit higher photocatalytic activity and enhanced SERS signals of adsorbed MB molecules as compared to the TNF. The enhanced photocatalytic and SERS activities can be explained as combined effects of enhanced visible light absorption, lower crystalline size, and slightly higher surface area. The observed results show that Ta doping induces new energy levels below the conduction band of TiO₂ because of Ti³⁺ defects, which inhibit the photogenerated charge recombination acting as electron traps and promote charge transfer mechanism acting as an intermediate state for TiO₂ to MB molecule electron transfer, and are mainly responsible for the enhanced photocatalytic and SERS activities, respectively.