A Simple Preparation Method for Full-Range Electron Tomography of Nanoparticles and Fine Powders

Abstract

Electron tomography has become a valuable and widely used tool for studying the three-dimensional nanostructure of materials and biological specimens. However, the incomplete tilt range provided by conventional sample holders limits the fidelity and quantitative interpretability of tomographic images by leaving a "missing wedge" of unknown information in Fourier space. Imaging over a complete range of angles eliminates missing wedge artifacts and dramatically improves tomogram quality. Full-range tomography is usually accomplished using needle-shaped samples milled from bulk material with focused ion beams, but versatile specimen preparation methods for nanoparticles and other fine powders are lacking. In this work, we present a new preparation technique in which powder specimens are supported on carbon nanofibers that extend beyond the end of a tungsten needle. Using this approach, we produced tomograms of platinum fuel cell catalysts and gold-decorated strontium titanate photocatalyst specimens. Without the missing wedge, these tomograms are free from elongation artifacts, supporting straightforward automatic segmentation and quantitative analysis of key materials properties such as void size and connectivity, and surface area and curvature. This approach may be generalized to other samples that can be dispersed in liquids, such as biological structures, creating new opportunities for high-quality electron tomography across disciplines.

Real-Time 3D Analysis During Tomographic Experiments using tomviz

“…3a) and C/Pt (Fig. 3b) [26] nanoparticles [27] were acquired on a FEI Tecnai F20 at 200 keV and 2°, 2°and 1°tilt intervals, respectively. Additional experimental information are available in the corresponding references for each dataset.…”

Atomically resolved tomographic reconstruction of nanoparticles from single projection: Influence of amorphous carbon support

“…STEM tomography reconstructs 3D structure from 2D projected images acquired at different angles by rotating or tilting the specimen [13], [14] . For reconstructing atomic resolution tomograms this technique faces several challenges; (1) the 'missing wedge' results in the incomplete acquisition of tilt series images due to limited tilt (± 70˚) of the sample holders [15] ,(2) radiation damage of beam sensitive samples limits types of sample that can be examined [16] and (3) it is extremely di cult to align tilt series images exactly to the common axis [17] . Hence, TEM based tomographic technique from a single projection at a low electron dose is suitable for tomographic reconstruction of nanoparticles [9], [18] .…”

Towards 3D Understanding of Non-spherical Nanoparticles by Transmission Kikuchi Diffraction (TKD) for Improved Particle Size Distribution by Electron Microscopy

“…Various versions of electron microscopy produce conventionally 2D projection images which may induce significant errors in the evaluation of the true, 3D size and, hence, are not suited for the metrological qualification of size measurement of nanoparticles of more complex shape. Electron tomography (ET) by sequential tilting the TEM sample (holder) is one extensive approach able to address the 3D shape of NPs by reconstruction of 3D images from 2D projection images [2][3][4]. Another way of extracting the accurate 3D size of crystalline nanoparticles is high-resolution TEM coupled with reconstruction from SAED on applied on single NPs [5].…”

“…of Science and Technology, Krakow, Malopolskie, Poland, 3 Università di Torino, Turin, Piemonte, Italy Accurate measurement of nanoparticle (NP) size for particles with non-spherical shape constitutes a challenging analytical problem in principle for all methods able to probe the size of nanoparticles [1]. Various versions of electron microscopy produce conventionally 2D projection images which may induce significant errors in the evaluation of the true, 3D size and, hence, are not suited for the metrological qualification of size measurement of nanoparticles of more complex shape.…”