Synthesis and gas sensing properties to NO2 of ZnO nanoparticles

In this work, we prepared ZnO nanoparticles with sizes ranging from 5 to 270 nm by annealing the precursor of zinc carbonate hydroxide at four different temperatures (200, 400, 600 and 800 °C) and investigated their morphology, structure and optical properties as well as sensing performances to NO2. The precursor with small particle size and narrow size distribution was synthesized by a simple method involving separate nucleation and aging steps (SNAS). Among four obtained ZnO samples, the ZnO-400 (annealed at 400 °C) exhibits the best optical properties and the highest sensing response to NO2. The ZnO-400 shows fast response (≤30 s) and recovery (≤120 s) to NO2 and high selectivity to NO2. Besides, we further discussed a correlation between the gas sensing response and the defects of ZnO nanoparticles.