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

Highlights • Excellent crystallinity and solution processability of In 2 O 3 QDs enable low temperature sensor fabrication and operation. • High response of 90@5 ppm H 2 S was achieved at near room temperature with fast response/recovery kinetics. • CuO formation through ligand exchange and annealing treatment helps achieve sensitive and selective response toward H 2 S. • O2− and O− were the main chemisorbed oxygen species on In 2 O 3 surfaces at near room temperature with the ratio of 1:1. Abstract Indium oxide (In 2 O 3) nanomaterials have been investigated extensively as promising candidates for gas sensor applications. Here, we fabricate near room temperature operable H 2 S-sensitive gas sensors based on In 2 O 3 colloidal quantum dots (CQDs). Room-temperature film deposition of In 2 O 3 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 H 2 S detection. The sensors exhibited high response up to 90 toward 5 ppm of H 2 S with response/recovery time of 72 s/200 s respectively, suggestive of a performance improvement compared to the In 2 O 3 -based H 2 S 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. [ABSTRACT FROM AUTHOR]