Tunable Chemical Reactivity and Selectivity of WO3/TiO2 Heterojunction for Gas Sensing Applications

Nowadays, there is a dramatically growing demand for nanocomposite mate-rials with new functionalities for their application in chemical gas sensors andother catalytic devices. Moreover, green synthesis methods are intensivelyemployed in the preparation of semiconductor nanostructures to reduce thehazardous effects on human health and the environment. Here the fabrica-tion of a nanocomposite material based on WO3 and TiO2 (WO3/TiO2) withunusual electronic band alignment and novel gas sensing properties isreported. The material is synthesized by an eco-friendly process based on thewater vapor-induced oxidation of tungsten/titanium metallic films. The pris-tine WO 3 is highly sensitive to acetone, where the response of the material isenhanced by its operating temperature. Instead, WO3/TiO2 composite showsprincipally different sensing performance and it has a good selective responseto carbon monoxide at a relatively low operating temperature. The obtainedresults indicate that the significant differences between the functionalities ofpristine WO 3 and WO3/TiO2 material can be attributed to the band alignmentand the direction of charge transfer in the WO3/TiO2 heterojunction. Hence,an efficient way for the development of WO 3 /TiO2 nanocomposites, whichcan be useful for the engineering and optimization of gas sensing and cata-lytic properties of WO 3, is presented.