Extremely sensitive ethanol sensor using Pt-doped SnO₂ hollow nanospheres prepared by Kirkendall diffusion

The pure and 0.3 wt% Pt-doped SnO₂ hollow nanospheres were prepared by the oxidation of pure and Pt-doped Sn nanoscrystals embedded in carbon matrix and their gas sensing characteristics were investigated. The formation of hollow morphology was attributed to the nanoscale Kirkendall effect due to rapid outward diffusion of Sn ions and relatively slow inward diffusion of oxygen. Pure SnO₂ hollow nanospheres showed a high response (resistance ratio) of 93.3 when exposed to 5 ppm ethanol. The response to 5 ppm ethanol was significantly increased to 1399.9 with doping 0.3 wt% Pt. In addition, selectivity to ethanol was also enhanced by Pt doping. Ultrasensitive and selective detection of ethanol in pure and Pt-doped SnO₂ nanospheres is explained by the effective electron depletion in hollow structures and catalytic promotion of gas sensing reaction.