Department of Chemistry, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan.
JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
J Phys Chem B. 2020 Mar 19;124(11):2209-2217. doi: 10.1021/acs.jpcb.9b11345. Epub 2020 Mar 5.
Tetraphenylethylene carboxylate (TPEC) aggregates are transformed by ice confinement, which is controlled by the initial concentration of sucrose employed as a cryoprotectant and temperature. The freezing of aqueous sucrose leads to the formation of micro- or nanoliquid phase confined in ice. Aggregation-induced emission (AIE) of tetraphenylethylene carboxylate (TPEC) in the ice-confined space is explored using fluorescence spectroscopy and lifetime measurements. The characteristics of AIE in the ice-confined space strongly depend on the initial sucrose concentration and temperature, which determine the size of the liquid phase. The AIE of TPEC in the ice-confined space can be classified into three regimes in terms of spectroscopic features. Loosely packed J aggregates of TPEC are formed in the microliquid phase (>2 μm). The fluorescence intensity increases, and the wavelength is hypsochromically shifted with a decrease in the size of the space, indicating that the molecular arrangement in the aggregate depends on the space size. The fluorescence lifetimes indicate polydisperse, loosely packed aggregation. No further change in aggregate structure is observed once the liquid phase size is decreased to ∼2 μm, and a spectroscopically identical structure is maintained upon further reduction of the space size to ∼0.5 μm. The molecular arrangement in the aggregate is independent of the space size in this regime. However, when the size of the space becomes smaller than ∼0.5 μm, the aggregate structure again starts to change into a more tightly packed aggregate and a hypsochromic shift of the fluorescence wavelength occurs again. The fluorescence lifetime indicates monodispersed aggregation in this submicrospace.
四苯乙烯羧酸酯（TPEC）聚集体通过冰限域进行转化，这由用作冷冻保护剂的蔗糖初始浓度和温度控制。水合蔗糖的冻结导致微或纳米液相被限制在冰中。通过荧光光谱和寿命测量探索了四苯乙烯羧酸酯（TPEC）在冰限域空间中的聚集诱导发光（AIE）。AIE 在冰限域空间中的特征强烈依赖于初始蔗糖浓度和温度，这决定了液相的大小。根据光谱特征，TPEC 在冰限域空间中的 AIE 可以分为三个区域。TPEC 的松散堆积 J 聚集体在微液相中形成（>2μm）。荧光强度增加，波长随着空间尺寸的减小而蓝移，表明聚集体中分子排列取决于空间尺寸。荧光寿命表明多分散、松散堆积的聚集。一旦液相尺寸减小到约 2μm，聚集体结构就不再发生变化，并且在进一步减小空间尺寸到约 0.5μm 时保持相同的光谱结构。在该区域，聚集体中的分子排列与空间尺寸无关。然而，当空间尺寸变得小于约 0.5μm 时，聚集体结构再次开始转变为更紧密堆积的聚集体，荧光波长再次发生蓝移。在这个亚微空间中，荧光寿命表明单分散聚集。
