Smartphone-assisted colorimetric sensing platform based on Cu(BDC) nanosheets derived CuS nanoparticles embedded in porous carbon with peroxidase-like activity for gallic acid detection

Gallic acid (GA) is a kind of polyhydroxyl phenolic compound, which has good antioxidant function and widely exists in plants, fruits, beverages and drugs. The quantitative detection of GA content is very important for the quality control of human health food and drugs. In this study, 2D (two-dimensional) Cu-benzenedicarboxylate (Cu-BDC) nanosheets are used as precursor to derive CuS nanoparticles embedded in porous carbon (CuS@C) with peroxidase-like activity, which can catalyze colorless 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H 2 O 2 , while the antioxidant GA can compete with TMB resulting in a concentration dependent color change in GA. Based on this competitive relationship, a colorimetric platform for GA detection is established with a linear range of 0.5–60 μM and a limit of detection of 0.19 μM under optimal conditions. The mechanism studies indicate that ·OH radicals are the primary active species. In addition, a smartphone-assisted GA quantitative detection mode is further constructed based on the RGB principle with a detection limit of 0.27 μM. The study offers a reliable method for the rapid visual detection of GA in the tea and health care products, and also provides a reference for the design of new nanozymes.