Synthesis, doping mechanisms, properties, and applications of bimetallic doped carbon dots (BM-CDs) in analytical, biomedical, environmental, and energy production fields: a review

Carbon dots (CDs) have attracted considerable attention as promising nanomaterials for analytical, biomedical, environmental, and energy-related applications, owing to their exceptional optical properties, excellent biocompatibility, and low toxicity. Doping represents a novel approach to improve the electronic structure and surface functionalities of CDs, which can be achieved by incorporating foreign metal ions. Among the various doping approaches, bimetallic doping is particularly noteworthy due to its synergistic effects, including altered band gaps, improved charge transfer, and the creation of new energy levels. By incorporating two distinct metal ions, referred to as bimetallic doping, the resulting doped CDs exhibit superior catalytic, optical, and electronic properties, resulting in enhanced quantum yield, fluorescence (FL), and selectivity, making them highly attractive for advanced technological applications. For the first time, this review provides a comprehensive overview of the diverse synthesis approaches, doping strategies, and properties of bimetallic doped CDs (BM-CDs) and highlights their broad applications across analytical, biomedical, environmental, and energy domains. Additionally, it addresses current challenges in their synthesis and offers perspectives on future research directions to advance their development and expand their utility across emerging fields.