Decoupling the Conflicting Roles of Photoactivation and Boosting Chemiresistor Response by Pulsed UV Light Modulation

UVphotoactivation has been widely employed to trigger the responseof semiconductor chemiresistors at room temperature (RT). Generally,continuous UV (CU) irradiation is applied, and an apparent maximalresponse could be obtained via optimizing UV intensity. However, owingto the conflicting roles of (UV) photoactivation in the gas responseprocess, we do not think the potential of photoactivation has beenfully explored. Herein, a pulsed UV light modulation (PULM) photoactivationprotocol has been proposed. Pulsed UV-on facilitates the generationof surface reactive oxygen species and refreshes the surface of chemiresistors,while pulsed UV-off avoids the side effects of UV-induced desorptionof the target gas and the decline of base resistance. PULM enablesdecoupling those conflicting roles of CU photoactivation, resultingin a drastic boost of response to trace (20 ppb) NO2 from1.9 (CU) to 131.1 (PULM UV-off), and a decline of limit of detectionfrom 2.6 ppb (CU) to 0.8 ppb (PULM) for a ZnO chemiresistor. Thiswork highlights that PULM allows full exploitation of the potentialof nanomaterials for sensitively detecting trace (ppb-level) toxicgas molecules and opens a new opportunity for designing highly sensitive,low-power consumed RT chemiresistors for ambient air quality monitoring.

Automated summary

This study proposes a pulsed UV light modulation (PULM) photoactivation protocol, which allows the exploitation of nanomaterials for sensitively detecting trace toxic gas molecules. PULM enables the generation of surface reactive oxygen species and refreshes the surface of chemiresistors without the side effects of UV-induced desorption and decline of base resistance. PULM significantly improves the response rate to 20 ppb NO2 from 1.9 (continuous UV) to 131.1 (PULM UV-off) and reduces the limit of detection from 2.6 ppb (continuous UV) to 0.8 ppb (PULM) for a ZnO chemiresistor.