Abstract

Highly sensitive and selective toluene sensors based on ordered mesoporous Co₃O₄have been successfully developed. The combined characterizations of X-ray diffraction (XRD) patterns, nitrogen adsorption?Cdesorption isothermal, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) indicate that mesoporous Co₃O₄ with ordered mesoporous structure and high surface area has been successfully prepared by the nanocasting method using mesoporous silica (SBA-15) as hard template and Co(NO₃)₂・6H₂O as cobalt source. It is also found that mesoporous Co₃O₄ thus obtained shows good response toward toluene with the concentrations ranging from 1 ppm to 1000 ppm. Furthermore, mesoporous Co₃O₄ also exhibits high selectivity for detection of toluene, compared to other interferences, such as ethanol, formaldehyde, ethanol, acetone, methanol and ammonia. Most importantly, mesoporous Co₃O₄exhibits better sensing performance than that of non-porous Co₃O₄ obtained by direct calcination of Co(NO₃)₂・6H₂O in the absence of any templates, which can be attributed to unique properties of mesopotous Co₃O₄, such as high surface area, open mesoporous structure as well as relatively small crystal size.