Recent Advances in Structural Characterization of Materials: Spectroscopic Methods
Sponsored by: MS&T Organization
Program Organizers: Chad Parish, Oak Ridge National Laboratory; Roumiana Petrova, New Jersey Institute of Tech; Jacob Jones, University of Florida; Zhonghou Cai, Argonne National Laboratory; Gang Chen, Ohio University
Thursday 8:00 AM
October 20, 2011
Room: C212
Location: Greater Columbus Convention Center
Session Chair: Chad Parish, Oak Ridge National Labs
8:00 AM Invited
X-Ray Transient Absorption Spectroscopy Studies on Interfacial Electron Transfer: xiaoyi zhang1; Grigory Smolentsev2; Sophie Canton2; Lin Chen1; 1Argonne National Lab; 2Department of Chemical Physics, Lund University
Photo-driven interfacial electron/charge transfer has important applications in solar energy utilization. Because the chemical and electronic properties of interfacial species undergo photoinduced electron transfer (PET) are largely determined by their structures in ground and excited states, directly visualizing these structures is necessary in molecular/material designs for target functions, ultimately, realizing rational designs of photovoltaic device. We have used X-ray transient absorption spectroscopy to study the electron transfer between dye and semiconductor nanocrystalline, mimicking dye-sensitized solar cell. Two examples will be presented, Ru(dcbpy)2(NCS)2 and Os(dcbpy)2(CN)2 adsorbed to TiO2 nanoparticle surface. The photoexcited Ru and Os complexes inject electrons to TiO2 semiconductors, resulting in interfacial charge transfer state. The electronic configuration as well as the internuclear distance changes of metal complexes in the charge separation state has been observed. These works have demonstrated the great potential of XTA in studying fundamental structural-functional correlations in solar electricity and fuel generation in interfacial systems.
8:40 AM Invited
Structural Characterization of Materials Using Synchrotron Based X-Ray Absorption and Scattering Techniques: Qing Ma1; 1DND-CAT/Northwestern University
Modern synchrotron radiation facilities have enable scientists to employ extensively X-ray absorption spectroscopy, and to a less extent, anomalous X-ray scattering, techniques for structural characterizations of materials. In this presentation, examples from researches mostly carried out at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) bending magnet beamline at the Advanced Photon Source will be presented to illustrate the usefulness of these techniques. These examples will be presented with emphasis on the strength and limitation of these techniques. It will be shown that their combination can be quite powerful in providing a better structural description for complex materials systems.
9:20 AM
Structure, Morphology and Oxidation State Determination of Iron-Substituted CuInS2 Materials Prepared by High-Temperature Solid-State Synthesis: Johanna Burnett1; Balamurugan Karuppannan1; Jacilynn Brant1; Jacqueline Sturgeon2; Kristin Bunker2; Karen Harris2; Jennifer Aitken1; 1Duquesne University; 2RJ Lee Group
CuInS2 (CISU) is an important photovoltaic material whose solar energy conversion efficiency is nearly twice that of traditional silicon-based materials. However, future availability of indium is of industrial concern. In this work, it was found that up to 15% of the indium in CISU can be replaced with iron, a more abundant metal, resulting in the series CuIn1-xFexS2, where x = 0-15. Using Reitveld refinements of X-ray powder diffraction data, the effects that this replacement has on the structure of the material has been investigated. X-ray photoelectron spectroscopy (XPS) allowed for the determination of the oxidation state of iron in the materials. XPS of a series of structurally related compounds were used to provide a library of binding energies for reference. XPS survey scans were used to verify the stoichiometry of the compounds. Scanning electron microscopy was used to investigate the morphology of the as-prepared ingots.
9:40 AM Break
10:00 AM Invited
Structural Accommodation of Energy-Related Materials during Energy Conversion and Storage: Faisal Alamgir1; 1Georgia Institute of Technology
We will look at examples of in-situ (and ex-situ) synchrotron-based experiments, specifically X-ray Absorption Spectroscopy (XAS), in the research of energy storage (Li-ion battery intercalation reactions), energy conversion (surface reactions on fuel-cell catalysts) and energy harvesting (catalytic H2 production from ethanol). Due to the tunability of synchrotron X-rays, species-specific information can be obtained from nearly every known constituent element of energy-related materials. Using the near-edge or the extended fine structure in an XAS spectrum, the chemical state and the local atomic structure from a material can be obtained from a single experiment. In addition, the high brightness, high coherence and short pulse trains allow synchrotron light to be used for species-specific, in-situ studies at high temporal and energy resolutions. Using a survey of the current state of research on materials for energy storage, conversion and harvesting, a vision of the future research in these areas will be presented.
10:40 AM Invited
Solid State Nuclear Magnetic Resonance Spectroscopy of Ordered and Disordered Materials: Randall Youngman1; 1Corning Incorporated
NMR applications in materials science continue to grow, due in part to advances in instrumentation and techniques. This adoption is a result of the structural information obtained from NMR, which is unconstrained by the extent of ordering. To demonstrate the broad applicability of NMR in materials science, we describe studies of materials ranging from highly ordered single crystals to disordered oxide glasses. NMR of mixed fluoride single crystals shows random mixing of Ca and Sr, and reveals multiple fluorine environments distinguished by their nearest neighbors. In a system exhibiting significantly less order, silicon pyrophosphate glass-ceramics, we utilize NMR to describe both the glass and crystal structures, and even gain insight into the extent and quality of crystallite formation. Finally, in disordered solids like oxide glasses, we are able to employ various NMR methods to understand cation and anion coordination environments, as well as interconnectivity between various glass-forming constituents.
11:20 AM
Concurrent Raman and Brillouin Scattering for Monitoring Polymer Network Assembly: Michael Aldridge1; John Kieffer1; 1University of Michigan
Raman spectroscopy is commonly used to measure chemical and structural changes in reacting molecular systems. This technique probes the bonding characteristics and symmetries of molecular units. Changes in the Raman spectra primarily reveal the relative concentrations of reacted vs. unreacted polymer building blocks, as a function of time. However, they tell little about the topological characteristics of the growing polymer network. Brillouin scattering, on the other hand, allows us to measure the complex mechanical modulus of the network at the molecular level. Real and imaginary parts provide a measure of structural integrity of the network and of the energy dissipated by mobile structural moieties, respectively. In-situ concurrent Brillouin and Raman measurements, taken from the same sample volume during the cure of thermosets, allow us to construct detailed structural models of these materials. We will illustrate the capabilities of this approach based on the examples of dicyclopentadiene and epoxy.