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Self-limiting directional nanoparticle bonding governed by reaction stoichiometry

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Science  11 Sep 2020:
Vol. 369, Issue 6509, pp. 1369-1374
DOI: 10.1126/science.aba8653

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Self-limiting bonding

Although many routes have been developed to link together colloidal particles into controlled superstructures from dimers all the way up to three-dimensional lattices, they generally depend on coating the nanoparticle surfaces in specific ways to control the way they link up. By contrast, Yi et al. developed a ligand chemistry such that, when two particles link together, it changes the electrostatic properties to limit subsequent bonding (see the Perspective by Gang). Particles are coated with complementary polymer strands that undergo an acid-base neutralization reaction. This bonding is controlled by the length of the flexible ligands, whereas the arrangement of the bonded particles is controlled by electrostatic repulsions, thus giving two parameters to tune the shape of the assemblies that form.

Science, this issue p. 1369; see also p. 1305

Abstract

Nanoparticle clusters with molecular-like configurations are an emerging class of colloidal materials. Particles decorated with attractive surface patches acting as analogs of functional groups are used to assemble colloidal molecules (CMs); however, high-yield generation of patchy nanoparticles remains a challenge. We show that for nanoparticles capped with complementary reactive polymers, a stoichiometric reaction leads to reorganization of the uniform ligand shell and self-limiting nanoparticle bonding, whereas electrostatic repulsion between colloidal bonds governs CM symmetry. This mechanism enables high-yield CM generation and their programmable organization in hierarchical nanostructures. Our work bridges the gap between covalent bonding taking place at an atomic level and colloidal bonding occurring at the length scale two orders of magnitude larger and broadens the methods for nanomaterial fabrication.

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