Microwave-Assisted Synthesis of Nitrogen-Doped Multi-Layer Graphene Quantum Dots with Oxygen-Rich Functional Groups

Strong green-luminescent nitrogen-doped multi-layer graphene quantum dots (N-GQDs) have been prepared via a microwave-assisted hydrothermal method using glucose and urea as the starting materials. The fabricated N-GQDs show a highly crystalline structure and consist of similar to 3-10 graphene layers with an N/C atomic ratio 5.7 %. The wavelength-dependent luminescence emission behaviour is observed with a photoluminescence quantum yield of 5.2 %. The combination of the unique optical properties introduced by nitrogen doping with the high solubility in aqueous medium offered by the surface oxygen-rich functional groups in N-GQDs provides additional advantages for their potential applications in biolabelling and bioimaging.