Tailoring the Optical Properties of Coal Pitch-Derived Carbon Dots by Graphitization Controlling

Carbon dots (CDs) have wide applications due to their unique physicochemical properties. Converting coal pitch into CDs is a valuable avenue toward new applications of traditional fossil fuels. The obtained CDs derived from coal pitch usually exhibit blue emission. Herein, a simple approach to tailor the optical properties of the coal pitch-derived blue-emissive CDs (b-CDs) is developed by post-hydrothermal treatment of b-CDs in sodium hydroxide solution. The obtained warm yellow-emissive CDs (y-CDs) show a broad emission from 400 to 800 nm range, with the maximum emission peak centered at similar to 600 nm. The red-shifted emission of y-CDs can be ascribed to the surface states with the improved extent of the pi-electron system caused by the post-hydrothermal treatment, which effectively increases the graphitization degree. The potential application of the obtained y-CDs as phosphors for a light-emitting diode (LED) is demonstrated. This study offers a feasible way to tailor the optical properties of CDs derived from coal pitch for wider applications.