Cobalt-nitrogen co-doped carbon dots for the colorimetric and fluorometric dual-mode detection of gallic acid

Gallic acid (GA), widely used in food and medicine production industries. Herein, a kind of newly synthesized cobalt-nitrogen co-doped carbon dots (Co,N-CDs) with dual functional properties of oxidase-like activity and photoluminescence property could oxidize the 3,3 ',5,5 '-tetramethylbenzidine (TMB) to oxTMB with a new ab-sorption peak at 653 nm. In addition, it was found that oxTMB performed a fluorescence-quenching effect on Co, N-CDs at 440 nm attributed to FRET (Fluorescence resonance energy transfer). Reductive GA could reduce oxTMB to TMB, weaken the blue color, and restore the fluorescence of Co,N-CDs. Thus, a colorimetric and fluorometric method for dual-mode detection of GA was established. The synthesis of the dual-signal probe was completed with a single and environmental precursor in just one step. Simultaneously, the dual-mode detection reduced detection limits, broadened the linear range and improved anti-interference ability. This method exhibited a satisfactory application prospect in the actual detection of GA in tea beverages.