Preparation of Zinc Oxide Monolayer Porous Hollow Sphere Array and Its Ultra-Fast Response to NO2 at Room Temperature under Ultraviolet Irradiation

By using monolayer polystyrene colloidal spheres as the template , ZnO array-film was in-situ synthesized on the plate electrodes for gas sensors by template-assisted hydrothermal method. Scanning electron microscopy ( SEM ) and high-resolution transmission electron microscopy ( HRTEM ) characterization results showed that the film was composed of ordered monolayer porous hollow spheres with pore size of about 4 nm. The gas-sensing performances of the prepared thin-film gas sensor were investigated. Under UV irradiation with a low optical radiation power ( 1. 7 mW/cm(2)) , the thin-film gas sensor based on ZnO monolayer hollow sphere array showed excellent NO2-sensing performances with a detection limit of 0. 098 mg/m(3), and the sensing response toward 2. 45 mg/m(3) NO2 gas could reach 5. 7 with an ultra-fast response/recovery speed ( 3 s/5 s) . With the finite difference time domain method , the local field intensity of the monolayer hollow sphere array-film was investigated , and it was found that the second-level response/recovery mechanism might be due to the relatively uniform local field intensity distribution of the monolayer hollow sphere array film.