Effect of solvothermal reaction temperature on the morphology of WO3 nanocrystals and their low-temperature NO2-sensing properties.

In this paper, solvothermally synthesized tungsten oxide (WO 3 ) nanocrystals were modified by changing the reaction temperature. The effect of reaction temperature on the morphology and NO 2 sensing properties of WO 3 nanocrystals was investigated. Numerous analytical techniques, such as field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM), have been employed to characterize their feature. The NO 2 -sensing properties of the sensors based on the WO 3 nanocrystals with various morphologies to NO 2 with the concentration ranging from 100 ppb to 3 ppm were examined at different temperatures ranging from room temperature (RT) to 250 °C. It is found that the solvothermal reaction temperature played a critical role on determining the morphology of the WO 3 nanocrystals, and all the sensors exhibited a high response, rapid response characteristics and excellent selectivity toward NO 2 at low operating temperature. Especially, the 170 and 180 °C solvothermally synthesized sensors showed an anomalous p-type conductive behavior at approximate below 38 and 55 °C, respectively. [ABSTRACT FROM AUTHOR]