Synthesis of coal pitch-derived carbon dots with yellow emission and improved photoluminescence quantum yield through pre-surface engineering and nitrogen doping†

Carbon dots (CDs) have unique advantages as the luminophores of optoelectronic devices. Taking advantage of the carbon-rich nature of coal pitch, converting coal pitch into CDs is an efficient avenue for the noncombustive use of coal pitch in response to the global carbon neutralization demand. However, to achieve coal pitch-derived CDs with long wavelength emission and high photoluminescence quantum yield (PLQY) remains a great challenge. Herein, a strategy to tailor the PL properties of coal pitch-derived CDs is developed. It includes introducing nitro groups on the surface of coal pitch (NO₂-coal pitch) followed by solvothermal treatment of NO₂-coal pitch and aspartic acid (ASP), which effectively promotes the dehydration and carbonization processes and favorably increases the content of pyrrolic N in the CDs. As a result, yellow-emissive CDs (y-CDs) with an improved PLQY of 34% are obtained. Transparent y-CD polymer films with solid-state fluorescence are fabricated, and their potential application for light emitting diodes (LEDs) is demonstrated. The current work provides a feasible way to regulate the PL properties of coal pitch-derived CDs for wide application.