Fluorescence/colorimetric intelligent sensor based on Fe-adsorbing carbon dots nanozymes for selective recognition and quantification of total antioxidant capacity in foods and cells

Constantly escalating oxidative stress greatly increases the daily demand, and total antioxidant capacity (TAC) have become an important indicator. Therefore, the development of effective methods for TAC evaluation remains to be a research hotspot. Herein, a fluorescence/colorimetric sensor based on Fe-adsorbing carbon dots nanozymes (Fe-CDs) was constructed through a rational design. Fe-adsorbing step quenched the fluorescence of carbon dots and restored it by adding antioxidants to achieve fluorescence detection. Furthermore, it endowed Fe-CDs with peroxidase (POD) activity necessary for achieving colorimetric detection. A dual-mode fluorescence/colorimetric sensor array based on Fe-CDs was further constructed to selectively recognize 7 antioxidants and accurately evaluate TAC in 5 actual samples. In addition, Fe-CDs demonstrated excellent accuracy and anti-interference performance in detecting ascorbic acid TAC in fruit juice based on fluorescence/colorimetric methods, with detection limits of 2.1 and 0.4 μM as well as linear ranges of 4–40 and 6.3–150 μM, respectively. Moreover, Fe-CDs indeed guided changes in glutathione content through fluorescence imaging at the cellular level