Extraction of graphitic carbon quantum dots by hydrothermal treatment commercially activated carbon: the role of cation–π interaction

Graphitic carbon quantum dots (GCQDs) are obtained by hydrothermal treatment of commercially available activated carbon in the presence of KOH. Transmission electron microscope observation indicated narrow particle size distribution between 1 and 6 nm with an average diameter 3.5 nm and high crystallinity of GCQDs. The as-prepared GCQDs exhibited bright yellow luminescence under UV light irradiation and a quantum yield of maximum 11.6 % at the excitation wavelength of 480 nm is achieved. In addition, GCQDs performed very well in the application of bio-imaging. The successful introduction of oxygen-related groups on GCQDs was evident by Fourier transform infrared and X-ray photoelectron spectroscopy measurements. A new mechanism based on hydrothermal induced crystallization and extraction of GCQDs by cation–π interaction is proposed to explain the formation of GCQDs.