The Study Of The Regulation Of Supramolecular Aggregation Structure And Photophysical Properties By Amphiphilic Molecules

Since Forster and Kasper’s discovery of the concentration quenching effect in 1954. Lots of studies on the photophysical properties and applications of luminescent compounds have been conducted, which contributes not only to understand the aggreagation and luminescene mechanism of luminescent compounds but also to provide stragties for designing and preparing new materials with novel functions such as chemical sensors, stimuli responsive materials and smart luminescent sytems etc. However, the research work in this field is still in its infancy. A great effort is still needed urgently to understand the correlation between the physical chemistry properties and the structures of amphiphiles self-assemblies.In this regards, this dissertation will introduce aggregation-caused quenching phenomenon (ACQ), aggregation-induced emission phenomenon (AIE) and process of aggregation-induced energy transfer respectively. The regulation mechanisms of the above aggregation process on the luminescence properties were also concluded. Based on the previous work in our lab, an amphiphilic Eu(Ⅲ) complex (EuL3+(Ⅰ)) with a coumarin unit as energy donor was designed and synthesized. The photophyscial properties of EuL3+(Ⅰ) in various solvents was studied. The photophysical properties of EuL+(Ⅰ) can be regulated through the co-assembly of EuL3+(Ⅰ) and negative surfactant and the regulation mechanism was investigated systematically. Based on this, positive surtactant, DTAB, can be detected efficiently by the principles of the constitutional dynamic characteristic of self-assemblies. Specifically, this thesis is mainly composed of the following two parts:In the first part, amphiphilic EuL3+(Ⅰ) having a coumarin unit as energy donor, a+3 charged head and a hydrophobic alkyl chain was designed and synthesized. The obtained compounds were characterized by using FTIR, NMR, MS and elemental analysis. EuL3+(Ⅰ) spontaneously self-assembles in water and gives nanoparticles with a diameter of 164 nm. This leads to the luminescence of Eu(Ⅲ) was quenched completely. It was found that the co-assembly of EuL3+(Ⅰ) with negative surfactant, SDS, could give vesicular nano-structures with a diameter of 105 nm. This process favors the deaggreation of the aggreagated coumarin units in EuL3+(Ⅰ), which could sensitize the luminescence of Eu(Ⅲ) significantly. By contrast, the molecularly dispersed complex EuL3+(Ⅰ) could give luminescence of Eu(Ⅲ) with high quantum yield, suggesting that the weak luminescence of EuL3+(Ⅰ) aquous solution should be ascribed to the self-assembly of EuL3+(Ⅰ) istead of the energy transfer from the excited state of Eu(Ⅲ) to the higher O-H vibration of the precoordinating water molecules.In the second part, EuL3+(Ⅰ)/SDS assembly was employed as a sensing platform to detect the positive surfactant, DTAB, by taking advantages of the constitutional dynamic characteristic of self-assemblies. It was found that SDS could trigger the luminescence of Eu(III) obviously (I/I0= 391). DTAB could co-assemble with EuL3+(Ⅰ)/SDS and lead to the aggregation of the coumarin units, resulting in the quenching of the luminescence of Eu(Ⅲ). The quenching efficiency is 0.43. The dection limit of EuL3+(Ⅰ)/SDS system for DTAB is 2.80 μM. Meanwile, nether other surfactants including TTAB, CTAB, SDS and TX100 nor the tested inorganic salts could affect the photophysical properties of Eu(Ⅲ) significantly, suggesting that EuL3+(Ⅰ)/SDS could sense and distinguish DTAB efficiently.