In-situ generation of highly dispersed Au nanoparticles on porous ZnO nanoplates via ion exchange from hydrozincite for VOCs gas sensing

The indoor volatile organic compounds (VOCs) have caught much attention because millions of people are suffering from indoor air pollution. To detect VOCs, various gas sensors with fast response, high sensitivity and high stability have been fabricated by nanocomposite technology. In this study, highly dispersed Au nanoparticles are deposited on porous ZnO nanoplates (Au@ZnO) via ion exchange method from hydrozincite [Zn5(CO3)2(OH)6] without the addition of any surfactants. By immersing hydrozincite precursors into 0.1%-5% HAuCl4 solutions and followed by annealing, several Au@ZnO sensors with size-limited Au nanoparticles are fabricated for the detection of nine types of VOCs. Comparing with pure ZnO nanoplates, the as-prepared Au@ZnO sensors show enhanced sensitivity by 2-9 times at 400 °C toward all nine types of VOCs. Also, fast response/recovery time and fine repeatability in the gas-sensing tests are attained. More oxygen species and active sites to the adsorbed VOCs molecules are generated by Au@ZnO hybrids, which lead to the improvement of ZnO-based gas sensor limitation.