Improvement of photoluminescence of graphene quantum dots with a biocompatible photochemical reduction pathway and its bioimaging application.

As a rising star in the family of fluorescent material, graphene quantum dots (GQDs) have attracted great attention because of their excellent properties such as high photostability against photobleaching and blinking, biocompatibility, and low toxicity. Herein, blue luminescent GQDs were prepared by photo-reducing GQDs with isopropanol. After photochemical reduction, the increasing of sp(2) domains and the formed hydroxyl in pGQDs can enhance the photoluminescence of GQDs. The quantum yield of the photo-reduced GQDs (pGQDs) was increased 3.7 fold. Because of its less negative surface charges and lower cytotoxicity than chemical reduced GQDs (cGQDs), the pGQDs were more easily uptaken by cells. This work may provide a simple and green pathway to enhance the QY of GQDs with satisfactory biocompatibility as fluorescent nanoprobes.