Enhanced Photocatalytic Performance of Carbon Quantum Dot (CQD) Modified TiO ₂ Nanocomposites for Organic Dye Degradation

ABSTRACT In this study, TiO 2 @CQD nanocomposites were successfully synthesized to enhance photocatalytic performance. The incorporation of Carbon Quantum Dots (CQDs) onto TiO 2 led to significant improvements compared to pure TiO 2 . Structural and optical characterizations, including XRD, TEM, UV–vis, and FTIR, confirmed the effective formation of a heterostructure and the successful attachment of CQDs. This heterostructure enhances visible‐light absorption while reducing the rapid recombination of electron–hole pairs due to efficient charge transfer between TiO 2 and CQDs. The photocatalytic efficiency of the nanocomposites was evaluated using two common organic dyes: Methylene Blue (MB) and Methyl Red (MR). Under optimized operational parameters (pH 7 and catalyst dosage of 50 mg/L), the TiO 2 @CQD composite achieved approximately 80% degradation of MB and nearly complete degradation (99%) of MR. The enhanced activity is mainly attributed to the increased light‐harvesting ability and synergistic electron–hole separation mechanisms facilitated by CQDs. Additionally, reusability tests demonstrated that the photocatalyst maintained its degradation efficiency even after six continuous cycles, indicating high stability, and durability. Overall, the results show that TiO 2 @CQD nanocomposites are efficient, stable, and environmentally promising photocatalysts for wastewater treatment applications.