Green, simple and large scale synthesis of N-doped graphene quantum dots with uniform edge groups by electrochemical bottom-up synthesis

We developed an electrochemical bottom-up synthesis of N-doped GQDs (N-GQDs) with a large number of well-defined edge groups for the first time. This progress is green (both atom utilization and yield are higher than 95%, without by-products), simple and suitable for large scale synthesis (10 g per batch). The exclusive edge group of the obtained N-GQDs is -NH2 because of the amino oxidative coupling of o-phenylenediamine, which results in unique excitation wavelength independence behavior. The high quantum yield (phi = 0.71) of yellow green PL is believed to originate from the localized pi state due to the graphitic doping of nitrogen. The edge groups have little influence on the spectral resolved PL lifetime as well as the size distribution. The low biotoxicity of N-GQDs is also proved by live cell fluorescent imaging.