Showing papers on "Electron tomography published in 2018"
TL;DR: In this paper, a new method of spectrally resolved photon-induced near-field electron microscopy (SRPINEM) was proposed to obtain nm-fs-resolved maps of nanoparticle plasmons with an energy resolution determined by the laser line width (20 meV in this work).
Abstract: The electronic, optical, and magnetic properties of quantum solids are determined by their low-energy (<100 meV) many-body excitations. Dynamical characterization and manipulation of such excitations rely on tools that combine nm-spatial, fs-temporal, and meV-spectral resolution. Currently, phonons and collective plasmon resonances can be imaged in nanostructures with atomic (sub-nm) and tens of meV space/energy resolution using state-of-the-art energy-filtered transmission electron microscopy (TEM), but only under static conditions, while fs-resolved measurements are common but lack spatial or energy resolution. Here, we demonstrate a new method of spectrally resolved photon-induced near-field electron microscopy (SRPINEM) that allows us to obtain nm-fs-resolved maps of nanoparticle plasmons with an energy resolution determined by the laser line width (20 meV in this work) and no longer limited by the electron beam and spectrometer energy spreading. This technique can be extended to any optically accessi...
75 citations
20 Apr 2018
TL;DR: An overview of the technique, discussion of sample suitability and information about sample preparation, data collection and data analysis is presented, and recent developments and future outlook are also discussed.
Abstract: Cryo-soft X-ray tomography is an imaging technique that addresses the need for mesoscale imaging of cellular ultrastructure of relatively thick samples without the need for staining or chemical modification. It allows the imaging of cellular ultrastructure to a resolution of 25–40 nm and can be used in correlation with other imaging modalities, such as electron tomography and fluorescence microscopy, to further enhance the information content derived from biological samples. An overview of the technique, discussion of sample suitability and information about sample preparation, data collection and data analysis is presented here. Recent developments and future outlook are also discussed.
71 citations
TL;DR: In this paper, fully aromatic polyamide films that serve as the active layer of state-of-the-art water filtration membranes were investigated using high-angle annular dark-field scanning transmission electron microscopy tomography.
Abstract: As water availability becomes a growing challenge in various regions throughout the world, desalination and wastewater reclamation through technologies such as reverse osmosis (RO) are becoming more important. Nevertheless, many open questions remain regarding the internal structure of thin-film composite RO membranes. In this work, fully aromatic polyamide films that serve as the active layer of state-of-the-art water filtration membranes were investigated using high-angle annular dark-field scanning transmission electron microscopy tomography. Reconstructions of the 3D morphology reveal intricate aspects of the complex microstructure not visible from 2D projections. We find that internal voids of the active layer of compressed commercial membranes account for less than 0.2% of the total polymer volume, contrary to previously reported values that are two orders of magnitude higher. Measurements of the local variation in polyamide density from electron tomography reveal that the polymer density is highest at the permeable surface for the two membranes tested and establish the significance of surface area on RO membrane transport properties. The same type of analyses could provide explanations for different flux variations with surface area for other types of membranes where the density is distributed differently. Thus, 3D reconstructions and quantitative analyses will be crucial to characterize the complex morphology of polymeric membranes used in next-generation water-purification membranes.
67 citations
TL;DR: This effort provides experimental verification of a theoretical kinematics model of DNA origami, which can be used as feedback to improve the design and control of motion via optimized DNA sequences and routing.
Abstract: Scaffolded DNA origami has proven to be a powerful and efficient technique to fabricate functional nanomachines by programming the folding of a single-stranded DNA template strand into three-dimensional (3D) nanostructures, designed to be precisely motion-controlled. Although two-dimensional (2D) imaging of DNA nanomachines using transmission electron microscopy and atomic force microscopy suggested these nanomachines are dynamic in 3D, geometric analysis based on 2D imaging was insufficient to uncover the exact motion in 3D. Here we use the individual-particle electron tomography method and reconstruct 129 density maps from 129 individual DNA origami Bennett linkage mechanisms at ~ 6-14 nm resolution. The statistical analyses of these conformations lead to understanding the 3D structural dynamics of Bennett linkage mechanisms. Moreover, our effort provides experimental verification of a theoretical kinematics model of DNA origami, which can be used as feedback to improve the design and control of motion via optimized DNA sequences and routing.
49 citations
TL;DR: Metal concentration, diffusivity, and particle size are important parameters that dictate the mechanical and phase stabilities of the hollow oxide shell, which in turn determine its barrier properties and the final hollow oxide morphology.
Abstract: The formation of hollow-structured oxide nanoparticles is primarily governed by the Kirkendall effect. However, the degree of complexity of the oxidation process multiplies in the bimetallic system because of the incorporation of more than one element. Spatially dependent oxidation kinetics controls the final morphology of the hollow nanoparticles, and the process is highly dependent on the elemental composition. Currently, a theoretical framework that can predict how different metal elements result in different oxide morphologies remains elusive. In this work, utilizing a combination of state-of-the-art in situ environmental transmission electron microscopy and three-dimensional (3D) chemically sensitive electron tomography, we provide an in situ and 3D investigation of the oxidation mechanism of the Ni–Fe nanoparticles. The direct measurements allow us to correlate the 3D elemental segregation in the particles with the oxidation morphologies, that is, single-cavity or dual-cavity hollow structure, and m...
46 citations
TL;DR: Kinetic environmental Operando 3D electron microscopy becomes possible, as well as real time observation of beam sensitive samples (polymers, biological objects) without prior preparation, which reduces their contrast and reactivity.
Abstract: Electron tomography in transmission electron microscopy provides valuable three-dimensional structural, morphological and chemical information of condensed matter at nanoscale. Current image acquisitions require at least tens of minutes, which prohibits the analysis of nano-objects evolving rapidly such as under dynamic environmental conditions. Reducing the acquisition duration to tens of seconds or less permits to follow in 3D the same object during its evolution under varying temperatures and pressures. We report Operando Electron nanotomography using image series acquired in less than 230 seconds instead of typically 15 min in the best cases so far. The in situ calcination of silica zeolites encaging silver nanoparticles, a catalytic nanosystem of potential interest for, e.g., nuclear waste treatments or selective heterogeneous catalysis, was successfully studied. Kinetic environmental Operando 3D electron microscopy becomes possible, as well as real time observation of beam sensitive samples (polymers, biological objects) without prior preparation, which reduces their contrast and reactivity.
30 citations
TL;DR: This work proposes the use of a dose-efficient approach, so-called multimode tomography, during which tilt series of low and high angle annular dark field scanning transmission electron microscopy projection images are acquired simultaneously, and demonstrates the application of this approach to identify the position of the seeds with respect to the twinning planes in anisotropic gold nanoparticles synthesized using a seed mediated growth approach.
Abstract: Three dimensional (3D) characterization of structural defects in nanoparticles by transmission electron microscopy is far from straightforward. We propose the use of a dose-efficient approach, so-called multimode tomography, during which tilt series of low and high angle annular dark field scanning transmission electron microscopy projection images are acquired simultaneously. In this manner, not only reliable information can be obtained concerning the shape of the nanoparticles, but also the twin planes can be clearly visualized in 3D. As an example, we demonstrate the application of this approach to identify the position of the seeds with respect to the twinning planes in anisotropic gold nanoparticles synthesized using a seed mediated growth approach.
25 citations
TL;DR: In this paper, the basic principles of transmission electron microscopy techniques for structural characterization, including recent methodological advancements, are described in relation to other methods and examples of structural characterization of zeolites will be given for each of the methods.
Abstract: Transmission electron microscopy (TEM) is an important tool for structure characterization of zeolite materials. Structural information can be obtained by different TEM techniques, for example electron diffraction (ED), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) and electron tomography (ET), each with its own advantages and limitations. These techniques are briefly introduced. Examples are given to show how these techniques can be used to solve various structure-related problems in zeolites. With this review we will describe the basic principles of transmission electron microscopy techniques for structural characterization, including recent methodological advancements. Advantages as well as challenges of using TEM for structural characterization will be described in relation to other methods. Examples of structural characterization of zeolites will be given for each of the methods.
24 citations
01 Jan 2018
TL;DR: In this article, a 3D analysis of complex pore structures using ET and high-resolution TEM is presented in the framework of the SPP 1570 (project DFG SP 648/4-3 ) and the research training group GRK 1896 (In situ Microscopy with Electrons, X-rays and Scanning Probes).
Abstract: “Deutsche Forschungsgemeinschaft” (DFG) within the framework of the SPP 1570 (project DFG SP 648/4-3 “3D analysis of complex pore structures using ET and high-resolution TEM”) and the research training group GRK 1896 (“In situ Microscopy with Electrons, X-rays and Scanning Probes”) as well as through the Cluster of Excellence “Engineering of Advanced Materials” at the Friedrich-Alexander-Universitat Erlangen-Nurnberg (Germany)
18 citations
TL;DR: The extension of STEM to cryomicroscopy and tomography of cells and macromolecules is summarized herein.
Abstract: Electron tomography provides a detailed view into the 3D structure of biological cells and tissues. Physical fixation by vitrification of the aqueous medium provides the most faithful preservation of biological specimens in the native, fully hydrated state. Cryo-microscopy is challenging, however, because of the sensitivity to electron irradiation and due to the weak electron scattering of organic material. Tomography is even more challenging because of the dependence on multiple exposures of the same area. Tomographic imaging is typically performed in wide-field transmission electron microscopy (TEM) mode with phase contrast generated by defocus. Scanning transmission electron microscopy (STEM) is an alternative mode based on detection of scattering from a focused probe beam, without imaging optics following the specimen. While careful configuration of the illumination and detectors is required to generate useful contrast, STEM circumvents the major restrictions of phase contrast TEM to very thin specimens and provides a signal that is more simply interpreted in terms of local composition and density. STEM has gained popularity in recent years for materials science. The extension of STEM to cryomicroscopy and tomography of cells and macromolecules is summarized herein.
16 citations
01 Jan 2018
TL;DR: The concepts for STEM imaging are significantly different than for TEM, and therefore the STEM imaging modality is described in detail, followed by STEM tomography concepts and applications.
Abstract: STEM modality provides major advantages for electron tomography of thicker (>300 nm) biological specimens, both for plastic-embedded, heavy-metal stained samples, and for vitrified, unstained cells. With the proliferation of modern TEM microscopes that allow for switching between TEM and STEM modes with relative ease, we expect the use of STEM tomography to increase. The concepts for STEM imaging are significantly different than for TEM, and therefore we will describe in detail the STEM imaging modality, followed by STEM tomography concepts and applications.
TL;DR: Recent advances in the field of microscopic imaging are discussed and atomic force microscopy has been used to study the change of mechanical properties of podocytes in diseased states which has been shown to be a culprit in podocyte maintenance.
Abstract: Together with endothelial cells and the glomerular basement membrane, podocytes form the size-specific filtration barrier of the glomerulus with their interdigitating foot processes. Since glomerulopathies are associated with so-called foot process effacement-a severe change of well-formed foot processes into flat and broadened processes-visualization of the three-dimensional podocyte morphology is a crucial part for diagnosis of nephrotic diseases. However, interdigitating podocyte foot processes are too narrow to be resolved by classic light microscopy due to Ernst Abbe's law making electron microscopy necessary. Although three dimensional electron microscopy approaches like serial block face and focused ion beam scanning electron microscopy and electron tomography allow volumetric reconstruction of podocytes, these techniques are very time-consuming and too specialized for routine use or screening purposes. During the last few years, different super-resolution microscopic techniques were developed to overcome the optical resolution limit enabling new insights into podocyte morphology. Super-resolution microscopy approaches like three dimensional structured illumination microscopy (3D-SIM), stimulated emission depletion microscopy (STED) and localization microscopy [stochastic optical reconstruction microscopy (STORM), photoactivated localization microscopy (PALM)] reach resolutions down to 80-20 nm and can be used to image and further quantify podocyte foot process morphology. Furthermore, in vivo imaging of podocytes is essential to study the behavior of these cells in situ. Therefore, multiphoton laser microscopy was a breakthrough for in vivo studies of podocytes in transgenic animal models like rodents and zebrafish larvae because it allows imaging structures up to several hundred micrometer in depth within the tissue. Additionally, along with multiphoton microscopy, lightsheet microscopy is currently used to visualize larger tissue volumes and therefore image complete glomeruli in their native tissue context. Alongside plain visualization of cellular structures, atomic force microscopy has been used to study the change of mechanical properties of podocytes in diseased states which has been shown to be a culprit in podocyte maintenance. This review discusses recent advances in the field of microscopic imaging and demonstrates their currently used and other possible applications for podocyte research.
TL;DR: The goal was to assess the nanostructural characteristics and correlate them with the optical properties of the AuNPs, particularly the localized surface plasmon resonance (LSPR) behavior, and to provide the identification of "hot-spots".
Abstract: Plasmonic Au nanoparticles (AuNPs) embedded into a TiO2 dielectric matrix were analyzed by combining two-dimensional and three-dimensional electron microscopy techniques. The preparation method was reactive magnetron sputtering, followed by thermal annealing treatments at 400 and 600 °C. The goal was to assess the nanostructural characteristics and correlate them with the optical properties of the AuNPs, particularly the localized surface plasmon resonance (LSPR) behavior. High-angle annular dark field-scanning transmission electron microscopy results showed the presence of small-sized AuNPs (quantum size regime) in the as-deposited Au–TiO2 film, resulting in a negligible LSPR response. The in-vacuum thermal annealing at 400 °C induced the formation of intermediate-sized nanoparticles (NPs), in the range of 10–40 nm, which led to the appearance of a well-defined LSPR band, positioned at 636 nm. Electron tomography revealed that most of the NPs are small-sized and are embedded into the TiO2 matrix, whereas...
TL;DR: In this paper, focused ion beam technology is combined with electron energy loss spectroscopy (EELS) to image localized surface plasmon resonance (LSPR) at the nanoscale.
Abstract: Plasmonic nanoantennas are pushing the limits of optical imaging resolution capabilities in near-field scanning optical microscopy (NSOM). Accordingly, these techniques are driving the basic understanding of photonic and optoelectronic nanoscale devices with applications in sensing, energy conversion, solid-state lighting, and information technology. Imaging the localized surface plasmon resonance (LSPR) at the nanoscale is a key to understanding the optical responses of a given tip geometry in order to engineer better plasmonic nanoantennas for near-field experiments. In recent years the advancement of focused ion beam technology provides the ability to directly modify plasmonic structures with nanometer resolution. Also, scanning transmission electron microscopy (STEM) with electron energy loss spectroscopy (EELS) is an established technique allowing imaging of LSPR. Specifically, the combination of these two techniques provides spectrally sensitive two-dimensional (2D) image information to better visua...
TL;DR: New imaging modalities are now available to extendcryo-tomography to thicker specimens: cryo-scanning transmission electron tomography (CSTET), soft X-raytomography (SXT), and serial surface imaging using the focused ion beam- scanning electron microscope (FIB-SEM).
TL;DR: In this article, an exemplar-based inpainting technique was proposed to deal with incomplete projection sets in electron tomography, which can be seen in the corresponding Fourier domain as a missing wedge.
TL;DR: It is demonstrated that STEM tomography is advantageous for visualizing the platelet canalicular system, which consists of an interconnected network of narrow (∼50-100 nm) membranous cisternae, whereas BF-STEM tomography can typically only visualize approximately half of the platelets volume due to a rapid non-linear loss of signal in specimens of thickness greater than ∼1.5 µm.
TL;DR: BundleTrac is an effective semi-automatic modeling approach in which a seed point is provided for each filament and the rest of the filament is computationally identified, and the potential of a denoising method that uses a polynomial regression to address the resolution and high-noise anisotropic environment of the density map is demonstrated.
Abstract: Cryo-electron tomography (cryo-ET) is a powerful method of visualizing the three-dimensional organization of supramolecular complexes, such as the cytoskeleton, in their native cell and tissue contexts. Due to its minimal electron dose and reconstruction artifacts arising from the missing wedge during data collection, cryo-ET typically results in noisy density maps that display anisotropic XY versus Z resolution. Molecular crowding further exacerbates the challenge of automatically detecting supramolecular complexes, such as the actin bundle in hair cell stereocilia. Stereocilia are pivotal to the mechanoelectrical transduction process in inner ear sensory epithelial hair cells. Given the complexity and dense arrangement of actin bundles, traditional approaches to filament detection and tracing have failed in these cases. In this study, we introduce BundleTrac, an effective method to trace hundreds of filaments in a bundle. A comparison between BundleTrac and manually tracing the actin filaments in a stereocilium showed that BundleTrac accurately built 326 of 330 filaments (98.8%), with an overall cross-distance of 1.3 voxels for the 330 filaments. BundleTrac is an effective semi-automatic modeling approach in which a seed point is provided for each filament and the rest of the filament is computationally identified. We also demonstrate the potential of a denoising method that uses a polynomial regression to address the resolution and high-noise anisotropic environment of the density map.
TL;DR: An instruction to ET including the physical principle, possibilities, and limitations including the development of innovative methods and important investigations performed in the authors' department and with their collaborators are provided.
Abstract: Electron tomography (ET) was developed to overcome some of the problems associated reconstructing three-dimensional (3D) images from 2D election microscopy data from ultrathin slices. Virtual sections of semithin sample are obtained by incremental rotation of the target and this information is used to assemble a 3D image. Herein, we provide an instruction to ET including the physical principle, possibilities, and limitations. We review the development of innovative methods and highlight important investigations performed in our department and with our collaborators. ET has opened up the third dimension at the ultrastructural level and represents a milestone in structural molecular biology.
TL;DR: Object segmentation can be viewed as a process of disconnecting the area of interested (or foreground area) from the background, and there is no established algorithm that is robust enough to segment all atomic columns when there is large thickness variation in a recorded image.
Abstract: Object segmentation can be viewed as a process of disconnecting the area of interested (or foreground area) from the background. It is a popular problem in the fields of medical image processing and diagnosis, video surveillance, autonomous driving, etc. There are many conventional algorithms developed for this task, including threshold-based methods, clustering-based methods, edge detection methods, graph methods, and etc [1]. Although many of these algorithms can achieve good performance for some predefined sceneries, they tend to fail when interferences from the background are strong and unpredictable. Particularly, for atomic resolution annular dark-field scanning transmission electron microscopy (ADF-STEM), so far there is no established algorithm that is robust enough to segment all atomic columns when there is large thickness variation in a recorded image. For example, without human assistance it is always difficult to segment/locate the thinner atomic columns that are close to the edge/surface of a nanoparticle due to their weaker signals.
TL;DR: The successful 3D reconstruction of a small molecule indicated that this method can be used as a supporting tool to current ET3D reconstruction methods for studying protein dynamics via structure determination from each individual particle of the same type of protein.
Abstract: Three-dimensional (3D) reconstruction of a single protein molecule is essential for understanding the relationship between the structural dynamics and functions of the protein. Electron tomography (ET) provides a tool for imaging an individual particle of protein from a series of tilted angles. Individual-particle electron tomography (IPET) provides an approach for reconstructing a 3D density map from a single targeted protein particle (without averaging from different particles of this type of protein), in which the target particle was imaged from a series of tilting angles. However, owing to radiation damage limitations, low-dose images (high noise, and low image contrast) are often challenging to be aligned for 3D reconstruction at intermediate resolution (1-3 nm). Here, we propose a computational method to enhance the image contrast, without increasing any experimental dose, for IPET 3D reconstruction. Using an edge-preserving smoothing-based multi-scale image decomposition algorithm, this method can detect the object against a high-noise background and enhance the object image contrast without increasing the noise level or significantly decreasing the image resolution. The method was validated by using both negative staining (NS) ET and cryo-ET images. The successful 3D reconstruction of a small molecule (<100 kDa) indicated that this method can be used as a supporting tool to current ET 3D reconstruction methods for studying protein dynamics via structure determination from each individual particle of the same type of protein.
TL;DR: In this article, electron tomography and complementary (scanning) transmission electron microscopy (STEM) are applied to investigate the origin of threading dislocations in the large lattice misfit, heteroepitaxial system of III-Sb on vicinal Si(001).
TL;DR: In this article, electron microscopy (EM) methods are described that allow the 3D ultrastructural analysis of virus-infected cells, and some sample preparation procedures where LM is integrated are also explained.
Abstract: Viruses use different strategies to interact with their host and perform a successful viral infection that results in the formation of new infectious viral particles and their propagation to new hosts. Understanding how viruses interact with their hosts requires the use of high-resolution techniques for the direct visualization of these interactions. Here electron microscopy (EM) methods are described that allow the 3D ultrastructural analysis of virus-infected cells. These methods can be implemented with light microscopy (LM) to certainly allocate virus-infected cells or cells displaying a specific/interesting phenotype caused by the interaction of viral proteins with the cellular machinery. Some sample preparation procedures where LM is integrated, known as correlative light electron microscopy (CLEM), are also explained in this chapter. All of these methods are applicable to any kind of cultured cells, including influenza virus-infected cells.
02 Jun 2018
TL;DR: It is expected that tomographic reconstructions of ultrathin nanopores will be valuable in elucidating the physics that underlie the many applications of silicon nanomembranes.
Abstract: Silicon nanomembrane technologies (NPN, pnc-Si, and others) have been used commercially as electron microscopy (EM) substrates, and as filters with nanometer-resolution size cut-offs. Combined with EM, these materials provide a platform for catching or suspending nanoscale-size structures for analysis. Usefully, the nanomembrane itself can be manufactured to achieve a variety of nanopore topographies. The size, shapes, and surfaces of nanopores will influence transport, fouling, sieving, and electrical behavior. Electron tomography (ET) techniques used to recreate nanoscale-sized structures would provide an excellent way to capture this variation. Therefore, we modified a sample holder to accept our standardized 5.4 mm × 5.4 mm silicon nanomembrane chips and imaged NPN nanomembranes (50–100 nm thick, 10–100 nm nanopore diameters) using transmission electron microscopy (TEM). After imaging and ET reconstruction using a series of freely available tools (ImageJ, TomoJ, SEG3D2, Meshlab), we used COMSOL Multiphysics™ to simulate fluid flow inside a reconstructed nanopore. The results show flow profiles with significantly more complexity than a simple cylindrical model would predict, with regions of stagnation inside the nanopores. We expect that such tomographic reconstructions of ultrathin nanopores will be valuable in elucidating the physics that underlie the many applications of silicon nanomembranes.
TL;DR: 3D tomographic reconstructions provide detailed 3D structural information of the surface oxidation layer of the Mo3Si system, revealing the evolution of oxidation behavior of Mo3 Si from early stage to mature stage and a model to explain the mechanism of the formation of the porous silica structure during the oxidation process.
Abstract: We report quantitative characterization of the high temperature oxidation process by using electron tomography and energy-dispersive X-ray spectroscopy. As a proof of principle, we performed 3D imaging of the oxidation layer of a model system (Mo3Si) at nanoscale resolution with elemental specificity and probed the oxidation kinetics as a function of the oxidation time and the elevated temperature. Our tomographic reconstructions provide detailed 3D structural information of the surface oxidation layer of the Mo3Si system, revealing the evolution of oxidation behavior of Mo3Si from early stage to mature stage. Based on the relative rate of oxidation of Mo3Si, the volatilization rate of MoO3 and reactive molecular dynamics simulations, we propose a model to explain the mechanism of the formation of the porous silica structure during the oxidation process of Mo3Si. We expect that this 3D quantitative characterization method can be applied to other material systems to probe their structure-property relationships in different environments.
22 Jan 2018
TL;DR: In this article, the typical limitations that occur in electron tomography of biological samples depending on the imaging modalities, with the focus on cryo electron microscopy and subtomogram averaging.
Abstract: Electron microscopes yield point resolution on the order of one angstrom, however the density maps from electron tomography typically have resolutions in the nanometre range. In this chapter I qualitatively discuss the typical limitations that occur in electron tomography of biological samples depending on the imaging modalities, with the focus on cryo electron tomography and subtomogram averaging.
TL;DR: In this paper, the growth process of 14H-type long-period stacking order (LPSO) formed in Mg97Zn1Gd2 cast alloys by single tilt-axis electron tomography (ET) was studied.
Abstract: We have studied three-dimensional (3D) structures and growth processes of 14H-type long-period stacking order (LPSO) formed in Mg97Zn1Gd2 cast alloys by single tilt-axis electron tomography (ET) us...
TL;DR: It is demonstrated here that electron tomography is useful in revealing both the surface and internal morphologies of the nanowires, opening up for applications in the analysis of more structurally complicated systems like radially asymmetrical nanowiring systems.
Abstract: For the purpose of functionalizing III-V semiconductor nanowires using n-doping, Sn-doped GaAs zincblende nanowires are produced, using the growth method of Aerotaxy. The growth conditions used are such that Ga droplets, formed on the nanowire surface, increase in number and concentrations when the Sn-precursor concentration is increased. Droplet-covered wires grown with varying Sn concentrations are analyzed by transmission electron microscopy and electron tomography, which together establish the positioning of the droplets to be preferentially on {-111}B facets. These facets have the same polarity as the main wire growth direction, [-1-1-1]B. This means that the generated Ga particles can form nucleation sites for possible nanowire branch growth. The concept of azimuthal mapping is introduced as a useful tool for nanowire surface visualization and evaluation. It is demonstrated here that electron tomography is useful in revealing both the surface and internal morphologies of the nanowires, opening up for applications in the analysis of more structurally complicated systems like radially asymmetrical nanowires. The analysis also gives a further understanding of the limits of the dopants which can be used for Aerotaxy nanowires.
TL;DR: In this paper, the authors used machine learning and tomography algorithms for spectral dimensionality reduction and 3D reconstruction in electron energy loss spectroscopy (EELS) and energy-dispersive X-ray spectroscope (EDX).
Abstract: Spectroscopic electron tomography (ET) has recently gained momentum thanks to the advances in instrumentation in electron energy loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDX) [1]. It however requires long exposure times and high beam currents compared to conventional ET, and results in huge multidimensional sets of data even when selecting relatively large tilt increments. It is therefore necessary to use sophisticated machine learning and tomography algorithms for spectral dimensionality reduction and 3D reconstruction.
TL;DR: In this paper, the first occurrence of Sr4Mn3O10 at the mesoscale, as platelets synthesized in molten strontium hydroxide at 600 °C with basal faces of few hundreds of nanometers and thicknesses ranging from 20 to 100 nm.
Abstract: Inorganic molten salts are known as fluxes for the synthesis of novel bulk inorganic compounds and of mesostructures and nanostructures with crystal habits different from those observed in more conventional solvents. However, they have not demonstrated the ability to provide mesostructures and nanostructures of complex metal oxides that are currently unreported at the mesoscale and nanoscale. In this report, we show the first occurrence of Sr4Mn3O10 at the mesoscale, as platelets synthesized in molten strontium hydroxide at 600 °C with basal faces of few hundreds of nanometers and thicknesses ranging from 20 to 100 nm. We address carefully the atom-scale structure by transmission electron microscopy, including electron energy loss spectroscopy and electron tomography. We then propose that the final morphology is driven by the surface charge of each facet through surface energy. The reactivity of these platelets is then addressed, highlighting cation leaching when in contact with acidic water, which results in crystalline–amorphous core–shell platelets that are active electrocatalysts towards the oxygen reduction reaction.