Rare earth doped metal oxide sensor for the multimodal detection of volatile organic compounds (VOCs)

Heated metal oxide sensors have been widely studied for their ability to give a reversible change in the electrical resistance following the interaction with a volatile compound. Another feature is their inherent cataluminescence (CTL) properties when these materials interact with specific volatiles. This study reports for the first time a zirconium oxide nanomaterial doped with a rare earth metal which gives combined resistance and cataluminescence responses, providing enhanced sensitivity and selectivity of detection via a multimodal response in a single sensor. The europium-doped zirconium oxide, ZrO2:Eu3+ was studied and compared with the undoped zirconium oxide, ZrO2, and tungsten oxide, WO3. Materials were characterised structurally and tested with a series of volatiles. Both the cataluminescence light emission and the resistance response were recorded at different temperatures (starting from 180 degrees C up to 400 degrees C) and then combined to achieve the dual modality response. Europium-doped zirconium oxide gave a better sensitivity in terms of cataluminescence response than the undoped zirconium oxide sensor; dual modality sensing is demonstrated for ethanol and acetone which give cataluminescence and resistance responses on both the undoped and europium doped zirconia.