Microstructure and Photoelectric Response of Gold Nanocrystalline on TiO2 Nanotube Arrays

In this paper, we report photoelectrical response of gold nanocrystalline on TiO2 nanotubes (TNTs) with Au morphology ranging from nanoparticles, thin nanoring to thick nanoring. The gold nanocrystallines are loaded on the TNT by the facile magnetron sputtering technique. Compared with pristine TNT, the gold-decorated TNTs have shown obvious light absorption at wavelength of 380–850 nm as well as dependence of surface plasmonic resonance (SPR) on Au morphology. Photocurrent response under white light illumination presents around 4 times enhancement on all gold-decorated nanotubes at an applied voltage of 0.2 V. Transient current measurement reveals different ramping up behavior on nanoparticles and nanoring-coated TNTs at the onset of illumination. Full-field electromagnetic wave simulation based on finite element analysis (FEA) indicates that the shifting of SPR peaks is a joint effect of the size/aspect ratio, morphology, and amount of the nanocrystalline Au. Meanwhile, the FEA indicates that instant current response upon illumination on gold nanoparticles and nanoring structures are dependent on the electric field distribution, the behavior of charge carriers along longitudinal dimension of the TNT arrays. This study provides a perspective on SPR effect related to the enhanced photocurrent response on TNT arrays.