Quietly Building Capabilities
elongation, and contortion in a spiral fashion, as illustrated in Figure 5. Te lithiation reaction front is characterized by continuous generation and annihilation of dislocations, which apparently is coupled with the lithium diffusion process. Tese unprecedented in situ observations provide vital information for a deeper understanding of how and why rechargeable batteries wear out over time. Tus, the creation and real-time observation of this “world’s smallest battery” [5] has uncovered mechanistic insights to stimulate new thinking to increase battery performance and longevity—results that were only possible by pushing the boundaries of in situ TEM. Future plans by scientists involved in this research will rely on access to the EMSL Quiet Wing. Specifically, further emphasis will be placed on in situ atomic-level structural and chemical observations of batteries during their operation, for the purpose of discovering new materials for better batteries. Biology: Nanomaterials
and Human Health. As
nanomaterials are more widely used in commercial applications, increased human exposure to these materials is expected. However, the impact of such exposure on health remains unclear, especially with respect to underlying mechanisms. A recent investigation [6] used EMSL’s HIM to collect images that characterize the interactions of engineered nanoparticles at the surface of alveolar epithelial cells from mouse lungs. Te use of HIM for biological samples is fairly new, but it presents key advantages, including sub-nanometer resolution, efficient charge control, small beam damage, and high depth of field. Te growth of the cells at the air-liquid interface and their exposure to aerosolized nanomaterials in ambient air closely mimicked in vivo exposure conditions, and the use of the Rutherford backscattered ion imaging mode—and an added Rutherford backscattering spectrometer—provided the contrast necessary for optimal specimen analysis. Zinc
Figure 6: Twenty-four-hour exposure images show the contrast difference between the secondary (A) and the Rutherford backscatter image (B). In the RBI Image, ZnO particles are shown in the filopodia and also in the cellular membrane. In both images, the field of view is 10 microns.
oxide (ZnO) engineered nanoparticles were chosen because they are used extensively in a wide variety of commercial applications. Te HIM enabled us to identify the spatial and temporal distribution of the particles and their dissolved ions at the cell membrane with unprecedented resolution and to bring new insights to the origin of their toxicity. Tis constitutes a very useful complement to SEM imaging for biological samples (Figure 6), establishing HIM as an excellent emerging tool for the life sciences. In addition to tracing processes at the interface of living cells with nanomaterials and other health-related studies, the HIM will enhance various biological disciplines and applications, including the study of microbial interactions with minerals, a high-impact area for environmental contaminant cleanup.
Conclusion and Future Prospects Te Quiet Wing provides an environment in which
ultra-sensitive instrumentation can exhibit its optimum performance unlimited by external disturbances. Tere are many experimental investigations that simply are not possible for our users without this facility. Examples include chemical (EELS) mapping on an atomic scale for catalytic, spintronics applications, and direct structure imaging in TEM. STM applications benefit from orbital-mediated and inelastic electron tunneling spectroscopy for electronic and vibrational structure characterization of adsorbed molecules. It should be stated that environmental limitations are not
the only constraints on imaging. Te extent to which users can closely collaborate, share expertise, and integrate various techniques will also largely determine the science impact. Beyond a new building, we are committed to helping accelerate critical science through a focus on both people and capabilities. EMSL continues to build and maintain a staff of experienced scientists for deep collaboration with users and is currently engaging scientific leaders around the world to not only enhance in situ capabilities but to set new “grand challenge” targets for unprecedented time resolution—microscopy’s next revolution.
Acknowledgments EMSL is a national scientific user facility sponsored by the
Figure 5: An artist’s rendering of in situ observations of a single SnO2 nanowire battery during charging with lithium ions (copper color). The diameter of the nanowire was ~200 nm.
52
Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. More information on the EMSL Quiet Wing is available at
http://www.emsl.pnl.gov/capabilities/facilities/quiet_wing.jsp.
www.microscopy-today.com • 2011 September
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