Synthesis of silver nanocrystal with an excellent oxidase-like activity and its application in colorimetric detection of D-penicillamine

Abstract

High-index facets of metal nanocrystal have often a higher catalytic activity compared with the low-index facets. However, the shape-controlled synthesis of silver nanocrystal still faces great challenges. In the study, we reported synthesis of silver nanocrystals using histidine-functionalized graphene quantum dots (His-GQDs) as a chelating agent and shape inducer. Silver ions were coordinated with His-GQDs to form stable complex and then heated at 180 °C for 3 h. The resulting Ag/His-GQD nanohybrid offers polygonal nanostructure. The architecture improves the exposure of high-index facets, leading to an improved oxidase-like activity. Ag/His-GQD was used as the mimetic enzyme for colorimetric detection of D-penicillamine. In the detection Ag/His-GQD catalyzes the oxidization of 3,3′,5,5′-tetramethylbenzidine into blue product. D-penicillamine can inhibit the catalytic activity of Ag/His-GQD and leads to a reduced oxidization rate, because sulfhydryl in D-penicillamine was combined with silver in the Ag/His-GQD to form Ag-S bond. The absorbance at 652 nm linearly decreases with increasing D-penicillamine concentration in the range from 0.1 to 1.25 μM with detection limit of 0.034 μM (S/N = 3). The proposed method exhibits a better sensitivity, selectivity and stability and was successfully applied in colorimetric detection of D-penicillamine. The study also provides a promising approach for synthesis of metal nanocrystals with excellent catalytic activity.