A Review of the Recent Advances of Carbon Dots in the Application of Photocatalytic Degradation of Methylene Blue Dye and their Future Prospects.

Methylene blue (MB) contamination from industrial effluents presents a persistent threat to aquatic ecosystems, prompting the search for advanced, sustainable remediation technologies. Carbon dots (CDs) have recently emerged as versatile photocatalysts, offering advantages such as strong light absorption, high photostability, tunable surface chemistry, and environmentally benign synthesis. This review uniquely integrates recent developments in CD-based photocatalysis for MB degradation, emphasizing the relationship between synthesis strategies, surface modifications, and photocatalytic efficiency. Unlike earlier surveys, it not only consolidates the latest experimental insights but also provides a comparative analysis of CDs with other nanophotocatalysts, highlighting their superior performance and limitations under various operational conditions. Mechanistic aspects-including charge separation, reactive oxygen species generation, and synergistic effects in composite systems-are critically examined. The novelty of this work lies in coupling mechanistic depth with an evaluation of scalability, stability, and cost-effectiveness, offering targeted research pathways to advance CDs from laboratory models to viable large-scale wastewater treatment solutions.