A Versatile AuNP Synthetic Platform for Decoupled Control of Size and Surface Composition

Abstract

While a plethora of protocols exist for the synthesis of sub-10-nm gold nanoparticles (AuNPs), independent control over the size and surface composition remains restricted. This poses a particular challenge for systematic studies of AuNP structure− function relationships and the optimization of crucial design parameters. To this end, we report on a modular two-step approach based on the synthesis of AuNPs in oleylamine (OAm) followed by subsequent functionalization with thiol ligands and mixtures thereof. The synthesis of OAm-capped AuNPs enables fine-tuning of the core size in the range of 2−7 nm by varying the reaction temperature. The subsequent thiol-for-OAm ligand exchange allows a reliable generation of thiol-capped AuNPs with target surface functionality. The compatibility of this approach with a vast library of thiol ligands provides detailed control of the mixed ligand composition and solubility in a wide range of solvents ranging from water to hexane. This decoupled control over the AuNP core and ligand shell provides a powerful toolbox for the methodical screening of optimal design parameters and facile preparation of AuNPs with target properties.

A Cross-Method Comparison of Sub-10 nm Nanoparticle Size Distribution

“…Homo-ligand AuNPs stabilized by MUS were prepared via thiol-for-OAm ligand exchange from four batches of differently-sized AuNPs that were initially protected by OAm. 42 As summarized in Tab S1, the core size of the four batches ranged from 2 -7 nm and varying degrees of size dispersity. Two binary mixtures were prepared by mixing MUS-NP1 and MUS-NP4 at weight ratios of 1:1 and 1:5, labeled as MUS-B1 and MUS-B2, respectively (Tab S2).…”

Synthetic guidelines for the precision engineering of gold nanoparticles

“…In recent years, aliphatic amines including oleylamine have attracted particular interest [41]. In fact, we have recently shown that the use of oleylamine as stabilising agent enables the decoupled control of AuNP size and surface composition, with the former being controlled by the reaction temperature in the initial synthesis and the latter by the subsequent exchange with prescribed thiol ligand mixtures (Figure 3) [42]. Note that this approach offers a decoupled control of size and surface composition by a subsequent thiol-for-oleylamine ligand exchange.…”

“…b) Average size and standard deviation.Note that this approach offers a decoupled control of size and surface composition by a subsequent thiol-for-oleylamine ligand exchange. Reprinted with permission from reference[42] under Creative Commons CC-BY license. Copyright 2018 American Chemical Society.…”

DoE-It-Yourself: A Case Study for Implementing Design of Experiments into Nanoparticle Synthesis

“…These experimental variables were chosen based on the available literature on this synthetic system. [12][13][14] The levels for each experimental variable in each experimental design are shown in Table 1…”