Superstructures of Multielement Colloidal Molecules: Efficient Pathways to Construct Reconfigurable Photonic and Phononic Crystals

Motivated by recent advances in synthesis and characterization of complex colloidal building blocks, the self-assembly behavior and transport properties of novel superstructures of multielement colloidal molecules are explored with applications in areas such as phononics, photonics, and photovoltaics. Using an analytical/computational framework, the connectivity landscape of various shapes of colloidal molecules is examined to propose new multicomponent superstructure phases that can self-assemble from binary mixtures of these building blocks. The identified superstructures are then investigated in terms of their tunable photonic/phononic properties. The dependence of photonic bandgaps on various features of the superstructures such as building block size and shape is studied. Each superstructure is composed of at least four different types of elements, which provides a desirable framework to obtain reconfigurable metamaterials. The calculations show that a binary superstructure of tetrahedral units can result in photonic bandgaps with sizes as large as 27% for material compositions with dielectric constant difference of 15. The new superstructures formed by colloidal molecules expand the existing self-assembly paradigms for colloidal particles. This paper also promotes future experimental and theoretical work for discovering more complex colloidal phases with a higher number of degrees of freedom to be utilized for engineering desired functional materials.