Graphene quantum dots supported by graphene oxide as a sensitive fluorescence nanosensor for cytochrome c detection and intracellular imaging.

A new class of cytochrome c (Cyt c) detection fluorescence sensor (GQDs-GO) based on graphene quantum dots (GQDs) supported by graphene oxide (GO) has been developed through simply mixing a certain amount of GQDs and GO. It is found that fluorescence "turn on" or "turn off" can be adjusted easily according to the concentration of Cyt c. When the concentration of Cyt c is lower than 1.9 μmol L-1, the fluorescence is "turn on", whereas it is "turn off" beyond 1.9 μmol L-1. The process is fast and can be completed within 10 s. By means of UV-vis absorption spectra, it is demonstrated that the changed fluorescence comes from the different interactions among GQDs, GO and Cyt c. Additionally, the GQDs-GO shows a high selectivity for Cyt c detection, and further exhibits favorable intracellular imaging in A549 cells. This study opens a new direction for developing a low-cost, highly efficient, GQDs-based fluorescence sensor for Cyt c detection, which make it very attractive for biological imaging applications.