Chemiresistive gas sensors employing solution-processed metal oxide quantum dot films

We report low-temperature chemiresistive gas sensors based on tin oxide colloidal quantum dots (CQDs), in which the benefits of CQDs such as extremely small crystal size, solution-processability, and tunable surface activity are exploited to enhance the gas-sensing effect. The sensor fabrication is simply employing spin-coating followed by a solid-state ligand exchange treatment at room temperature in air ambient. The optimal gas sensor exhibited rapid and significant decrease in resistance upon H2S gas exposure when operated at 70 °C, and it was fully recoverable upon gas release. We observed a power law correlation between the sensor response and H2S gas concentration, and the sensing mechanism was discussed using the completely depletion model with a flat band diagram.