Study Of Synthesis,Functionalization And Fluorescence Performance Of Graphene Quantum Dots

Graphene quantum dots have photoluminescent properties and have been used in chemical sensing,biosensing,bioimaging,nanomedicine,photocatalysis and electrocatalysis applications since discovery.The precise control of graphene quantum dots can make the application of graphene quantum dots more extensive.In this paper,starting from the preparation of graphene quantum dots,the properties of the fluorescence spectrum(peak position and intensity)and the effects of fluorescence quantum efficiency are explored by controlling the preparation conditions and doping methods.The main work was as follows:(1)Using citric acid as a precursor,graphene quantum dots(GQDs)emitting 468 nm fluorescence under 365 nm excitation were successfully prepared by hydrothermal method.(2)In order to explore the influence of hydrothermal time on GQDs,the duration of hydrothermal heating was 10 minutes,20 minutes,30 minutes,and 40 minutes,respectively,and the strongest fluorescence intensity was found at 30 minutes.With the increase of hydrothermal time,the fluorescence spectrum of GQDs has a slight red shift of about 6 nm.The red shift may be due to the increase in the degree of oxidation due to the prolonged hydrothermal time.(3)In the preparation of GQDs,the amount of citric acid was controlled.The amount of citric acid used in the same hydrothermal time was 0.25 g,0.5 g,0.75 g,and 1 g,respectively,and the highest quantum efficiency of 0.75 g was found.(4)Nitrogen-sulfur-doped graphene quantum dots(N,S-GQDs)were successfully prepared using L-cysteine as the nitrogen source,sulfur source and citric acid as the carbon source.N,S-GQDs were found under the same amount of citric acid.Compared with GQDs,there is a blue shift of fluorescence around 40 nm.The phenomenon of blue shift shows that N,S doping changes the fluorescence characteristics of quantum dots,and the fluorescence quantum efficiency increases significantly.(5)The N,S-GQDs obtained in the above experiments were used as the detectors,and the detection of Fe3+was achieved with the utility of the fluorescence quenching principle.