Graphene Quantum Dots With Its Amino-functionalization Prepared By Microwave-hydrothermal Method

Graphene quantum dots as new members of the family of graphene, ithas gained the extensive research because of its unique quasi zero dimensionalstructure and photoluminescence properties. However, the preparation ofgraphene quantum dots with fluorescence performance study is still the researchfocus at present.In this paper, the raw material graphene oxide was one-step synthesized byultrasonic oxidation method, The graphene quantum dots which excited byultraviolet light was then successfully synthesized by microwave-assistedhydrothermal method. X-ray diffraction was used to analyze the crystal structureof the products; thermogravimetric was used to analyze thermal stability of theprecursor, determine the optimum reaction temperature; the morphology and sizeof graphene quantum dots were characterized by transmission electronmicroscopy; UV absorption spectra and the fluorescence spectra were used tostudy the control rules and effect of reaction conditions on the luminescenceproperties of products.Green graphene quantum dots were prepared by microwave assistedsolvothermal method using N, N-dimethyl formamide as the ammonia source.As confirmed by the structural analysis, the GQDs were edge-terminated with aprimary amine, and the size was less than10nm, which was closer to zerodimension state. The results prove that the amine functionalized graphenequantum dots show more rich luminescence performance, such as excitationwavelength dependence and up-conversion luminescence performance, whichexpand the graphene quantum dots emission in the visible light rang.The results prove that the morphology and fluorescence intensity were influencecd by so many hydrothermal conditions such as temperature andreaction time, pH value, as well as microwave power and microwave processingtime. The mechanism in synthesizing graphene quantum dots by microwave-assisted hydrothermal method was discussed. Graphene quantum dots withoptimal luminescent properties were obtained when microwave power at800Wfor10minutes, pH=10, hydrothermal temperature at190℃for6hours.