Fabrication of zinc–histidine-functionalized graphene quantum dot framework amphiphilic nanoparticles and application in the synthesis of polystyrene microspheres for adsorption of Cu2+ by Pickering emulsion polymerization

Abstract

The paper reports a facile synthesis of histidine-functionalized graphene quantum dots (His-GQDs) via a thermal pyrolysis of citric acid and histidine. The resulting His-GQDs are composed of the graphene sheets with the average size of 3.2 nm and shows high water-solubility. Zn²⁺ reacted with the His-GQD to produce Zn–His-GQD framework nanoparticles by coordination bonds, which exhibit a better amphiphilicity with pristine His-GQDs. The styrene-in-water emulsion stabilized by the framework nanoparticles offer an excellent stability and pH-switching behaviour, and was successfully applied in the emulsion polymerization of styrene. The as-prepared polystyrene microspheres coated with His-GQD were used for the adsorption of Cu²⁺ from water. The adsorption capacity of Cu²⁺ reaches to 61 mg g⁻¹ with high reusability. This study also provides a prominent approach for fabrication of GQD-based functional materials, which could have a wide range of potential applications such as in emulsion polymerization, sensor, catalysts and energy storage.