State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China.
Institute of Advanced Structure Technology, Beijing Key Laboratory of Lightweight Multi-functional Composite Materials and Structures, Beijing Institute of Technology, Beijing 100081, China.
Langmuir. 2020 Nov 17;36(45):13682-13688. doi: 10.1021/acs.langmuir.0c02602. Epub 2020 Nov 3.
Nanoemulsions as colloidal dispersions of deformable nanodroplets promise wide range of applications in pharmaceuticals, cosmetics, and agriculture. The main limitation that reduces their industrial applications is stability, with Ostwald ripening acting as the main destabilization mechanism. Different from the conventional methods by functionalizing nanoemulsions with adequate ripening inhibitors, here we propose an alternative strategy to stabilize nanoemulsions by inhibiting Ostwald ripening. We report via Lattice Boltzmann method (LBM) and theoretical analysis that the evolution of droplets can be manipulated with the help of solid substrates, either along or against the direction of Ostwald ripening. It turns out that through pinning contact line of sessile droplets, heterogeneous substrates or solid nanoparticles can behave as a scaffold to suppress Ostwald ripening, to regulate droplet morphology and to enhance droplet stability. The identical curvature and unexpected stability of scaffolding droplets are then interpreted with free energy analysis. In addition, by simulating substrates with various heterogeneities and solid particles of different shapes, we demonstrate that it is a common phenomenon that scaffolding droplets can evolve beyond Ostwald ripening.
纳米乳剂是可变形纳米液滴的胶体分散体，有望在制药、化妆品和农业领域得到广泛应用。降低其工业应用的主要限制因素是稳定性，奥斯特瓦尔德熟化是主要的失稳机制。与用适当的熟化抑制剂功能化纳米乳剂的传统方法不同，我们在这里提出了一种通过抑制奥斯特瓦尔德熟化来稳定纳米乳剂的替代策略。我们通过格子玻尔兹曼方法（LBM）和理论分析报告说，借助固体基底可以操纵液滴的演化，无论是沿着还是逆着奥斯特瓦尔德熟化的方向。事实证明，通过固定不滚动液滴的接触线，异质基底或固体纳米颗粒可以作为支架来抑制奥斯特瓦尔德熟化，调节液滴形态并增强液滴稳定性。然后通过自由能分析解释了支架液滴的相同曲率和出乎意料的稳定性。此外，通过模拟具有不同异质性的基底和不同形状的固体颗粒，我们证明了支架液滴可以超越奥斯特瓦尔德熟化的普遍现象。
