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29 results

Page 1 of 2

  • A Ptychographic Approach for Low Dose Electron Imaging of Organic Molecules

  • Kayla Nguyen, Yi Jiang, Blanka Janicek, Priti Kharel, Pinshane Huang
  • Journal:
    / Volume 27 / Issue S1 / August 2021
    Published online by Cambridge University Press:
    30 July 2021, pp. 2484-2486
    Print publication:
    August 2021
    • Article
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  • Dose-Efficient Cryo-STEM Imaging of Vitrified Biological Samples

  • Katherine Spoth, Yue Yu, Kayla Nguyen, Zhen Chen, David Muller, Lena Kourkoutis
  • Journal:
    / Volume 26 / Issue S2 / August 2020
    Published online by Cambridge University Press:
    30 July 2020, pp. 1482-1483
    Print publication:
    August 2020
    • Article
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  • AirSEM: Electron Microscopy in Air, without a Specimen Chamber

  • David A. Muller, Kayla X. Nguyen, Yimo Han, Barnaby D. A. Levin, Megan E. Holtz
  • Journal:
    / Volume 24 / Issue S1 / August 2018
    Published online by Cambridge University Press:
    01 August 2018, pp. 342-343
    Print publication:
    August 2018
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  • Characterization of Sulfur and Nanostructured Sulfur Battery Cathodes in Electron Microscopy Without Sublimation Artifacts

  • Barnaby D.A. Levin, Michael J. Zachman, Jörg G. Werner, Ritu Sahore, Kayla X. Nguyen, Yimo Han, Baoquan Xie, Lin Ma, Lynden A. Archer, Emmanuel P. Giannelis, Ulrich Wiesner, Lena F. Kourkoutis, David A. Muller
  • Journal:
    / Volume 23 / Issue 1 / February 2017
    Published online by Cambridge University Press:
    23 February 2017, pp. 155-162
    Print publication:
    February 2017

  • Lithium sulfur (Li–S) batteries have the potential to provide higher energy storage density at lower cost than conventional lithium ion batteries. A key challenge for Li–S batteries is the loss of sulfur to the electrolyte during cycling. This loss can be mitigated by sequestering the sulfur in nanostructured carbon–sulfur composites. The nanoscale characterization of the sulfur distribution within these complex nanostructured electrodes is normally performed by electron microscopy, but sulfur sublimates and redistributes in the high-vacuum conditions of conventional electron microscopes. The resulting sublimation artifacts render characterization of sulfur in conventional electron microscopes problematic and unreliable. Here, we demonstrate two techniques, cryogenic transmission electron microscopy (cryo-TEM) and scanning electron microscopy in air (airSEM), that enable the reliable characterization of sulfur across multiple length scales by suppressing sulfur sublimation. We use cryo-TEM and airSEM to examine carbon–sulfur composites synthesized for use as Li–S battery cathodes, noting several cases where the commonly employed sulfur melt infusion method is highly inefficient at infiltrating sulfur into porous carbon hosts.

  • Spatial Resolution in Scanning Electron Microscopy and Scanning Transmission Electron Microscopy Without a Specimen Vacuum Chamber

  • Kayla X. Nguyen, Megan E. Holtz, Justin Richmond-Decker, David A. Muller
  • Journal:
    / Volume 22 / Issue 4 / August 2016
    Published online by Cambridge University Press:
    25 July 2016, pp. 754-767
    Print publication:
    August 2016

  • A long-standing goal of electron microscopy has been the high-resolution characterization of specimens in their native environment. However, electron optics require high vacuum to maintain an unscattered and focused probe, a challenge for specimens requiring atmospheric or liquid environments. Here, we use an electron-transparent window at the base of a scanning electron microscope’s objective lens to separate column vacuum from the specimen, enabling imaging under ambient conditions, without a specimen vacuum chamber. We demonstrate in-air imaging of specimens at nanoscale resolution using backscattered scanning electron microscopy (airSEM) and scanning transmission electron microscopy. We explore resolution and contrast using Monte Carlo simulations and analytical models. We find that nanometer-scale resolution can be obtained at gas path lengths up to 400 μm, although contrast drops with increasing gas path length. As the electron-transparent window scatters considerably more than gas at our operating conditions, we observe that the densities and thicknesses of the electron-transparent window are the dominant limiting factors for image contrast at lower operating voltages. By enabling a variety of detector configurations, the airSEM is applicable to a wide range of environmental experiments including the imaging of hydrated biological specimens and in situ chemical and electrochemical processes.

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