Solvothermal synthesis and gas-sensing performance of Co3O4 hollow nanospheres

Co3O4 hollow nanospheres with a diameter of 200–300 nm were synthesized by a surfactant-assisted solvothermal method. X-ray diffraction and Raman spectrum measurements demonstrate that the products are pure face-centered cubic Co3O4. Transmission electron microscopy and selected area electron diffraction analyses reveal that the walls of Co3O4 hollow nanospheres have a uniform thickness of ∼40 nm and are constructed by an oriented aggregation of Co3O4 nanocrystals. The optical absorption properties of the Co3O4 hollow nanospheres were investigated by UV–vis spectroscopy and the results indicate that the Co3O4 hollow nanospheres are semiconducting with direct band gaps of 2.23, 1.25 and 1.00 eV. The gas-sensing performance of the as-prepared Co3O4 hollow nanospheres was investigated towards a series of typical organic solvents and fuels. The Co3O4 hollow nanospheres show good sensing performances towards toluene and acetone vapors with rapid response and high sensitivity at low operating temperature.