Fast-response and high sensitivity gas sensors based on SnO2 hollow spheres

SnO2 hollow nanospheres have been synthesized by heat treatment of a mixture composed of SnCl4 and carbon microspheres. The SnO2 nanospheres are 100 nm in size and composed of large amount of SnO2 nanocrystals with diameters of ~ 6 nm, which is close to two times of the Debye length of SnO2. It was found that the sensitivity to 1000 ppm ethanol obtained with SnO2 hollow nanosphere-based sensors is as high as 75. The response and recovery time are only 4 and 10 s, respectively. Such excellent sensing properties can be ascribed to the small-size nanocrystals and porous structure of SnO2 hollow nanospheres, which lead to large diffusion constant.