【作者】 丁宁；

【导师】 杜新贞；

【作者基本信息】 西北师范大学 ， 分析化学， 2008， 硕士

【摘要】 本论文主要研究了紫外吸收剂4-(N,N-二甲氨基)苯甲酸-2-乙基己基酯(EHDMAB)在胶束中的光谱性质及结合位点。共分为四章。第一章:本章介绍了胶束相关超分子化学与紫外吸收剂领域的研究概况及进展。简要概述了EHDMAB的结构性质和其在防晒剂方面的应用。同时还介绍了分子内扭转电荷转移(TICT)化合物对二甲氨基苯甲酸酯类化合物在光物理和光化学领域的研究发展历程及其在荧光传感和分子识别方面的应用。第二章:本章通过紫外/可见吸收光谱和荧光光谱对EHDMAB在不同极性有机介质中的光谱、光物理行为进行了具体的研究。结果表明:随溶剂极性的增大,EHDMAB的最大吸收波长红移,精细结构消失,吸收带变向平滑;激发态分子发生分子内电荷转移,与基态相比偶极矩变大,出现双重荧光,荧光峰向长波波长方向移动,相对荧光强度也随之减小。这一实验结果将为设计新的以光诱导电荷转移为基础的荧光传感提供理论依据,EHDMAB可用作荧光探针。第三章:本章考察了非离子表面活性剂聚氧乙烯十二烷基醚(PLE)、聚环氧乙烷-聚环氧丙烷-聚环氧乙烷(P123)存在下EHDMAB的吸收光谱和双重荧光光谱。结果表明,线状的EHDMAB可增溶在胶束中,2-乙基己基碳链朝向胶束内核,而N,N-二甲氨基朝向胶束-水界面且处于适宜的极性微环境中;胶束环境有利于EHDMAB分子对紫外光的吸收,从而使TICT荧光增强;并根据EHDMAB和表面活性剂分子的结构和大小,解释了EHDMAB分子在胶束中的增溶位点,荧光猝灭的光谱测量进一步提供了有力的佐证。第四章:本章在阳离子表面活性剂十六烷基三甲基溴化铵(CTMAB)、十六烷基氯化吡啶(CPC)和阴离子表面活性剂十二烷基硫酸钠(SDS)胶束溶液中,研究了EHDMAB的双重荧光和紫外吸收。当EHDMAB增溶在离子型胶束溶液中时,紫外吸收增强,可观察到具有较长波长的EHDMAB TICT荧光,特别是位于CPC胶束Stern层中的吡啶阳离子可强烈猝灭EHDMAB分子的双重荧光,所吸收的紫外辐射主要通过TICT荧光和非辐射去活化衰减。按照EHDMAB分子TICT荧光在有机溶剂中的极性依赖性,说明EHDMAB分子的4-(N,N-二甲氨基)在不同胶束中处于不同的极性环境;根据EHDMAB和表面活性剂分子的结构和大小分析,EHDMAB分子的4-(N,N-二甲氨基)应朝向胶束的极性头基团,而2-乙基己基链则朝向疏水性的胶束内核。动态荧光猝灭测量为EHDMAB分子在不同胶束中的位置进一步提供了佐证。更多还原

【Abstract】 Spectral properties and solubilization location of 2-ethylhexyl 4-(N,N-Dimethylamino)benzoate (EHDMAB) in micelles were introduced briefly. This paper consisted of four chapters.Chapter 1: The recent advances in supramolecular inclusion complexes of surfactants had been reviewed. The structure, the properties and the application of EHDMAB in sun-screening products and its molecular recognition and fluorescent sensing based on the twisten intramolecular charge transfer (TICT) mechanism were described briefly.Chapter 2: The photophysical properties of EHDMAB in various organic solvents were characterized by UV absorption and fluorescence spectra. The results obtained indicate that the absorption maximum shifts to the red with increasing solvent polarity. Dipole moment in excited state was larger than that in ground state, which is due to twisted intramolecular charge transfer. It was found that with increasing polarity of solvent the dual fluorescence occurred and the TICT emission shifted to long wavelength at the same time. And the fluorescence intensity decreased. This finding would provide a theoretic gist based on intramolecular charge transfer for fluorescent sensing.Chapter 3: Absorption and dual fluorescence of EHDMAB were examined in non-ionic surfactants micelles of polyoxyethylene (n=10) (PLE) and poly(ethylene glycol)-block- poly(propylene glycol)-block-poly(ethylene glycol) (P123). It was found that linear EHDMAB molecule was solubilized in micelles with its flexible hydrophobic 2’-ethylhexyl chain toward the micellar core and with its dimethylamino moiety toward the micelle-water interface and in a moderate polar environment. UV absorption of EHDMAB was improved, resulting in greatly enhanced TICT emission. The binding sites of EHDMAB in micelles were explained at molecular level in terms of molecular structures and size of surfactants and EHDMAB. Dynamic fluorescence quenching provide further evidences for the solubilization position and orientations of EHDMAB.Chapter 4: Dual fluorescence and UV absorption of EHDMAB were investigated in cationic surfactants micelles of cetyltrimethylammonium bromide (CTMAB) and cetyl pyridinium chloride (CPC) and anionic surfactants micelles of sodium dodecylsulphate (SDS). When EHDMAB was solubilized in ionic micelles, the UV absorption of EHDMAB was enhanced. TICT emission with longer wavelength was observed in micelles. In particular, dual fluorescence of EHDMAB was significantly quenched by the positively charged pyridinium ions arranged in the Stern layer of CPC micelles. UV radiation absorbed mainly decays via TICT emission and radiationless deactivation. The dimethylamino group of EHDMAB experiences different polar environments in different micelles according to the polarity dependence of TICT emission of EHDMAB in organic solvents. In terms of the molecular structures and sizes of EHDMAB and surfactants, each individual EHDMAB molecule should be buried in micelles with its dimethylamino group toward the polar head groups of different micelles and with its 2’-ethylhexyl chain toward the hydrophobic micellar core. Dynamic fluorescence quenching measurements of EHDMAB provide further support for the location of EHDMAB in different micelles.更多还原