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Published in Chad A. Mirkin, Spherical Nucleic Acids, 2020
Soyoung E. Seo, Martin Girard, Monica Olvera de la Cruz, Chad A. Mirkin
Anisotropic colloidal crystals are materials with novel optical and electronic properties. However, experimental observations of colloidal single crystals have been limited to relatively isotropic habits. Here, we show DNA-mediated crystallization of two types of nanoparticles with different hydrodynamic radii that form highly anisotropic, hexagonal prism microcrystals with AB2 crystallographic symmetry. The DNA directs the nanoparticles to assemble into a nonequilibrium crystal shape that is enclosed by the highest surface energy facets (AB2(1010) and AB2(0001)). Simulations and theoretical arguments show that this observation is a consequence of large energy barriers between different terminations of the AB2(1010) facet, which results in a significant deceleration of the (1010) facet growth rate. In addition to reporting a hexagonal colloidal crystal habit, this work introduces a potentially general plane multiplicity mechanism for growing nonequilibrium crystal shapes, an advance that will be useful for designing colloidal crystal habits with important applications in both optics and photocatalysis.
Self-Assembly and Nanochemistry Techniques for the Fabrication of Metamaterials
Published in Filippo Capolino, Applications of Metamaterials, 2017
Virginie Ponsinet, Ashod Aradian, Philippe Barois, Serge Ravaine
As a first example, building units such as monodisperse silica or PS nanospheres have been organized by colloidal self-assembly to fabricate 3D colloidal crystals through the use of a large number of techniques. A widely used technique is gravity sedimentation. It is a rather simple but slow process, taking as long as 4 weeks to get good crystals [111]. Another self-assembly technique, introduced by Park et al., is called the cell method [112]: An aqueous dispersion of spherical particles is injected into a cell formed by two glass substrates and a frame of photoresist, placed on the surface of the bottom substrate. One side of the frame has channels that can retain the particles, while allowing the solvent to flow through. The particles settle down in the cell to form a crystalline structure. This technique is particularly useful for fabrication of thin photonic crystals in water. A disadvantage is that when a crystal dries, defects are formed inside its structure. When one needs a large area of dry crystalline structure, the vertical deposition method provides better results [113]. This method produces a very long-range order. Strong capillary forces at the meniscus region induce crystallization of nanoparticles in a 3D-ordered structure. When the meniscus is swept across a vertically placed substrate, a colloidal crystal is formed. This movement of the meniscus can be realized, for example, by solvent evaporation.
Fabrication of Artificial Melanin-Based Structural Color Materials through Biomimetic Design
Published in Akihiro Miyauchi, Masatsugu Shimomura, Biomimetics, 2023
Optical phenomena that produce structural colors include thin-film interference, multilayer interference, diffraction gratings, and scattering. The development of artificial structural color materials utilizing these properties is ongoing. Among them, much research has been conducted on structural color materials using colloidal crystals, which are assemblies of colloidal particles. A periodic structure in which monodisperse colloidal particles having a particle diameter of several hundred nm close to the wavelength of light and that are regularly arranged is called a colloidal crystal structure. It is known that the structural color of colloidal crystal structures conforms to the following Bragg-Snell equation (12.1) [8]: mλ=83d2(n2−sin2θ), where m is the diffraction grating, λ is the light wavelength, d is the distance between particles, n is the refractive index of the colloidal particles, and θ is the auxiliary angle of the incident angle. The coloration, saturation, and angle dependencies of the structural colors produced from colloidal crystals are controlled by the particle size, refractive index, blackness, and assembled structure of the particles used. Based on these four parameters, research and development of artificial structural color materials are proceeding from various viewpoints [9].
Rapid fabrication of colloidal crystal films by spin coating using polymeric particles synthesized by dispersion polymerization
Published in Particulate Science and Technology, 2023
Thi Thu Hien Nguyen, Hoai Han Nguyen, Young-Seok Kim, Young-Sang Cho
Over the past decades, colloidal crystals have been studied intensively for various applications including chemical or biosensors, electrode materials for solar cells, and catalytic supports using macroporous inverted structures (MacConaghy et al. 2014; Kim and Yi 2016; Liao et al. 2021; Karg et al. 2015; Boane et al. 2021; Stein, Li, and Denny 2008). Among them, reflective color filter using colloidal crystal can be considered as a promising application, since commercial effort has been made by industries such as Opalux and Corning (Yu et al. 2014). Due to selective reflection of visible light at specific wavelength, colloidal crystals can be used as photonic crystal, which can be applied to reflective pigment for reflective displays (Lee et al. 2013). Though lithographic approaches can be adopted for the fabrication of photonic crystal, colloidal self-assembly as bottom-up approach is more advantageous in that expensive equipment are not necessary and economic raw materials can be used for the synthesis of building block particles of colloidal crystal.
Progress in polydopamine-based melanin mimetic materials for structural color generation
Published in Science and Technology of Advanced Materials, 2020
The structural color produced by the interaction of light and a microstructure does not fade as long as the microstructure is maintained, and light energy can be converted to color. Artificial fabrication of structural color materials is achieved by incorporating optical phenomena that generate structural colors, e.g. thin film interference, multilayer interference, diffraction, and scattering, into the material design to form a microstructure. The development of structural color materials that take advantage of the characteristics of each optical phenomenon is in progress [1–5]. In particular, colloidal crystals generated by assembling colloidal particles have a wide range of designs, and many studies on these materials have been conducted [6–10]. A structure in which monodisperse colloidal particles with a particle diameter of several hundred nm, close to the wavelength of light, are regularly arranged is called a colloidal crystal structure. The structural color produced by fcc (111) planes of the colloidal crystal structure is known to follow the Bragg-Snell Equation (1) shown below [11].
Bonding interactions between ligand-decorated colloidal particles
Published in Molecular Physics, 2018
Tine Curk, Urban Bren, Jure Dobnikar
For immobile (quenched disorder) ligands, the heterogeneity of interactions can be appreciable even when the fraction of formed bonds approaches zero (). For example, in the case of very short linkers, the ensemble average of the interaction, Equation (6), is dominated by a rare interaction between two particles that happen to have many binders grafted on complementary positions. For such cases, the ensemble average is still given by Equations (6) and (7), but the heterogeneity (variance in the pair interaction) also plays a major role. Very large heterogeneity of interaction is usually not desired in applications because a vast number of particle pairs will exhibit weak interaction, while only a few pairs will dominate. A degree of heterogeneity, however, can be beneficial for colloidal crystal formation because the strong-binding pairs form the nucleus which can then grow by the addition of the weaker-binding particles [18].