Self‐Assembled Photonic Structures

Abstract

Photonic crystals have proven their potential and are nowadays a familiar concept. They have been approached from many scientific and technological flanks. Among the many techniques devised to implement this technology self-assembly has always been one of great popularity surely due to its ease of access and the richness of results offered. Self-assembly is also probably the approach entailing more materials aspects owing to the fact that they lend themselves to be fabricated by a great many, very different methods on a vast variety of materials and to multiple purposes. To these well-known material systems a new sibling has been born (photonic glass) expanding the paradigm of optical materials inspired by solid state physics crystal concept. It is expected that they may become an important player in the near future not only because they complement the properties of photonic crystals but because they entice the researchers' curiosity. In this review a panorama is presented of the state of the art in this field with the view to serve a broad community concerned with materials aspects of photonic structures and more so those interested in self-assembly.

A colloidoscope of colloid-based porous materials and their uses

“…Polydisperse particles, which are unable to crystallize in an ordered matrix, can be used to prepare amorphous assemblies without long-range order ( Figure 3B). 4,82 Simplistic and scalable approaches such as spray coating 83,84 or layer-by-layer assembly 85,86 of particles that are not suitable for crystallization due to high attractive forces or insufficient crystallization time can still be used to prepare disordered assembly structures in an experimentally straightforward way. Indeed, as we discuss in detail in several of the following sections, order is not necessary for every application of CBPM, and controlled disorder may even create desired properties.…”

“…87 A size mismatch, however, will result in disordered crystal structures. 4,82 Additionally, the porous materials of an inverse opal can be backfilled by smaller colloidal particles ( Figure 4B,iii), producing more complex materials with higher porosity and choice of materials. 88,140 (iv) Crack formation and homogeneity.…”

“…Historically, many different types of thin films of opals, inverse opals, and other colloid-derived materials have been used for their photonic properties. 82,162 Since scattering can greatly reduce the saturation of a photonic color, adding absorbing elements to the matrix can enhance the color of the structure. Figure 8A shows examples of different structural colors that can be created from powderized inverse opal films.…”

“…While typically order is necessary for photonic structures, disordered colloidal structures-which still exhibit structural coloration-have also been studied. 4,82,[180][181][182] For many color applications, the iridescent structural color of photonic crystal materials is undesirable. Nature has solved this problem by incorporating disorder into its photonic structures in order to increase their angular visibility, for example in the feather shown in Figure 1A,i-ii.…”

Tunable structural color in organisms and photonic materials for design of bioinspired materials

“…From the viewpoint of bottom-up nanotechnology, nanostructured colloidal crystals can be fabricated using a simple and low cost process. A large number of research papers on opal photonic crystals were published in the past decade, as reviewed in references [53][54][55][56][57][58][59][60].…”