Materials Science Division, Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550, USA.
Materials Measurement Science Division, National Institute for Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA.
J Colloid Interface Sci. 2018 Jun 15;520:81-90. doi: 10.1016/j.jcis.2018.02.078. Epub 2018 Mar 3.
Many applications of deep eutectic solvents (DES) rely on exploitation of their unique yet complex liquid structures. Due to the ionic nature of the DES components, their diffuse structures are perturbed in the presence of a charged surface. We hypothesize that it is possible to perturb the bulk DES structure far (>100 nm) from a curved, charged surface with mesoscopic dimensions.
We performed in situ, synchrotron-based ultra-small angle X-ray scattering (USAXS) experiments to study the solvent distribution near the surface of charged mesoporous silica particles (MPS) (≈0.5 µm in diameter) suspended in both water and a common type of DES (1:2 choline Cl-:ethylene glycol).
A careful USAXS analysis reveals that the perturbation of electron density distribution within the DES extends ≈1 μm beyond the particle surface, and that this perturbation can be manipulated by the addition of salt ions (AgCl). The concentration of the pore-filling fluid is greatly reduced in the DES. Notably, we extracted the real-space structures of these fluctuations from the USAXS data using a simulated annealing approach that does not require a priori knowledge about the scattering form factor, and can be generalized to a wide range of complex small-angle scattering problems.
许多深共晶溶剂 (DES) 的应用都依赖于其独特而复杂的液体结构的开发。由于 DES 成分的离子性质，它们的扩散结构在带电表面存在时会受到干扰。我们假设有可能通过介观尺寸的弯曲带电表面来干扰大块 DES 结构（远大于 100nm）。
我们进行了基于同步加速器的原位超小角 X 射线散射 (USAXS) 实验，以研究悬浮在带电荷的介孔二氧化硅颗粒 (MPS)（直径约为 0.5µm）中的水和常见类型的 DES（1:2 胆碱 Cl-：乙二醇）中溶剂的分布。
仔细的 USAXS 分析表明，DES 中电子密度分布的扰动延伸到颗粒表面以外约 1μm，并且可以通过添加盐离子（AgCl）来操纵这种扰动。DES 中的填充孔流体的浓度大大降低。值得注意的是，我们使用模拟退火方法从 USAXS 数据中提取了这些波动的实空间结构，该方法不需要关于散射形式因子的先验知识，并且可以推广到广泛的复杂小角散射问题。
