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image credit: Gavin Campbell and Stephanie Moffitt




Atomic-Scale View of Interfacial Processes with X-rays


Our research program includes the development of novel X-ray probes and the characterization of surface, interface, and thin-film structures with atomic resolution. We conduct our experiments using both in-house and synchrotron X-ray facilities. The latter have greatly enhanced chemical and structural sensitivity for studying systems as dilute as one-hundredth of an atomic monolayer.



XSW image of Zn2+ ions at the
rutile (110) -aqueous interface.

In addition to using more conventional X-ray scattering and spectroscopy techniques, we have developed a number of methods for generating X-ray standing waves with differing characteristic length scales. We use these periodic X-ray probes to pinpoint the lattice location of adsorbate atoms on crystalline surfaces, to measure strain within epitaxially grown semiconductor and ferroelectric thin films, and to locate heavy atoms within ordered ultrathin organic films.

Using a state-of-the-art surface science facility at the Advanced Photon Source, we perform in situ analysis of surface structures and phase transformations of MBE-grown ordered atomic monolayers on semiconductor and complex oxide surfaces. We also use X-ray standing waves, high-resolution X-ray diffraction, and X-ray absorption spectroscopy for structural characterization of buried strained-layer semiconductor heterostructures, ferroelectric thin films and the water/crystalline interface.




Research Highlights


Lithiation of conversion-type thin film electrodes


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The role of nickel buffer layer thicknesses in controlling the Li-ion conversion reaction of Ni/NiO multilayer electrodes is established. The results reveal the topological controls over Li+ transport in digitized architectures for the rational design of multilayer electrodes in lithium ion batteries.

Ref: G. Evmenenko, T. T. Fister, D. B. Buchholz, F. C. Castro, Q. Li, J. Wu, V. P. Dravid, P. Fenter, M. J. Bedzyk. Lithiation of multilayer Ni/NiO electrodes: Criticality of nickel layer thicknesses on conversion reaction kinetics. Physical Chemistry Chemical Physics 19 (30), 20029-20039 (2017)



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The nanoscale confinement of NiO layers within a Ni/NiO multilayer electrode directs lithium transport and reactivity, leading to coherent lithiation. Demonstrates the important role of metal/metal oxide interfaces in controlling lithium ion conversion reactions.

Ref: G. Evmenenko, T. T. Fister, D. B. Buchholz, Q. Li, K.-S. Chen, J. Wu, V. P. Dravid, M. C. Hersam, P. Fenter, M. J. Bedzyk. Morphological evolution of multilayer Ni/NiO thin film electrodes during lithiation. ACS Applied Materials & Interfaces 8 (31), 19979-19986 (2016)


Polymorphism in peptide amphiphile assemblies


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Peptide amphiphiles (PA) can assemble in a variety of morphologies. To understand how electrostatics drives the transformation in morphology and molecular packing, we studied the assembly of a charge-tunable (via pH) ionic PA by a combination of solution small and wide angle X-ray scattering (SAXS/WAXS), cryo-transmission electron microscopy (Cryo-TEM) and Monte-Carlo simulations.

Ref: Gao, C. Olvera de la Cruz. M., Bedzyk, M. J., J. Phys. Chem. B 121, 1623-1628 (2017)



Group Poster 2015


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                                                             click the image to download the poster!



INTERFACIAL SCIENCE by its very nature brings together a diverse interests in oxide films, catalysis,semiconductors, nano-science, bio-membranes, surface physics, corrosion, and electrochemistry.

One of many grand challenges in the overall interdisciplinary field of interfacial science is the need to observe and control the assembly of atoms, molecules and supported nanoparticles at well-defined interfaces in complex environments.

With atomic resolution and high penetrating power, we are developing and applying sophisticated
in situ X-ray methods to meet these challenges.


The Beam Team

Source: Northwestern Magazine

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Lightning flashes across the night sky above the Advanced Photon Source at
Argonne National Laboratory near Lemont, Ill.
Photoclip from Northwestern Magazine WINTER 2014.
Courtesy of Argonne National Laboratory.

At the Advanced Photon Source, Northwestern researchers use extremely bright X-rays to do atomic-level basic research that is critical to the creation of new drugs, innovative catalysts, better batteries and new sources of energy.

“....These are the brightest, most intense X-rays available in the Western Hemisphere,” says Michael Bedzyk, professor of materials science and engineering at the McCormick School of Engineering and Applied Science and co-director of the Northwestern Synchrotron Research Center. Bedzyk’s own group uses the X-rays to explore how atoms align at the interfaces that separate two different materials...."

Read the whole story here c


Mar. 27 2014

Catalysts Caught in the Act Undergo Radical Rearrangements During Reactions

Source: SCIENCE AND RESEARCH HIGHLIGHTS of Advanced Photon Source

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The atomic-scale structure and chemical properties of catalysts remain surprisingly mysterious, despite the critical roles that catalysts play in a variety of industrial and environmental applications. Researchers working at the U.S. Department of Energy Office of Science's Advanced Photon Source teased out structural and chemical information about a single layer of vanadium oxide, a catalyst, supported on the surface of a titanium oxide crystal, making it possible for scientists to improve catalysts by strategically altering their structures.



Jan. 23 2014

Atomic-Scale Study of Ambient-Pressure Redox-Induced Changes for an Oxide-Supported Submonolayer Catalyst: VOx/α-TiO2(110)

Source: ACS Live Slides

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These slide presentations are created by Zhenxing Feng about his published research in the Journal of Physical Chemistry Letters, and include his own voice describing the research as the slides automatically advance. Pleast listen to Zhenxing telling you an interesting story about "Atomic-Scale Study of Ambient-Pressure Redox-Induced Changes for an Oxide-Supported Submonolayer Catalyst: VOx/α-TiO2(110)"


Sep. 30 2013

Study: Acidity Can Change Cell Membrane Properties

Source: News from McCormick

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Understanding and controlling bilayers’ properties is vital for advances in biology and biotechnology. Now an interdisciplinary team of Northwestern University researchers has determined how to control bilayers’ crystallization by altering the acidity of their surroundings. The research, published September 24 in the Proceedings of the National Academy of Sciences, sheds light on cell function and could enable advances in drug delivery and bio-inspired technology.

Using x-ray scattering technology at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) at Argonne National Laboratory’s Advanced Photon Source, the researchers analyzed the resulting crystallization formed by the bilayers’ molecules.


Equipments and Facilities


Northwestern University Facilities
       •  Cu 12 kW two-circle diffractometer
       •  18 kW four-circle diffractometer
       •  Rigaku ATX-G thin film diffractometer
    Bedzyk Group UHV Lab
       •  Rigaku Small Angle X-ray Scattering System
       •  UHV MBE growth and characterization system

Argonne National Lab Facilities
    Advanced Photon Source (APS)
       •  Auxillary equipments
       •  Beamline 5ID-C at DND-CAT
       •  Beamline 33ID-D at UNI-CAT