Metal Oxid Semiconductor Nanowires And Their Applications In Ultrasensitive Detections

In recent years, nanomaterials and nanotechnology have attracted much attention because of their unique performances in chemical, micro-electronics, optoelectronics, biomedical spectroscopy, chinaware and cosmetic. Semiconductor nanomaterials, owing to their unique electrics performance and large surface-to-volume ratio, have found a wide range of application in gas sensing and surface-enhanced Raman scattering (SERS). In this paper, firstly, degenerately Sb-doped SnO2 nanowires (NWs) were mixed with un-doped ZnO NWs (1:10), then, gas sensing investigation of this mixed material was taken. In addition, SERS applications of SnO2 NWs were also studied here.ZnO is a n-type semiconductor material and has good gas sensing to some kinds of reducing gas, for instance, ethanol, carbon monoxide (CO), and sulfureted hydrogen (H2S), but the resistivity of un-doped ZnO NWs was too large to be detected. Un-doped SnO2 NWs also have a large resistivity that can be hardly detected, however, doping with appropriate elements, such as indium (In) and antimony (Sb), can modulate the optical and electrical properties of SnO2 NWs, addition of these elements would greatly reduce the resistivity of SnO2 NWs, but the gas sensing performance of SnO2 NWs would reduce. The mixture of un-doped ZnO NWs and degenerately Sb-doped SnO2 NWs gave both good gas sensing performance and appropriate resistivity for gas sensing detecting. Gas sensing sensitivity in 0.1 ppm ethanol was 3.3. When the concentration of ethanol was 1 ppm, the sensitivity was about 14, much larger than that of conventional semiconductor materials in the same conditions.Applications of nanomaterials in SERS are also introduced in this paper. Here we have studied the SERS effect of Rhodamine B, Isothiocyanate (RBITC) on several easily prepared SERS substrates with large enhancement factors and easy preparation processes. They were SnO2 NWs decorated with Au nanoparticles (NPs) by vacuum sputter, Au-decorated SnO2 NWs by colloidal gold method, a single SnO2 NW coated with many colloidal gold NPs and branched SnO2 NWs with Au-droplets on the tips of branches. Bulk NWs have three-dimensional (3D) porous network structure, which made the Au-decorated NWs have better SERS effect than Au-coated two-dimensional (2D) flat substrate. We also found that SnO2 NWs decorated with Au NPs by colloidal gold method gave good SERS performances than that by vacuum sputter. In addition, SERS effects of a single Au-coated SnO2 NW and branched SnO2 NWs were also detected in our experiments, enhancement factors of them were 1.1×107 and 1.0×107, respectively.