Ni-Fe Bimetallic Hydrogel with Bifunctional Enzyme Activity for Colorimetric Detection of Phenolic Pollutants

Abstract

Phenol-containing wastewater is an important source of water pollution in the environment. It is important and challenging to develop simple and rapid analytical methods for the detection of these trace contaminants in natural environments. Natural enzymes are often selected for colorimetric detection due to their excellent catalytic activity along with corresponding color changes with special substrates. Compared with natural enzymes, artificial nanozymes have been widely concerned owing to the characteristics such as high stability, tunable catalytic activity, easy preparation and large-scale production. Herein, a bimetallic hydrogel 3-QW-NiFe with peroxidase-like and oxidase-like activities was designed and prepared by a simple and green synthesis method. The catalytic mechanism was investigated by various spectra including UV-vis, fluorescence, and EPR spectra, which suggested that the peroxidase-like activity and the oxidase-like activity of 3-QW-NiFe metallohydrogel were realized by the hydroxyl radical and superoxide anion produced in the reaction process respectively. Based on the peroxidase-like activity of 3-QW-NiFe, a colorimetric sensor was constructed for the discrimination of m-bihydroxybenzene with good selectivity and low detection limit (0.033 μM) in a linear range (0.5–12 μM). Furthermore, the oxidase-like activity was used for the colorimetric detection of hydroquinone. The smartphone-assisted detection method was also constructed, which helps to realize fast and on-site visual detection without the need of any analytical instruments. In addition, the assay based on 3-QW-NiFe metallohydrogel can be successfully applied to detect phenolic pollutants in the water samples. With these advantages and the convenient operation, the proposed colorimetric assay for the detection of m-AP and HQ in this study can be applied for real-time environmental monitoring, opening new avenues for the detection of phenol contaminants in natural environments.

Keywords: Ni-Fe bimetallic hydrogel, bifunctional enzyme activity, Colorimetric detection, smartphone-assisted detection, phenolic pollutants