Chlorine Gas Sensing Performance of On-Chip Grown ZnO, WO3, and SnO2 Nanowire Sensors

摘要

Monitoring toxic chlorine (Cl-2) at the parts per -billion (ppb) level is crucial for safe usage of this gas. Herein, ZnO, WO3, and SnO2 nanowire sensors were fabricated using an on-chip growth technique with chemical vapor deposition. The Cl-2 gas-sensing characteristics of the fabricated sensors were systematically investigated. Results demonstrated that SnO2 nanowires exhibited higher sensitivity to Cl-2 gas than ZnO and WO3 nanowires. The response (R-Cl2/R-air) of the SnO2 nanowire sensor to 50 ppb Cl-2 at 50 degrees C was about 57. Hence, SnO2 nanowires can be an excellent sensing material for detecting Cl-2 gas at the ppb level under low temperatures. Abnormal sensing characteristics were observed in the WO3 and SnO2 nanowire sensors at certain temperatures; in particular, the response level of these sensors to 5 ppm of Cl-2 was lower than that to 2.5 ppm of Cl-2. The sensing mechanism of the SnO2 nanowire sensor was also elucidated by determining Cl-2, responses under N-2 and dry air as carrier gases. We proved that the Cl-2 molecule was first directly adsorbed on the metal oxide surface and was then substituted for pre-adsorbed oxygen, followed by lattice oxygen.