Effects of Surface Passivation on Photoluminescence Properties and Biomedical Imaging of Graphene Quantum Dots

摘要

Owing to fluorescence properties and small size, graphene quantum dots (GQDs) have been investigated for biomedical imaging. Although GQDs demonstrate some desirable properties, poor stability and low biocompatibility have limited their applications in various aspects. Therefore, in this study, we synthesized surface-passivated GQDs and studied their properties. GQDs were prepared using thermal exfoliation of graphite oxide, followed by nitric acid refluxing. Then GQDs were passivated with polyethylene glycol (PEG) using hydrothermal at 120 °C for 72 h. Both GQDs and GQDs-PEG were characterized by transmission electron microscopy, UV-Vis absorption and photoluminescence spectroscopy. Compared with GQDs, GQDs-PEG exhibit higher fluorescence intensity and fluorescent quantum yield. Also, GQDs-PEG demonstrates less cytotoxicity than GQDs in terms of cell survival rate in MTT assay. Our findings demonstrate that both fluorescence characteristics and biocompatibility of GQDs can be improved by PEG surface passivation, and GQDs-PEG is desirable for biomedical imaging.