Hydrothermal Synthesis and Improved CH₃OH-Sensing Performance of ZnO Nanorods With Adsorbed Au NPs

The high-density and well-aligned zinc oxide (ZnO) nanostructures with adsorbed gold (Au) nanoparticles (NPs) grown on indium-tin-oxide (ITO) glass substrates were used as a gas-sensing material. The Au NPs-adsorbed nanorod (NR) arrays were successfully grown on the substrates via the simple hydrothermal method at various Au NP sputter deposition times (0 and 30 s). The crystal characteristics, surface morphologies, and elemental distributions were studied by using the X-ray diffraction (XRD) spectrometry, the field-emission scanning electron microscopy (FE-SEM), and the high-resolution transmission electron microscopy (HR-TEM) with an energy dispersive X-ray (EDX) elemental mapping analysis, respectively. The NR structures were vertical to the substrate surface with hexagonal wurtzite structure and single-crystalline performance. All sensors were prepared in a self-made chamber, indicating that the response of the sample toward methanol (CH
₃
OH) vapor at different working temperatures was enhanced by Au adsorption. Additionally, the sensor showed a remarkably enhanced response (62.65%) to 1000 ppm CH
₃
OH at the optimal operating temperature of 150 °C. Simultaneously, the sensor evidently displayed stable and repeatable behavior, and selectivity toward the CH
₃
OH vapor with no substantial response to isopropyl alcohol, acetone, and ethanol vapors. The designed sensor in this investigation may detect harmful gas in the Internet of Thing applications.