Ultrasensitive detection of trimethylamine using Rh-doped SnO2 hollow spheres prepared by ultrasonic spray pyrolysis

An ultrasensitive trimethylamine (TMA) sensor was achieved using Rh-doped SnO2 hollow spheres prepared by ultrasonic spray pyrolysis followed by heat treatment at 500 °C, and the effects of Rh doping on TMA sensing characteristics were investigated. The response (resistance ratio) of the Rh-doped SnO2 hollow spheres to 5 ppm TMA at 400 °C was 1177.5, which is 33 times higher than that of pure SnO2 hollow spheres. The detection limit of the sensor was as low as 5 ppb. In addition, the Rh-doped SnO2 hollow spheres showed negligible cross-responses to HCHO, benzene, toluene, p-xylene, NH3, CO, H2, and NO2, and a decreased cross-response to C2H5OH, whereas pure SnO2 hollow spheres did not show selective detection of a specific gas. The ultrahigh sensitivity and selective detection to TMA were attributed to the electronic interactions between Rh and SnO2 and the high catalytic activity of Rh to TMA.