Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, Karnataka, India.
J Chem Phys. 2012 Apr 7;136(13):134506. doi: 10.1063/1.3700226.
Colloidal suspensions made up of oppositely charged particles have been shown to self-assemble into substitutionally ordered superlattices. For a given colloidal suspension, the structure of the superlattice formed from self-assembly depends on its composition, charges on the particles, and charge screening. In this study we have computed the pressure-composition phase diagrams of colloidal suspensions made up of binary mixtures of equal sized and oppositely charged particles interacting via hard core Yukawa potential for varying values of charge screening and charge asymmetry. The systems are studied under conditions where the thermal energy is equal or greater in magnitude to the contact energy of the particles and the Debye screening length is smaller than the size of the particles. Our studies show that charge asymmetry has a significant effect on the ability of colloidal suspensions to form substitutionally ordered superlattices. Slight deviations of the charges from the stoichiometric ratio are found to drastically reduce the thermodynamic stability of substitutionally ordered superlattices. These studies also show that for equal-sized particles, there is an optimum amount of charge screening that favors the formation of substitutionally ordered superlattices.
已证明由带相反电荷的粒子组成的胶体悬浮液会自组装成取代有序的超晶格。对于给定的胶体悬浮液，自组装形成的超晶格的结构取决于其组成、粒子上的电荷和电荷屏蔽。在这项研究中，我们针对通过硬球 Yukawa 势相互作用的等大小和带相反电荷的二元混合物胶体悬浮液，计算了在不同电荷屏蔽和电荷不对称性值下的压力-组成相图。在这些条件下，系统中的热能与粒子的接触能相等或更大，德拜屏蔽长度小于粒子的尺寸。我们的研究表明，电荷不对称性对胶体悬浮液形成取代有序超晶格的能力有重大影响。发现电荷偏离化学计量比的微小偏差会极大地降低取代有序超晶格的热力学稳定性。这些研究还表明，对于等大小的粒子，存在着有利于形成取代有序超晶格的最佳电荷屏蔽量。
