Hollow and porous nickel sulfide nanocubes prepared from a metal-organic framework as an efficient enzyme mimic for colorimetric detection of hydrogen peroxide

Hollow, porous NiS nanocubes were prepared by a hydrothermal method starting from Ni–Co Prussian blue analogue nanocubes as the template. The morphology and structure of the NiS nanocubes were tuned by adjustment of the ion-exchange rate and the degree of chemical etching, and they were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and nitrogen sorption measurements. The NiS nanocubes are shown to act as a peroxidase mimic that can catalyze the oxidization of 3,3′,5,5′-tetramethylbenzidine by hydrogen peroxide (H2O2), producing a visible color change, for which the absorbance is best measured at 652 nm. The outstanding activity may result from the unique structure of the NiS nanocubes. The catalytic oxidation follows Michaelis–Menten kinetics and shows a ping-pong mechanism of enzyme action. The findings were used to develop a rapid, sensitive, and selective colorimetric H2O2 assay with a response that is linear in the 4–40 μM range with a detection limit of 1.72 μM (signal-to-noise ratio of 3).