Optimization of high efficiency blue emissive N-, S-doped graphene quantum dots

Graphene quantum dots (GQDs) with bright emission at short wavelengths have attracted much attention due to their importance in various applications such as light-emitting diodes. During or after synthesis, several parameters can significantly improve the optical properties of GQDs. This study presents a facile solvothermal method with low-cost precursors using glutamic acid as the carbon source to realize blue emitting GQDs. The positive effects of urea and 1-octanethiol as nitrogen and sulfur dopants on the photoluminescence quantum yield (PLQY) of the prepared GQDs were demonstrated and optimized. The results confirmed the formation of 2.2 nm nanoparticles with a bright emission around 381 nm with a full width at half maximum of 58 nm and a PLQY approaching 70 %. The decay lifetime of the emission also showed a tri-exponential profile with an average lifetime of 2.4 ns. The simplicity of the preparation method without any post-treatment process, together with a high PLQY of 70 % at short wavelengths, nominates the prepared GQDs for optoelectronics and UV light-driven biological purposes. •Sulfur and nitrogen co-doped graphene QDs were prepared via solvothermal technique.•Graphene QDs with average size of 2.4 nm showed bright and pure blue emission.•Upon optimization of several experimental parameters, PLQY of around 70 % was realized.•Decay lifetime of PL, confirmed tri-exponential pathways with average lifetime of 2.4 ns.