Implicit Solvent Model for the Interfacial Configuration of Colloidal Nanoparticles and Application to the Self-Assembly of Truncated Cubes

This study outlines the development of an implicit solvent model that reproduces the behavior of colloidal nanoparticles at a fluid-fluid interface. The center-point of this formulation is the generalized Quaternion-based Orientational Constraint (QOCO) method. The model captures 3 major energetic characteristics that define the nanoparticle configuration – position (orthogonal to the interfacial plane), orientation, and inter-nanoparticle interaction. The framework encodes physically relevant parameters that provide an intuitive means to simulate a broad spectrum of interfacial conditions. Results show that for a wide range of shapes, we are able to replicate the behavior of an isolated nanoparticle at an explicit fluid-fluid interface, both qualitatively and quantitatively. Furthermore, the family of truncated cubes is used as testbed to analyze the effect of changes in the degree of truncation on the potential-of-mean-force landscape.

Thereafter, a large number of nanoparticles are simulated in a molecular dynamics setting, using coarse-grained polybead nanoparticles^[1],[2]. In agreement with experiments^[2]-[7], we observe the formation of bilayer honeycomb and monolayer square lattices. Finally, by exploring a broader range of interfacial conditions, we identify and suggest the assembly mechanism for a set of novel superlattice configurations.

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