Synthesis Of Graphene Quantum Dots And The Study Of Their Fluorescence Property

Graphene quantum dots are a kind of photoluminescence material. It can be applied in biological imaging, fluorescence detection, photo-catalysis, photovoltaic devices and other fields, which caused the wide attention of researchers. But the researches on the mechanism of the fluorescence and the precisely control of the fluorescence remain less and still at the exploratory stage. This paper focuses on the preparation of graphene quantum dots, and explores the influence of the peak position of fluorescence, fluorescence intensity and the fluorescence quantum efficiency by doping and controlling of the preparation conditions. This paper mainly carried out the following work:(1) The GQDs was synthesized with a bottom-up method from citric acid of uniform size. The PL peak is at450nm with365nm UV light. When controlling the preparation conditions, we got the best heating temperature, heating time and the pH value of the highest fluorescence quantum efficiency.(2) We synthesized the N-GQDs using the citric acid and ammonia as the carbon source and nitrogen source. The size increase and we found that the fluorescence of N-GQDs have blue shift and the fluorescence is much stronger than that of GQDs.(3) In the preparation of N-GQDs, we found that the fluorescence peaks have a red shift with the heating time increase between5-90min; Under the same heating time, we controlled the concentration of citric acid respectively1mg/mL,2mg/mL,10mg/mL,100mg/mL, found that the QY of the N-GQDs with the concentration of2mg/mL reached42%.(3) We studied the influence of pH vale on the fluorescent of N-GQDs. We controlled the pH value and made it in the range of3～11.The QY and the dispensability in alkaline conditions are better, the highest QY is which the pH=9, the QY is low under the condition of acid.(4) Using the N-GQDs with the highest QY as testing objects, we detected the Fe3+ions with the principle of fluorescence quenching. The lows concentration of Fe3+ions which we can detect is100μM. And we got a quenching fitting line between the concentration of Fe3+and quenching ratio.