Gold Decoration and Photoresistive Response to Nitrogen Dioxide of WS Nanotubes.

Composites of WS nanotubes (NT-WS ) and gold nanoparticles (AuNPs) were prepared using aqueous HAuCl solutions and subjected to surface analysis. The obtained materials were jointly characterized by X-ray photoelectron (XPS), Raman scattering (RSS), and ultraviolet photoelectron (UPS) spectroscopies. Optical extinction spectroscopy and electron energy loss spectroscopy in the scanning transmission electron microscopy regime (STEM-EELS) were also employed to study plasmon features of the nanocomposite. It was found that AuNPs deposition is accompanied by a partial oxidative dissolution of WS , whereas Au-S interfacial species could be responsible for the tight contact of metal nanoparticles and the disulfide. A remarkable sensitivity of n-type resistance of NT-WS and Au-NT-WS to the adsorption of NO gas was also demonstrated at room temperature using periodical illumination by a 530 nm light-emitting diode. Au-NT-WS nanocomposites are found to possess a higher photoresponse and enhanced sensitivity in the 0.25-2.0 ppm range of NO concentration, as compared to the pristine NT-WS . This behaviour is discussed within the physisorption-charge transfer model to explore sensing properties of the nanocomposites.