Surfactant-Mediated Two-Dimensional Crystallization of Colloidal Crystals
Title: Surfactant-Mediated Two-Dimensional Crystallization of Colloidal Crystals
Authors: Laurence Ramos, T.C. Lubensky, Nily Dan, Philip Nelson, D.A. Weitz
Source: Science 286, 2325 (1999) http://www.sciencemag.org/content/286/5448/2325.full.pdf
In this article, the authors develop a new method of forming self-assembled ordered structures of particles in a colloidal suspension, using charged surfactants to stabilize the ordered structure. They find that using a specific surfactant causes the formation of robust two-dimensional crystals of latex particles suspended in solution. The authors briefly describe the physical properties of the crystals and suggest possible uses, including use as templates for growth of other nanostructured materials, such as photonic devices.
Self-assembly of particles requires careful balancing of attractive and repulsive forces and thermal motion of the particles. If the attractive forces between particles are too great compared to the available thermal energy, the particles will instantly stick to each other, forming a disordered aggregate state. Ordinarily, Coulombic interaction is considered too strong of an attractive force to form any kind of ordered state, and previous work with charged surfactants and particles seemed to support this idea. However, the authors realized that surfactants by themselves can self-assemble into several very interesting ordered structures, and that the interactions between these ordered structures and charged particles had not yet been investigated. The methods they chose to study this problem are outlined in the following sections.