Efficient Preparation and Optoelectronic Properties of Coal Liquefaction Asphalt-based Carbon Quantum Dots

Coal liquefaction asphalt, a byproduct of the direct coal liquefaction process, was employed as a high-quality carbon precursor in this study. Fluorescent carbon quantum dots (CQDs) were synthesized through sulfuric acid oxidative depolymerization. The preparation process was statistically optimized using Response Surface Methodology (RSM), determining key technical parameters: a reaction temperature of 58 ℃, a duration of 2.1 hours, and a sulfuric acid-to-asphalt mass ratio of 17.5:1. This optimized approach successfully yielded blue-fluorescent CQDs characterized by uniform particle size (2–8 nm), high production yield, and superior fluorescence quantum yield. Structural characterization revealed that the synthesized CQDs possess a graphitized core-shell structure, primarily composed of aggregates based on three aromatic rings. Their surface is functionalized with oxygen-rich groups, including hydroxyl (–OH), carboxylic acid (–COOH), and sulfonic acid (–SO₃H) moieties. Optical performance tests demonstrated that the CQDs exhibit wavelength-dependent fluorescence emission characteristics under 340 nm ultraviolet excitation, with a maximum emission peak at 394 nm and a relatively high fluorescence quantum yield of 32.5%. In addition, CQDs exhibited excellent photoelectric conversion ability, generating reactive oxygen species (ROS) such as ·O₂⁻ and ·OH under light to disrupt bacterial structure, with an average bactericidal efficiency of 97.27%. This research provides a novel and valuable strategy for the high-value-added utilization of coal asphalt.