| Metal nanoparticles have been widely used in catalysis,energy storage,sensing and other fields due to their unique catalytic activity and excellent electrical conductivity.However,metal nanoparticles are prone to agglomerate and form larger particles during use,leading to a decrease in catalytic activity.Moreover,the metal nanoparticles lack three-dimensional structure,which leads to the obstruction of electrolyte transfer and the inability to produce mutual synergy between the particles.These greatly limit the application of metal nanoparticles.In recent years,the combination of metals and graphene has realized the improvement of the dispersion of nanoparticles and the formation of three-dimensional high-speed conductive network.However,the lack of strong interactions and large energy level differences between metals and graphene results in poor dispersion of the composites and slow electron/energy transfer rates between metals and graphene.Therefore,the controllable preparation of metal composites by functionalized graphene quantum dot is of great practical significance.The paper focuses on the research goals:increasing the exposure of high-index crystal faces,constructing stable three-dimensional structures,improving the dispersion of metals on graphene sheets and speed up electron/energy transfer between them,and expanding application fields.The research on the controllable preparation of metal composites by functionalized graphene quantum dot has been carried out,so as to achieve a significant improvement in the catalytic performance of metal composites.More exposure of high-index crystal faces is achieved by using functionalized graphene quantum dot to modulate crystal growth.Histidine-functionalized graphene quantum dot（His-GQD）was used as chelating agent,stabilizer and shape inducer to prepare polyhedral His-GQD-Ag composites.Studies have shown that the polyhedral His-GQD-Ag has more exposed high-index crystal faces,thus showing high oxidase-like activity.It has been successfully applied to the highly sensitive colorimetric determination of D-penicillamine,the detection limit reached 3.4×10-2μmol L-1.The construction of stable three-dimensional structures is achieved by the coordination and self-assembly between the multifunctional groups of functionalized graphene quantum dot and metal nanoparticles.Aspartic acid-arginine functionalized graphene quantum dot（Asp-Arg-GQD）was used as reducing agent,stabilizer and crosslinking agent to prepare Asp-Arg-GQD-Ru composites with three-dimensional structure.Studies have shown that the three-dimensional structure Asp-Arg-GQD-Ru enhances the connection between different Ru particles,thereby showing high stability and electrocatalytic activity.It has been successfully applied to the highly sensitive electrochemical determination of carbendazim,the detection limit reached 4.0×10-3μmol L-1.The fabrication of three-dimensional,highly dispersed and Schottky heterojunction graphene-graphene quantum dot-metal composites is achieved by exploiting theπ-πstacking,coordination and semiconducting properties of functionalized graphene quantum dot.Studies have shown that the small size and high dispersion of metals on graphene sheets bring more exposure of active sites,thus exhibiting high catalytic activity.Meanwhile,the formation of heterojunctions accelerates the electron/energy transfer rate,which further improves the catalytic activity of the composites.The prepared G-His-GQD-Ag was used for the electrochemical determination of acetamiprid with a detection limit of 4.0×10-17 mol L-1.The prepared G-His-GQD-AgNi was used for the colorimetric determination of malathion with a detection limit of 3.1 ng m L-1.The application field is expanded by combining graphene-graphene quantum dot-metal composites with temperature responsive and self-healing materials.A temperature-responsive composite membrane was prepared by combining G-His-GQD-Pd with poly（N-isopropylacrylamide）（PNIPAM）,which was used to construct a temperature-controlled switching electrochemical sensor for the highly sensitive determination of 4-nitrophenol,with a detection limit of 0.10μmol L-1.Composite membrane with self-healing and temperature responsive was prepared by combining G-His-GQD-Ag,PNIPAM and poly（ionic liquid）s,which was used to construct an intelligent temperature-controlled switching electrochemical sensor for the highly sensitive determination of chloramphenicol,with a detection limit of7.3×10-3μmol L-1. |
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