Direct imaging of liquid-nanoparticle interface with atom probe tomography

TL;DR

This paper demonstrates for the first time that atom probe tomography can directly image the liquid-nanoparticle interface at near-atomic resolution, revealing detailed chemical and structural information about the electrical double layer and water distribution.

Contribution

The study introduces a novel method for direct 3D imaging of liquid-nanoparticle interfaces using atom probe tomography, enabling atomic-scale analysis of the interface structure and composition.

Findings

Visualization of the water-gold interface at near-atomic resolution

Detection of an electrical double layer rich in water molecules

Confirmation of consistent water density in bulk regions

Abstract

Understanding the structure and chemical composition at the liquid-nanoparticle (NP) interface is crucial for a wide range of physical, chemical and biological processes. In this study, direct imaging of the liquid-NP interface by atom probe tomography (APT) is reported for the first time, which reveals the distributions and the interactions of key atoms and molecules in this critical domain. The APT specimen is prepared by controlled graphene encapsulation of the solution containing nanoparticles on a metal tip, with an end radius in the range of 50 nm to allow field ionization and evaporation. Using Au nanoparticles (AuNPs) in suspension as an example, analysis of the mass spectrum and three-dimensional (3D) chemical maps from APT provides a detailed image of the water-gold interface with near-atomic resolution. At the water-gold interface, the formation of an electrical double layer (EDL) rich in water (H2O) molecules has been observed, which results from the charge from the binding between the trisodium-citrate layer and the AuNP. In the bulk water region, the density of reconstructed H2O has been shown to be consistent, reflecting a highly packed density of H2O molecules after graphene encapsulation. This study is the first demonstration of direct imaging of liquid-NP interface using APT with results providing an atom-by-atom 3D dissection of the liquid-NP interface.