Room-temperature volatile organic compounds sensing based on WO3·0.33H2O, hexagonal-WO3, and their reduced graphene oxide composites

Abstract

Nanostructured orthorhombic WO₃·0.33H₂O, hexagonal h-WO₃ and their RGO composites (RGO-WO₃·0.33H₂O and RGO-h-WO₃) are reported for the purpose of efficient sensing of volatile organic compounds (VOCs) (e.g. acetone, methanol, benzene, toluene, and m-xylene). The materials were prepared at 140 °C by one-pot microwave-assisted hydrothermal (MAH) synthesis from Na₂WO₄·2H₂O and graphite oxide (in the case of composite) suspension in acid medium, without using any reducing, organic, or capping reagent. A three-dimensional (3D) nanocolumn bundles-like morphology was obtained for WO₃·0.33H₂O and RGO-WO₃·0.33H₂O. Whereas with subsequent heat treatment at 400 °C, it was possible to obtain h-WO₃ and RGO-h-WO₃ composites while preserving the nanocolumn bundles-like morphology. The sensing properties of these materials were investigated by exposing them to various VOCs at room temperature and at 55% relative humidity. We found that all the materials behave as a p-type semiconductor after being exposed to reducing gases. Response to 100 ppm of acetone to the RGO-h-WO₃ sensor was observed to be 20% larger than the h-WO₃ sensor.