低共熔溶剂中多色稀土发光增强超分子凝胶的构筑及性能

Color Tunable Rare-earth Containing Supramolecular Gels with Improved Luminescent Properties Assembled in a Deep Eutectic Solvent

将氯化胆碱和尿素按照摩尔比1∶2合成低共熔溶剂(ChU),小分子胶凝剂脱氧胆酸钠(NaDC)在ChU中质量分数为1%时开始形成低共熔凝胶,随着浓度增加,样品逐渐由澄清变为浑浊直至不透明;流变学测试结果表明,其机械强度也随之增强.通过显微镜观测得知,此凝胶由密堆积且长度达几十微米的纤维聚集体交联而成.设计并合成了与ChU溶剂具有相同阳离子且具有高效荧光的稀土铕和铽配合物[choline]_(3)[Ln(dpa)_(3)](Ln-dpa,Ln=Eu^(3+),Tb^(3+),dpa=2,6-吡啶二甲酸),将二者共掺杂到NaDC/ChU低共熔凝胶中,获得具有多色荧光的稀土凝胶软材料.研究表明,相比常规体系,低共熔溶剂的引入及凝胶基质对稀土配合物的有效隔离和束缚极大提升了稀土材料的光物理性质.

In this paper,a kind of environmentally friendly deep eutectic solvent(ChU)was obtained from chloline chloride and urea with a molar ratio of 1∶2.As a low molecular weight gelator,sodium deoxycholate(NaDC)could form gel in ChU with a mass fraction even as low as 1%.With increasing NaDC concentration in ChU,such clear gel gradually became cloudy and then opaque,accompanied with the increasing mechanical strength revealed by rheological testing.The NaDC/ChU gel was formed by densely packed fiber aggregates with tens of microns in length under optical microscopic observations.The well-designed rare-earth complexes,i.e.[choline]_(3)[Ln(dpa)_(3)](Ln-dpa,Ln=Eu^(3+),Tb^(3+),dpa=2,6-pyridinic acid)were fabricated,which had the same cationic group with ChU and excellent luminescent properties.Then,color tunable supramolecular gels were constructed through doping Eu-dpa or Tb-dpa into NaDC/ChU gels.The results showed that the introduction of deep eutectic solvent as well as the effective isolation and binding of gel matrix greatly improved the photophysical properties of such supramolecular gels compared with other solvent systems or powder states.This work develops a simple and universal strategy to prepare color tunable rare-earth containing supramolecular gel soft materials with highly luminescent efficiency and is also the first attempt in deep eutectic solvent.