Review on green carbon dot-based materials for the photocatalytic degradation of dyes: fundamentals and future perspective

Abstract

Water pollution has become more prevalent as the discharge of dyes from industries into water bodies has increased in modern life. Photocatalytic approaches are among the most effective dye degradation methods to address these issues. In this regard, carbon nanodots (CDs), well-known as quasi-spherical zero-dimensional nanomaterials, have replaced semiconductor quantum dots in recent years. CDs derived from green sources have appealed to the interest of scientists due to their tuneable fluorescence behavior, biocompatibility, large-scale production, excellent photostability, and eco-friendliness compared to CDs derived from chemical precursors. Moreover, a colossal of works reported CDs as an outstanding photocatalyst candidate for efficient dye degradation. Therefore, the study first focuses on the green synthetic routes employed for CDs and metal/non-metal infused CDs synthesis in this review article. Then, the structural, optical, and morphological properties of CDs and metal/non-metal infused CDs synthesis are discussed. The next objective discusses the fundamental motive of the review article, i.e., the potential roles of CDs and metal/non-metal infused CDs in light-harvesting, charge transfer dynamics, and surface catalytic reaction for dye degradation. It also emphasizes the various factors influencing photodegradation, such as pH, dopant, dye concentration, photocatalyst loading, light intensity, irradiation time, and temperature. Furthermore, the role of several radical scavengers on the photocatalyst in responsibly identifying active species and improving the photodegradation mechanism of dyes are briefly discussed. Besides, the reusability, stability, and cytotoxicity aspects are emphasized. To conclude, the drawbacks and the probable solutions to overcome the research gap in future routes of CDs as photocatalysts are discussed.