The sustainable valorization of coal into advanced functional carbon materials represents an important strategy for expanding the application landscape of carbon resources beyond conventional energy uses. In this work, coal-derived carbon quantum dots (C-CQDs) were synthesized via an ultrafiltration-assisted mild oxidation approach using an abundant carbonaceous precursor. The as-prepared C-CQDs were subsequently integrated with silica and amino-functionalized silica matrices through a one-pot sol−gel strategy to develop single-component white-light-emitting solid-state (SS) phosphors. Reference samples were also prepared, which do not contain CQDs, to elucidate the role of C-CQDs in governing emission behavior. The incorporation of C-CQDs enabled broadband emission spanning the entire visible region, leading to efficient white light generation. Notably, the sol−gel reaction proceeded without a conventional base catalyst when amino-functionalized precursors were employed, highlighting the self-catalytic role where the surface functional groups of C-CQDs facilitate hydrolysis and condensation reactions. Among the prepared materials, the composites containing both silica and amino-functionalized silica (AS-CQD and AS-CQD-WE) exhibited Commission Internationale de l’Eclairage (CIE) coordinates of (0.30, 0.34) and (0.30, 0.35), respectively, which are close to pure white light. The correlated color temperatures (CCTs) for both samples are 6976 and 6987 K, respectively, corresponding to cool daylight. A prototype of the white-light-emitting device was fabricated using indigenous SS phosphors combined with a 365 nm UV LED within a 3D-printed enclosure, demonstrating potential practical applicability. The developed phosphors showed low cytotoxicity toward human cells and thermal stability up to 150 °C maintaining structural integrity without appreciable mass loss. Furthermore, the indicative unit fabrication cost (₹60.9) of the white-light-emitting device (WLED) highlights the economic feasibility of the approach. Overall, this study presents a scalable and environmentally benign strategy for transforming coal into SS phosphors, positioning coal-derived CQDs as promising materials for energy-efficient lighting and sustainable optoelectronic applications.
Gogoi et al. (Tue,) studied this question.