Alternative approaches to fabrication of gold-modified TiO 2 nanotubes

Abstract

Three approaches, impregnation–reduction, deposition and direct assembly, are used to fabricate gold-modified TiO 2 nanotubes. Prepared materials are characterized with powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV–visible absorption spectroscopy and BET, etc. The gold-modified TiO 2 nanotubes prepared via various procedures exhibit distinct difference in structure. By impregnation–reduction approach, gold-modified TiO 2 nanotubes with large gold particles are fabricated. The gold particles are either deposited on or encapsulated in TiO 2 nanotubes. However, by using gold hydrophilic colloidal dispersion as gold precursor, gold particles in the modified TiO 2 nanotubes are very small. Gold particles only adhere to the outer surface of TiO 2 nanotubes after deposition process, whereas adhere to not only the outer but also the inner walls of TiO 2 nanotubes after direct assembly process. A possible mechanism is proposed to illustrate the formation of gold-modified nanotubes that are prepared by direct assembly process.