ZnO quantum dots decorated carbon nanotubes-based sensors for methanol detection at room temperature

Abstract

In this work, a highly sensitive methanol gas sensor at room temperature is reported based on ZnO quantum dots (QDs) decorated carbon nanotubes (CNTs) systesized via thermal vapor deposition process following by metal sparking technique with varying sparking times. The FE-SEM, TEM and XPS characterizations confirm a high quality of ZnO QDs decoration (average particle size of ~2.5 nm) on CNTs surfaces (average diameter of ~30 nm). The gas-sensing results show that the ZnO QDs decorated CNTs with the sparking time of 30 s own the highest response to methanol compared with those of other the sparking times and undecorated one as well as high selectivity to methanol against acetone, ammonia, dimethylformamide, ethanol, formaldehyde and toluene at room temperature. The methanol-sensing mechanism of ZnO QDs decorated CNTs sensor can be discussed based on the low-temperature reducing reaction process enhanced via CNTs-ZnO QDs (p-n) heterojunctions and quantum-size effects.