Energy Dispersive X-ray Tomography for 3D Elemental Mapping of Individual Nanoparticles

Abstract

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial resolution, and is even capable of providing atomically resolved elemental maps. In this technique, a highly focused electron beam is incident upon a thin sample and the energy of emitted X-rays is measured in order to determine the atomic species of material within the beam path. This elementally sensitive spectroscopy technique can be extended to three dimensional tomographic imaging by acquiring multiple spectrum images with the sample tilted along an axis perpendicular to the electron beam direction.Elemental distributions within single nanoparticles are often important for determining their optical, catalytic and magnetic properties. Techniques such as X-ray tomography and slice and view energy dispersive X-ray mapping in the scanning electron microscope provide elementally sensitive three dimensional imaging but are typically limited to spatial resolutions of > 20 nm. Atom probe tomography provides near atomic resolution but preparing nanoparticle samples for atom probe analysis is often challenging. Thus, elementally sensitive techniques applied within the scanning transmission electron microscope are uniquely placed to study elemental distributions within nanoparticles of dimensions 10-100 nm.Here, energy dispersive X-ray (EDX) spectroscopy within the STEM is applied to investigate the distribution of elements in single AgAu nanoparticles. The surface segregation of both Ag and Au, at different nanoparticle compositions, has been observed.

Statistical Evaluation of the Solid-Solution State in Ternary Nanoalloys

“…Note that each i th entry on the compositional list corresponds to the ternary composition x i = ( x i Pd , x i Rh , x i Ru ) of a pixel column and its statistical weight is based on the normalized number of atoms f i as obtained from XEDS analysis. We anticipate that this approach is not only limited to two-dimensional STEM–XEDS data but also applicable for compositional data obtained from other experimental techniques in general, for example, atom probe tomography or three-dimensional STEM–XEDS tomography …”

“…We anticipate that this approach is not only limited to two-dimensional STEM−XEDS data but also applicable for compositional data obtained from other experimental techniques in general, for example, atom probe tomography 11 or three-dimensional STEM−XEDS tomography. 20 To evaluate the applicability of this display method, we generated three datasets corresponding to equiatomic A−B−C nanospheres of ∼5 nm in diameter with the total number of atoms N = n A + n B + n C = 4094 in three hypothetical scenarios, that is, uniformly mixed solid solution, heterogeneously decomposed (A−BC), and core (BC)−shell (A) particle models (Figure 4). We also considered the compositional distributions in three-dimensional space and their corresponding two-dimensional projections.…”

Where Is the Drug? Quantitative 3D Distribution Analyses of Confined Drug-Loaded Polymer Matrices

“…Polymeric membranes have been examined with energy dispersive X-ray analyses, obtaining a two-dimensional map, 19 and this technique has also been successfully used for 3D mapping of nanoparticles. 20 Dispersive X-ray Absorption Spectroscopy (μED-XAS) 5 tomography has been utilized and was able to resolve both 2D and 3D spatial distribution of chemical species from different iron mineral standards. 21 Alternatively, Raman spectroscopy has been used to evaluate the distribution of a drug inside a 3D printed tablet.…”

“…In the literature, the distribution of impregnated or encapsulated material has been studied with various techniques. Polymeric membranes have been examined with energy dispersive X-ray analyses, obtaining a two-dimensional map, and this technique has also been successfully used for 3D mapping of nanoparticles . Dispersive X-ray absorption spectroscopy (μED-XAS) tomography has been utilized and was able to resolve both 2D and 3D spatial distribution of chemical species from different iron mineral standards .…”

Transfer of Individual Micro‐ and Nanoparticles for High‐Precision 3D Analysis Using 360° Electron Tomography

“…Such investigations especially necessitate site‐specific characterization techniques like atom probe tomography (APT), the broad spectrum of transmission electron microscopy (TEM) techniques, or single particle measurements of physical properties using, for example, near‐field optical or spectroscopic techniques. Complementary to 2D imaging and analytical TEM techniques, electron tomography (ET) enables the 3D analysis of micro‐ and nanoparticles regarding their 3D morphology, chemical properties (e.g., composition or ionization states), and physical properties (e.g., plasmonic eigenmodes). In particular, 360° ET enables the investigation of freestanding samples without support and therefore avoids severe missing‐wedge artifacts resulting from the limited tilt angular range in conventional ET .…”