The correlation between the ethylene response and its oxidation over TiO2 under UV irradiation

The anatase and rutile TiO2 film sensors were prepared by drop-coating method with calcination at 450 and 600 °C, respectively. After tested the ethylene sensing property over the as-prepared TiO2 sensors under UV irradiation, it was found that the anatase TiO2 as well as the rutile sensor exhibited a response to ethylene in the dry nitrogen atmosphere, but with anatase showing a much lower response to ethylene (almost no response) than rutile in the dry air atmosphere (containing oxygen). Moreover, this difference to the ethylene response between the anatase TiO2 sensor and the rutile one was also observed in a wet air atmosphere under UV irradiation. Based on the results of photocatalytically oxidizing ethylene over anatase and rutile TiO2, it is proposed that the weak gas response to ethylene over the anatase TiO2 under UV irradiation can be attributed to the oxidation of ethylene itself. This also suggests that a good photo-assisted semi-conductor sensor should have a strong photoresponse property but a weak photocatalytic performance for the sensed gas.