Visible light-assisted room temperature gas sensing with ZnO-Ag heterostructure nanoparticles

Noble metal-metal oxide nanohybrids play an ever-increasing role in photocatalytic applications. Here, a ZnO-Ag nanoparticle prepared by a modified polymer-network gel method was utilized for room temperature light-assisted NO2 gas detection. Since a heterojunction forms between the two materials and surface oxygen vacancies increase, the sensitivities of the sensors to NO2 gas (0.5–5 ppm) under various light (λ = 365–520 nm) illumination conditions are enhanced in comparison with those of pure ZnO sensor. Surface plasmon resonance (SPR) was found to result in the excellent visible-light performance of this ZnO-Ag nanostructure. More importantly, by tuning the working wavelength using different LED light sources, we can obtain an optimized sensitivity. When blue-green LED (470 nm, 75 mW/cm2) is used, the 3 mol% Ag-loaded ZnO sensor shows the highest sensitivity as well as superior stability and selectivity. The effect of humidity on the sensor performance is also discussed in detail.