Multidimensional Characterization of Mixed Ligand Nanoparticles Using Small Angle Neutron Scattering

Abstract

The properties of ligand protected gold nanoparticles are determined by the synergistic interplay of their structural components, including the metal core, the ligand shell, and its solvation. However, the simultaneous characterization of all these components remains a major challenge given their distinctly different chemical nature. In the case of mixed ligand nanoparticles, this task becomes daunting due to the presence of intercorrelated additional parameters such as the ligand ratio, ligand spatial distribution, and the solvation of the heterogeneous ligand shell. Here we show that small angle neutron scattering (SANS) is a tool capable of simultaneously characterizing the core and the ligand shell of monodisperse mixed ligand gold nanoparticles. We systematicall y examine how each parameter (e.g. the core size, the thickness and composition of the ligand shell, and the mixed ligand spatial heterogeneity) affects nanoparticles' scattering profile. Quantitative information on these parameters is retrieved using ana lytical fitting as well as 3D modelling. Importantly, we show that SANS can evaluate the solvation degree of mixed ligand protected gold nanoparticles, a challenging task for any other characterization methods.

Metallic-Nanoparticle-Based Sensing: Utilization of Mixed-Ligand Monolayers

“…Mass spectroscopy has been used to determine ligand ratios in the monolayer , and has also been shown to provide information on ligand phase separation . Other spectroscopic methods for the determination of monolayer ligand composition include XPS and TGA. ,, When specific types of molecules containing isotopes or free radicals are present in the monolayer, SANS and EPR can also be powerful tools for ligand chacterization. − For nanoparticle films, electrical conductivity measurements can also be used for the ligand monolayer characterization of the films. Due to their sensitivity to interparticle separation, both the resistivity and the impedance of the films are sensitive to changes in the monolayer composition , and could be used to determine the ligand composition of the films.…”

Analytical Methods for Characterization of Nanomaterial Surfaces

“…Stellacci and coworkers showed that SANS could distinguish nanomaterials that differed only a few angstroms in their size or only a few molecules in their ligand shell. 72 Two ligands, 11mercaptoundecanoic acid (MUA) and 1-octanethiol (OT), were conjugated to AuNPs. Two different samples were prepared where only one ligand was deuterated: MUA-(OT-d) AuNP and (MUA-d)-OT AuNP.…”

Synthetic guidelines for the precision engineering of gold nanoparticles

“…Atomic emission spectroscopy (AES) may provide yield values with no a priori knowledge of the analysed nanoparticles. Furthermore, there is also a need for the development and implementation of techniques that offer in situ information of the ligand shell, such as small angle neutron scattering (SANS) [60] and quartz crystal microbalance with dissipation monitoring [61].…”