Precision Nanoconfined Self-Assembly of ACQ Carbon Dots for Enhanced Solid-State Fluorescence

Carbon dots (CDs) are promising fluorescent nanomaterials, however, they are often hindered by aggregation caused quenching (ACQ) in solid-state application because of close π–π stacking interactions. Furthermore, the challenges still exist in the development of CDs-based solid-state fluorescent materials with stable structure and high fluorescence intensity. To address this challenge, a general and robust polymer directed nanoconfined self-assembly strategy is developed, enabling the fabrication of regular morphology, structurally ultra-stable and solid-state fluorescent CDs assemblies using hydrophilic star-liked di-block copolymer unimolecular micelles as templates. The absolute photoluminescence quantum yield (PLQY) of these fluorescent solid-state CD assemblies reaches 21.46%, significantly higher than 0.12% observed in traditional ACQ solid-state CDs. The enhanced solid-state fluorescent property is attributed to the prevention of the π–π stacking of CDs, the restricted movement of surface groups and the suppression of non-radiative transition processes via the polymer directed nanoconfined self-assembly of CDs. The fluorescence intensity of CDs assemblies can also be precisely tuned by adjusting the polymerization time of polymer template. Based on these advantages, the CDs assemblies are employed as luminescent materials in the identification of latent fingerprints (LFP), flexible films and 3D printing functional hydrogels.