Anomalous conductivity-type transition sensing behaviors of n-type porous α-Fe2O3 nanostructures toward H2S

Porous urchin-like alpha-Fe2O3 nanostructures with n-type semiconducting properties were used as gas sensing materials. Interestingly, it was observed abnormal n-p transition sensing behavior induced by the variation of working temperature and p-n transition sensing behavior related to the increase of H2S concentration. Large density of unstable surface states resulting from high surface-to-volume ratio would be beneficial for the formation of a surface inversion layer and account for the n-p transition. Furthermore, the as-prepared sensor showed good H2S sensing performances with short response/recovery time within 5/10s, and relatively low detection limit of 1 ppm. These results help us to understand the sensing mechanism of alpha-Fe2O3 and hint the potential application of the as-prepared sensor in monitoring H2S. (c) 2011 Elsevier B.V. All rights reserved.