Oxidizing gas sensing properties of the n-ZnO/p-Co3O4 composite nanoparticle network sensor

Abstract

ZnO/Co3O4 (ZnO/Co3O4=4:1) composite nanoparticles were synthesized via a facile solvothermal route. The 4:1 ZnO/Co3O4 composite nanoparticle network sensor showed significantly enhanced NO2 gas sensing performance compared to its pure ZnO nanoparticle sensor counterpart. The ZnO/Co3O4 composite nanoparticle sensor showed responses of 346–1602% to 0.1–5ppm of NO2 at room temperature under UV illumination at 3.7mW/cm2, whereas ZnO nanoparticle sensors showed responses of 264–707%. The former also showed faster response to NO2 gas and higher selectivity to NO2 gas than the latter. The responses of the sensors to NO2 increased with increasing UV illumination intensity. In addition, the underlying mechanism for the enhanced sensing performance of the ZnO/Co3O4 composite nanoparticle sensor toward a strong oxidizing gas NO2 under UV illumination was examined. Particular emphasis was placed on the role of the p/n junction in the composite nanoparticle sensor.