Rapid, Acid-Free Synthesis of High-Quality Graphene Quantum Dots for Aggregation Induced Sensing of Metal Ions and Bioimaging

Graphene quantum dots (GQDs) are zerodimensional materials that exhibit characteristics of both graphene and quantum dots. Herein, we report a rapid, relatively green, one-pot synthesis of size-tunable GQDs from graphene oxide (GO) by a sonochemical method with intermittent microwave heating, keeping the reaction temperature constant at 90 degrees C. The GQDs were synthesized by oxidative cutting of GO using KMnO4 as an oxidizing agent within a short span of time (30 min) in an acid-free condition. The synthesized GQDs were of high quality and exhibited good quantum yield (23.8%), high product yield (>75%), and lower cytotoxicity (tested up to 1000 mu g/mL). Furthermore, the as-synthesized GQDs were demonstrated as excellent fluorescent probes for bioimaging and label-free sensing of Fe(III) ions, with a detection limit as low as 10 x 10(-6) M.