1
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Noisternig SM, Rentenberger C, Gammer C, Karnthaler HP, Kotakoski J. Probing the interaction range of electron beam-induced etching in STEM by a non-contact electron beam. Ultramicroscopy 2024; 265:114019. [PMID: 39094366 DOI: 10.1016/j.ultramic.2024.114019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Revised: 07/11/2024] [Accepted: 07/18/2024] [Indexed: 08/04/2024]
Abstract
Beside its main purpose as a high-end tool in material analysis reaching the atomic scale for structure, chemical and electronic properties, aberration-corrected scanning transmission electron microscopy (STEM) is increasingly used as a tool to manipulate materials down to that very same scale. In order to obtain exact and reproducible results, it is essential to consider the interaction processes and interaction ranges between the electron beam and the involved materials. Here, we show in situ that electron beam-induced etching in a low-pressure oxygen atmosphere can extend up to a distance of several nm away from the Ångström-size electron beam, usually used for probing the sample. This relatively long-range interaction is related to beam tails and inelastic scattering involved in the etching process. To suppress the influence of surface diffusion, we measure the etching effect indirectly on isolated nm-sized holes in a 2 nm thin amorphous carbon foil that is commonly used as sample support in STEM. During our experiments, the electron beam is placed inside the nanoholes so that most electrons cannot directly participate in the etching process. We characterize the etching process from measuring etching rates at multiple nanoholes with different distances between the hole edge and the electron beam.
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Affiliation(s)
- Stefan Manuel Noisternig
- University of Vienna, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Vienna, Austria; Austrian Academy of Sciences, Erich Schmid Institute of Materials Science, Jahnstraße 12, 8700, Leoben, Austria.
| | - Christian Rentenberger
- University of Vienna, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Vienna, Austria
| | - Christoph Gammer
- Austrian Academy of Sciences, Erich Schmid Institute of Materials Science, Jahnstraße 12, 8700, Leoben, Austria
| | - H Peter Karnthaler
- University of Vienna, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Vienna, Austria
| | - Jani Kotakoski
- University of Vienna, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Vienna, Austria
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2
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Moradifar P, Liu Y, Shi J, Siukola Thurston ML, Utzat H, van Driel TB, Lindenberg AM, Dionne JA. Accelerating Quantum Materials Development with Advances in Transmission Electron Microscopy. Chem Rev 2023. [PMID: 37979189 DOI: 10.1021/acs.chemrev.2c00917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2023]
Abstract
Quantum materials are driving a technology revolution in sensing, communication, and computing, while simultaneously testing many core theories of the past century. Materials such as topological insulators, complex oxides, superconductors, quantum dots, color center-hosting semiconductors, and other types of strongly correlated materials can exhibit exotic properties such as edge conductivity, multiferroicity, magnetoresistance, superconductivity, single photon emission, and optical-spin locking. These emergent properties arise and depend strongly on the material's detailed atomic-scale structure, including atomic defects, dopants, and lattice stacking. In this review, we describe how progress in the field of electron microscopy (EM), including in situ and in operando EM, can accelerate advances in quantum materials and quantum excitations. We begin by describing fundamental EM principles and operation modes. We then discuss various EM methods such as (i) EM spectroscopies, including electron energy loss spectroscopy (EELS), cathodoluminescence (CL), and electron energy gain spectroscopy (EEGS); (ii) four-dimensional scanning transmission electron microscopy (4D-STEM); (iii) dynamic and ultrafast EM (UEM); (iv) complementary ultrafast spectroscopies (UED, XFEL); and (v) atomic electron tomography (AET). We describe how these methods could inform structure-function relations in quantum materials down to the picometer scale and femtosecond time resolution, and how they enable precision positioning of atomic defects and high-resolution manipulation of quantum materials. For each method, we also describe existing limitations to solve open quantum mechanical questions, and how they might be addressed to accelerate progress. Among numerous notable results, our review highlights how EM is enabling identification of the 3D structure of quantum defects; measuring reversible and metastable dynamics of quantum excitations; mapping exciton states and single photon emission; measuring nanoscale thermal transport and coupled excitation dynamics; and measuring the internal electric field and charge density distribution of quantum heterointerfaces- all at the quantum materials' intrinsic atomic and near atomic-length scale. We conclude by describing open challenges for the future, including achieving stable sample holders for ultralow temperature (below 10K) atomic-scale spatial resolution, stable spectrometers that enable meV energy resolution, and high-resolution, dynamic mapping of magnetic and spin fields. With atomic manipulation and ultrafast characterization enabled by EM, quantum materials will be poised to integrate into many of the sustainable and energy-efficient technologies needed for the 21st century.
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Affiliation(s)
- Parivash Moradifar
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Yin Liu
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Jiaojian Shi
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road MS69, Menlo Park, California 94025, United States
| | | | - Hendrik Utzat
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States
| | - Tim B van Driel
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Aaron M Lindenberg
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road MS69, Menlo Park, California 94025, United States
| | - Jennifer A Dionne
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Department of Radiology, Stanford University, Stanford, California 94305, United States
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3
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Identifying and imaging polymer functionality at high spatial resolution with core-loss EELS. Ultramicroscopy 2023; 246:113688. [PMID: 36701963 DOI: 10.1016/j.ultramic.2023.113688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 01/06/2023] [Accepted: 01/16/2023] [Indexed: 01/19/2023]
Abstract
Electron energy loss spectroscopy (EELS) is a proven tool for probing materials chemistry at high spatial resolution. Core-loss EELS fine structure should allow measurement of local polymer chemistry. For organic materials, sensitivity to radiolysis is expected to limit the resolution achievable with EELS: but core-loss EELS has proven difficult at any resolution, yielding inconsistent spectra that compare unfavorably with theoretically analogous x-ray absorption spectra. Many of the previously identified shortcomings should not be limiting factors on modern equipment. This study establishes that EELS can generate identifiable carbon K-edge spectra for a range of common polymer types and chemistry, and demonstrates fine structure features matching prior x-ray absorption spectra. EELS fine structure features broaden intuitively with the instrument's energy resolution, and beam-induced features are readily differentiated by collecting spectra at a series of doses. The results are demonstrated with spectrum images of a model polymer blend, and used to estimate practical pixel sizes that can be used for mapping core-loss EELS as a function of electron dose.
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4
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Yang H, Konečná A, Xu X, Cheong SW, Batson PE, García de Abajo FJ, Garfunkel E. Simultaneous Imaging of Dopants and Free Charge Carriers by Monochromated EELS. ACS NANO 2022; 16:18795-18805. [PMID: 36317944 DOI: 10.1021/acsnano.2c07540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Doping inhomogeneities in solids are not uncommon, but their microscopic observation and understanding are limited due to the lack of bulk-sensitive experimental techniques with high enough spatial and spectral resolution. Here, we demonstrate nanoscale imaging of both dopants and free charge carriers in La-doped BaSnO3 (BLSO) using high-resolution electron energy-loss spectroscopy (EELS). By analyzing high- and low-energy excitations in EELS, we reveal chemical and electronic inhomogeneities within a single BLSO nanocrystal. The inhomogeneous doping leads to distinctive localized infrared surface plasmons, including a previously unobserved plasmon mode that is highly confined between high- and low-doping regions. We further quantify the carrier density, effective mass, and dopant activation percentage by EELS and transport measurements on the bulk single crystals of BLSO. These results not only represent a practical approach for studying heterogeneities in solids and understanding structure-property relationships at the nanoscale, but also demonstrate the possibility of infrared plasmon tuning by leveraging nanoscale doping texture.
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Affiliation(s)
- Hongbin Yang
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey08854, United States
| | - Andrea Konečná
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860Castelldefels, Barcelona, Spain
- Central European Institute of Technology, Brno University of Technology, 61200Brno, Czech Republic
| | - Xianghan Xu
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey08854, United States
| | - Sang-Wook Cheong
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey08854, United States
| | - Philip E Batson
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey08854, United States
| | - F Javier García de Abajo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860Castelldefels, Barcelona, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010Barcelona, Spain
| | - Eric Garfunkel
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey08854, United States
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey08854, United States
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5
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Elibol K, Downing C, Hobbs RG. Nanoscale mapping of shifts in dark plasmon modes in sub 10 nm aluminum nanoantennas. NANOTECHNOLOGY 2022; 33:475203. [PMID: 35944508 DOI: 10.1088/1361-6528/ac8812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 08/09/2022] [Indexed: 06/15/2023]
Abstract
In this work, we report the fabrication and spectroscopic characterization of subwavelength aluminum nanocavities-consisting of hexamer or tetramer clusters of sub 10 nm width Al nanorods-with tunable localized surface plasmon resonance (LSPR) energies on suspended SiNxmembranes. Here the volume plasmon (VP) and LSPR modes of lithographically-fabricated Al nanocavities are revealed by low-loss electron energy-loss spectroscopy (EELS) in an aberration corrected scanning transmission electron microscope (STEM). We show that the existence of grain boundaries (GBs) in these nanocavities results in shifts in the VP energy and a reduction in the VP lifetime. We map the VP energy and lifetime across GBs and we observe a decrease in VP energy and lifetime at GBs that is consistent with a reduction in free carrier density and increased plasmon scattering at these locations. Dipolar LSPR modes resonant in the UV and blue regions of the electromagnetic spectrum as well as higher-energy optically dark quadrupolar and hexapolar LSPR modes are also observed and mapped by STEM and EELS. All LSPR modes are confirmed via electromagnetic simulations based on the boundary element method. Both tetramer and hexamer structures support the excitation of dipolar bright and dipolar dark modes. Finally, we find that asymmetries in fabricated nanorod hexamer and tetramer nanocavities result in a mode mixing leading to a shift in dipolar dark LSPR modes.
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Affiliation(s)
- Kenan Elibol
- School of Chemistry, Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and Bio-Engineering Research Centre (AMBER), Trinity College Dublin, Dublin 2, Ireland
| | - Clive Downing
- School of Chemistry, Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and Bio-Engineering Research Centre (AMBER), Trinity College Dublin, Dublin 2, Ireland
| | - Richard G Hobbs
- School of Chemistry, Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and Bio-Engineering Research Centre (AMBER), Trinity College Dublin, Dublin 2, Ireland
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6
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Egerton R, Watanabe M. Spatial Resolution in Transmission Electron Microscopy. Micron 2022; 160:103304. [DOI: 10.1016/j.micron.2022.103304] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/05/2022] [Accepted: 05/19/2022] [Indexed: 10/18/2022]
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7
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OUP accepted manuscript. Microscopy (Oxf) 2022; 71:i174-i199. [DOI: 10.1093/jmicro/dfab050] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 11/20/2021] [Accepted: 01/28/2022] [Indexed: 11/14/2022] Open
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8
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Egerton RF, Zhu Y. OUP accepted manuscript. Microscopy (Oxf) 2022; 72:66-77. [PMID: 35535685 DOI: 10.1093/jmicro/dfac022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/09/2022] [Accepted: 05/09/2022] [Indexed: 11/13/2022] Open
Abstract
We first review the significance of resolution and contrast in electron microscopy and the effect of the electron optics on these two quantities. We then outline the physics of the generation of secondary electrons (SEs) and their transport and emission from the surface of a specimen. Contrast and resolution are discussed for different kinds of SE imaging in scanning electron microscope (SEM) and scanning-transmission microscope instruments, with some emphasis on the observation of individual atoms and atomic columns in a thin specimen. The possibility of achieving atomic resolution from a bulk specimen at SEM energies is also considered.
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Affiliation(s)
- R F Egerton
- Physics Department, University of Alberta, Edmonton, Alberta T1W 2E2, Canada
| | - Y Zhu
- Electron Microscopy and Nanostructure Group, Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY 11973, USA
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9
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Velazco A, Béché A, Jannis D, Verbeeck J. Reducing electron beam damage through alternative STEM scanning strategies, Part I: Experimental findings. Ultramicroscopy 2021; 232:113398. [PMID: 34655928 DOI: 10.1016/j.ultramic.2021.113398] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/31/2021] [Accepted: 09/20/2021] [Indexed: 12/22/2022]
Abstract
The highly energetic electrons in a transmission electron microscope (TEM) can alter or even completely destroy the structure of samples before sufficient information can be obtained. This is especially problematic in the case of zeolites, organic and biological materials. As this effect depends on both the electron beam and the sample and can involve multiple damage pathways, its study remained difficult and is plagued with irreproducibility issues, circumstantial evidence, rumors, and a general lack of solid data. Here we take on the experimental challenge to investigate the role of the STEM scan pattern on the damage behavior of a commercially available zeolite sample with the clear aim to make our observations as reproducible as possible. We make use of a freely programmable scan engine that gives full control over the tempospatial distribution of the electron probe on the sample and we use its flexibility to obtain multiple repeated experiments under identical conditions comparing the difference in beam damage between a conventional raster scan pattern and a newly proposed interleaved scan pattern that provides exactly the same dose and dose rate and visits exactly the same scan points. We observe a significant difference in beam damage for both patterns with up to 11 % reduction in damage (measured from mass loss). These observations demonstrate without doubt that electron dose, dose rate and acceleration voltage are not the only parameters affecting beam damage in (S)TEM experiments and invite the community to rethink beam damage as an unavoidable consequence of applied electron dose.
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Affiliation(s)
- A Velazco
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium; NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - A Béché
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium; NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - D Jannis
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium; NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - J Verbeeck
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium; NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
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10
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Chen J. Advanced Electron Microscopy of Nanophased Synthetic Polymers and Soft Complexes for Energy and Medicine Applications. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:2405. [PMID: 34578720 PMCID: PMC8470047 DOI: 10.3390/nano11092405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/02/2021] [Accepted: 09/10/2021] [Indexed: 11/23/2022]
Abstract
After decades of developments, electron microscopy has become a powerful and irreplaceable tool in understanding the ionic, electrical, mechanical, chemical, and other functional performances of next-generation polymers and soft complexes. The recent progress in electron microscopy of nanostructured polymers and soft assemblies is important for applications in many different fields, including, but not limited to, mesoporous and nanoporous materials, absorbents, membranes, solid electrolytes, battery electrodes, ion- and electron-transporting materials, organic semiconductors, soft robotics, optoelectronic devices, biomass, soft magnetic materials, and pharmaceutical drug design. For synthetic polymers and soft complexes, there are four main characteristics that differentiate them from their inorganic or biomacromolecular counterparts in electron microscopy studies: (1) lower contrast, (2) abundance of light elements, (3) polydispersity or nanomorphological variations, and (4) large changes induced by electron beams. Since 2011, the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory has been working with numerous facility users on nanostructured polymer composites, block copolymers, polymer brushes, conjugated molecules, organic-inorganic hybrid nanomaterials, organic-inorganic interfaces, organic crystals, and other soft complexes. This review crystalizes some of the essential challenges, successes, failures, and techniques during the process in the past ten years. It also presents some outlooks and future expectations on the basis of these works at the intersection of electron microscopy, soft matter, and artificial intelligence. Machine learning is expected to automate and facilitate image processing and information extraction of polymer and soft hybrid nanostructures in aspects such as dose-controlled imaging and structure analysis.
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Affiliation(s)
- Jihua Chen
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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11
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Samokhvalov A. Understanding the structure, bonding and reactions of nanocrystalline semiconductors: a novel high-resolution instrumental method of solid-state synchronous luminescence spectroscopy. Phys Chem Chem Phys 2021; 23:7022-7036. [PMID: 33876074 DOI: 10.1039/d0cp06709a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This Perspective Article describes the recent advancements in studies of nanocrystalline metal oxides using a novel ultra-high resolution method, solid-state synchronous luminescence spectroscopy (SS-SLS). Semiconductors notably include titanium dioxide and these studies shed light on the detailed electronic structure, composition, and their reactions. First, we critically discuss the limitations of the major existing non-spectroscopic and spectroscopic methods of characterization of electronic structure of nanocrystalline semiconductors and insulators. Second, we describe the foundations and the setup of SS-SLS as an enhanced-resolution, facile, non-contact, non-destructive, and highly capable method of studies of nanomaterials. Third, the following insights are featured which are obtained by SS-SLS, but are not available by other methods: (a) detection of traps of electric charge (specific mid-gap states); (b) discrimination between "surface" and "bulk" sites; (c) in situ studies of composite nanomaterials and mechanisms of reactions, (d) the derivative SS-SLS for accurate determination of energies of absorption and emission. The specific advantages of SS-SLS versus other methods and in direct comparison with "conventional" photoluminescence spectroscopy are highlighted. Finally, new opportunities and challenges of SS-SLS are presented. SS-SLS is an advanced spectroscopic method with significant potential to aid academia and industry in studies of chemo-sensing, photocatalysis, optoelectronic materials, applied surface science, development of instrumental analysis, and studies of mechanisms of surface and "bulk" chemical reactions.
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Affiliation(s)
- Alexander Samokhvalov
- Department of Chemistry, Morgan State University, 1700 East Cold Spring Lane, Baltimore, MD 21251, USA.
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12
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Tee B, Vos M, Trombini H, Selau F, Grande P, Thomaz R. The influence of radiation damage on electrons and ion scattering measurements from PVC films. Radiat Phys Chem Oxf Engl 1993 2021. [DOI: 10.1016/j.radphyschem.2020.109173] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Parent LR, Gnanasekaran K, Korpanty J, Gianneschi NC. 100th Anniversary of Macromolecular Science Viewpoint: Polymeric Materials by In Situ Liquid-Phase Transmission Electron Microscopy. ACS Macro Lett 2021; 10:14-38. [PMID: 35548998 DOI: 10.1021/acsmacrolett.0c00595] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A century ago, Hermann Staudinger proposed the macromolecular theory of polymers, and now, as we enter the second century of polymer science, we face a different set of opportunities and challenges for the development of functional soft matter. Indeed, many fundamental questions remain open, relating to physical structures and mechanisms of phase transformations at the molecular and nanoscale. In this Viewpoint, we describe efforts to develop a dynamic, in situ microscopy tool suited to the study of polymeric materials at the nanoscale that allows for direct observation of discrete structures and processes in solution, as a complement to light, neutron, and X-ray scattering methods. Liquid-phase transmission electron microscopy (LPTEM) is a nascent in situ imaging technique for characterizing and examining solvated nanomaterials in real time. Though still under development, LPTEM has been shown to be capable of several modes of imaging: (1) imaging static solvated materials analogous to cryo-TEM, (2) videography of nanomaterials in motion, (3) observing solutions or nanomaterials undergoing physical and chemical transformations, including synthesis, assembly, and phase transitions, and (4) observing electron beam-induced chemical-materials processes. Herein, we describe opportunities and limitations of LPTEM for polymer science. We review the basic experimental platform of LPTEM and describe the origin of electron beam effects that go hand in hand with the imaging process. These electron beam effects cause perturbation and damage to the sample and solvent that can manifest as artefacts in images and videos. We describe sample-specific experimental guidelines and outline approaches to mitigate, characterize, and quantify beam damaging effects. Altogether, we seek to provide an overview of this nascent field in the context of its potential to contribute to the advancement of polymer science.
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Affiliation(s)
- Lucas R. Parent
- Innovation Partnership Building, The University of Connecticut, Storrs, Connecticut 06269, United States
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14
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Egerton RF, Venkatraman K, March K, Crozier PA. Properties of Dipole-Mode Vibrational Energy Losses Recorded From a TEM Specimen. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2020; 26:1117-1123. [PMID: 32867870 DOI: 10.1017/s1431927620024423] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The authors discuss the dipole vibrational modes that predominate in the energy-loss spectra of ionic materials below 1 eV, concentrating on thin-film specimens of typical transmission electron microscopy (TEM) thickness. The thickness dependence of the intensity is shown to be a useful guide to the bulk or surface character of vibrational peaks. The lateral and depth resolution of the energy-loss signal is investigated with the aid of finite-element calculations.
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Affiliation(s)
- Ray F Egerton
- Physics Department, University of Alberta, Edmonton, Alberta, CanadaT6G 2E1
| | - Kartik Venkatraman
- School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ85281, USA
| | - Katia March
- Eyring Materials Center, Arizona State University, Tempe, AZ85281, USA
| | - Peter A Crozier
- School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ85281, USA
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15
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Ayoola HO, Li CH, House SD, Bonifacio CS, Kisslinger K, Jinschek J, Saidi WA, Yang JC. Origin and Suppression of Beam Damage-Induced Oxygen-K Edge Artifact from γ-Al2O3 using Cryo-EELS. Ultramicroscopy 2020; 219:113127. [DOI: 10.1016/j.ultramic.2020.113127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 09/06/2020] [Accepted: 09/29/2020] [Indexed: 10/23/2022]
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16
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Mohn MJ, Biskupek J, Lee Z, Rose H, Kaiser U. Lattice contrast in the core-loss EFTEM signal of graphene. Ultramicroscopy 2020; 219:113119. [PMID: 32987248 DOI: 10.1016/j.ultramic.2020.113119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 08/14/2020] [Accepted: 09/13/2020] [Indexed: 10/23/2022]
Abstract
The realization of chromatic aberration correction enables energy-filtered transmission electron microscopy (EFTEM) at atomic resolution even for large energy windows. Previous works have demonstrated lattice contrast from ionization-edge signals such as the L2,3 edges of silicon or titanium. However, the direct interpretation as chemical information was found to be hampered by contributions from elastic contrast with dynamic scattering, especially for thick samples. Here we demonstrate that even for thin samples with light atoms, the interpretation of the ionization-edge signal is complicated by inversions from bright-atom to dark-atom contrast. Our EFTEM experiments for graphene show lattice contrast in the carbon K-edge signal, and we find bright-atom and dark-atom contrast for different defoci.
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Affiliation(s)
- Michael J Mohn
- Materialwissenschaftliche Elektronenmikroskopie, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
| | - Johannes Biskupek
- Materialwissenschaftliche Elektronenmikroskopie, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Zhongbo Lee
- Materialwissenschaftliche Elektronenmikroskopie, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Harald Rose
- Materialwissenschaftliche Elektronenmikroskopie, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Ute Kaiser
- Materialwissenschaftliche Elektronenmikroskopie, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
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17
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Das PP, Guzzinati G, Coll C, Gomez Perez A, Nicolopoulos S, Estrade S, Peiro F, Verbeeck J, Zompra AA, Galanis AS. Reliable Characterization of Organic & Pharmaceutical Compounds with High Resolution Monochromated EEL Spectroscopy. Polymers (Basel) 2020; 12:polym12071434. [PMID: 32605004 PMCID: PMC7408036 DOI: 10.3390/polym12071434] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/22/2020] [Accepted: 06/23/2020] [Indexed: 11/16/2022] Open
Abstract
Organic and biological compounds (especially those related to the pharmaceutical industry) have always been of great interest for researchers due to their importance for the development of new drugs to diagnose, cure, treat or prevent disease. As many new API (active pharmaceutical ingredients) and their polymorphs are in nanocrystalline or in amorphous form blended with amorphous polymeric matrix (known as amorphous solid dispersion—ASD), their structural identification and characterization at nm scale with conventional X-Ray/Raman/IR techniques becomes difficult. During any API synthesis/production or in the formulated drug product, impurities must be identified and characterized. Electron energy loss spectroscopy (EELS) at high energy resolution by transmission electron microscope (TEM) is expected to be a promising technique to screen and identify the different (organic) compounds used in a typical pharmaceutical or biological system and to detect any impurities present, if any, during the synthesis or formulation process. In this work, we propose the use of monochromated TEM-EELS, to analyze selected peptides and organic compounds and their polymorphs. In order to validate EELS for fingerprinting (in low loss/optical region) and by further correlation with advanced DFT, simulations were utilized.
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Affiliation(s)
- Partha Pratim Das
- NanoMegas SPRL, Boulevard Edmond Machtens 79, B1080 Brussels, Belgium; (A.G.P.); (A.S.G.)
- Electron Crystallography Solutions SL, Calle Orense 8, 28020 Madrid, Spain
- Correspondence: (P.P.D.); (S.N.)
| | - Giulio Guzzinati
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium; (G.G.); (J.V.)
| | - Catalina Coll
- LENS-MIND, Department of Electronics and Biomedical Engineering, Universitat de Barcelona, 08028 Barcelona, Spain; (C.C.); (S.E.); (F.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Alejandro Gomez Perez
- NanoMegas SPRL, Boulevard Edmond Machtens 79, B1080 Brussels, Belgium; (A.G.P.); (A.S.G.)
| | - Stavros Nicolopoulos
- NanoMegas SPRL, Boulevard Edmond Machtens 79, B1080 Brussels, Belgium; (A.G.P.); (A.S.G.)
- Correspondence: (P.P.D.); (S.N.)
| | - Sonia Estrade
- LENS-MIND, Department of Electronics and Biomedical Engineering, Universitat de Barcelona, 08028 Barcelona, Spain; (C.C.); (S.E.); (F.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Francesca Peiro
- LENS-MIND, Department of Electronics and Biomedical Engineering, Universitat de Barcelona, 08028 Barcelona, Spain; (C.C.); (S.E.); (F.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Johan Verbeeck
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium; (G.G.); (J.V.)
| | | | - Athanassios S. Galanis
- NanoMegas SPRL, Boulevard Edmond Machtens 79, B1080 Brussels, Belgium; (A.G.P.); (A.S.G.)
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18
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Zachman MJ, Hachtel JA, Idrobo JC, Chi M. Emerging Electron Microscopy Techniques for Probing Functional Interfaces in Energy Materials. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201902993] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Michael J. Zachman
- Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Jordan A. Hachtel
- Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Juan Carlos Idrobo
- Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Miaofang Chi
- Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA
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19
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Zachman MJ, Hachtel JA, Idrobo JC, Chi M. Emerging Electron Microscopy Techniques for Probing Functional Interfaces in Energy Materials. Angew Chem Int Ed Engl 2019; 59:1384-1396. [PMID: 31081976 DOI: 10.1002/anie.201902993] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Revised: 05/01/2019] [Indexed: 11/10/2022]
Abstract
Interfaces play a fundamental role in many areas of chemistry. However, their localized nature requires characterization techniques with high spatial resolution in order to fully understand their structure and properties. State-of-the-art atomic resolution or in situ scanning transmission electron microscopy and electron energy-loss spectroscopy are indispensable tools for characterizing the local structure and chemistry of materials with single-atom resolution, but they are not able to measure many properties that dictate function, such as vibrational modes or charge transfer, and are limited to room-temperature samples containing no liquids. Here, we outline emerging electron microscopy techniques that are allowing these limitations to be overcome and highlight several recent studies that were enabled by these techniques. We then provide a vision for how these techniques can be paired with each other and with in situ methods to deliver new insights into the static and dynamic behavior of functional interfaces.
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Affiliation(s)
- Michael J Zachman
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Jordan A Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Juan Carlos Idrobo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Miaofang Chi
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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20
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Low-dose (S)TEM elemental analysis of water and oxygen uptake in beam sensitive materials. Ultramicroscopy 2019; 208:112855. [PMID: 31634656 DOI: 10.1016/j.ultramic.2019.112855] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 07/18/2019] [Accepted: 10/07/2019] [Indexed: 11/23/2022]
Abstract
The performance stability of organic photovoltaics (OPVs) is largely determined by their nanoscale morphology and composition and is highly dependent on the interaction with oxygen and water from air. Low-dose cryo-(S)TEM techniques, in combination with OPV donor-acceptor model systems, can be used to assess oxygen- and water-uptake in the donor, acceptor and their interface. By determining a materials dependent critical electron dose from the decay of the oxygen K-edge intensity in Electron Energy Loss Spectra, we reliably measured oxygen- and water-uptake minimizing and correcting electron beam effects. With measurements below the dose limit the capability of STEM-EDX, EFTEM and STEM-EELS techniques are compared to qualitatively and quantitatively measure oxygen and water uptake in these OPV model systems. Here we demonstrate that oxygen and water is mainly taken up in acceptor-rich regions, and that specific oxygen uptake at the donor-acceptor interphase does not occur. STEM-EELS is shown to be the best suitable technique, enabling quantification of the local oxygen concentration in OPV model systems.
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21
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Zotta MD, Jois S, Dhakras P, Rodriguez M, Lee JU. Direct Measurement of the Electron Beam Spatial Intensity Profile via Carbon Nanotube Tomography. NANO LETTERS 2019; 19:4435-4441. [PMID: 31203629 DOI: 10.1021/acs.nanolett.9b01228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Electron microscopes are ubiquitous across the scientific landscape and have been improved to achieve ever smaller beam spots, a key parameter that determines the instrument's resolution. However, the traditional techniques to characterize the electron beam have limited effectiveness for today's instruments. Consequently, there is an ongoing need to develop detection technologies that can potentially measure the smallest electron beam, which is valuable for the continual advancement of microscope performance. We report on a new electron beam detector based on a single-wall carbon nanotube. The nanotubes are atomically smooth, have a well-defined diameter that is similar in size to the finest electron probes, and can be used to directly measure the beam profile. Additionally, by rotating the nanotube in a plane perpendicular to the beam path and scanning the beam at different angles, we can apply tomographic reconstruction techniques to determine the spatial intensity profile of an electron beam accurately.
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Affiliation(s)
- Matthew D Zotta
- Colleges of Nanoscale Science and Engineering , SUNY-Polytechnic Institute , Albany , New York 12203 , United States
| | - Sharadh Jois
- Colleges of Nanoscale Science and Engineering , SUNY-Polytechnic Institute , Albany , New York 12203 , United States
| | - Prathamesh Dhakras
- Colleges of Nanoscale Science and Engineering , SUNY-Polytechnic Institute , Albany , New York 12203 , United States
| | - Miguel Rodriguez
- Colleges of Nanoscale Science and Engineering , SUNY-Polytechnic Institute , Albany , New York 12203 , United States
| | - Ji Ung Lee
- Colleges of Nanoscale Science and Engineering , SUNY-Polytechnic Institute , Albany , New York 12203 , United States
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22
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Low dose scanning transmission electron microscopy of organic crystals by scanning moiré fringes. Micron 2019; 120:1-9. [DOI: 10.1016/j.micron.2019.01.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/30/2019] [Accepted: 01/30/2019] [Indexed: 11/17/2022]
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23
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Schefold J, Meuret S, Schilder N, Coenen T, Agrawal H, Garnett EC, Polman A. Spatial Resolution of Coherent Cathodoluminescence Super-Resolution Microscopy. ACS PHOTONICS 2019; 6:1067-1072. [PMID: 31024982 PMCID: PMC6473507 DOI: 10.1021/acsphotonics.9b00164] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Indexed: 05/29/2023]
Abstract
We investigate the nanoscale excitation of Ag nanocubes with coherent cathodoluminescence imaging spectroscopy (CL) to resolve the factors that determine the spatial resolution of CL as a deep-subwavelength imaging technique. The 10-30 keV electron beam coherently excites localized plasmons in 70 nm Ag cubes at 2.4 and 3.1 eV. The radiation from these plasmon modes is collected in the far-field together with the secondary electron intensity. CL line scans across the nanocubes show exponentially decaying tails away from the cube that reveal the evanescent coupling of the electron field to the resonant plasmon modes. The measured CL decay lengths range from 8 nm (10 keV) to 12 nm (30 keV) and differ from the calculated ones by only 1-3 nm. A statistical model of electron scattering inside the Ag nanocubes is developed to analyze the secondary electron images and compare them with the CL data. The Ag nanocube edges are derived from the CL line scans with a systematic error less than 3 nm. The data demonstrate that CL probes the electron-induced plasmon fields with nanometer accuracy.
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Affiliation(s)
- Joris Schefold
- Center
for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Sophie Meuret
- Center
for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Nick Schilder
- Center
for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Toon Coenen
- Center
for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
- Delmic B.V., Kanaalweg
4, 2628
EB Delft, The Netherlands
| | - Harshal Agrawal
- Center
for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Erik C. Garnett
- Center
for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Albert Polman
- Center
for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
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24
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Radiation damage to organic and inorganic specimens in the TEM. Micron 2019; 119:72-87. [DOI: 10.1016/j.micron.2019.01.005] [Citation(s) in RCA: 174] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 01/15/2019] [Accepted: 01/16/2019] [Indexed: 02/07/2023]
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25
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Melo LGA, Hitchcock AP. Electron beam damage of perfluorosulfonic acid studied by soft X-ray spectromicroscopy. Micron 2019; 121:8-20. [PMID: 30875488 DOI: 10.1016/j.micron.2019.02.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 02/08/2019] [Accepted: 02/19/2019] [Indexed: 10/27/2022]
Abstract
Scanning transmission X-ray microscopy (STXM) was used to study chemical changes to perfluorosulfonic acid (PFSA) spun cast thin films as a function of dose imparted by exposure of a 200 kV electron beam in a Transmission Electron Microscope (TEM). The relationship between electron beam fluence and absorbed dose was calibrated using a modified version of a protocol based on the positive to negative lithography transition in PMMA [Leontowich et al, J. Synchrotron Rad. 19 (2012) 976]. STXM was used to characterize and quantify the chemical changes caused by electron irradiation of PFSA under several different conditions. The critical dose for CF2-CF2 amorphization was used to explore the effects of the sample environment on electron beam damage. Use of a silicon nitride substrate was found to increase the CF2-CF2 amorphization critical dose by ∼x2 from that for free-standing PFSA films. Freestanding PFSA and PMMA films were damaged by 200 kV electrons at ∼100 K and then the damage was measured by STXM at 300 K (RT). The lithography cross-over dose for PMMA was found to be ∼2x higher when the PMMA thin film was electron irradiated at 120 K rather than at 300 K. The critical dose for CF2-CF2 amorphization in PFSA irradiated at 120 K followed by warming and delayed measurement by STXM at 300 K was found to be ∼2x larger than at 300 K. To place these results in the context of the use of electron microscopy to study PFSA ionomer in fuel cell systems, an exposure of 300 e-/nm2 at 300 K (which corresponds to an absorbed dose of ∼20 MGy) amorphizes ∼10% of the CF2-CF2 bonds in PFSA. At this dose level, the spatial resolution for TEM imaging of PFSA is limited to 3.5 nm by radiation damage, if one is using a direct electron detector with DQE = 1. This work recommends caution about 2D and 3D morphological information of PFSA materials based on TEM studies which use fluences higher than 300 e-/nm2.
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Affiliation(s)
- Lis G A Melo
- Dept. Chemistry and Chemical Biology, McMaster University, Hamilton, ON, L8S4M1, Canada.
| | - Adam P Hitchcock
- Dept. Chemistry and Chemical Biology, McMaster University, Hamilton, ON, L8S4M1, Canada
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26
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Ilett M, Brydson R, Brown A, Hondow N. Cryo-analytical STEM of frozen, aqueous dispersions of nanoparticles. Micron 2019; 120:35-42. [PMID: 30763878 DOI: 10.1016/j.micron.2019.01.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/30/2019] [Accepted: 01/30/2019] [Indexed: 01/10/2023]
Abstract
In situ characterisation of nanoparticle dispersion and surface coatings is required to further our understanding of the behaviour of nanoparticles in aqueous suspension. Using cryogenic transmission electron microscopy (cryo-TEM) it is possible to analyse a nanoparticle suspension in the frozen, hydrated state; however, this analysis is often limited to imaging alone. This work demonstrates the first use of analytical scanning TEM (STEM) in the examination of nanoparticles captured in a layer of vitreous ice. Imaging and analysis of frozen hydrated suspensions by both STEM energy dispersive X-ray (EDX) spectroscopy and electron energy loss spectroscopy (EELS) under cryogenic conditions demonstrates the identification and separation of CeO2, Fe2O3, ZnO and Ag nanoparticles in suspension. Damage caused by the electron beam was shown to occur at far higher electron fluences in STEM (<2000 e-/Å2) compared to CTEM (<100 e-/Å2) due to diffusion limited damage by the radiolysis products generated in vitreous ice. Further application of cryo-analytical STEM was undertaken on barium titanate biomarker nanoparticles dispersed in cell culture media to show the formation of a Ca and P rich coating around the nanoparticles when suspended in the media. This previously unreported coating changes the surface chemistry of the biomarkers when exposed to cells. Thus we show that the technique has the potential to advance our understanding of the fundamental behaviour of nanoparticles in complex aqueous suspensions.
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Affiliation(s)
- Martha Ilett
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Rik Brydson
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Andy Brown
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Nicole Hondow
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK.
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27
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Hachtel JA, Huang J, Popovs I, Jansone-Popova S, Keum JK, Jakowski J, Lovejoy TC, Dellby N, Krivanek OL, Idrobo JC. Identification of site-specific isotopic labels by vibrational spectroscopy in the electron microscope. Science 2019; 363:525-528. [DOI: 10.1126/science.aav5845] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 12/28/2018] [Indexed: 01/25/2023]
Abstract
The identification of isotopic labels by conventional macroscopic techniques lacks spatial resolution and requires relatively large quantities of material for measurements. We recorded the vibrational spectra of an α amino acid, l-alanine, with damage-free “aloof” electron energy-loss spectroscopy in a scanning transmission electron microscope to directly resolve carbon-site–specific isotopic labels in real space with nanoscale spatial resolution. An isotopic red shift of 4.8 ± 0.4 milli–electron volts in C–O asymmetric stretching modes was observed for 13C-labeled l-alanine at the carboxylate carbon site, which was confirmed by macroscopic infrared spectroscopy and theoretical calculations. The accurate measurement of this shift opens the door to nondestructive, site-specific, spatially resolved identification of isotopically labeled molecules with the electron microscope.
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28
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Zaluzec NJ. Improving the sensitivity of X-ray microanalysis in the analytical electron microscope. Ultramicroscopy 2018; 203:163-169. [PMID: 30522788 DOI: 10.1016/j.ultramic.2018.11.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 11/04/2018] [Accepted: 11/13/2018] [Indexed: 10/27/2022]
Abstract
A study of the influence of experimental parameters on the sensitivity of x-ray energy dispersive spectroscopy in the analytical electron microscope from 20-200 kV is conducted. Optimization of conditions in the next generation of aberration corrected AEM instrument coupled with an array configuration of SDD detectors can potentially yield a 10-20 fold improvement over older Si(Li) systems still in use today.
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Affiliation(s)
- Nestor J Zaluzec
- Photon Science Division, Argonne National Laboratory, Argonne, IL 60439, United States.
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29
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Maigné A, Wolf M. Low-dose electron energy-loss spectroscopy using electron counting direct detectors. Microscopy (Oxf) 2018; 67:i86-i97. [PMID: 29136165 DOI: 10.1093/jmicro/dfx088] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 09/29/2017] [Indexed: 11/12/2022] Open
Abstract
Since the development of parallel electron energy loss spectroscopy (EELS), charge-coupled devices (CCDs) have been the default detectors for EELS. With the recent development of electron-counting direct-detection cameras, micrographs can be acquired under very low electron doses at significantly improved signal-to-noise ratio. In spectroscopy, in particular in combination with a monochromator, the signal can be extremely weak and the detection limit is principally defined by noise introduced by the detector. Here we report the use of an electron-counting direct-detection camera for EEL spectroscopy. We studied the oxygen K edge of amorphous ice and obtained a signal noise ratio up to 10 times higher than with a conventional CCD.We report the application of electron counting to record time-resolved EEL spectra of a biological protein embedded in amorphous ice, revealing chemical changes observed in situ while exposed by the electron beam. A change in the fine structure of nitrogen K and the carbon K edges were recorded during irradiation. A concentration of 3 at% nitrogen was detected with a total electron dose of only 1.7 e-/Å2, extending the boundaries of EELS signal detection at low electron doses.
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Affiliation(s)
- Alan Maigné
- Molecular Cryo-Electron Microscopy Unit, Okinawa Institute of Science and Technology Graduate School, Okinawa Prefecture, Kunigami District, Onna, Tancha 191-1, 904-0495,Japan
| | - Matthias Wolf
- Molecular Cryo-Electron Microscopy Unit, Okinawa Institute of Science and Technology Graduate School, Okinawa Prefecture, Kunigami District, Onna, Tancha 191-1, 904-0495,Japan
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30
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Comparison of 3D cellular imaging techniques based on scanned electron probes: Serial block face SEM vs. Axial bright-field STEM tomography. J Struct Biol 2018; 202:216-228. [PMID: 29408702 DOI: 10.1016/j.jsb.2018.01.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 01/26/2018] [Accepted: 01/30/2018] [Indexed: 11/22/2022]
Abstract
Microscopies based on focused electron probes allow the cell biologist to image the 3D ultrastructure of eukaryotic cells and tissues extending over large volumes, thus providing new insight into the relationship between cellular architecture and function of organelles. Here we compare two such techniques: electron tomography in conjunction with axial bright-field scanning transmission electron microscopy (BF-STEM), and serial block face scanning electron microscopy (SBF-SEM). The advantages and limitations of each technique are illustrated by their application to determining the 3D ultrastructure of human blood platelets, by considering specimen geometry, specimen preparation, beam damage and image processing methods. Many features of the complex membranes composing the platelet organelles can be determined from both approaches, although STEM tomography offers a higher ∼3 nm isotropic pixel size, compared with ∼5 nm for SBF-SEM in the plane of the block face and ∼30 nm in the perpendicular direction. In this regard, we demonstrate that STEM tomography is advantageous for visualizing the platelet canalicular system, which consists of an interconnected network of narrow (∼50-100 nm) membranous cisternae. In contrast, SBF-SEM enables visualization of complete platelets, each of which extends ∼2 µm in minimum dimension, whereas BF-STEM tomography can typically only visualize approximately half of the platelet volume due to a rapid non-linear loss of signal in specimens of thickness greater than ∼1.5 µm. We also show that the limitations of each approach can be ameliorated by combining 3D and 2D measurements using a stereological approach.
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31
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Egerton RF. Calculation, consequences and measurement of the point spread function for low-loss inelastic scattering. Microscopy (Oxf) 2017; 67:i52-i59. [DOI: 10.1093/jmicro/dfx089] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 09/28/2017] [Indexed: 11/14/2022] Open
Affiliation(s)
- R F Egerton
- Department of Physics, University of Alberta, Edmonton, Canada T6G 2E1
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