Hydrothermal synthesis and Ta doping of TiO2 nanorods: Effect of soaking time and doping on optical and charge transfer properties for enhanced SERS activity

In this work, an alkali hydrothermal synthesis of TiO2 nanorods (NRs) and Ta doped TiO2 NRs has been reported for enhanced optical and charge transfer (CT) properties with an emphasis on post synthesis soaking treatment. Highly uniform and crystalline TiO2 NRs with a band gap of 2.95 eV were obtained using TiO2 nanopowder as a precursor by optimizing the soaking time in HCl solution. Similarly, Ta doped TiO2 NRs with a band gap of 2.58 eV were obtained. The formation mechanisms of undoped TiO2 NRs by varying soaking time and Ta doped TiO2 NRs have been discussed along with their enhanced surface enhanced Raman scattering (SERS) activity towards the detection of methylene blue. Undoped TiO2 NRs obtained at optimized soaking time exhibited enhanced SERS activity as compared to TiO2 nanopowder. Interestingly, Ta doped TiO2 NRs exhibited further enhancement in SERS activity. This could be explained as synergic effects of soaking treatment and Ta doping which induce surface/lattice defects in TiO2 crystal and abundant energy levels below the conduction band of TiO2.