Feng Dong, Weng Ding, Wang Jiadao
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, PR China.
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, PR China.
J Colloid Interface Sci. 2019 Jul 15;548:312-321. doi: 10.1016/j.jcis.2019.04.039. Epub 2019 Apr 15.
Self-assembly of two types of particles into the binary colloidal crystals (BCCs) leads to the peculiar features which the monocomponent colloidal crystals do not possess. However, the self-assembly methods of the BCCs are still limited.
A facile, cost-effective and controllable approach was presented to fabricate the BCCs by directly dripping silica particle suspensions containing water and ethanol into the monodisperse polytetrafluoroethylene (PTFE) colloidal solutions. The BCCs composed of the silica and PTFE particles were formed at the air-liquid interface and picked up using the target substrates, followed by the corrosion of silica particles. Using this strategy, various ordered porous PTFE films including homo-pore-size mono/multilayer and hetero-pore-size bilayer films were prepared. The chemical composition of the porous films was well controlled.
The dissolution of ethanol resulted in the interfacial tension gradient, and thus the Marangoni convection and the relative movement of the liquid and the particles emerged. The silica particles were trapped at the air-liquid interface and the PTFE particles filled the interstitial spaces between the silica particles. After the porous films were sintered at temperatures above the melting point of PTFE, the PTFE particles were transformed into nanofibers, leading to the transferability, excellent superhydrophobicity and environmental durability.
两种类型的粒子自组装成二元胶体晶体（BCCs）会产生单组分胶体晶体所不具备的独特特性。然而，BCCs的自组装方法仍然有限。
提出了一种简便、经济高效且可控的方法，通过将含有水和乙醇的二氧化硅颗粒悬浮液直接滴入单分散聚四氟乙烯（PTFE）胶体溶液中来制备BCCs。由二氧化硅和PTFE颗粒组成的BCCs在气液界面形成，并用目标基板拾取，随后对二氧化硅颗粒进行腐蚀。使用这种策略，制备了各种有序的多孔PTFE膜，包括同孔径单层/多层膜和异孔径双层膜。多孔膜的化学成分得到了很好的控制。
乙醇的溶解导致界面张力梯度，从而出现马兰戈尼对流以及液体和颗粒的相对运动。二氧化硅颗粒被困在气液界面，PTFE颗粒填充二氧化硅颗粒之间的间隙。在多孔膜在高于PTFE熔点的温度下烧结后,PTFE颗粒转变为纳米纤维，从而具有可转移性、优异的超疏水性和环境耐久性。
