Two novel laccase-like nanozymes based on azole ligands for constructing pH-dependent sensor array for recognizing halogenated phenolic pollutants.

Halogenated phenolic compounds are widely used in industrial processes such as paper manufacturing and pesticide production. They are priority pollutants that need to be controlled and are discharged with industrial wastewater. Halogenated phenolics have much greater environmental impacts than phenolics due to elevated toxicity and reduced biodegradability caused by halogen substitution. Since the type and location of halogens have great influence on their toxicity and existing differentiation methods rely on large-scale instruments, there is an urgent need to develop new and convenient sensing technologies for the simultaneous identification and detection of halogenated phenols (including fluorophenols, chlorophenols and bromophenols) for more targeted pollution control. In this work, we prepared two novel laccase-like nanozymes using asymmetric azole ligands (thiazole-2-carboxylic acid and imidazole-2-carboxylic acid) coordinated with Cu, and constructed a four-channel sensor array by taking advantage of the difference in their ability to catalyze the color development of halogenated phenols and 4-aminoantipyrine under pH = 7 and pH = 8 conditions. The sensor array was able to accurately discriminate eight halogenated phenols in the range of 5-100 μM, and allowing for accurate quantitative analysis. The method has good anti-interference ability to other non-target phenols, and can realize accurate differentiation of halogenated phenols in real water bodies. Even in the presence of high concentrations of common ions or heavy metal ions, halogenated phenolic pollutants can be accurately identified. The good stability and anti-interference ability make the senor array has a great potential for application and is expected to provide a basis for environmental pollution control.