Unveiling a novel nanozyme cofactor: a highly activated Fe-CDs-derived colorimetric sensor array for comprehensive authentication of diverse tea products

Tea has antioxidant, anti-aging, hypotensive, and other functions. The tea polyphenol profile is of great significance for the identification and quality control of diverse tea products. Herein, an iron-doped carbon dots (Fe-CDs) with peroxidase-like activity was synthesized to construct a colorimetric sensor array for the tea polyphenols analysis in a complex matrix. Unexpectedly, it is found that the addition of tea polyphenols leads to an admirable increase in the activity of Fe-CDs, indicating the role of tea polyphenols as a cofactor of Fe-CDs nanozyme. The exploration based on multiple techniques reveals that the polyphenols can absorb on the Fe-CDs surface to form the new complex and effectively enhance the catalytic performance of Fe-CDs. This enhancement effect is closely related to the elemental doping, surface condition of nanozyme, and the polyphenol concentration. Taking TMB as the substrate, the colorimetric fingerprint generated in the presence of different tea polyphenols are extracted from the sensing array. The results of principal component analysis (PCA) and hierarchical clustering analysis (HCA) show that five tea polyphenols of different types, concentrations, and tea polyphenol mixtures of different proportions are successfully distinguished through pattern recognition methods. Moreover, the identification of tea leaves from different years and types, as well as various tea drinks, has been further realized. This study not only paves a new direction for enhancing the nanozyme activity, but provides an effective and convenient strategy for the quality control of tea products.