Synthesis, structure, and UV-enhanced gas sensing properties of Au-functionalized ZnS nanowires

Au-functionalized ZnS nanowires were prepared for use as gas sensors. Scanning electron microscopy revealed the diameters and lengths of the nanowires ranging from 20 to 100 nm and from a few tens to a few hundreds of micrometers, respectively. X-ray diffraction and transmission electron microscopy revealed that ZnS nanowires and Au nanoparticles were monocrystalline and polycrystalline, respectively. The responses of multiple networked ZnS nanowire sensors to 1–5 ppm NO2 were increased 1.6- to 1.9-fold and 2.8- to 5.4-fold by Au functionalization and a combination of Au functionalization and UV irradiation, respectively. Au-functionalized ZnS nanowire sensors showed responses of 168–313% to 1–5 ppm NO2 at 300 °C in the dark. These values are comparable or superior to most semiconductor oxide one-dimensional nanostructures-based sensors reported in the literature. Furthermore, Au-functionalized ZnS nanowire sensors showed far higher responses (291–884%) to 1–5 ppm NO2 at 300 °C under UV illumination. The NO2 gas sensing mechanism of the Au-functionalized ZnS nanowire sensors under UV illumination is discussed.