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 anelectron generator for the reduction of gold ions on thesurface of TiO2 nanoparticles. It was observed that theTiO2 plays not only as a support for the goldnanoparticles but also as a storage of electronsproduced by the EAB within the particles. Thesestored electrons dramatically increase the reduction ofgold ions and hence we have observed the formationof the Au@TiO2 nanocomposites within 90 min. A mechanism of the nanocomposite formation is alsoproposed. The as-synthesized nanocomposites werecharacterized by UV–Vis absorption spectroscopy tomonitor the proper formation of the nanocomposites.X-ray diffraction and transmission electron microscopicanalyses 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 biogenicroute represents a unique pathway for the low cost,eco-friendly, rapid, and controlled synthesis of nanostructured Au@TiO2 hybrid systems which will trulyrevolutionize the synthetic fields of nanocomposites.