Abnormal p-type sensing response of TiO2 nanosheets with exposed {001} facets

TiO2 nanosheets with exposed {001} high-energy facets were used as gas sensing materials. Interestingly, the sensor displayed a regular n-type response to alcohol with high sensitivity at high temperatures above 250 °C, but abnormal p-type sensing behavior over a wide temperature range from room temperature to 120 °C. Such an unusual p-type sensing response, unprecedented for n-type TiO2 nanomaterials, was attributed to the proton transfer between alcohol molecules and adsorbed water molecules on the surface of TiO2 nanosheets. The present work provides a new insight into the gas sensing mechanism of metal oxide nanostructures.