UV-activated gas sensing properties of ZnS nanorods functionalized with Pd

Pd-functionalized ZnS nanorods were prepared for use as gas sensors. Scanning electron microscopy revealed the diameters and lengths of the nanorods ranging from 30 to 80 nm and from 2 to 5 mu m, respectively. The diameter of Pd nanoparticles ranged from 2 to 5 nm. Transmission electron microscopy revealed that ZnS nanorods and Pd nanoparticles were monocrystalline and amorphous, respectively. The responses of multiple networked ZnS nanorods sensors to 1-5 ppm NO2 were increased substantially by a combination of Pd functionalization and UV irradiation. Pristine ZnS nanorod sensors at room temperature in the dark showed a response (similar to 100%) almost independent of NO2 concentration in a NO2 concentration range of 1-5 ppm. Pristine ZnS nanorod sensors showed enhanced responses of 214-603% to 1-5 ppm NO2 at room temperature under UV illumination. Pd-functionalized ZnS nanorods sensors showed further enhanced responses of 355-1511% to 1-5 ppm NO2 at room temperature under UV illumination. The NO2 gas sensing mechanism of the Pd-functionalized ZnS nanorods sensors under UV illumination is discussed in depth. (C) 2013 Elsevier B.V. All rights reserved.