Self-assembled multi-layer simple cubic photonic crystals of oppositely charged colloids in confinement

Abstract

Designing and fabricating self-assembled open colloidal crystals have become one major direction in soft matter community because of many promising applications associated with open colloidal crystals. However, most of the self-assembled crystals found in experiments are not open but closepacked. Here by using computer simulation, we systematically investigate the self-assembly of oppositely charged colloidal hard spheres confined between two parallel hard walls, and we find that the confinement can stabilize multi-layer NaCl-like (simple cubic) open crystals. The maximal layers of stable NaCl-like crystal increases with decreasing the inverse screening length. More interestingly, at finite low temperature, the large vibrational entropy can stabilize some multi-layer NaCl-like crystals against the most energetically favoured close-packed crystals. In the parameter range studied, we find upto 4-layer NaCl-like crystal to be stable in confinement. Our photonic calculation shows that the inverse 4-layer NaCl-like crystal can already reproduce the large photonic band gaps of the bulk simple cubic crystal, which open at low frequency range with low dielectric contrast. This suggests new possibilities of using confined colloidal systems to fabricate open crystalline materials with novel photonic properties. arXiv:1902.05455v1 [cond-mat.soft]

Packing core–corona particles on a spherical surface

“…As a result, the study of confinement has been used not only as a way to understand the behavior of the confined objects but as a general way of tuning colloidal self-assembly. 21–26…”

“…As a result, the study of confinement has been used not only as a way to understand the behavior of the confined objects but as a general way of tuning colloidal self-assembly. [21][22][23][24][25][26] The way the confined nanoparticles assemble on the surface of the confining sphere will depend on the interactions between them. For example, purely repulsive soft colloidal particles interacting via a generalized elastic potential are able to assemble open structures when confined to two dimensions and minimal energy polyhedra when confined to the surface of a spherical shell.…”

Disorder explains dual‐band reflection spectrum in spherical colloidal photonic supraparticle assemblies

“…[43] Morphologies span the range from order to disorder, as capillary flows tend to support the formation of crystalline domains while frustrated crystallization in curved confinements introduces either homogeneous disorder [10] or voids and cracks, whichever morphology is energetically favorable. In experimental reality, photonic superstructures from monodisperse spherical colloidal nanoparticles can show a continuous and in part multimodal photonic behavior, [39,54,55] often attributed to an angle-dependent multiple Bragg diffraction from spectrally narrow bands or interference effects of Bragg reflections [38] with disorderinduced broad Mie scattering, [56] the details of which are yet to be understood.…”

“…[20] Recently, Sankaewtong et al presented about the design and fabrication of enduringly stable multilayer PCs from two different classes of colloidal nanospheres of opposite surface charge state. [55] They perform optical simulations for simple cubic PCs. Here a two-layer photonic membrane already exhibits a significant photonic bandgap (PBG), with four-layer PC reproducing the PBG of a bulk PC.…”

Self-assembly of core-corona particles confined in a circular box

“…Additionally, systems of physical relevance like the growth of colloidal crystals under confinement [11][12][13][14], the transport of particles in channels [15,16] and others, have contributed to the interest in studying the arrangement of particles under these conditions. As a result, the study of confinement has been used not only as a way to understand the behavior of the confined objects but as a general way of tuning colloidal self-assembly [17][18][19][20][21][22].…”