Preparation of Ultrasmall AIE Nanoparticles with Tunable Molecular Packing via Freeze Assembly

Advances in the development of aggregation-induced emission luminogens (AIEgens) depend on understanding how the molecular packing affects their luminescent properties and on making nanoparticles (NPs) with desired sizes. Although reported strategies have advanced the field, rational control of molecular packing and efficient fabrication of AIEgen NPs sub-5.5 nm in diameter remain pressing issues. Here we report a “freeze assembly” strategy, in which the diameter of AIEgen NPs can be precisely tuned from ∼3 nm to hundreds of nanometers, and a molecular packing in kinetically trapped states that are not easily captured by conventional assembly methods can be obtained, leading to tunable fluorescence emissions. Therefore, this study provides a significant tool to fabricate organic luminescent nanomaterials with diameters smaller than 5 nm, which is of critical importance for biomedical applications; meanwhile, tuning molecular packing in nanoparticles displaying different fluorescence may help to shed new light on the mechanism of AIEgens.

聚集诱导发光分子（aggregation-induced emission luminogens，AIEgens）的研发进展，取决于对分子堆积如何影响其发光性能的认知，以及制备具有预期尺寸的纳米颗粒（nanoparticles，NPs）。尽管已有报道的策略推动了该领域的发展，但对分子堆积的理性调控，以及高效制备直径小于5.5 nm的AIEgen纳米颗粒，仍是亟待解决的关键问题。本文报道一种“冷冻组装”策略，借助该策略可将AIEgen纳米颗粒的直径精准调控在约3 nm至数百纳米的范围内，同时可获得传统组装方法难以捕获的动力学捕获态分子堆积结构，进而实现荧光发射的可调性。因此，本研究为制备直径小于5 nm的有机发光纳米材料提供了极具价值的工具，该类材料在生物医学应用中具有至关重要的意义；同时，调控纳米颗粒的分子堆积以实现差异化荧光表现，或可为阐明AIEgens的作用机制提供全新思路。