A glycine-functionalized graphene quantum dots synthesized by a facile post-modification strategy for a sensitive and selective fluorescence sensor of mercury ions

Abstract

In this work, we have developed a facile method for the synthesis of glycine-functionalized graphene quantum dots (Gly-GQDs) through post-modification of graphene quantum dots with Gly under alkaline conditions. The as-synthesized Gly-GQDs exhibit an excellent blue emission at 444 nm, independent of excitation, as well as a high quantum yield (QY) of 35.7%. The Gly-GQDs have a narrow size distribution with an average size of 5.9 nm. Moreover, the as-prepared Gly-GQDs showed a better selective and sensitive recognition capability towards mercury ion (Hg²⁺) in aqueous solutions with a low detection limit of 8.3 nM, compared with GQDs and other nitrogen-doped GQDs synthesized through the one-step solvent thermal method. Gly-GQDs are successfully applied for the determination of Hg²⁺ in real water samples. This work shows a new promising approach for the design and synthesis of desirable GQDs with a given function.

Keywords: Fluorescence detection; Graphene quantum dots; Mercury ions; Post-modification.