ESRF-The European Synchrotron, 38043 Grenoble, France.
J Chem Phys. 2018 Jan 7;148(1):014904. doi: 10.1063/1.5008400.
The evolution of interactions and dynamics of Janus colloidal particles suspended in quasi-binary liquid mixtures undergoing phase separation is presented. The experimental system consisted of silica-nickel Janus particles dispersed in mixtures of 3-methylpyridine, water, and heavy water. Colloidal microstructure and dynamics were probed by ultra-small-angle X-ray scattering and ultra-small-angle X-ray photon correlation spectroscopy, respectively. The observed static and dynamic behaviors are significantly different from those found for Stöber silica colloids in this mixture. The Janus particles manifest a slow aggregation below the coexistence temperature and become strongly attractive upon phase separation of the solvent mixture. In the two-phase region, particles tend to display surfactant-like behavior with silica and nickel surfaces likely preferring water and 3-methylpyridine rich phases, respectively. While the onset of diffusiophoretic motion is evident in the dynamics, it is gradually suppressed by particle clustering at the investigated colloid volume fractions.
呈现了悬浮在经历相分离的准二元液体混合物中的 Janus 胶体粒子的相互作用和动力学的演变。实验系统由分散在 3-甲基吡啶、水和重水混合物中的二氧化硅-镍 Janus 粒子组成。胶体微结构和动力学分别通过超小角 X 射线散射和超小角 X 射线光子相关光谱进行探测。观察到的静态和动态行为与在该混合物中发现的 Stöber 二氧化硅胶体有很大的不同。Janus 粒子在共存温度以下表现出缓慢的聚集，并且在溶剂混合物相分离时变得强烈吸引。在两相区域中，粒子倾向于表现出表面活性剂样的行为，其中二氧化硅和镍表面可能分别优先选择富含水和 3-甲基吡啶的相。虽然在动力学中明显出现扩散泳动的开始，但在研究的胶体体积分数下，粒子团聚逐渐抑制了扩散泳动。
