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Vertically aligned zinc oxide (ZnO) nanorod (NR) arrays were successfully grown through a cheap hydrothermal route synthesis method (HTM) (95 °C, 3 h) prepared by 25 mM zinc nitrate hexahydrate Zn(NO3)2·6H2O and 25 mM hexamethylenetetramine (C6H12N4, HMTA). After simple photochemical deposition treatment 0.5 mM chloroauric acid (HAuCl4·4H2O) under ultraviolet (UV) light irradiation, the noble gold nanoparticles (Au NPs) obviously decorated onto the ZnO NR surface. One-dimensional (1D) ZnO NR arrays without and with decorated Au NPs were called ZAuO-0 and ZAuO-1 nanostructures, respectively. Field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM) were performed to explore the surface morphologies and elemental compositions of 1D NR arrays. All nanostructures synthesized easily at a low temperature were structurally uniform with good crystal performance and perpendicular to the substrate surface. The morphological images explored that the average length and diameter of the 1D ZAuO-0 nanostructures were 1.78 μm and 76.9 nm, whereas the average length and diameter of the 1D ZAuO-1 nanostructures were 1.81 μm and 78.2 nm, respectively. 1D ZnO nanostructures were analyzed with an X-ray diffraction (XRD) instrument, and results exhibited that all samples had a hexagonal wurtzite phase with the (002) plane as the most preferred c-axis orientation. The optical characteristics of all devices were investigated by photoluminescence (PL) analysis and UV–visible absorbance, and the results revealed the excitonic- (UV) and defect-related (green) emission regions. Energy-dispersive X-ray spectroscopy (EDX) was further performed to study the composition of the 1D ZAuO-1 NR arrays, which were found to comprise Zn (53.85 atom %), O (44.36 atom %), and Au (1.79 atom %) contents. As a result, all sensors performed best at 270 °C and had the optimal detection ethanol (C2H5OH) gas concentration of 100 ppm. Moreover, the 1D ZAuO-1 sensor exhibits a superior gas response performance (86.9%) over the 1D ZAuO-0 sensor (68.9%) and has good selectivity over ethanol gas. These remarkable ethanol-sensing features revealed the potential of the prepared 1D ZAuO-1 NR arrays as promising gas sensors.
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