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

Porous urchin-like α-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 5/10 s, and relatively low detection limit of 1 ppm. These results help us to understand the sensing mechanism of α-Fe2O3 and hint the potential application of the as-prepared sensor in monitoring H2S.