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 (WO3) nanocrystals were modified by changing the reaction temperature. The effect of reaction temperature on the morphology and NO2 sensing properties of WO3 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 NO2-sensing properties of the sensors based on the WO3 nanocrystals with various morphologies to NO2 with the concentration ranging from 100 ppb to 3 ppm were examined at different temperatures ranging from room temperature (RT) to 250 degrees C. It is found that the solvothermal reaction temperature played a critical role on determining the morphology of the WO3 nanocrystals, and all the sensors exhibited a high response, rapid response characteristics and excellent selectivity toward NO2 at low operating temperature. Especially, the 170 and 180 degrees C solvothermally synthesized sensors showed an anomalous p-type conductive behavior at approximate below 38 and 55 degrees C, respectively. (C) 2016 Elsevier B.V. All rights reserved.