Dumbbells, chains, and ribbons: anisotropic self-assembly of isotropic nanoparticles

31 March 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Functionalizing the surface of metal nanoparticles can assure their stability in solution or mediate their self-assembly into aggregates with controlled shapes. Here we present a computational study of the colloidal aggregation of gold nanoparticles (Au NPs) isotropically functionalized by a mixture of charged and hydrophobic ligands. We show that, by varying the relative proportion of the two ligands, the NPs form anisotropic aggregates with markedly different topologies: dumbbells, chains, or ribbons. In all cases, two kinds of connections keep the aggregates together: hydrophobic bonds and ion bridges. We show that the anisotropy of the aggregates derives from the NP shell reshaping due to the formation of the hydrophobic links, while ion bridges are accountable for the “secondary structure” of the aggregates. Our findings provide a general physical principle that can also be exploited in different self-assembled systems: anisotropic/directional aggregation can be achieved starting from isotropic objects through a soft moldable surface.

Keywords

gold nanoparticles
colloidal self-assembly
coarse-grained molecular dynamics
supramolecular aggregation

Supplementary materials

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Electronic Supplementary Information
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Model and methods; supplementary figures.
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