School of Chemical, Biological, and Materials Engineering, The University of Oklahoma , Norman, Oklahoma 73019, United States.
J Phys Chem B. 2013 Nov 7;117(44):13922-9. doi: 10.1021/jp407495z. Epub 2013 Oct 28.
The equilibrium behavior of ellipsoidal Janus nanoparticles at water-oil interfaces was investigated using dissipative particle dynamics simulations. It was found that the orientation of the nanoparticles with respect to the interface depends on nanoparticle aspect ratio, on the amount of polar vs nonpolar surface groups, and on the interactions between the nanoparticles surface groups and aqueous and nonaqueous solvents. The changes in nanoparticle orientation are not always monotonic, probably because of a competition between different driving forces. For nanoparticles of high aspect ratio, steric effects seem to cause an isotropic-to-nematic phase transition as the surface coverage increases. It was observed that at a sufficiently high surface coverage the nanoparticles are most effective at reducing the interfacial tension when they lay with their longer axis parallel to the interface. The simulation results presented could be useful for the design of Pickering emulsions.
采用耗散粒子动力学模拟研究了各向异性 Janus 纳米椭球在油水界面的平衡行为。结果表明，纳米粒子相对于界面的取向取决于纳米粒子的纵横比、极性与非极性表面基团的比例，以及纳米粒子表面基团与水相和非水相溶剂之间的相互作用。纳米粒子取向的变化并不总是单调的，这可能是因为不同驱动力之间存在竞争。对于高纵横比的纳米粒子，由于空间位阻效应，当表面覆盖率增加时，可能会发生各向同性-向列相转变。结果表明，在足够高的表面覆盖率下，当纳米粒子的长轴平行于界面时，它们在降低界面张力方面最为有效。所提出的模拟结果可能有助于 Pickering 乳液的设计。
