Crystalline arrays of submicron-sized particles through colloidal route

Abstract

Advances in colloidal science have made it possible to fabricate crystalline arrays of submicron-sized colloidal particles (popularly known as colloidal crystalline arrays (CCAs) or colloidal crystals (CCs)) with lattice parameters close to the wavelength of light. Light travelling through such crystals experiences a periodic variation of refractive index, analogous to periodic potential energy of an electron in the atomic crystal. This variation in refractive index in three dimensions with hundreds of nanometres periodicity is responsible for photonic band structure in these crystals. Thus these crystals are known as photonic crystals and have several emerging applications such as Bragg diffraction devices, optical filters and switches, sensors, nonbleachable colour materials, etc. Large single crystalline domains are crucial for some of these applications and lithography-based approaches are unrealistic. The present article gives an overview of various self-assembly methods for fabricating polycrystalline as well as large-sized CCAs using suspensions of nearly monodisperse dielectric particles. It also discusses light-based techniques for characterizing their structure and disorder in real and Fourier space. Recent developments in growing CCAs with the desired symmetry and orientation are also highlighted.