Self-limiting directional nanoparticle bonding governed by reaction stoichiometry

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.

Plasmonic Properties of Colloidal Assemblies

“…Synthetically, the number of satellites can be precisely adjusted up to moderate satellite numbers through the very recently established concept of self‐limiting directional nanoparticle bonding. [ 69 ] This work was already discussed in the context of linear plasmonic trimers above, but depending on the ratio of reactive (acid and base) groups on the complementary plasmonic NPs, a wider range of satellite numbers can be precisely adjusted as well (see Figure a). Because the inter‐NP junctions are rich with charged groups, electrostatic repulsion interactions of these junctions lead to a symmetrical equilibrium arrangement of the satellite NPs.…”

“…Therefore, this transition in optical extinction spectra could be used to monitor the dynamic re‐arrangement of trimer structures that gradually approach their (linear) equilibrium structures. [ 69 ] Furthermore, it can be speculated that the D 3h ‐to‐D ∞h (or vice versa) transition may be realized with an adaptive polymer. To do this, the position of the central NP must be fixed while the others can change their position like satellites in orbit.…”

“…Adapted with permission. [ 69 ] Copyright 2020, AAAS. Definition of abbreviations: scattering efficiency ( Q sct ), wavelength (λ), full width at half maximum (FWHM).…”

“…Both the homogeneous as well as the heterogeneous trimer chains can be realized experimentally by a new supracolloidal synthesis paradigm, which is the self‐limiting directional nanoparticle bonding. [ 69 ] This concept lies on the salt‐bridge formation between an inner poly‐acid polymer block of a diblock terpolymer grafted onto one type of NPs and an inner poly‐base block of a complementary diblock terpolymer grafted on another type of NPs. For both cases, an outer, surface‐remote PEG‐block serves to provide colloidal stability of the derived self‐assembled clusters.…”

“…e) Scanning electron microscopy image of a heterogeneous silver-gold-silver trimer chain (scale bar is 100 nm). Adapted with permission [69]. Copyright 2020, AAAS.…”