A simple biogenic route to rapid synthesis of Au@TiO2 nanocomposites by electrochemically active biofilms

Deposition of gold on titanium dioxide (TiO2) nanoparticles is highly beneficial for maximizing the efficiency of many photocatalytic reactions. In this study, we have reported for the first time the use of an electrochemically active biofilm (EAB) for the synthesis of Au@TiO2 nanocomposite with sodium acetate as the electron donor. The EAB acts as an electron generator for the reduction of gold ions on the surface of TiO2 nanoparticles. It was observed that the TiO2 plays not only as a support for the gold nanoparticles but also as a storage of electrons produced by the EAB within the particles. These stored electrons dramatically increase the reduction of gold ions and hence we have observed the formation of the Au@TiO2 nanocomposites within 90 min. A mechanism of the nanocomposite formation is also proposed. The as-synthesized nanocomposites were characterized by UV–Vis absorption spectroscopy to monitor the proper formation of the nanocomposites. X-ray diffraction and transmission electron microscopic analyses were performed to determine the structural and microstructural properties of the nanocomposites. High-resolution transmission electron micrographs depict the proper formation of the Au@TiO2 nanocomposites with gold nanoparticle size varying from 5 to 10 nm with an increase in the gold precursor concentration. Zeta potential measurements were used to investigate surface charges of the as-synthesized nanocomposites. This novel biogenic route represents a unique pathway for the low cost, eco-friendly, rapid, and controlled synthesis of nanostructured Au@TiO2 hybrid systems which will truly revolutionize the synthetic fields of nanocomposites.