Investigation of humidity sensor based on Au modified ZnO nanosheets via hydrothermal method and first principle

In this paper, Au modified ZnO (Au/ZnO) nanosheets with high humidity performance were prepared by hydrothermal method. The position and the energy band of Au atoms in ZnO single crystals were simulated by first-principles based on density-functional theory (DFT), and the mechanism of Au/ZnO humidity sensors was studied further. The calculations show that Au atoms are adsorbed on the surface of ZnO supercell to provied more oxygen vacancies. Therefore, more water molecules can be adsorbed on the Au/ZnO humidity sensor to react with more electrons and hence to enhance the performance of the humidity sensor. Experiments show that the performance of humidity sensor based on Au/ZnO can be improved by changing the concentration of the modifier Au nanoparticles. Au/ZnO (0.5 mM HAuCl4) humidity sensor exhibits approximately 5 orders of magnitude variation in impedance realization with RH in a range from 11% to 95%, and it exhibits good linearity and narrow hysteresis loop ((similar to)3.0%), as well as short response (16 s) time and recovery time (28 s). The performance of Au/ZnO humidity can be improved by modifier Au nanoparticles, because the Au/ZnO have more surface oxygen defects and special electronic storage capabilities. These results indicate that Au/ZnO nanosheets have a potential in the manufacture of humidity sensors and provide a new idea for high performance of ZnO humidity sensors.