Co3O4-SnO2 nanobox sensor with a PN junction and semiconductor-conductor transformation for high selectivity and sensitivity detection of H2S

Uniform Co3O4-SnO2 nanoboxes have been synthesized successfully by a facile annealing treatment. Their hollow and cubic structure can be retained successfully during calcination. Due to their hollow structure and PN junction, these Co3O4-SnO2 nanobox sensors can detect H2S with high sensitivity at a low temperature of 180 degrees C. In addition, it was found that the Co3O4 -SnO2 nanobox sensors obtained at a higher annealing temperature displayed a higher sensitivity and lower recovery time to H2S in a temperature range of 500 to 700 degrees C. X-ray photoelectron spectroscopy (XPS) was employed to confirm that the changes in resistance and the high sensitivities of the sensors are significantly attributable to the transformation of Co3O4 to CoSx with high conductivity under an H2S atmosphere.