A Review of Electronic Nose Based on One Dimensional Metal-Oxide Nanostructures: Its Current Status and Future Trends

Chemical and biological sensor systems have a profound influence on personal safety, medical diagnosis, detection of pollutants and environmental toxins, and in the transportation industries. For decades, although a wide range of smart and sophisticated sensors have been developed over a generation, new sensor strategies of ever increasing sensitivity, selectivity, and lower cost seem to be still in demand. As promising candidates, one dimensional nanostructures such as nanowires, nanotubes, nanorods etc. have been suggested to function as highly-sensitive and highly-selective sensors, which could potentially be massively multiplexed in devices of small size. Many groups have successfully demonstrated electronic and optical type sensors of this approach over the past two decades, utilizing a variety of multicomponent array strategies to create ???electronic noses:e-noses???. In most sensors surface-chemical processes are transduced into measurable signals. The advent of MEMS microfabrication techniques and nanotechnology has significantly altered the e-nose paradigm. Because of their very high surface-to-volume ratios, nanoparticles and nanowires can in principle be used to create very sensitive sensors leading to e-nose designs with enhanced sensitivities and selectivities. Although research on the metal-oxide nanowires such as In2O3, SnO2, ZnO and CuO as sensors is still considered to be in early stages, several encouraging experiments have been reported that are interesting in their own right and indicative of a promising future.clos