Investigating the effect of pH on the photoluminescence properties and particle size of graphene quantum dots

Among the carbon materials, graphene oxide and graphene quantum dots have attracted many researchers’ attention due to their luminescent properties. Graphene quantum dots are graphene sheets smaller than 100 nm that exhibit unique optical and electronic properties due to quantum confinement and edge effects. Carbonization of carbon materials is one of the methods of preparing quantum dots, which leads to the control of particle size. In this research, graphene quantum dots were prepared by the citric acid carbonization method, and pH’s effect on photoluminescence and particle size was investigated. Examining the properties of the synthesized samples showed that when the pH changes, the size of the graphene quantum dots increases with the introduction of OH groups, and the surface chemistry changes a little compared to pH 8, and at pH 10 and 12, the radiation wavelength and, accordingly, the particle size increase.