Engineering Solid-State Fluorescent Carbon Dots with Aggregation-Induced Emission by Fatty Amine Chains-Regulated Charge Transfer and π-π Stacking

Carbon dots (CDs) are an encouraging green luminescent material; however, the aggregation-caused quenching (ACQ) effect poses a significant limitation for their use in solid-state devices. By adjusting precursor fatty amine chains, this paper synthesized four solid-state emissive CDs with aggregation-induced emission (AIE) properties (Lx-CDs). When water is introduced, the generation of Lx-CDs aggregates creates the switching off of the carbon-core emission (blue) in acetic acid solution and the switching on of the surface-state emission (orange). Results demonstrate that the disulfide bond and fatty amine chain structures allow considerable inhibition in the distance of aromatic skeletons, causing the aggregation-state emission, and the multiple interactions in aggregates can reduce the non-radiative processes benefiting the AIE. Besides, the fast and slow fluorescence species can be confirmed to correspond to the emission paths of carbon-core and surface-state, respectively. The solid-state emission wavelength, photoluminescence quantum yield (PLQY), and AIE strength can be engineered by the fatty amine chain regulated charge transfer and π-π stacking. This study not only reveals the intrinsic mechanism of carbon-core and surface-state luminescence dynamics in AIE CDs but also provides a method for controlling fluorescence wavelength and enhancing the emission of aggregated particles using precursor fatty amine chain length.