Synthesis of gold-coated branched ZnO nanorods for gas sensor fabrication

In this work, atypical zinc oxide nanorods (ZnO NRs) on quartz substrates were successfully synthesized using simple, low-cost, and environmentally friendly hydrothermal method. The ZnO NRs were grown on a pre-seeded seed layer of ZnO nanocrystals using the spin coating process. Gold nanoparticles (Au NPs) were sputtered on the ZnO NRs film. The structure and morphology of the produced nanostructures were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The XRD analysis revealed that the ZnO NRs were single crystalline with hexagonal wurtzite structure grown with preferred orientation of (002). The SEM morphology shows a semi-hierarchical ZnO NRs with an estimated diameter of 200–400 nm and length of 4–5 μm. The optical properties of the ZnO NRs film were investigated using UV-visible spectrophotometers. The obtained bandgap of ZnO film was 3.0 eV. Electrical and thermal properties were also measured. The resistance changes versus temperature variation of ZnO NRs were given a semiconductor behavior. The gas sensor was fabricated based on bare ZnO NRs and Au NPs/ZnO NRs hybrid. The second nanostructure exhibited an enhanced sensor sensitivity toward ethanol gas at an optimized working temperature of 325 °C.