Fluctuation-Driven Anisotropic Assembly in Nanoscale Systems

Abstract

We demonstrate that the self-assembly of spherical nanoparticles (NPs), grafted isotropically with polymeric ligands, into anisotropic structures is a manifestation of the fluctuations inherent in small number statistics. Computer simulations show that the organization of ligand atoms around an individual NP is not spatially isotropic for small numbers of grafts and ligand monomers. This inherent, spatially asymmetric ligand distribution causes the effective, two-body inter-NP potential to have a strong orientational dependence, which reproduces the anisotropic assembly observed ubiquitously for these systems. In contrast, ignoring this angular dependence does not permit us to capture NP self-assembly. This idea of fluctuation-driven behavior should be broadly relevant, and, for example, it should be important for the assembly of ligand-decorated quantum dots into arrays.

Perspective: Outstanding theoretical questions in polymer-nanoparticle hybrids

“…In this context, studies by Bozorgui et al, 141 Lane and Grest, 110 and Chakravarty et al 151 clearly show that polymer chains do not "uniformly" cover the NP, even in the hypothetical limit where the graft points are randomly distributed on the surface (Fig. 2).…”

“…Even in the case of uniform grafting sites, the conformational fluctuations of the small number of polymer chains ensure that the NPs are frequently anisotropically covered by the polymer corona. 141 This fact has been shown to strongly impact the self-assembled NP structures that form. Below, we outline some outstanding issues in this regard.…”

Limiting the valence: advancements and new perspectives on patchy colloids, soft functionalized nanoparticles and biomolecules

“…Both experiments 198 and simulations 199 have shown that these grafted nanoparticles robustly self-assemble into a variety of superstructures that are anisotropic typically observed only in systems of anisotropically interacting units. This result, which stems from the deformability of the polymeric corona, holds for both homogeneously and inhomogeneously grafted units at low and intermediate grafting densities.…”

Derivation of coarse-grained potentials via multistate iterative Boltzmann inversion

“…[34][35][36][37][38] Several approaches have been developed to derive and optimize CG forcefields. [39][40][41][42][43][44][45] Among these, the iterative Boltzmann inversion (IBI) method 39 has become a popular choice due to its straightforward nature, general applicability to a wide range of systems, and basis in structural properties. The IBI method relies on self-consistently adjusting a given potential to achieve convergence with target structural data; for nonbonded interactions this target data takes the form of the radial distribution function (RDF) between interaction sites and the potential is iteratively updated according to…”