▎ 摘　　要

Functionalization is a promising approach to modify the physical and chemical properties of graphene quantum dots (GQDs). However, the synthesis of functionalized GQDs (F-GQDs) is usually conducted with strong acids. Thus, the sustainable synthesis route of F-GQDs remains a challenge. This is important for suitable optimization of GQDs to be applied in sustainable photovoltaic applications, especially dye-sensitized solar cells owing to the strong attachment of functional group elements. This study presents a detailed study of optical, structural, and chemical changes that occurred in GQDs during the functionalization process by adding an ionic liquid, 1-ethyl1-methylpyrrolidium bis(trifluoromethylsulfonyl)imide via hydrothermal synthesis approach using an ecofriendly route comprising only cellulose and deionized (DI) water. The presence of ionic liquid provides fundamental elements (nitrogen (N), fluorine (F), and sulfur (S)), which are added to GQDs producing F-GQDs. The optimum result shows that the 20 wt% N, F, S functionalized GQDs have the largest UV-vis absorption and photoluminescence emission. The F-GQDs also revealed a single crystalline hexagonal graphene-like honeycomb structure in transmission electron microscopy and increased roughness relatively from atomic force microscopy. Moreover, the Fourier transform infrared and x-ray photoelectron spectroscopy have also confirmed the presence of C-N, C=S, C-F, and N-H functional groups in the F-GQDs produced.