Void-Based Assembly of Colloidal Crystals

摘要: Colloidal crystals form the basis of numerous technologies, and are especially applicable in the field of optics, as their stacking planes naturally manipulate light via diffraction. Thus, they have many applications as, for instance, optical band gaps and filters. However, precise control over the crystal structure is generally required for these applications, and defects often naturally arise due to polymorphism. At present, there are two broad paradigms which are employed to overcome this: the “top-down” and “bottom-up” approaches. In the former, some external directing mechanism, such as a planar template, is employed to direct the structure of the colloidal crystal as it forms [1]; in this case, the information which encodes for the final crystal structure is contained within the template. In the latter, the colloids themselves are chemically or physically modified such that their effective interactions are tuned to thermodynamically bias the formation of the desired crystal [2]. However, the top-down approach requires the production of a suitable template a priori and has limited utility when attempting to design highly complex three-dimensional crystals. Furthermore, in many cases it is either too difficult to experimentally achieve theoretical bottom-up designs, or the modifications required can have adverse effects on the resulting properties of the crystal [3]. Therefore, it is desirable to have another route to input this information.