Preparation of Graphene Quantum Dots and Their Application in Cell Imaging

Objective. This study aims to increase the fluorescence quantum yield by improving the conditions of preparing graphene quantum dots (GQDs) through the solvothermal route and observe the GQDs performance in imaging oral squamous cells.Methodology. The following experimental conditions of GQDs preparation through the solvothermal route were improved: graphene oxide (GO)/N-N dimethyl formamide (DMF) ratio, filling percentage, and reaction time. A fluorescence spectrophotometer was used to measure photoluminescence, and the peak values were compared. Methylthiazolyldiphenyl-tetrazolium (MTT) bromide was used to detect the cytotoxicity of GQDs, which was compared with that of cadmium telluride quantum dots (CdTe QDs). GQDs were cultured with tongue cancer cells. After the coculture, a laser scanning confocal microscope (LSCM) was used to observe cell imaging.Results. The optimal conditions of GQD preparation through the solvothermal route included the following: 10 mg/mL GO/DMF ratio, 80% filling percentage, 12 h reaction time, and 17.4% fluorescence quantum yield. As the cell concentration increased, the GQD and CdTe QD groups exhibited a decreasing cell survival rate, with the decrease in the CdTe QD group being more significant. The LSCM observations showed bright green fluorescence images.Conclusion. The improved experimental conditions increased the fluorescence quantum yield of GQDs. In this study, the prepared GQDs exhibited low cytotoxicity level and satisfactory cell imaging performance.