High sensitivity and selectivity of ZnO nanoparticle-decorated 1D a-MoO₃ nanobelts toward ethanol by microwave heating

One-dimensional layer structure a-MoO₃ nanobelts with abundant oxygen defects were effectively synthesized through a hydrothermal route and decorated by ZnO nanoparticles via a liquid-phase chemical process. ZnO nanoparticles (NPs) with a size of approximately 50 nm were uniformly dispersed on the a-MoO₃ nanobelt surface, forming an n-n heterostructure at the two-phase interface. The crystalline structure, microtopography, element composition, valence state, surface-to-volume ratios, optical properties, and work function of the ZnONP-decorated a-MoO₃ samples were analyzed. ZnONP-decorated a-MoO₃ nanobelts with different proportions of ZnO were synthesized and subjected to ethanol sensing. The 25% loaded ZnONP-decorated a-MoO₃ nanobelts were found to offer the best response (R_a/R_g = 19.2 at 100 ppm), which was 3.6 times higher than that of pristine α-MoO₃ (5.37) with a low detection limit (108 ppb). The response time was significantly lower (14–27 s) than that of pristine a-MoO₃ (5–8 s). Furthermore, the sensor has ultrahigh selectivity and reliable stability for ethanol. Layered MoO₃ nanobelts have a unique sensing mechanism, which is the catalytic oxidation of lattice oxygen on the MoO₃ surface to form oxygen vacancies and free electrons. The excellent sensing performance was ascribed to the unique 1-D nanobelt morphology of the a-MoO₃ carrier, the abundance of oxygen defects, and the formation of heterojunction barriers at the two-phase interface.