Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich , 8093 Zurich, Switzerland.
Langmuir. 2013 Nov 26;29(47):14386-95. doi: 10.1021/la403240k. Epub 2013 Nov 15.
Interactions between colloidal particles are strongly affected by the particle surface chemistry and composition of the liquid phase. Further complexity is introduced when particles are exposed to shear flow, often leading to broad variation of the final properties of formed clusters. Here we discover a new dynamical effect arising in shear-induced aggregation where repeated aggregation and breakup events cause the particle surface roughness to irreversibly increase with time, thus decreasing the bond adhesive energy and the resistance of the aggregates to breakup. This leads to a pronounced overshoot in the time evolution of the aggregate size, which can only be explained with the proposed mechanism. This is demonstrated by good agreement between time evolution of measured light-scattering data and those calculated with a population-balance model taking into account the increase in the primary particle nanoroughness caused by repeated breakup events resulting in the decrease of bond adhesive energy as a function of time. Thus, the proposed model is able to reproduce the overshoot phenomenon by taking into account the physicochemical parameters, such as pH, till now not considered in the literature. Overall, this new effect could be exploited in the future to achieve better control over the flow-induced assembly of nanoparticles.
胶体颗粒之间的相互作用强烈地受到颗粒表面化学性质和液相组成的影响。当颗粒暴露于剪切流中时，情况会变得更加复杂，这通常会导致形成的聚集体的最终性质发生广泛变化。在这里，我们发现了一个新的动力学效应，即在剪切诱导聚集过程中，由于反复的聚集和破裂事件，导致颗粒表面粗糙度随时间不可逆地增加，从而降低了键合的黏附能和聚集体抵抗破裂的能力。这导致聚集体尺寸的时间演化出现明显的过冲，只有通过所提出的机制才能解释这一现象。这通过将考虑了由反复破裂事件引起的初级颗粒纳米粗糙度增加的群体平衡模型与测量的光散射数据的时间演化进行很好的吻合得到了证明，从而导致键合黏附能随时间的降低。因此，所提出的模型通过考虑到目前在文献中尚未考虑的物理化学参数（如 pH 值），能够再现过冲现象。总的来说，这种新的效应可以在未来用于更好地控制纳米颗粒的流动诱导组装。
