Modulation of cobalt spin state to enhance enzyme-like activity of cobaltous oxide for colorimetric sensing analysis of phenolic compound.

Herein, a novel porous S-CoO/C composite with spatial confinement effect is synthesized. Notably, doped sulfur can have the reaction with Co site of CoO and trigger the d-p orbital hybridization between 3p orbital of sulfur and 3d orbital of cobalt. The d-p orbital hybridization effect can not only increase the content of oxygen vacancy, but also drive the transformation of Co sites from low to high spin states. Benefitting from these changes, more unpaired electrons are generated in S-CoO/C. As a result, the S-CoO/C exhibits moderate oxidase-like property and excellent peroxidase-like activity. In view of the superb peroxidase-like activity of S-CoO/C, a colorimetric assay is proposed for detecting H2O2 and hydroquinone using TMB as the substrate, and developed detection methods have great advantage being a low LOD, a high recovery and a broad linear range. Furthermore, established colorimetric assay displays excellent analysis performance even in real samples.