Synthesis Of TeO₂ Nanowires And Application To Gas Sensor

As a wide band gap metal oxide semiconductor, TeO2 materials (Eg=4.05 eV, at 300 K) are widely used for infrared remote sensing, solar cell, catalyzer of petroleum cracking, colourant of ceramic and glass, and so on due to their outstanding optical-electrical, thermoelectric and catalytic properties. However, the investigation on the sensing properties of TeO2 materials is just beginning, and is mainly focused on the TeO2 thin films. Thus, to obtained TeO2 materials with higher specific surface area, TeO2 nanowires were prepared by thermal evaporation method and were optimized in order to obtain TeO2 nanowires with fine crystallinity, high surface-to-volume, and large yield, so that it can be used in sensing tests as a potential gas sensor.The metallic Te powders were used as the source material in the experiments. TeO2 nanowires were prepared under different experimental conditions, such as substrate type, heating temperature, heating time, and air flow rate. In addition, experimental conditions were optimized according to the characterization results of XRD, SEM, and EDS. The results show that TeO2 nanowires prepared on Au-coated glass substrate at the heating temperature of 450? for 2h and air flow rate of OmL/min show the best fine crystallinity, high surface-to-volume, and large yield. TeO2 nanowires obtained under the optimal experimental conditions were further observed and analyzed using TEM and FTIR.Gas sensors were fabricated by dispersing these TeO2 nanowires on the planar Au electrode. The sensing properties were investigated to methanol, ethanol, and propanol by mixing detected gas and air in static state. The results show that TeO2 nanowires show significant response and recovery properties to three types of alcohol gases. The response speed and recovery speed are quick. The highest response of TeO2 nanowires to these alcohol gases is found at room temperature and 50?, leading to reduce the energy consumption and prolong the service life of gas sensors. The response of TeO2 nanowires to detected gas increases with increasing detected gas concentrations. Moreover, TeO2 nanowires show excellent methanol selectivity relative to ethanol and propanol.It is conluded that TeO2 nanowires grow via VS growth mechanism by comparing the characterizations of VLS and VS growth mechanisms. The growth process of TeO2 nanowires is simulated according to SEM images. According to the experimental results and theoretical analysis, the sensing mechanism of TeO2 nanowires is clarified systematically. Finally, it presents to develop new type of gas sensor by microstructure design of the nanomaterial to promote the development of gas sensor in the future.