Quasi-one-dimensional (Q1D) nanowires/nanorods are promising as a low-cost material for high-speed UV photoconductive nanoscale detectors and gas sensors metal oxide nanowires, such as zinc oxide (ZnO), tin oxide (SnO2), indium oxide (In2O3), aluminum oxide (Al2O3), gallium oxide (Ga2O3), tungsten oxide (WO3), and vanadium oxide have UV light and chemical sensing properties.

Zinc oxide nanowires

Zinc oxide nanowires (NWs) have unique properties, such as high sensitivity under ambient conditions, and that they are a potential candidate for use as a sensing material, ZnO is a low-cost material which is simple to fabricate, making it attractive for research and industrial applications. Pt-coated ZnO nanorods as sensors are capable of detecting ppm concentrations of hydrogen at room temperature. It is known that point defects in zinc oxide strongly influence the electrical properties which are extremely important for the gas sensor applications. For instance, ZnO with a high density of oxygen vacancies has been shown to have a high electrical conductivity. The surface defects such as oxygen vacancies can dominate the electronic/chemical properties and adsorption behaviors of metal oxide surfaces.

Synthesis

Researcher Lupan of University of Central Florida, USA and his colleagues report on the Synthesis of ZnO nanowires.ZnO nanowires were grown on a Si(1 0 0) substrate by the chemical vapor deposition (CVD) procedure at a low pressure. Metallic zinc of high purity (99.999%) and an oxygen–argon mixture (15 vol. % of oxygen) were the starting reactants. The synthesis was performed in a two zone quartz flow reactor. In the first zone zinc was evaporated and in the second zone zinc vapors interacted with oxygen. Silicon [(1 0 0)-oriented wafer] substrates were arranged in the second zone. The temperature of zinc evaporation was 670degC and the growth temperature was 650degC. An oxygen–argon mixture was fed to the reactor at a rate of 1 l/h. The consumption of zinc was 20–28 g/h. The synthesis of ZnO nanowires/nanorods proceeded at approximately 30:1 Zn-to-O molar ratio. The pressure in the reactor was maintained at a level of 5 Torr. The synthesis was conducted for 30 min on substrates located at different distances from the zinc source. A high density of 200 nm nanowires was found to grow over the entire ZnO film predeposited on Si. ZnO nanowires are uniform and have single crystal structure without dislocations and stacking faults.

Uses

CVD-grown ZnO nanowires can be used as sensing material in nanosensors, nanowires/nanorods are promising as a low-cost material for high-speed UV photoconductive nanoscale detectors and gas sensors.