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 (ϕ = 0.71) of yellow green PL is believed to originate from the localized π 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.