Facile Synthesis of Water-Soluble, Highly-Fluorescent Graphene Quantum Dots from Graphene Oxide Reduction for Efficient Cell Labelling

Abstract

In this work, we report a simple, one-step, green procedure to fabricate strong blue and yellow photoluminescent graphene quantum dots (GQDs) as by-product of the synthesis of mesoporous graphene hydrogel (GHs). The graphene hydrogel was obtained by chemical reduction of graphene oxide using ascorbic acid at mild temperature. As a consequence of the network formation, small fluorescent GQDs can be isolated from the residual solvent, purified from the by-products and finally concentrated to produce GQDs. The GQDs chemistry and morphology were characterized by X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The GQDs mean diameter was about 5–10 nm and they exhibited an intense luminescence in the visible range with an excitation wavelength-dependent fluorescence. Our experiments showed that GQDs were easily internalized in living cells and furthermore, such internalization did not adversely affect cell viability.