Innovative electrochemical synthesis of highly defective Ta2O5/Cu2O nanotubes inactivating bacteria under low-intensity solar irradiation

This study presents an innovative electrochemical preparation of Ta2O5 nanotubes (NTs) decorated with Cu2O nanoparticles (NPs). The Ta2O5/Cu2O nanotubes led to fast bacterial inactivation under low-intensity solar irradiation. The Cu2O decoration on Ta2O5 nanotubes accelerated the E. coli inactivation kinetics by several orders of magnitude compared to bare Ta2O5 nanotubes. Systematic characterization of the surface properties of Ta2O5/Cu2O nanotubes is reported. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), XPS-spectroscopy, and energy dispersive X-ray spectroscopy (EDX) were used to understand the structural, morphological and chemical composition of the decorated nanotubes. UV-VIS spectroscopy, photo-luminescence (LP), and surface reflectivity further allowed to understand the effect of photons on the nanotube interfaces giving insight into the role of structural defects, oxygen vacancies and Cu2O decoration. The oxygen vacancies formation and contribution to the bacterial inactivation have been highlighted. The bandgap of Ta2O5/ Cu2O decreased upon increasing the Cu2O addition to Ta2O5 NTs. A differentiated mechanism for bacterial inactivation is suggested under low-intensity solar light (50 mW/cm2) for Ta2O5 NTs and Ta2O5/Cu2O NTs. The high photocatalytic activity of Ta2O5 possibly involved the surface and bulk electron diffusion steps, leading to the generation of the observed surface catalytic sites. A mechanism has been proposed for the antibacterial activity of the prepared nanotubes.