Sphere-like CoS with nanostructures as peroxidase mimics for colorimetric determination of H2O2 and mercury ions

Abstract

CoS, which was prepared using a facile solvothermal method, and characterized using various analytical techniques, was demonstrated for the first time to exhibit intrinsic peroxidase-like activity. CoS catalyzed the oxidation of the peroxidase substrate 3,3′,5,5′-tetramethylbenzidine in the presence of H₂O₂ rendering the reaction solution blue, which is the principle used for H₂O₂ sensing. The mechanism of the CoS catalysis was also investigated. Under optimal conditions, the linearity of H₂O₂ detection ranged from 0.05 to 0.8 mM (R² = 0.9965). More importantly, using the reducibility of glutathione and the strong affinity to thiol compounds exhibited by mercury ions (Hg²⁺), a novel “off–on” colorimetric sensor for Hg²⁺ determination was designed using CoS as a peroxidase mimics. The analytical platform for Hg²⁺ determination was developed, ranging from 0.25 to 3 μM (R² = 0.9965). The limit of detection was 0.1 μM. CoS exhibited several advantageous features including good chemical stability, ease of preparation, simple purification, and excellent reproducibility.