Multicolour light emission from chlorine-doped graphene quantum dots

Multicolour emission is realized in chlorine-doped GQDs (Cl-GQDs) prepared by a facile hydrothermal method using fructose and hydrochloric acid as source materials. The average diameter of a Cl-GQD is about 5.4 nm with 2 at.% Cl. The emission colour of the Cl-GQDs can be tuned successively from blue to white, orange, green and red simply by varying the excitation wavelength between 300 and 600 nm. The multicolour emission from the Cl-GQDs can be attributed to Cl doping, which introduces additional energy levels between C pi and C pi*. The multicolour Cl-GQDs should find applications in bioimaging and optoelectronic devices.