Synthesis of ZnO@poly-o-methoxyaniline nanosheet composite for enhanced NH₃-sensing performance at room temperature

Poly-o-methoxyaniline (POMA) and zinc oxide (ZnO) composites were prepared via in situ polymerization and characterized by thermogravimetry thermal analysis, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and N₂ sorption measurement. The composites show different morphology when the ratio of POMA and ZnO varies. At a ratio of 2:2, the composite shows thinner nanosheet structure with smooth surface and exhibits best response to NH₃ at room temperature. The ZnO@POMA nanosheet sensor shows good selectivity and a wide response range (linear ranges from 0.05-1 pmm and 10-100 ppm of NH₃). The lowest detection limit reaches 0.05 ppm. The sensor exhibits good reversibility. Based on the testing results of ultraviolet diffuse reflection spectroscopy and Kelvin probe technique, the adsorption and desorption of NH₃ molecules on the sensing material and the formation of p-n heterostructure between ZnO and POMA and their synergistic effects are further explained. More importantly, the sensor possessed excellent moisture resistance. The overall test results of ZnO@POMA show that the sensor has good practical applicability for detecting trace NH₃ at room temperature.