Dual-Channel Ratiometric Colorimetric Sensor Array for Quantification and Discrimination of o-, m-, and p-Phenols

Abstract

The determination of trace o-, m-, and p-phenols in food samples was of great significance, but it is still very challenging due to the low concertation and complex matrix. In comparison to traditional sensors based on the “lock-and-key” strategy, the sensor arrays that mimicked the human olfactory system exhibited excellent universality and efficiency in assays of structural analogs. Herein, we described a costless and robust colorimetric sensor array for quantification and discrimination of o-, m-, and p-phenols. The obtained Cu2(OH)3Cl and Ni-doped Cu2(OH)3Cl with peroxidase-like (POD) activity were served as nanozymes to accelerate the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) with H2O2. UV–vis absorbance spectroscopy displayed remarkable enhancements both at 652 nm and 450 nm, individually attributable to the formation of single and dual electron-oxidized TMB (TMBox) substances. Then varied phenols regulated the absorbance via specific electron transfer processes. With the two peaks as dual signals, a ratiometric colorimetric sensor array based on nanozymes (i.e., Cu2(OH)3Cl and Ni-doped Cu2(OH)3Cl) was designed to monitor different phenols. The ratio (I652/I450) was recorded to quantify phenols sensitively, where internal reference ruled out interferences from the environment and equipment. Moreover, this array was also explored for simultaneous discrimination of o-, m-, and p-phenols. By integrating with colorimetric fingerprints and principal component analysis (PCA), each kind of phenol can be distinctly discriminated even at a very low concentration. This work demonstrated the reliability of a ratiometric sensor array for the recognition of multiple phenols.