Designing a Bernal Spiral from Patchy Colloids

Abstract

A model potential for colloidal building blocks is defined with two different types of attractive surface sites, described as complementary patches and antipatches. A Bernal spiral is identified as the global minimum for clusters with appropriate arrangements of three patch-antipatch pairs. We further derive a minimalist design rule with only one patch and antipatch, which also produces a Bernal spiral. Monte Carlo simulations of these patchy colloidal building blocks in the bulk are generally found to corroborate the global optimization results. KeywordsBernal spiral; patchy colloids; self-assembly; patch-antipatch; anisotropic interactionsThe synthesis of colloidal particles is important in such areas as paints, hygiene products, drug delivery, and nanotechnology. Their diversity makes such particles attractive candidates for the design of self-assembling nanodevices. 1 Much recent synthetic effort has been spent on moving beyond simple spherical colloids to anisotropic particles of various shapes. [2][3][4] Colloidal particles have also been synthesized with "sticky patches" on their surfaces, which interact with patches on other particles. 2,4 This functionality suggests the possibility for self-assembly of complex structures via a bottom-up approach, without the need for the detailed control required in a top-down method. Self-assembly is governed by the interactions between the building blocks, so in principle, rational design of building blocks, tuning their mutual interactions, can lead to systems that self-assemble into specific target structures. 3 Simulation of self-assembling systems is a useful tool in guiding the synthesis of particles, which can suggest interesting synthetic targets. 5 Rational design of building blocks for selfassembly is greatly facilitated if the final structure can be predicted as a function of the building block parameters. The corresponding energy landscape contains all the information necessary for such a prediction, both in terms of the energetically favorable minima, and the pathways between them, which determine the structures that can easily be assembled. [6][7][8] The simplest model of colloidal particles involves hard spheres with a short-range squarewell attraction, 9 but other potentials such as the Lennard-Jones and Morse forms have also been considered. [10][11][12][13] Anisotropic building blocks open up rich avenues for sophisticated self-assembly into a variety of target structures. 3,14 Isotropic models are not sufficient for describing these * To whom correspondence should be addressed dw34@cam.ac.uk. Europe PMC Funders GroupAuthor Manuscript ACS Nano. Author manuscript; available in PMC 2014 January 17. An assembly of particles with a diamond-like crystal structure has been suggested as a synthetic target due to the potentially interesting photonic properties, 18,19 and numerical studies of patchy particles have been carried out to investigate whether they will crystallize to form this lattice. 20 Creating a patchy particle that will assemble into th...

Assembly of particle strings via isotropic potentials

“…These are multi-stranded, percolated networks of anisotropic aggregates. A special case of these structures with three helical chains is commonly referred to as Bernal spirals 30,32,47,48 which have six nearest neighbours, and a representative snapshot is shown in Fig. 6e.…”

Morphological analysis of chiral rod clusters from a coarse-grained single-site chiral potential

“…To prevent particles from evaporating during quenches, we enforced a percolating graph of rod centres, where a path can be constructed between all particles such that the minimum distance between each pair is less than a chosen percolation distance. 44 A harmonic compression was applied to help produce such a structure, which was turned off once the root-mean-square force was below a chosen cut-off value. Once a percolating structure had been found, any step that produced a disconnected structure after local minimisation was rejected.…”

Exploring energy landscapes: from molecular to mesoscopic systems

“…a three-stranded helix composed of a chain of face-sharing tetrahedra, 126 using patchy colloids. 127 The target structure was realised as the global minimum for a finite-sized cluster of patchy colloids, with two different types of attractive surface sites, described as complementary patches and antipatches. For these patchy colloids, Morgan et al defined a model potential, which involved an isotropic component, describing the interaction between spherical cores, and an anisotropic component governed by two types of complementary patches.…”