Near room temperature operable H2S sensors based on In2O3 colloidal quantum dots

Indium oxide (In2O3) nanomaterials have been investigated extensively as promising candidates for gas sensor applications. Here, we fabricate near room temperature operable H2S-sensitive gas sensors based on In2O3 colloidal quantum dots (CQDs). Room-temperature film deposition of In2O3 CQDs followed by surface ligand exchange treatment through Cu inorganic salts was employed to construct the sensor devices. Combined with a moderate annealing treatment, the long-chain ligands surrounding the quantum dot surfaces were completely removed to enhance gas adsorption and carrier transport, simultaneously resulting in the formation of CuO that may act as a catalytic promoter or form p-n heterojunction for selective H2S detection. The sensors exhibited high response up to 90 toward 5 ppm of H2S with response/recovery time of 72 s/200 s respectively, suggestive of a performance improvement compared to the In2O3-based (HS)-S-2 sensors reported in existing literature. The power law analysis indicated that the main oxygen species adsorbed on the surfaces were O-2(-) and O- with the proportion of approximate 1:1 at near room temperature. The gas-sensing mechanism was attributed to the decisive role of surface states in determining the electrical conduction of quantum dot gas sensors.