Green Synthesis Of Green-luminescent Graphene Quantum Dots And Its Cytotoxicity

Objective:To improve the fluorescence quantu yield of GQDs by ameliorative photo-Fenton reaction and hydrothermal process, and to evaluate the cytotoxicity of GQDs.Materials and methods:GQDs were prepared by ameliorative photo-Fenton reaction and hydrothermal process. UV-visible absorption and normalized photoluminescence (PL) spectra were performed to characterize the optical properties of GQDs and the quantum yields of GQDs (in water).Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) analyses, powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy were performed to characterize the microstructures.The toxicity of GQDs was evaluated by CKK-8, LDH, ROS and Annexin-V apoptosis assay.Results:(1) Preparation and characterization:The as-prepared GQDs emitted intense green luminescence and the fluorescence quantum yield was as high as24.6%(excited at320nm). The as-prepared GQDs were nanocrystals with lateral dimensions in the range of2.3-6.4nm and had C-N and-NH2groups. The as-prepared GQDs also exhibited an excitation dependent PL behavior. The strongest emission peak located at490nm (excited at320nm).(2) Cytotoxicity experiments:As-prepared GQDs showed low cytotoxicity on Hela cells below the concentration of200ug/mL. The cell viability was nearly80%, the LDH release amount was11.45%, the ROS level was202.8%and cell apoptosis was23.44%. These indexes revealed dose-dependent.Conclusion:The as-prepared GQDs had strong photoluminescence and good biocompatibility, which suggested they had great potential in biological or medical applications.