Balazs Daniel M, Dunbar Tyler A, Smilgies Detlef-M, Hanrath Tobias
Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States.
Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States.
Langmuir. 2020 Jun 9;36(22):6106-6115. doi: 10.1021/acs.langmuir.0c00524. Epub 2020 May 26.
We investigated the physicochemical and transport phenomena governing the self-assembly of colloidal nanoparticles at the interface of two immiscible fluids. By combining in situ grazing-incidence small-angle X-ray scattering (GISAXS) with a temporal resolution of 200 ms and electron microscopy measurements, we gained new insights into the coupled effects of solvent spreading, nanoparticle assembly, and recession of the vapor-liquid interface on the morphology of the self-assembled thin films. We focus on oleate-passivated PbSe nanoparticles dispersed across an ethylene glycol subphase as a model system and demonstrate how solvent parameters such as surface tension, nanoparticle solubility, aromaticity, and polarity influence the mesoscale morphology of the nanoparticle superlattice. We discovered that a nanoparticle precursor monolayer film spreads in front of the bulk solution and influences the fluid spreading across the subphase. Improved understanding of the impact of kinetic phenomena (i.e., solvent spreading and evaporation) on the superlattice morphology is important to describe the formation mechanism and ultimately enable the assembly of high-quality superlattices with long-range order.
我们研究了在两种不混溶流体界面处控制胶体纳米粒子自组装的物理化学和传输现象。通过将具有200毫秒时间分辨率的原位掠入射小角X射线散射（GISAXS）与电子显微镜测量相结合，我们对溶剂铺展、纳米粒子组装以及气液界面后退对自组装薄膜形态的耦合效应有了新的认识。我们重点研究了分散在乙二醇亚相上的油酸盐钝化的PbSe纳米粒子作为模型系统，并展示了诸如表面张力、纳米粒子溶解度、芳香性和极性等溶剂参数如何影响纳米粒子超晶格的中尺度形态。我们发现纳米粒子前驱体单层膜在本体溶液之前铺展，并影响流体在亚相上的铺展。更好地理解动力学现象（即溶剂铺展和蒸发）对超晶格形态的影响对于描述形成机制并最终实现具有长程有序的高质量超晶格的组装至关重要。
