Rapid and sensitive colorimetric sensor for H2O2 and Hg2+ detection based on homogeneous iodide with high peroxidase-mimicking activity

Abstract

Peroxidase reaction is known as a classical reaction that is widely used in the analytical chemistry field because of not only the important peroxide analytes but also the key role of H2O2 detection in various coupled enzyme systems. For this reason, exploiting appropriate enzymes with good catalytic properties, low cost, easy preparation, and simple operation for the reaction becomes extremely important for acquiring desired analytical performance. Herein, we proposed a simplified, rapid, and universal colorimetric platform based on the peroxidase-mimicking activity of I− for sensing applications. The I− species exhibited the peroxidase-like ability to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue TMBox in the presence of H2O2 via the I2 intermediate. Compared with natural bio-enzymes and emerging nanozymes, the homogeneous I− mimic provided excellent activity to trigger the color reaction faster. More importantly, commercial reagents were able to be used directly, thus avoiding the tedious preparation and purification processes required in bio-enzymes and nanozymes. As a result, the fabricated platform could be used to detect H2O2 within 3 min, providing a linear range of 1.7–166.7 μM and a detection limit of 1.1 μM. Given that Hg2+ could suppress the color reaction through formation HgI2, the Hg2+ target (20–80 nM) was also determined rapidly. Practical measurements demonstrated the reliability of the colorimetric assay. It is believed that the general platform based on the H2O2 + TMB + I− reaction holds broader applications in other analytical systems.