Enhanced NO₂ sensing aptness of ZnO nanowire/CuO nanoparticle heterostructure-based gas sensors

Designing heterostructure materials for better gas sensing performance is a key for obtaining low-temperature gas sensor device technologies. Herein, CuO nanoparticle-ZnO nanowire heterostructure-based gas sensors have been fabricated by thermal evaporation followed by annealing in argon and air atmospheres and named respectively as NWG and NWA sensors. X-ray diffraction demonstrates the monoclinic structure of CuO and hexagonal wurtzite structure of ZnO and, thus, the formation of heterostructure. Morphological analysis confirms the ZnO nanowires (NWs) were well-linked to CuO nanoparticles (NPs). At an optimized temperature of 150 °C, the heterostructure sensor exhibits a maximum response (NWG, 175%) to NO₂ over other oxidizing/reducing target gases on the exposure of 100 ppm concentration. This heterostructure sensor, noteworthy, responds to an extremely low exposure of NO₂ gas (1 ppm). The interactions of oxidizing NO₂ gas with ZnO/CuO heterostructure sensors has effectively been scrutinized using impedance spectroscopy analysis.