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 <i>o</i>-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.