Dept of Materials Science and Engineering
Canadian Centre for Electron Microscopy- Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, L8S 4M1, Canada
gbotton chez mcmaster.ca
From Catalysis to Plasmonics : Probing the Structure of Nanoscale Materials with STEM and EELS
Résumé : Electron energy loss spectroscopy is an invaluable technique to study the detailed structure and the chemical state of materials at unprecedented spatial resolution. In today’s modern aberration-corrected electron microscopes, it is possible to tackle problems requiring the highest energy resolution, down to 10-30meV, and highest spatial resolution, down to the Ångström level, so that atomic resolved spectroscopy with high spectroscopic sensitivity and resolution can be obtained.
In this presentation, various examples of applications of aberration-corrected electron energy loss spectroscopy will be given. First of all, the detection of low-loss features in plasmonic nanostructures and nanoantennas, down to the mid-infrared part of the electron energy loss spectrum, will be shown by imaging resonances down to 0.17eV [2,3] and hybridization effects with strong field enhancements between nanostructures. We will then highlight detailed structural and analytical work in a number of alloy nanoparticles systems ranging from fundamentals of phase stability and surface segregation to catalysts used for fuel cells. We will present test cases where single monolayer segregation is observed in nanoalloys  and graphene  used for fuel cell catalyst applications, using a combination of high-angle annular dark-field STEM imaging, EELS elemental mapping and simulations. We will show an example of in-situ electrochemistry studies displaying the evolution of individual nanocatalysts during cyclic voltammetry  and identical location high-resolution imaging whereby it is possible to clearly show the dissolution of Pt from catalyst nanoparticles. This powerful technique can also be used to study of the structure and substitutional effects from single atom dopants in phosphors , metallic alloys , high-temperature superconductors  and semiconducting nanowires used for LED applications .
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