Self-assembled Au/TiO2/CNTs ternary nanocomposites for photocatalytic applications

Abstract

Titanium dioxide TiO2 is a very important semiconducting material under extensive investigation due to its photoinduced reactivity in many modern technological applications. In order to reduce the recombination for photo-generated charge carriers (electrons and holes) in the TiO2 materials, we report in this work that both carbon nanotubes (CNTs) and noble metals such as Au nanoparticles can make nonvalent contacts to the functional TiO2 phase in preparation of ternary nanocomposites Au/TiO2/CNTs. In our current approach, xero-gel coating of TiO2 is first synthesized on the surface of CNTs via a surfactant-modified sol-gel process. In this connection, conversion of xero-gel TiO2 to anatase TiO2 can be achieved through ambient heating at 300-500 °C for the TiO2/CNTs. The premade monodisperse gold nanoparticles (AuNPs) with controllable sizes can then be uniformly distributed on the surface of TiO2 coatings, with assistance of bidentate ligand 3-mercaptopropionic acid (MPA) that provide linkage between the AuNPs and the TiO2 phase. It has been further demonstrated that the crystallinity of TiO2, the inter-particle distance and the weight of AuNPs can be controlled facially with this self-assembly method. Compared to the binary TiO2/CNTs reported in the literature, our optimized Au/TiO2/CNTs nanocomposite system has shown a higher catalytic activity toward organic pollutant degradation and mineralization due to possible reduction in recombination of photo-generated charge carriers in the photocatalytic processes. © 2010 American Scientific Publishers.