Yi Sijing, Wang Jiao, Feng Zhenyu, Chen Xiao
Key Laboratory of Colloid and Interface Chemistry, Shandong University , Ministry of Education, Jinan, 250100, China.
J Phys Chem B. 2017 Oct 5;121(39):9302-9310. doi: 10.1021/acs.jpcb.7b07653. Epub 2017 Sep 22.
Soft materials of europium β-diketonate complexes constructed in lyotropic liquid crystals (LLCs) mediated by ionic liquids (ILs) are impressive for their excellent luminescence performance and stability. For the aim to further improve their mechanical processability and luminescent tunablility, the polyoxyethylene phytosterols (BPS-n) were introduced here as structure directing agents to prepare relatively "rigid" lamellar luminescent LLCs in 1-butyl-3-methyl-imidazolium hexafluorophosphate by doping europium β-diketonate complexes with different imidazolium counterions. As a result of the solvophobic sterol ring structure of BPS-n, the more effective isolation and confinement effects of europium complexes could be achieved. The longest fluorescence lifetime and the highest quantum efficiency reported so far for europium containing lyotropic organized soft materials were thus obtained. Changing the molecular structures of BPS-n with different oxyethylene chains or doped complexes with imidazolium counterions of different alkyl chain lengths, the spacings of lamellar LLC matrixes and position of dispersed complexes became tunable. The measured luminescent and rheological properties for such composite LLCs showed a dependence on the rigidity and isolation capability afforded by sterol molecules. It was also found that the increase of counterion alkyl chain length would weaken the LLC matrix's confinement and isolation effects and therefore exhibit the deteriorated luminescence performance. The enhanced luminescence efficiency and stability of doped BPS-n LLCs reflected the excellent segregation of europium complexes from each other and therefore the reduced self-quenching process. The obtained results here present the designability of LLC matrixes and their great potential to promote achieving the luminescence tunability of soft materials.
由离子液体（ILs）介导在溶致液晶（LLCs）中构建的铕β - 二酮配合物软材料，因其出色的发光性能和稳定性而令人印象深刻。为了进一步提高其机械加工性能和发光可调性，本文引入聚氧乙烯植物甾醇（BPS - n）作为结构导向剂，通过掺杂具有不同咪唑鎓抗衡离子的铕β - 二酮配合物，在1 - 丁基 - 3 - 甲基咪唑六氟磷酸盐中制备相对“刚性”的层状发光LLCs。由于BPS - n的疏溶剂甾醇环结构，可以实现对铕配合物更有效的隔离和限制作用。从而获得了迄今为止含铕溶致有序软材料报道的最长荧光寿命和最高量子效率。通过改变具有不同氧乙烯链的BPS - n的分子结构或掺杂具有不同烷基链长度咪唑鎓抗衡离子的配合物，层状LLC基质的间距和分散配合物的位置变得可调。对这种复合LLCs测量的发光和流变性质显示出对甾醇分子提供的刚性和隔离能力的依赖性。还发现抗衡离子烷基链长度的增加会削弱LLC基质的限制和隔离作用，因此表现出发光性能的恶化。掺杂BPS - n的LLCs发光效率和稳定性的提高反映了铕配合物彼此之间出色的分离，因此减少了自猝灭过程。本文获得的结果展示了LLC基质的可设计性及其在促进实现软材料发光可调性方面的巨大潜力。
