One-step controlled synthesis of ZnO-ZnSe hollow nanospheres with surface defects for selective detection of NO₂

The introduction of surface defects in sensing materials is an important means to improve sensor performance. In this work, we design a simple one-step route to synthesize ZnO-ZnSe without any template or surfactant, and obtain ZnO-ZnSe hollow spherical composite with a diameter of ∼ 200 nm. The shell of the hollow spheres is assembled by nanoparticles with a lot of surface defects after sintering at 800 °C in N₂ atmosphere. The surface defects can promote the sensing materials release more electrons and facilitate the reaction of oxygen ions on the material surface. It is beneficial to the adsorption of NO₂ on sensing materials for enhancing the sensing performance. The composite shows excellent sensitivity for 10 ppm NO₂ at 170 °C, which is 5.32 times that of pure ZnO. And the sensor can recover quickly within 28 s after responding to NO₂. It is also satisfactory for the sensor to detect the lowest concentration of 100 ppb. The chemical characterizations such as DRS, PL, XPS, GC–MS, and Kelvin probe are used, combined with the calculation of DFT theory to further explore the synergy effect of the formation of ZnO and ZnSe heterojunction and the surface defects caused by high-temperature sintering on the improvement of sensor performance.