Luminescent Carbon Dots: Rational Engineering and Mechanistic Insights

ABSTRACT Carbon dots (CDs) featuring bright photoluminescence (PL) have emerged as a focal point of research due to their extraordinary attributes, including low toxicity, inexpensive synthesis, eco‐friendliness, and outstanding biocompatibility. To date, various methodologies for synthesizing CDs have been recorded; however, the origin of their luminescence is still a debatable point, which hinders the achievement of the desired optical properties. Likewise, there persists a need for thorough analysis that encompasses experimentally guided structural design and mechanistic understanding of CDs’ PL, involving fluorescence (FL) and afterglow luminescence. This review aims to provide a comprehensive account of spectral elaborations from the deep ultraviolet (DUV) to the near‐infrared (NIR) region, inherent to distinct exciton transition pathways. Furthermore, by carefully integrating pieces of the mechanistic puzzle owing to underlying emission centers, we systematically explore the impact of structural engineering on FL modulation, which material scientists could set foot on in the future. Subsequently, we delve into recent findings to elucidate the transition from FL to afterglow luminescence in CDs with the aid of involved substrates to harvest triplet excitons. Ultimately, we discuss practical challenges and emerging opportunities for scalable synthesis and spatially governed optical properties.