The Self-assembly And Application Of Molecules With Aggregation-induced Emission Property

Aggregation-induced emission（AIE） refers to the phenomenon of molecules which are almost non-emissive in dilute solution state but become highly luminescent in aggregation state. The discovery of AIE effect promotes the development of the luminescent material. Molecule self-assembly has been the main stream of fabrication strategy for novel functional nanomaterials. Introducing AIE moiety into bolaamphiphiles can fabricate luminescent functional nanomaterials. The luminescent materials based on AIE effect are widely utilized in bio-sensing and chemo-sensing applications due to their high sensitivity and selectivity, instantaneous response and simplicity. In this paper, we combined molecule self-assembly and AIE effect to fabricate light-response luminescent material and explored the application in ion detection. This thesis includes the following two parts:1. Concentration-dependent and light-responsive self-assembly of bolaamphiphiles bearing a-cyanostilbene based photochromophore. Combining light-responsive and fluorescent properties of a-cyanostilbene derivatives, a-cyanostilbene was introduced into bolaamphiphiles self-assembly, and a new bolaamphiphile bearing 1-cyano-1,2-bis（phenyl）ethene（CNBE） has been synthesized. The self-assembly of this molecule in aqueous solution is concentration-dependent. Two distinct morphologies, mono-molecular layered lamellas and helical nanofibres have been obtained with the as-prepared molecular configuration. Note worthily, the helical nanofibres provide an experimental evidence for the pure twisted structure in the liquid crystals, which is theoretically proposed by De Gennes. Due to the photoisomerization of CNBE, the self-assembled nanostructures undergomorphological changes upon irradiation. Different type of nanostructures were obtained at different concentrations（higher / lower the critical transformation concentration） or without / with irradiation by UV light in the solution state. These structures are no longer exist after being dried on substrates, but formed nanofibres, which can be attributed to the strong dewetting effect. This work illustrates concentration-dependent and light-responsive self-assembly and provides a novel avenue for fabricating smart soft materials.2. Highly selective fluorescent chemosensor based on benzothiazole for detection of Zn²⁺. Zn²⁺ ion plays an important role in the biological processes, and therefore the detection of Zn²⁺ ion is a key issue for environmental and biological systems. The chemosensors based on fluorescence signal were widely used in ion detection due to their simplicity, low cost, high sensitivity, reproducibility and instantaneous response. Thus, we designed and synthesized a new chemosensor based on benzothiazole（denoted by BTA-12）. The fluorescent intensity of the chemosensor enhanced significantly with existence of Zn²⁺ ion. The control experiments show that the analogous ions(Pb²⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Mg²⁺, Cd²⁺, Na⁺ and K⁺) do not have fluorescence enhancement effect; and some of them even quench the fluorescence dramatically. The intensity increase upon addition of Zn²⁺ is due to the formation of coordination complex and further aggregation of the complexes. As a chemosensor, BTA-12 shows a high sensitivity, good selectivity and low detection limit. BTA-12 might be potentially applicable for detection of Zn²⁺ in biological or environmental systems.