Ultrathin CeO 2 nanosheets as bifunctional sensing materials for humidity and formaldehyde detection

Issues like morphology control and further multifunctional applications are of significant importance for rare earth nano-oxides, e.g., cerium dioxide (CeO2) nanostructures, however, relevant results in this respect are rather limited up to now. In the present work, ultrathin CeO2 nanosheets were synthesized through a facile low-temperature hydrothermal method. The structure, morphology and specific surface area of these CeO2 nanosheets were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and N2 adsorption–desorption. Significantly, CeO2 nanosheets have the potential as bifunctional sensing materials to detect both humidity and formaldehyde vapor. The CeO2 nanosheet humidity sensor exhibited excellent sensing characteristics in the relative humidity range of 11%–97% with the response value as high as 3.1 × 104. Meanwhile, the CeO2 nanosheet gas sensor showed superior sensitivity and repeatability with fast response/recovery speed toward formaldehyde vapor at 300 °C. Finally, the humidity and formaldehyde sensing mechanism were discussed as well.