Self-assembly preparation of gold nanoparticles-TiO2 nanotube arrays binary hybrid nanocomposites for photocatalytic applications

Increasing interest has been devoted to preparing gold nanoparticle (GNP) functionalized TiO2 nanotube array (TNTA) nanocomposites (GNP/TNTA) for photocatalytic applications. Nonetheless, achieving accurate control of surface assemblies of GNPs tethered on the TNTA substrate is far from satisfactory. Thus, in our work, applying 3-mercaptopropionic acid (MPA) as an interconnecting ligand, tailor-made monodispersed GNPs are evenly deposited on the interior and exterior surfaces of TNTAs with significant monodispersity via a self-assembly approach. The intrinsic self-assembly mechanism leading to the GNP/TNTA hybrid nanostructure is highlighted and ascertained. The photocatalytic performances of GNP/TNTAs are systematically evaluated in the photodegradation of organic dye pollutants under UV light irradiation. The ensemble of results indicates that the hierarchical nanostructure of the GNP/TNTA nanocomposite obtained via this self-assembly approach exhibits remarkably enhanced photocatalytic performance compared to its counterparts of P25 particulate film, a flat anodic TiO2 layer (FTL), and GNP/FTL, in which well-dispersed GNPs and conducting titanium substrate are proposed to play crucial roles as efficient “electron traps” for the transfer of the photogenerated electrons and thus retard the recombination of photogenerated electron–hole pairs during the harvesting of photon-energy. In addition, the detection of increased amounts of highly active species (especially hydroxyl radicals) on the GNP/TNTAs by photoluminescence (PL) and electron spin resonance spectra (ESR) techniques further confirms the proposed mechanism. It is hoped that our knowledge regarding this simple self-assembly approach may cast new insight into the design and fabrication of noble-metal NPs/1-D nanotubular semiconductor hybrid nanomaterials for a wide range of photocatalytic applications.