Highly crystalline and ordered nanoporous SnO2 thin films with enhanced acetone sensing property at room temperature

Abstract

Gas sensing with highly ordered nanoporous materials is attracting much attention because of its promising capability for detecting toxic gases at room temperature. In this study, highly organized, transparent, crystalline nanoporous Pd-doped SnO₂ thin films are obtained through a 120 °C post-synthetic water vapour hydrothermal treatment of the as-deposited film. Characterization by XRD, SEM, TEM, HRTEM, Raman spectroscopy and XPS reveals that Pd-doped SnO₂ thin films have a highly ordered nanostructure, highly crystalline cassiterite, small particle size, and outstanding particle interconnectivity. The best results with respect to porosity, nanostructured ordering, as well as the sensing behaviour are obtained by the tin dioxide thin films doped with 4 wt% palladium prepared with spin-coating at 30% relative humidity, aging for 2 h at 60 °C and for 12 h at 120 °C and 95% relative humidity, and gradual calcination at 300 °C. The acetone response of the SnO₂ sensing film with 4 wt% Pd-doping level is found to be substantially improved up to 14.64 at 100 ppm with a short response time of ∼30 s at room temperature. In general, the synthesis procedure described in this report has the advantage of being easy, cost efficient, highly reproducible and therefore highly suitable for the fabrication of high performance ordered nanoporous crystalline materials for applications including gas sensing, photocatalysis, and 3rd generation photovoltaics.