Novel Electro-Spun Nanograined ZnO/Au Heterojunction Nanofibers and Their Ultrasensitive NO2 Gas Sensing Properties

Novel nanograined ZnO/Au heterostructured nanofibers have been successfully prepared using two-step process via electro-spinning method followed by thermal oxidation and their surface bound NO2 sensing properties were analyzed. The ZnO/Au heterojunction nanofibers exhibited typical nanograined structure with 1D morphology consisting of two distinct lattice fringes with d spacing values of 0.14 +/- 0.5 nm and 0.28 +/- 0.5 nm corresponding to Au [111] and ZnO [101] respectively. Defects and surface bound properties were examined using Room temperature Photoluminescence (RTPL) spectroscopy, Xray photo-electron spectroscopy (XPS) and X-ray diffraction analysis. The existence of Au, Zn and O in 4 f, 2p and 1 s states and chemisorbed oxygen species on the surface were structurally confirmed after the careful evaluation and proves the purity of synthesis. NO2 gas sensor property analysis of ZnO/Au heterojunction nanofibers showed an extraordinary sensor response (S=98) and selectivity at a lower operating temperature of 350 degrees C than pristine ZnO nanofibers (450 degrees C). The enhanced sensing behavior of the heterostructured nanofibers are ascribed to the synergetic effect of Au nanoclusters at the interface which act as spill-over zone favoring physisorption and defect mediated sensing process.