Solid-State Phosphors from Coal-Derived Carbon Quantum Dots

With unique optical and chemical properties, carbon quantumdots(CQDs) find tremendous applications in chemistry, biology, and materialsscience to medicine. To expand the applicability of coal-derived CQDsfrom the liquid to solid state, we herein report the sustainable synthesisof solid phosphors from coal-derived CQDs using poly(vinyl alcohol)(PVA) and silica (SiO2) as an organic and inorganic matrix.Two coal-derived CQDs were obtained using an eco-friendly ultrasonic-assistedwet oxidation method. The structural and chemical properties of theCQDs were extensively investigated and compared with commercial CQDs.The coal-derived CQDs exhibited blue fluorescence with 8.9 and 14.9%quantum yields. The CQDs were found to be self-co-doped with nitrogenand sulfur heteroatoms through surface and edge functional groups.Solid-state fluorescence of PVA/CQD composite films confirmed thatthe CQDs retained their excellent blue emission in a dry solid matrix.A facile one-pot sol-gel method was employed to fabricate SiO2/CQD phosphors with the unique fluorescence emission. Dueto their special structural features, coal-derived CQDs favored theheterogeneous nucleation and rapid formation of SiO2/CQDphosphors. Further, coal-derived CQDs caused high-intensity whitelight emission with CIE coordinates of (0.312, 0.339) by endowinga suitable band gap structure in a SiO2/CQD solid phosphorfor potential optical applications.

Automated summary

With unique properties, carbon quantum dots (CQDs) have various applications in different fields. This study presents a sustainable synthesis of solid phosphors from coal-derived CQDs using poly(vinyl alcohol) (PVA) and silica (SiO2) as matrix. The obtained CQDs exhibited blue fluorescence and were self-co-doped with nitrogen and sulfur heteroatoms. The solid-state fluorescence of PVA/CQD composite films and SiO2/CQD phosphors were successfully achieved, and the latter showed high-intensity white light emission for potential optical applications.