TiO₂/Pt/TiO₂ Sandwich Nanostructures: Towards Alcohol Sensing and UV Irradiation-Assisted Recovery

Abstract

The TiO 2 /Pt/TiO 2 sandwich nanostructures were synthesized by RF magnetron sputtering and demonstrated as an alcohol sensor at room-temperature operation with a fast recovery by UV irradiation. The TiO 2 /Pt/TiO 2 layers on SiO 2 /Si substrate were confirmed by Auger electron spectroscopy with the interdiffusion of each layer. The TiO 2 /Pt/TiO 2 layers on printed circuit board show the superior sensor response to alcohol in terms of the sensitivity and stability compared to the nonsandwich structure, that is, the only Pt layer or the TiO 2 /Pt structures. Moreover, the recovery time of the TiO 2 /Pt/TiO 2 was improved by UV irradiation-assisted recovery. The optimum TiO 2 /Pt/TiO 2 with thicknesses of the undermost TiO 2 layer, a Pt layer, and the topmost TiO 2 layer being 50 nm, 6 nm, and 5 nm, respectively, showed the highest response to ethanol down to 10 ppm. Additionally, TiO 2 /Pt/TiO 2 shows an excellent sensing stability and exhibits different sensing selectivity among ethanol, methanol, and 2-propanol. The sensing mechanism could be attributed to the change of Pt work function during vapor adsorption. The TiO 2 layer plays an important role in UV-assisted recovery by photocatalytic activity and the topmost TiO 2 acts as protective layer for Pt.