Highly sensitive and selective trimethylamine sensors using Ru-doped SnO2 hollow spheres

The 0.45 mol% Ru-doped SnO2 (Ru–SnO2) hollow spheres, each with a shell thickness of ∼17 nm, were prepared by the uniform coating of Ru- and Sn-precursors onto SiO2 microspheres with diameters of ∼300 nm, followed by heat treatment at 350 °C and subsequent removal of the core SiO2 using a dilute HF solution. The Ru–SnO2 hollow spheres showed high responses to 5 ppm trimethylamine (TMA) at 350 °C with negligible cross-responses to toluene, benzene, NH3, CO, H2, and C3H8 and decreased cross-responses to C2H5OH, while undoped SnO2 hollow spheres showed similar responses to TMA and C2H5OH. The selective and sensitive detection of TMA that was achieved in Ru-doped SnO2 hollow spheres is explained in relation to the catalytic sensitization of Ru and the gas-accessible hollow morphology of the thin shell configurations.