Crown ether-like structure in graphene quantum dots: Ultra-sensitive photoluminescence sensor for Ca2+ in vitro

Due to the weak coordination of alkaline−earth metal ions (such as Mg 2+ , Ca 2+ and Sr 2+ ), the design for corresponding fluorescent probes in vitro is much harder than those for heavy metal ions (such as Cu 2+ , Hg 2+ and Pb 2+ ). In this paper, the crown ether-like structure was introduced in graphene quantum dots (C-GQDs) via the hydrothermal treatment of alizarin . With the strong coordination of crown ether-like structure in C-GQDs’ lattice, C-GQDs show much lower detection limit to Ca 2+ (2 pM) than that of surface modified graphene quantum dots (100 pM). Moreover, the selectivity of C-GQDs can be controlled by the size modulation of crown ether-like structure. Precursors with different structures were carried out to modulate the size of crown ether-like structure in C-GQDs. The obtained C-GQDs show good selectivity for Mg 2+ , Sr 2+ , and Ba 2+ , respectively. Finally, we also show the successful detection of Ca 2+ in vitro based on C-GQDs.