Synthesis strategies, luminescence mechanisms, and biomedical applications of near-infrared fluorescent carbon dots

Carbon dots (CDs) are widely used in biomedical imaging and cancer therapy due to their excellent water solubility, low toxicity, satisfying biocompatibility, and good tissue permeability. Among them, near-infrared (NIR) fluorescent CDs (λem > 650 nm) could effectively avoid the interference of spontaneous biological fluorescence, have strong tissue penetration ability, which can realize high-resolution fluorescence imaging of deep tissues, and hence show great potential in the biomedical field. Therefore, the controlled synthesis and regulation the photochemical and photophysical properties of NIR fluorescent CDs has also become a research hotspot. This review aimed to systematically summarize the synthesis strategies, luminescence mechanisms, and biomedical applications of NIR fluorescent CDs in the last 10 years. The challenges and perspectives in the synthesis and applications of NIR fluorescent CDs were also discussed.