Rational Design of Fe1–Co1/NC Diatomic Nanozyme-Based Electronic Tongues: Discriminating Active Substances in Licorice

Herein, by the pyrolysis and alkali leaching of zeolitic imidazolate framework-8 (ZIF-8)@SiO2, followed by Fe and Co doping, a novel Fe1Co1/NC nanozyme, with adjacent Fe and Co dual-atom pairs decorated on an N-doped carbon support, is exactly built. Due to the synergistic effect of adjacent Fe and Co dual-atom pairs, the peroxidase-like activity of Fe1Co1/NC is significantly enhanced, far exceeding those of Fe1/NC and Co1/NC. Based on this, we propose a simple colorimetric electronic tongue consisting of Fe1Co1/NC, chromogenic substrates (3,3',5,5'-tetramethylbenzidine) (TMB), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and o-phenylenediamine (OPD) and H2O2 to identify seven active substances in licorice. The mechanism of action of this tongue is that different active substances have differential degrees of inhibition on the three nanozyme-catalyzed reactions (Fe1Co1/NC-TMB-H2O2, Fe1Co1/NC-ABTS-H2O2, and Fe1Co1/NC-OPD-H2O2). The collected absorbance variation data, i.e., the colorimetric fingerprint patterns, are analyzed by linear discriminant analysis, realizing the identification of the seven active substances with 100% accuracy. This work provides insights into the rational design of dual-atom catalysts with nanozyme activities for the discrimination of multiple targets.