Advances in Photoluminescence and Quenching Mechanism of Carbon Dots

Carbon dots (CDs) are zero-dimensional carbon nanomaterials with sizes below 10 nm, with high fluorescence quantum yields, variable emission colours, and excellent photostability. Due to their different structural origins and complex surface chemicals, CDs display complex photoluminescence behaviors (PL) and different fluorescence suppression responses. This review systematically summarizes recent advances in understanding the PL mechanisms of CDs, including carbon-core emission, surface emission, molecular emission and crosslink emission. In addition, fluorescence quenching processes triggered by various analytical techniques are discussed, including dynamic quenching, static quenching, Förster resonance energy transfer (FRET), photoinduced electron transfer (PET), and the inner filter effect (IFE). Emphasis is placed on mechanistic understanding and experimental differentiation strategies. A clear understanding of these fundamental mechanisms is essential for optimizing the fluorescence properties of CDs and the design of highly sensitive and selective fluorescence sensors. Finally, potential research directions and applications of CDs based on these mechanical insights are also highlighted.