Bottom-up preparation of nitrogen doped carbon quantum dots with green emission under microwave-assisted hydrothermal treatment and their biological imaging.

Carbon quantum dots (CDs) have standout as one of the most important carbon nanomaterials owing to their small size, optical properties, biocompatibility and low toxicity. These CDs have been extensively explored for various applications especially in the biomedical fields. Although great efforts have been devoted to the fabrication of CDs through both top-down and bottom-up methods, most of these CDs exhibited blue emission under UV light irradiation. In this work, we reported a novel, green, economic approach for preparation of nitrogen doped CDs by directly microwave-assisted heating small organic molecules at 120°C for 5min using Glu and amino group of MPD as the precursors and ethylene glycol as solvent. Thus prepared CDs emit green fluorescence when they were irradiated under 365nm UV light. Compared with other synthetic methods, this microwave-assisted heating method does not require strict reaction conditions and is easy for operation. The CDs display unique luminescence properties, high water dispersibility and good biocompatibility. These remarkable features make CDs great potential for various biomedical applications. Taken together, a microwave-assisted heating method has been developed for bottom-up preparation of green emission CDs in a rather mild route. Owing to the facile experimental procedure and outstanding features of CDs, this work will open up a new avenue for fabrication and biomedical applications of CDs.