Direct Imaging of Liquid–Nanoparticle Interfaces with Atom Probe Tomography

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 watergold 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 trisodiumcitrate 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.

Ion-Induced Bending with Applications for High-Resolution Electron Imaging of Nanometer-Sized Samples

“…"Stand-Out" Nanowire with Embedded NPs. A gold NP (Au NP) solution was prepared as previously reported, 44 and the average size of the Au NPs was ∼25 nm. The Au NP suspension was pipetted onto a half-grid (Mo or Cu) pillar apex, followed by drying for 2 min at ambient temperature before transfer into the SEM chamber.…”

Graphene encapsulation enables vitreous ice sample for APT and near-atomic reconstruction of nanoparticle-liquid interface

“…The authors acknowledge funding from the Australian Research Council (DP180103955) and also the contributions from coauthors in [1][2][3]. This work was performed in part at the Melbourne Centre for Nanofabrication (MCN), Victorian Node of the Australian National Fabrication Facility (ANFF).…”

“…This suggests contact freezing of graphene-encapsulated liquid specimens is an effective approach to ensure the near-native state of frozen samples. Using gold nanoparticles (AuNPs) in suspension as an example, analysis of the mass spectrum and three-dimensional (3D) chemical maps (Figure 2) from APT provides a detailed image of the water-gold interface at near-atomic resolution [3]. A locally dense region of Au + ions has been reconstructed, representing a portion of an individual AuNP.…”

Understanding the Effects of Graphene Coating on the Electrostatic Field at the Tip of an Atom Probe Tomography Specimen

“…Additionally, the hydrated nature of these samples can cause the formation of crystalline ice at cryogenic temperatures (McCarroll et al, 2020), which modifies the native structure of the specimen. Although some relatively successful APT experiments have been reported in biology (Narayan et al, 2012;Taniguchi et al, 2012;Narayan & Subramaniam, 2015;Adineh et al, 2016Adineh et al, , 2018Perea et al, 2016;Rusitzka et al, 2018;Stephenson et al, 2018;Sundell et al, 2019;Qiu et al, 2020aQiu et al, , 2020bQiu et al, , 2020c, and with other organic materials (Prosa et al, 2010;Gordon et al, 2013;Eder et al, 2017;Proudian et al, 2019), more development is required in terms of sample preparation and handling in order to improve the conditions/ state in which these sensitive specimen are introduced/analyzed in the atom probe.…”