Resistive gas sensors based on colloidal quantum dot (CQD) solids for hydrogen sulfide detection

Colloidal quantum dot (CQD) is emerging as new substitution gas sensing materials due to the excellent accessibility of gas molecules to CQD surfaces realized via surface ligand removal. Here we demonstrated highly sensitive and selective H-2 S gas sensors based on PbS CQD solids. The sensor resistance decreases upon H-2 S gas exposure and the response is defined as the ratio of the sensor resistance in clean air to that in H-2 S gas. As the operating temperature increased within the range 50-135 degrees C, the sensor response increased while the response and the recovery time decreased. The sensor was fully recoverable toward 50 ppm of H2 Sat 108 degrees C and the highest response was 2389 at 135 degrees C with the response and recovery time being 54s and 237s, respectively. The dependence of sensor response on the H2 S gas concentration in the range of 10-50 ppm is linear, suggesting a theoretical detection limit of 17 ppb toward H-2 Sat 135 degrees C. Meanwhile, the sensor showed superb response selectivity toward H2S against SO2, NO2 and NH3. We propose that the PbS CQDs film where the surface states determine the conduction type via remote doping may undergo a p-to-n transition due to H2S exposure at elevated temperatures. (C) 2014 Elsevier B.V. All rights reserved.