Aggregation-induced emission of carbon quantum dots: Mechanisms and applications

Carbon quantum dots (CQDs) are a type of zero-dimensional carbon-based nano-luminescent material with excellent fluorescent properties and have potential applications in many areas. Usually, the fluorescence of CQDs is quenched when they aggregate, limiting further exploration of their application. In recent years, research on CQDs with aggregation-induced emission (AIE) features has shown promise in addressing the issue of poor luminescence efficiency upon aggregation, although the underlying mechanisms are not yet fully understood. Here, inter-dots/molecular excitonic and intra-dots/molecular electron-vibration couplings are employed to potentially explore the mechanism of aggregation-caused quenching and AIE of CQDs. In addition, the CQDs with AIE feature are classified into two categories, the CQDs possessing intrinsic AIE properties (AIE-CQDs) and the exogenous CQDs (endowed-AIE-CQDs). The detailed research progress on both types is also summarized. Furthermore, the documented applications of AIE-CQDs and endowed-AIE-CQDs in biomedical imaging, chemical analysis, and solid-state lighting are summarized based on their enhanced fluorescence and redshifted emission wavelengths upon aggregation.