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Spectral Properties and Solubilization Location of 2'-Ethylhexyl 4-(N,N-Dimethylamino)benzoate in Micelles
?Ning Ding,Xin-zhen Du* ,Chun Wang ,Xiao-quan Lu
Author NameAffiliationE-mail
?Ning Ding College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China  
Xin-zhen Du* College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China duxz@nwnu.edu.cn 
Chun Wang College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China  
Xiao-quan Lu College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China  
Abstract:
Dual fluorescence and UV absorption of 2'-ethylhexyl 4-(N,N-dimethylamino)benzoate (EHDMAB) were investigated in cationic, non-ionic and anionic micelles. When EHDMAB was solubilized in different micelles, the UV absorption of EHDMAB was enhanced. Twisted intramolecular charge transfer (TICT) emission with longer wavelength was observed in ionic micelles, whereas TICT emission with shorter wavelength was obtained in non-ionic micelles. In particular, dual fluorescence of EHDMAB was significantly quenched by the positively charged pyridinium ions arranged in the Stern layer of cationic micelles. UV radiation absorbed mainly decays via TICT emission and radiationless deactivation. The dimethylamino group of EHDMAB experiences different polar environments in ionic and non-ionic 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.
Key words:  Dual fluorescence, Twisted intramolecular charge transfer, UV absorption, Surfactant, 2'-Ethylhexyl 4-(N,N-dimethylamino)benzoate, UV absorber, Sunscreen
FundProject:国家自然科学基金
Spectral Properties and Solubilization Location of 2'-Ethylhexyl 4-(N,N-Dimethylamino)benzoate in Micelles
丁宁,杜新贞*,王春,卢小泉
摘要:
在阳离子、非离子和阴离子表面活性剂胶束溶液中,研究了4-(N,N-二甲氨基)苯甲酸2'-乙基己基酯(EHDMAB)的双重荧光和紫外吸收.当EHDMAB增溶在不同的胶束溶液中,紫外吸收增强,在离子型胶束溶液中,可观察到具有较长波长的EHDMAB分子内扭转电荷转移(TICT)荧光,相反,在非离子型胶束溶液中,可观察到具有较短波长TICT荧光,特别是位于阳离子胶束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,EHDMAB分子的4-(N,N-二甲氨基)在离子型胶束和非离子型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.
关键词:  双重荧光,分子内扭转电荷转移,紫外吸收,表面活性剂,4-(N,N-二甲氨基)苯甲酸2'-乙基己基酯
DOI:10.1088/1674-0068/21/02/163-168
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