A dual-functional single-atom Fe nanozyme-based sensitive colorimetric sensor for tannins quantification in brandy

Traditional methods of tannins detection suffer from complex pretreatment, long detection time, and limited sensitivity. Modern techniques like liquid chromatography require expertise, involve tedious result processing, and lack effective data visualization. Therefore, there is a need for an alternative detection method that simplifies pretreatment and detection steps, reduces analysis time, and provides visualized results. In this study, a novel colorimetric sensor based on single-atom Fe nanozyme (Fe@CN-20) was developed for tannins detection. Fe@CN-20 exhibited laccase-like and oxidase-like activities, enabling simultaneous oxidation of tannins and a substrate called TMB. Tannins competed with TMB, allowing quantification of tannins content. The Fe@CN-20/TMB system provided a detection range of 5-100 mg/L tannic acid, with a detection limit of 0.13 mg/L (S/N = 3). Analysis time was approximately 30 min. The platform successfully quantified tannins in brandy, showing less than 5% deviation compared to the standard method. The sensor was simple, sensitive, rapid, and provided strong visualization.