Sensitive and selective NO2 gas sensor based on WO3 nanoplates

Gas sensors based on a chemiresistive metal oxide semiconductor are widely used including nitrogen dioxide (NO2) at a moderate temperature. In this work efforts are taken to fabricate NO2 gas sensor using thin films of tungsten oxide (WO3) grown directly on to a soda-lime glass substrate without assistance of any seed layer by a simple and a facile hydrothermal technique. As per our knowledge, the deposition of nanostructured WO3 thin films without assistance of any seed layer on the glass substrate was rarely reported. The WO3 thin film samples were synthesized at various deposition times ranging from 3 h to 7 h and were characterized by X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy and Brunauer-Emmett-Teller techniques. The surface morphological and structural characterization showed the two dimensional (2D) nanoplate-like structure of as synthesized WO3 thin films with plate thickness ranging from 90 to 150 nm and had an orthorhombic structure, respectively. Moreover, the 2D nanoplates of WO3 exhibited a gas response ∼10 for 5 ppm for toxic NO2 gas at relatively low operating temperature. The new synthesis route and sensing behavior of as synthesized WO3 nanoplates revealed a promising candidate for the fabrication of the cost effective gas sensors.