Three-dimensional ordered SnO2 inverse opals for superior formaldehyde gas-sensing performance

Inverse opals (IO), as a special kind of macroporous material with large surface to volume ratio and ordered layer structure, have great application potential in highly sensitive gas sensing area. In this paper, macroporous SnO2 IO were synthesized by a simply PMMA template method and their porous sizes were controlled ranging of 140-400 nm. The performance of the SnO2 IO sensors to formaldehyde (HCHO) gas was systemically studied. The results indicated that the sensing properties of the SnO2 IO sensors to HCHO were highly improved than the traditional sensors, depending strongly on the porous sizes. The response of the SnO2 IO sensors increased gradually with the increase of porous size. The response of the optimum SnO2 sensor was as high as 629 for 100 ppm HCHO gas detection and the practical detection limit was as low as 10 ppb, which was one of the best levels for the detection of HCHO gas. And more, they also demonstrated fast response dynamics and long time stability.