Highly luminescent aggregate-induced emission from polyethylene glycol-coated carbon quantum dot clusters under blue light illumination

Carbon quantum dots (CQDs) have been considered as one of the most promising fluorescent nanomaterials. However, it is very challenging to prepare CQD clusters with ultrahigh quantum yield (QY) along with aggregate-induced fluorescence. Herein, through one-pot solvothermal treatment, highly luminescent aggregate-induced emission (AIE) from polyethylene glycol (PEG)-coated CQD clusters was obtained under blue light illumination (450 nm). The PEG-coated CQD clusters were uniformly dispersed within n-hexane and propylene glycol methyl ether acetate, enabling highly fluorescent green and red emission with a narrow full width at half maximum at 540 and 620 nm, respectively. The QY value was strongly enhanced through implementing the PEG coating, due to the AIE-enhanced fluorescence mechanism. The aggregated states formed in the presence of PEG were primarily due to multiple intermolecular interactions between the N-doped CQDs and PEG network. Such immensely dynamic interactions populate the radiative decay pathways, and subsequently lead to a higher PL intensity. Considering these favorable attributes, the novel solvothermal technique developed in this work paves the way for synthesizing PEG-coated CQD clusters with finely tunable optical properties used in high-performance sensors as well as next-generation energy/biological devices.