Cobalt and nickel bimetallic sulfide nanoparticles immobilized on montmorillonite demonstrating peroxidase-like activity for H2O2 detection

Abstract

In this study, ternary transition metal sulfide (cobalt and nickel sulfides) nanoparticles were anchored on the surface of montmorillonite (MMT) by a facile one-pot hydrothermal method. These nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Interestingly, for the first time, the obtained nanocomposites were found to possess intrinsic peroxidase-like activity, and they could rapidly catalyze the oxidation of the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxTMB in 3 min; also, clear color change could be quantified by absorbance at 652 nm using a UV-vis spectrophotometer. Studies showed that different proportions of cobalt sulfides and nickel sulfides in the nanocomposites affected the catalytic level of the intrinsic peroxidase-like activity. Co–Ni–S-3/MMT nanocomposites (NCs) exhibited the highest peroxidase-like activity compared with Co–S/MMT NCs and Ni–S/MMT NCs, suggesting that ternary transition metal sulfides (cobalt and nickel sulfides) possessed enhanced peroxidase-like activity compared with binary transition metal sulfides (cobalt sulfides or nickel sulfides). Similar to natural enzymes, Co–Ni–S-3/MMT NCs, as a peroxidase mimic, followed the typical Michaelis–Menten kinetics well and exhibited good affinity towards H₂O₂ and TMB. Moreover, the detection limit of H₂O₂ was determined to be as low as 1.5 μM, and the linear range was from 3 to 100 μM. Based on the peroxidase-like activity of the nanocomposites, a sensitive colorimetric sensor was designed and conveniently used for the detection of H₂O₂ in a contact lens solution.