Symposium Organizers
Julie Herberg Lawrence Livermore National Laboratory
Yue Wu University of North Carolina-Chapel Hill
Phil Grandinetti The Ohio State University
Sophia Hayes Washington University
Ian Farnan University of Cambridge
MM1: Magnetic Resonance Studies on Hydrogen Storage Materials
Session Chairs
Monday PM, November 27, 2006
Liberty (Sheraton)
2:30 PM - **MM1.1
NMR to Determine Rates of Motion and Structures in Metal-Hydrides.
Mark Conradi 1 , Tim Ivancic 1 , Michael Mendenhall 1 , Caleb Browning 2 , Peter Notten 3 4 , W. Peter Kalisvaart 4 , Pieter Magusin 4 , Natalie Adolphi 5 , Robert Bowman 6 , Sonjong Hwang 6
1 Department of Physics, Washington University, St. Louis, Missouri, United States, 2 , Legget and Platt, Inc, Carthage, Missouri, United States, 3 , Philips Research Laboratory , Eindhoven Netherlands, 4 , Eindhoven University of Technology, Eindhoven Netherlands, 5 , New Mexico Resonance, Inc., Alburquerque, New Mexico, United States, 6 Jet Propulsion Lab, Caltech, Pasadena, California, United States
Show AbstractMeasurements of nuclear magnetic resonance relaxation times allow the rates of H and D motion in metal-hydrides to be determined. A first example compares the rates of H motion in the newly developed electrode material Mg65Sc35Pd2.4Hx with x = 220 to the well-known LaNi5Hx and its Ni-substituted analogs. A second example is the so-called anomalous relaxation found at and above 800 K in several metal-hydrides. There, relaxation measurements reveal that rapid H exchange between metal and gas phases, not a new motion, is responsible for the additional relaxation. Finally, magic-angle spinning (MAS) NMR of metal-deuterides can reveal multiple inequivalent D-sites and the rate of motion between them. The examples YD2+x and ZrNiDx are discussed.
3:00 PM - MM1.2
NMR Studies of the Mg-Sc-H System.
Son-Jong Hwang 1 , Robert Bowman 2 1 , M. Conradi 3 , T. Ivancic 3 , M. Mendenhall 3 , P. Notten 4 5 , W. Kalisvaart 4 , P. Magusin 4
1 , California Institute of Technology, Pasadena, California, United States, 2 , Jet Propulsion Laboratory, Pasadena, California, United States, 3 Department of Physics, Washington University, St. Louis, Missouri, United States, 4 , Eindhoven University of Technology, Eindhoven Netherlands, 5 , Philips Research Laboratory, Eindhoven Netherlands
Show AbstractAlthough MgH2 has a high reversible storage capacity of 7.6 wt.% hydrogen, its slow sorption kinetics have proven to be a major detriment to most potential applications. Reaction kinetics are improved by alloying magnesium with other metals, like nickel. Recently, novel alloys of magnesium and scandium with excellent hydrogen storage capacity and improved sorption kinetics have been developed [1] where the ternary hydride formed from Mg-Sc alloys has a CaF2-type crystal structure, which is more favorable for hydrogen motion than the rutile structure of MgH2. Measurements of proton nuclear magnetic resonance relaxation times have indicated the rates of H motion in Mg65Sc35Pd2.4Hx with x = 220 are faster than for both MgH2 and ScH2. Both static and magic-angle spinning (MAS) NMR measurements of the protons and 45Sc nuclei have been performed to assess phase compositions and structures in the Mg-Sc-H samples in as-prepared condition and after hydride degradation was observed following heating during NMR measurements at elevated temperatures. These results will be presented and related to the crystal structure determinations using x-ray and neutron diffraction [2]. 1. W. P. Kalisvaart, R. A. H. Niessen and P. H. L. Notten, J. Alloys Comp. 417 (2006) 280. 2. M. Latroche, W. P. Kalisvaart, and P. H. L. Notten, Submitted to J. Solid St. Chem. (2006).
3:15 PM - MM1.3
NMR - A Sensitive Tool for Probing Minority Adsorption Sites in Carbon Based Hydrogen Storage Materials.
Alfred Kleinhammes 1 , Shenghua Mao 1 , Qiang Chen 1 , Yue Wu 1 , Michael Chung 2 , Jeff Blackburn 3 , Michael Heben 3
1 Department of Physics and Astronomy and Curriculum in Applied and Materials Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 2 Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States, 3 , National Renewable Energy Laboratory (NREL), Golden, Colorado, United States
Show AbstractMM2: Contrast Agents for Magnetic Resonance Studies
Session Chairs
Monday PM, November 27, 2006
Liberty (Sheraton)
4:30 PM - **MM2.1
Contrast Agents for Clinical Magnetic Resonance Imaging.
Peter Caravan 1 , Vincent Jacques 1
1 , Epix Pharmaceuticals, Cambridge, Massachusetts, United States
Show AbstractMonday 11/27New Presenter - *MM2.1 @ 3:30 pmContrast Agents for Clinical Magnetic Resonance Imaging. Vincent Jacques.
5:00 PM - **MM2.2
Investigation of Dendron-Functionalized Superparamagnetic Nanoparticles for Potential Use as MRI Contrast Agents.
Boyd Goodson 1 , Indrajit Saha 1 , Chuansong Duanmu 1 , Brooke Crase 1 , Kathleen Chaffee 1 , Ashley Davis 2 , Yong Gao 1
1 Chemistry and Biochemistry, Southern Illinois University, Carbondale, Illinois, United States, 2 , Western Illinois University, Macomb, Illinois, United States
Show AbstractSuperparamagnetic iron oxide nanoparticles (SPIONs) have attracted increasing attention because of their large magnetic moments and relatively high biological tolerability, enabling them to act as effective MRI contrast agents. Correspondingly, considerable effort has also been directed towards the development of functional molecules that may be conjugated to such nanoparticles to alter their behavior for synthetic or biomolecular imaging applications. For example, dendrimers have recently been investigated as synthetic matrices for the creation of novel SPION/dendrimer aggregates for MR imaging, as well as (non-covalently attached) cellular transfection agents for FDA-approved iron oxide MR contrast agents. In particular, dendron surface structures offer a number of potentially advantageous properties: Like the more common polymer coatings, dendrons offer greatly enhanced solubility/stability for SPIONs in aqueous environments. However unlike most polymer coatings, dendrons possess tightly controlled size and molecular structure, and offer the possibility of tunable environmental response and cellular uptake. More generally, the tunable, well-defined, and relatively monodisperse characteristics of the cores and surface functionalities of such nanoparticles should enable them to serve as effective platforms for fundamental studies of the relationships between a given SPION property, the SPION medium, and the observed MR behavior—as well as for the continued development of novel nanoparticle systems targeted for specific applications. Here we report a novel strategy for the synthesis of core/shell iron oxide/dendron-coated nanoparticles that exhibit tunable solubility in various solvents (Gao Group). 1H NMR relaxation properties of water-soluble SPIONs coated with three different generations of melamine dendrons were studied within in vitro ‘phantom’ samples—including the observation of generation-dependent molar relaxivities. As expected, very low R1m molar relaxivities were observed for all SPIONs under our conditions. However, large R2m and R2*m values were observed (~100-300 and ~500-800 Hz/mM Fe, respectively); moreover, the transverse relaxivities can be systematically varied by nearly an order of magnitude in response to interrelated changes in solution pH and/or ionic strength. Such sensitivity to the local environment points the way towards the development of so-called ‘molecular-switch’ contrast agents. We have also observed corresponding (mono-exponential) CPMG echo time (τ) dependences of apparent T2 values, and we report on our efforts to understand these effects in greater detail. Finally, preliminary studies of cellular toxicity, uptake, and 1H relaxation properties within HeLa cell cultures will be discussed.
5:30 PM - MM2.3
Development of Targeted Monodisperse γ-Fe2O3 Nanoparticle Contrast Agents.
Kristi Hultman 1 , Adrienne Grzenda 2 , Anthony Raffo 3 , Paul Harris 3 , Stephen O'Brien 1 , Truman Brown 4
1 Applied Physics, Columbia University, New York, New York, United States, 2 Surgery, Columbia University, New York, New York, United States, 3 Medicine-Oncology, Columbia University, New York, New York, United States, 4 Radiology and Biomedical Engineerying, Columbia University, New York, New York, United States
Show Abstract5:45 PM - MM2.4
Using the Xenon Biosensor as a Selective MRI Contrast Agent.
Lana Chavez 1 2 , Leif Schroeder 1 2 , Thomas Lowery 1 3 , Christian Hilty 1 2 , Sandra Garcia 1 2 , Katherine Koen 1 2 , David Wemmer 1 3 , Alexander Pines 1 2
1 College of Chemistry, University of California, Berkeley, Berkeley, California, United States, 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract
Symposium Organizers
Julie Herberg Lawrence Livermore National Laboratory
Yue Wu University of North Carolina-Chapel Hill
Phil Grandinetti The Ohio State University
Sophia Hayes Washington University
Ian Farnan University of Cambridge
MM3: Novel Magnetic Resonance Studies
Session Chairs
Tuesday AM, November 28, 2006
Liberty (Sheraton)
9:30 AM - **MM3.1
Nondestructive Testing of Materials by Single-Sided NMR
Bluemich Bernhard 1 , Federico Casanova 1 , Juan Perlo 1
1 ITMC, RWTH Aachen University, Aachen Germany
Show AbstractConventional NMR is executed with stationary equipment involving large magnets which accommodate the sample in their center to make use of high and homogeneous magnetic fields. The frequently used word “sample” acknowledges an invasive procedure of separating a small entity from a larger one for analysis. Small magnets with inhomogeneous fields and small spectrometers make NMR mobile for use at the site of interest, and single-sided sensors like the NMR-MOUSE make NMR non-invasive and non-destructive. Single-sided NMR was developed for well logging in the oil industry, where a small sensor investigates a large object at different positions. The same principles has been realized for materials testing with the NMR-MOUSE. A variety of methods has been developed that acquire the information contained in a single pixel of an NMR image by the NMR-MOUSE, as image contrast does not require homogeneous fields. Advances in methodical developments have led to multi-dimensional methods for imaging and correlations of parameters like relaxation and diffusion. Moreover, high-resolution chemical shift resolved spectra of protons from liquids within large containers have already been measured by single-sided NMR, and the field profile has been tailored to shape a flat, thin sensitive volume for high-resolution depth profiling. These advances enable a large variety of new investigations, addressing the defect analysis of rubber products, the life time prediction of polymer pipes, the stratigraphy of skin and old master paintings, as well as the preservation of historical findings concerning old buildings and mummies like the 5000 year old ice man from Tyrol.
10:00 AM - **MM3.2
Magnetic Resonance Force Microscopy – the Quest for a Molecular Structure Microscope.
John Mamin 1 , Martino Poggio 1 , Christian Degen 1 , Daniel Rugar 1
1 , IBM Research Division, Almaden Research Center, San Jose, California, United States
Show AbstractMagnetic resonance force microscopy (MRFM) has been proposed as a method for greatly improving the sensitivity and spatial resolution of magnetic resonance imaging, perhaps even to the atomic level. The technique reached a significant milestone in 2004 when it successfully detected the magnetic resonance signal from a single electron spin buried in a silica sample [1]. The experiment achieved 25 nm spatial resolution in one-dimension and showed evidence for a rotating frame Stern-Gerlach effect. After a brief review of the electron spin work, I will describe our progress in applying the same techniques to detection of nuclear spins. In particular, I will describe NMR detection of the naturally occurring statistical polarization in small ensembles, and present recent solid-state 2D NMR imaging results. Finally, I will discuss the challenges of pushing the technique toward the detection of individual nuclear spins.[1] D. Rugar, R. Budakian, H. J. Mamin and B. W. Chui, Nature 430, 329 (2004).
10:30 AM - **MM3.3
High Speed 1H MAS NMR Investigations of Water Dynamics in Materials.
Todd Alam 1 , May Nyman 2 , Tina Nenoff 3 , Sarah McIntyre 1
1 Department of Electronic and Nanostructured Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Department of Geochemistry, Sandia National Laboratories, Albuquerque, New Mexico, United States, 3 Department of Surfaces and Interface Sciences, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractHigh speed 1H MAS NMR continues to see increased use in the analysis of materials. The fast MAS spinning greatly reduces the homonuclear 1H-1H dipolar coupling increasing the spectral resolution observed. Our group has demonstrated that two dimensional (2D) double quantum (DQ) 1H MAS NMR experiments can be used to analyze the dynamics of water within both inorganic and organic materials.[1,2] From the analysis of the DQ spinning sideband patterns it is possible to extract an effective 1H-1H dipolar coupling constant (Deff), from which a motional order parameter of the water species (Swater) can be calculated. In some instances the distribution of the water motional order parameters can also be evaluated. In this presentation several different examples of 1H DQ NMR measurements of water dynamics will be presented. The first example includes the 1H MAS NMR and DQ NMR of local proton environments within the alkali hexaniobate material, X7[HNb6O19] nH2O (where X = Na, K, Rb and Cs). In these materials the water order parameter varied not only as a function of counter ion, but was also dependent on the specific water environment. The second example involves the dynamics of water in SOMS (Sandia Octahedral Molecular Sieves), and the variation with Titanium substitution within the framework. The role and impact of these observed water dynamics on the material properties and chemistry will be discussed. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.[1] T. M. Alam, M. Nyman, B. R. Cherry, J. M. Segall, L. E. Lybarger, “Multinuclear NMR Investigations of the Oxygen, Water, and Hydroxyl Environments in Sodium Hexaniobate”, J. American Chemical Society, 126(17), 5610-5620 (2004).[2] G.P. Holland, B.R. Cherry, and T.M. Alam, “Distribution Effects on 1H Double-Quantum MAS NMR Spectra”, J. Magnetic Resonance, 167, 161-167 (2004).
11:15 AM - MM3.4
High-Resolution Solid-State NMR Methods For Probing Hydrogen-Bonding Interactions.
Steven Brown 1
1 Department of Physics, University of Warwick, Coventry United Kingdom
Show AbstractA key challenge in materials science is the availability of advanced characterisation techniques that are capable of providing local atomic-level structural information, such that the structure-property relations that link specific favourable bulk properties of a material with molecular-level structure can be established. This presentation focuses on the structures formed by the self assembly of synthetically modified guanosines that have exhibited promising molecular electronic properties, e.g., they are photoconductive and act as a rectifier. [R. Rinaldi, G. Maruccio, A. Biasco, V. Arima, R. Cingolani, T. Giorgi, S. Masiero, G. P. Spada, G. Gottarelli, Nanotechnology 2002, 13, 398.] Solid-state NMR interactions – notably chemical shift and J couplings – are powerful probes of hydrogen bonding. Using N-H…N hydrogen-bond mediated 2hJNN couplings, the hydrogen-bonding partners can be unambiguously identified in refocused INADEQUATE spectra, [S. P. Brown, M. Pérez-Torralba, D. Sanz, R. Claramunt, and L. Emsley, J. Am. Chem. Soc. 124, 1152 (2001).;F. Fayon, D. Massiot, M. H. Levitt, J. J. Titman, D. H. Gregory, L. Duma, L. Emsley, and S. P. Brown J. Chem. Phys. 122, 194313 (2005).] while hydrogen-bonding strength can be quantified by the determination of the J couplings in spin-echo experiments. [S. P. Brown, M. Pérez-Torralba, D. Sanz, R. Claramunt, and L. Emsley, Chem. Comm. 1852 (2002).; L. Duma, W. C. Lai, M. Carravetta, L. Emsley, S. P. Brown, and M. H. Levitt, ChemPhysChem 5, 815 (2004).] Recently, we have shown that different intermolecular hydrogen-bonding arrangements in the synthetically modified guanosines that lead to different modes of self-assembly, namely quartet or ribbon formation, are distinguished in 15N refocused INADEQUATE spectra. [T. N. Pham, S. Masiero, G. Gottarelli, and S. P. Brown, J. Am. Chem. Soc 127, 16018 (2005)] Moreover, the development of low-load 1H decoupling approaches has enabled the quantitative determination of these small 2hJNN couplings (~6 Hz), with a clear correlation between the J coupling magnitude and the NH…N distance, and hence hydrogen-bonding strength, being observed.
MM4: Magnetic Resonance Studies on Fuel Cells, Batteries, and Other Energy Related Materials I
Session Chairs
Tuesday PM, November 28, 2006
Liberty (Sheraton)
11:45 AM - **MM4.1
NMR Studies of Materials.
Jeff Reimer 1
1 Chemical Engineering, UC Berkeley, Berkeley, California, United States
Show Abstract12:15 PM - **MM4.2
NMR Studies of Paramagnetic Materials: Battery Materials and Environmental Chemistry.
Julien Breger 1 , Ulla Gro Nielsen 1 , Jongsik Kim 1 , Clare Grey 1
1 , SUNY Stony Brook, Stony Brook, New York, United States
Show Abstract12:45 PM - MM4.3
Nuclear Magnetic Resonance and Muon Spin Resonance Studies of Lithium Battery Materials.
Jeremy Titman 1 , Duncan Gregory 2 , Andrew Powell 1
1 Chemistry, University of Nottingham, Nottingham United Kingdom, 2 Chemistry, University of Glasgow, Glasgow United Kingdom
Show AbstractLithium batteries are used for mobile communication and computing applications because of their high energy densities. In recent years much effort has been devoted to the discovery of new materials which can be used to make electrodes for lithium batteries. Potential improvements include increased energy storage capacities and extended charging lifetimes, as well as economic benefits, such as reduced cost.Although it suffers from a low decomposition potential which curtails it usefulness, lithium nitride has been extensively studied. This is because it possesses the highest reported Li+ ion conductivity for a crystalline material, with a strong anisotropy observed at ambient temperature. Low levels of Li+ vacancies in the graphitic [Li2N] ab planes of the Li3N layered structure are responsible for the faster contribution which occurs perpendicular to the crystallographic c axis. It was suggested that these vacancies are generated by the presence of hydrogen as NH2-.Recently, interest in Li3N was rekindled by the suggestion that the ternary compound Li2.6Co0.4N might be suitable as an improved anode material, in particular because of its high capacity. We have shown that it is possible to synthesize a range of similar ternary phases Li3-x-yMxN (M=Co, Ni, Cu; y = Li vacancy) with controlled and reproducible vacancy and substitution levels. We have studied their structure and transport properties by neutron and X-ray diffraction, solid-state NMR and muon spin resonance (μSR).Our X-ray and neutron diffraction studies show that most of these materials have Li3N defect structures in which vacancies in the [Li2N] plane are disordered with retention of the Li3N structure. The Li vacancy concentrations are up to 50 times higher than in Li3N, suggesting improved Li+ transport properties. With increasing x the Li - N bond within the [Li2N] planes lengthens providing more open diffusion properties and a reduced Ea for intra-layer Li+ hopping, although these beneficial effects are countered to some extent by a concomitant reduction in the layer spacing. This picture is supported by our solid-state NMR studies of Li+ diffusion. For example, the intra-layer Li hopping time measured by NMR is reduced by as much as 50 % on substitution with Cu, while the corresponding Ea decreases gradually as x for Ni increases. μSR provides complimentary information. For example, at temperatures above 160 K the muon depolarization rate decreases rapidly due to the onset of Li+ diffusion. SQUID magnetometry shows that the Co-substituted phases are strongly paramagnetic. Therefore, in contrast to diamagnetic Li3N and the weakly paramagnetic Ni- and Cu-doped phases, no information about Li+ dynamics can be gained from NMR. However, a combination of zero and longitudinal-field μSR measurements allows the paramagnetic contribution to muon relaxation from fluctuating Co electronic moments to be separated from the dipolar contribution associated with Li+ diffusion.
MM5: Magnetic Resonance Studies on Nanomaterials
Session Chairs
Tuesday PM, November 28, 2006
Liberty (Sheraton)
2:30 PM - **MM5.1
Employ Guest Fatty Acid Molecules to Measure the Magnetic Structure of Titanate Nanotubes & Study the Molecular Dynamics of Nanoconfined Fatty Acids Via NMR.
Xiaoping Tang 1 , Martyn Rekowski 1 , Yue Wu 2
1 Dept of Physics, University of Louisville, Louisville, Kentucky, United States, 2 Physics & Astronomy, University of North Carolina, Chapel Hill, North Carolina, United States
Show Abstract3:00 PM - MM5.2
2D HETCOR MAS NMR and Hyperpolarized 129Xe NMR for the Study of Nanostructured Materials.
Roberto Simonutti 1
1 Materials Science Department, University of Milan-Bicocca, Milan Italy
Show Abstract3:15 PM - MM5.3
Electron Spin Resonance in Magnetic Nanoparticles. Effects of Temperature and Interparticle Interactions.
Natalia Noginova 1 , Andrey Andreyev 2 , Joseph McClure 1 , Emmanuel Giannelis 3 , Vadim Atsarkin 4
1 , NSU, Norfolk, Virginia, United States, 2 Summer Research, NSU, Norfolk, Virginia, United States, 3 , Cornell University, Ithaca, New York, United States, 4 , IRE, Moscow Russian Federation
Show AbstractThe electron spin resonance technique has been applied to study the magnetization dynamics in broad temperature range in both concentrated magnetic fluid and diamagnetically diluted systems containing superparamagnetic maghemite nanoparticles. The ESR spectrum demonstrates an interesting double feature shape with a narrow peak at g=2, and is strongly dependent on the temperature and nanoparticle concentration. To describe the overall spectrum shape, a “quantization” model is used which involves summation of resonance transitions corresponding to various orientations of the particle’s magnetic moment. The interparticle interaction was taken into account to explain the concentration dependence and effects of field freezing. The longitudinal spin-relaxation time was estimated.
3:30 PM - MM5.4
Translational and Rotational Motion of Small Penetrants in AF1600 Nanocomposites.
Darryl Aucoin 1 , Junyan Zhong 1 , Guoxing Lin 1 , Wen-Yang Wen 1 , Alan Jones* 1
1 Carlson School of Chemistry and Biochemistry, Clark University, Worcester, Massachusetts, United States
Show AbstractTranslational and rotational motions of dichloromethane were observed in a composite of poly(2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene), also referred to as AF1600, with fumed silica using NMR. Pulsed field gradient diffusion measurements show that adding fumed silica to AF1600 results in a great enhancement of the diffusion coefficient of dichloromethane. Similar diffusion enhancement behavior has been previously reported in pentane, cyclohexane, and toluene in AF1600 nanocomposites.[1] Spin-lattice relaxation time measurements of this system indicate two domains: one containing larger free volume elements that support faster dynamics and one containing smaller free volume elements that support slower dynamics. Adding the fumed silica disrupts the packing of polymer chains resulting in an increase of free volume and improved connections between domains supporting rapid translation. The lattice model simulation is performed to assist in understanding the mechanism of how the addition of fumed silica improves penetrant diffusion in nanocomposite polymer systems. [2]References:[1] J. Zhong, G. Lin, W.-Y. Wen, A. A. Jones, S. Kelman and B. D. Freeman, Translation and Rotation of Penetrants in Ultrapermeable Nanocomposite Membrane of Poly(2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene) and Fumed Silica Macromolecules, 38 (9), 3754 -3764, 2005.[2] G. Lin, J. Zhang, H. Cao, and A. A. Jones, A Lattice Model for the Simulation of Diffusion in Heterogeneous Polymer Systems. Simulation of Apparent Diffusion Constants as Determined by Pulse-Field-Gradient Nuclear Magnetic Resonance J. Phys. Chem. B, 107 (25), 6179 -6186, 2003.* Posthumous
3:45 PM - MM5.5
Characterizing the Size of Nanoparticles in Biological and Synthetic Nanocomposites by Advanced Solid State NMR.
Aditya Rawal 2 1 , Mufit Akinc 4 1 , Surya Mallapragada 3 1 , Klaus Schmidt-Rohr 2 1
2 Chemistry, Iowa State University, Ames, Iowa, United States, 1 Ames Laboratory, DOE, Ames, Iowa, United States, 4 Material Science & Engineering, Iowa State University, Ames, Iowa, United States, 3 Chemical Engineering, Iowa State University, Ames, Iowa, United States
Show AbstractOrganic-inorganic nanocomposites are attractive materials due to their potential for unusual combinations of properties, such as stiffness and toughness. A prime example is bone, a composite of nanoparticles of apatite (a calcium phosphate) dispersed at ~40 vol% in collagen, a fibrous protein. The result is a remarkably light and strong material, adaptable and easily repairable. We will present various NMR approaches for estimating the size of nanoparticles (phosphates (31P), silicates (29Si), carbonates and nanodiamond (13C), etc.) in an organic matrix. We will focus on bone and biomimetic materials synthesized by precipitating calcium phosphate onto micelles of block copolymers. Due to the selectivity of multinuclear NMR, the inorganic particles can be studied in the presence of the organic matrix; in other words, no harsh sample pretreatments are required.For measuring the thickness of the nanoparticles, we have developed and perfected a new NMR method, X{1H} HeteronucleAr Dephasing by Strong Homonuclear Interactions of Protons (HARDSHIP), which uses the strongly distant-dependent dipolar couplings between the abundant protons in the organic and X-nuclei in the inorganic phase. This approach requires a pulse sequence with heteronuclear dephasing only by the polymer or surface protons, but not by dispersed OH or water protons in the inorganic phase, which can be distinguished based on their longer transverse relaxation times T2,H. The pulse sequence alternates heteronuclear recoupling for ~0.15 ms with periods of homonuclear dipolar dephasing, refocusing the evolution of the long-T2,H protons within two rotation periods. For the short-T2,H matrix protons, the dephasing rate depends simply on the heteronuclear second moment, which enables quantitative simulations. Homonuclear interactions do not affect the dephasing because long-range 1H-X approximately commute with short-range 1H-1H couplings, and each heteronuclear recoupling period is short. The method also enables us to prove the presence of certain species in the nanocrystals, e.g. of carbonate in bioapatite.When 1H is present in the nanoparticles, 1H spin diffusion between the inorganic and organic phases can be used for roughly estimating their size. For instance, the magnetization of long-T2,H protons of nanoparticles in an organic matrix with little mobility can be selected by T2-filtering, and its spin-diffusion monitored in 1H NMR spectra. If the matrix contains mobile polymer segments with sharp 1H lines, two-dimensional 1H-X wideline separation experiments with 1H spin diffusion can be used conveniently to prove the formation of nanometer-sized particles. In nanoparticles of low 1H concentration, 1H-X correlation NMR can provide selective spectra of the particle surface (organic-inorganic interface) and of its core. The amount of surface material, which is a measure of the particle size, can be quantified by suitably chosen 1H-X double-resonance methods.
MM6: Magnetic Resonance Studies on Biomaterials
Session Chairs
Tuesday PM, November 28, 2006
Liberty (Sheraton)
4:30 PM - *MM6.1
Magnetic Resonance Microscopy Analysis of Biofilm Polymer Dynamics and Bioreactor Transport.
Sarah Codd 1 4 , Anna Lysova 3 , Jennifer Hornemann 2 4 , Robb Fell 2 4 , Joseph Seymour 2 4 , Philip Stewart 2 4
1 Mechanical and Industrial Engineering, Montana State University, Bozeman, Montana, United States, 4 Center for Biofilm Engineering, Montana State UniversityCenter, Bozeman, Montana, United States, 3 , International Tomography Center, Novosibirsk Russian Federation, 2 Chemical and Biological Engineering, Montana State University, Bozeman, Montana, United States
Show AbstractBiofilms are spatially heterogeneous microbial communities which grow on surfaces. They are composed of cells surrounded by a hydrogel (extracellular polymeric substance EPS). They can be beneficial such as microbial biofilms in environmental remediation or detrimental in causing infections and industrial corrosion. They impact transport phenomena in geophysical, medical and environmental systems. Modeling the time and spatial transport of nutrients and antimicrobial agents requires knowledge over a hierarchy of scales ranging from the cell and EPS polymer level to the macroscale dimensions over which flow occurs. Several groups have applied MRM techniques to study transport in biofilm systems[3, 5]. Dynamic MRM has been used to characterize the bulk advective transport in a biofilm capillary reactor [2, 6]. The biofilm generates significant non-axial flows indicating mixing by a complex flow field. Ways of statistically evaluating the observed oscillatory flow scaling with the capillary diameter are being explored. The EPS gel influences the macroscale by impacting the boundary condition for momentum, mass and energy conservation at the wall [1]. MRM techniques are capable of spectrally and spatially resolving diffusion coefficients and their application to polymeric materials is well established. We are applying these methods to the biofilm matrix and observing the impact of antibiotic activity on the diffusion of the various spectral peaks. The detailed composition of the EPS is unknown but likely contains polysaccharides, proteins and even DNA. The polymer translational diffusion indicates multiple populations of polysaccharides and other biopolymers with diffusion coefficients ranging from the order of 10-9 to 10-13 m2/s indicating a broad size range and composition of biopolymers. The amount of biopolymeric substance in highly restricted environments due to polymer size or gel structure can be determined from the spectrally resolved diffusion data [7]. By observing changes in the diffusion we are able to monitor variations in the polymer material properties during aging and various antimicrobial assaults. Depth resolved NMR spectra have been used to infer metabolism in biofilms[4]. Extension of our experiments to the spatial dimension measures changes that occur in the biofilm material structure as a function of depth due to environmental conditions and anti-microbial assaults.[1] de Gennes, P.-G. 1979. Scaling Concepts in Polymer Physics. Ithaca: Cornell University Press.[2] Gjersing, E. L., Codd, S. L., et al. Biotech. and Bioeng. 89. 822-834 (2005).[3] Hoskins, B. C., Fevang, L., et al. J. Mag. Reson. 139. 67-73 (1999).[4] Majors, P. D., McLean, J. S..et al. J. Micro. Meth. 62. 337-344 (2005).[5] Manz, B. J. Mag. Reson. 169. 60-67 (2004).[6] Seymour, J. D., Codd, S. L.,.et al. J. Mag. Reson. 167. (2004).[7] Vogt, M., Flemming, H.-C., Veeman, W. S. J. Biotech. 77. 137-146 (2000).
5:00 PM - MM6.2
Dynamic Behaviour of Cocoon Silks Produced by Bombyx Mori by Means of Nuclear Relaxation Properties in the Solid State.
Marco Geppi 1 , Silvia Borsacchi 1 , Silvia Cappellozza 2 , Donata Catalano 1 , Vincenzo Ierardi 1 , Giulia Mollica 1
1 Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Pisa Italy, 2 Sezione Specializzata per la Bachicoltura, Istituto Sperimentale per la Zoologia Agraria, Padova Italy
Show AbstractThe understanding of the molecular structural and dynamic properties of silk, and of their link with the macroscopic mechanical properties is an important task because of the extensive applications of this material in fields ranging from textile industry to biotechnologies [1]. In particular, the influence of some variables, such as the origin of the silkworm and its alimentary regimen on the properties of Bombyx Morii silk may represent an important piece of knowledge for future technological improvements or in the optimization of industrial processes.Here we present a 1H and 13C low- and high-resolution solid state NMR study of several cocoons arising either from different origins (Turkish, Chinese, Japanese) or from silkworms raised with a natural (mulberry-tree leaves) or an artificial diet.The results obtained for both “natural” or dried samples from 13C and 1H spectra recorded by different techniques, 1H FID analysis, spin-lattice relaxation times and T1ρ-T2 correlation experiments [2], have been discussed in terms of structural and dynamic properties. Most of these properties result to be common to all the cocoons, while some differences can be highlighted either for cocoons arising from silkworms of different origin [3] or having undergone different diets.Some of the aspects that are here discussed concern in particular the side-chain dynamics, the role of water, its interaction with silk and its influence on the dynamic and nuclear properties of the two protein fractions (sericin and fibroin), the influence of silkworm individual variability, as well as the determination of spin-lattice relaxation sinks and the presence of dynamic heterogeneity.[1]C. Zhao, T. Asakura, Progr. Nucl. Magn. Reson. Spectr. 39 (2001) 301.[2]M. Geppi, A.M. Kenwright, B.J. Say, Solid State NMR 15 (2000) 195.[3]S. Borsacchi, S. Cappellozza, D. Catalano, M. Geppi, V. Ierardi, Biomacromolecules 7 (2006) 1266.
5:15 PM - MM6.3
Trabecular Bone Structure via Diffusion-based NMR Methods.
HyungJoon Cho 1 , Eric Sigmund 1 , Yi-Qiao Song 1
1 , Schlumberger, Ridgefield, Connecticut, United States
Show Abstract5:45 PM - MM6.5
Solid State NMR Characterization of Nano-crystalline hydroxy-carbonate Apatite Using 1H-31P-13C Triple Resonance Experiments.
Florence Babonneau 1 , Christian Bonhomme 1 , Satoshi Hayakawa 2 , Akiyoshi Osaka 2
1 Chimie de la Matiere Condensee, Universite Pierre et Marie Curie/Paris6, Paris France, 2 Faculty of Engineering, Okayama University, Okayama Japan
Show AbstractTues 11/28New Presenter - MM6.5 @ 4:15 amSolid State NMR Characterization of Nano-crystalline hydroxy-carbonate Apatite Using 1H-31P-13C Triple Resonance Experiments. Christian Bonhomme
MM7: Poster Session I
Session Chairs
Wednesday AM, November 29, 2006
Exhibition Hall D (Hynes)
9:00 PM - MM7.1
Characterization of H and D Motion in ZrNiHx and ZrNiDx by NMR Relaxation Times.
Mark Conradi 1 , Tim Ivancic 1 , Caleb Browning 2 , Robert Bowman 3
1 Physics-1105, Washington University, Saint Louis, Missouri, United States, 2 , Legget and Platt, Inc, Carthage, Missouri, United States, 3 Jet Propulsion Lab, Caltech, Pasadena, California, United States
Show AbstractRelaxation studies of the intermetallics ZrNiHx and ZrNiDx were performed using hydrogen and deuterium NMR in the beta (x = 0.85) and gamma phases (x = 2.6 and 3.0). Correlation times for atomic diffusion in the hydride were determined based on the temperature dependence of spin-lattice and spin-spin relaxation times. The hydrogen motion is shown to be thermally activated over the temperature range 300-550 K, and the activation energies for diffusion are determined. The deuterium NMR spectra exhibit incomplete line narrowing with temperature, indicating that the average electric field gradient is not zero when averaged over the deuterium atom sites of these non-cubic unit cells. The temperatures of minima in T1 and T2 for the deuterides indicate that the motion rates are similar for the D and H systems. However, the activation energies taken from the temperature dependences of the deuterides’ T1 and T2 are much smaller than for the hydrides, indicating the deuteride relaxation rates have additional contributions. The spectrum of ZrNiD1.87 reveals a coexistence of two phases, in agreement with the phase diagram.
9:00 PM - MM7.11
Portable, Low-cost, Ex-situ NMR with Laser-Lathe Microcoils.
Vasiliki Demas 1 2 3 , Julie Herberg 2 , Vince Malba 2 , Tony Bernhardt 2 , John Franck 1 3 , Jeff Reimer 1 3 , Alex Pines 1 3 , Robert Maxwell 2
1 Chemistry & Chemical Engineering, University of California, Berkeley, California, United States, 2 CBNS, Lawrence Berkeley National Laboratory, Livermore, California, United States, 3 MSD & EETD, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractNuclear magnetic resonance spectroscopy (NMR) is of unsurpassed versatility in its ability to non-destructively probe for chemical identity. Portable, low-cost NMR sensors would enable on site identification of potentially hazardous substances, such as signatures from production of nuclear, chemical, and biological weapon agents, narcotics, explosives, toxins, and poisons. There exist, however, problems that need to be overcome in the design of such sensors: (a) small-scale magnets produce inhomogeneous magnetic fields and therefore undesired Larmor frequency distributions that conceal much of the useful spectral information, and (b) sensitivity in most experiments decreases due to the inherently low and strongly inhomogeneous fields associated with portable instruments. Our approach has been to: (a) try to improve the field of low cost magnets either with hardware (e.g. magnet design and construction of “shim coils”) or via special pulse sequences, where the field is “effectively shimmed” to appear homogeneous to the sample, and (b) to use microcoils to improve sensitivity and to allow focusing in smaller regions and therefore smaller static field variations.Microcoils, inherently have large sample filling factors and efficient coupling of the excitation and detection radio frequencies to the sample. LLNL has developed a fabrication methodology suited for development and construction of any desired geometry microcoils with laser lithography. It has been already shown that small NMR coils of various geometries can be prepared to exact specification on curved surfaces with micron level feature sizes. We are currently setting up a table top system consisted of a 2-Tesla permanent Halbach magnet weighing less than 2 kg, and able to fit in the palm of a hand. The system uses the first generation portable, single resonance (0.002-100MHz) RF spectrometer from Tecmag Inc. The system is run on a laptop with NTNMR software for instrument control and data processing. A picture of the system is shown below.We have developed an RF microcoil probe based on transmission line designs. Initial NMR results have been obtained with with 360 mm O.D coil, yielding 17ppm resolution; a 100 mm coil has been built. The field of the magnet has been mapped and linear shims have been built using the Laser Lathe microcoil fabrication technologies developed in the Lawrence Livermore Labs. These coils will be tested both as conventional shims as well as for “effective shimming”, based on the series of ex-situ methodologies developed in the Pines lab, where combinations of RF inhomogeneities, frequency and amplitude modulated RF pulses and amplitude modulated gradients pulses are used to impart a spatially dependent phase.
9:00 PM - MM7.13
23Na, 27Al, 29Si NMR: Fading mechanism of Ultramarine Pigments.
Eleonora Del Federico 1 , Lindsey Tyne 1 , Cyndi O'Hern 1 , Jacob Newman 2 , Johannes Schelvis 2 , Sophia Kapetanaki 2 , Alexej Jerschow 2
1 Mathematics and Science, Pratt Institute, Brooklyn, New York, United States, 2 Chemistry, New York University, New York, New York, United States
Show AbstractUltramarines are a family of pigments widely used as colorants in artists’ paints, coatings, plastics, cosmetics, and various industrial materials. They are aluminosilicates characterized by a sodalite framework with the generic formula [Al3Si3O12]3- (also known as the β-cage"). Strong paramagnetic (S3-., S2-.) and diamagnetic (S4 or S3Cl) chromophores are encapsulated within the cages and are responsible for the color of these pigments.Solid-state 27Al MAS NMR studies showed that the fading mechanisms inUltramarine pigments, both in acids and alkaline environments, is initiated via de-alumination leading to cage destruction which in turn triggers the release of the occluded chromophores. This results in color loss and the emergence of extraframework Aluminum.New 29Si MAS studies at 17.6T provide more insight into these processesand suggest that, upon acid attack on the aluminosilicate framework dealumination occurs, leading to framework rearrangement and the formation of new cages richer in 29Si. 23Na MAS NMRdata is another valuable indicator for framework destruction, suggesting a loss of Na+ ions, via degradation by lime mortar.In addition, 27Al, 29Si, and 23Na shifts of several shades of ultramarine pigments are shown to correlate well with the intensities of Raman signals corresponding to the chromophores S3-. and S2-., as well as, with colorimetric parameters.These findings are important for the design of proper conservation treatments and preservation procedures for artwork containing ultramarine pigments.
9:00 PM - MM7.14
The DIVAM Filter: A NMR Signal Selection Method that is Tunable to Various Structural Domains Within Semicrystalline Materials.
Paul Hazendonk 1 , Tony Montina 1
1 Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada
Show AbstractSolid-state NMR spectroscopy is widely applied in structural studies of semi-crystalline materials, since it can be used to make measurements on both its crystalline and amorphous components. Since it is often necessary to obtain spectra specific to a domain of choice, several experiments have been developed that exploit either differences in the spin-dynamics or relaxation behavior between these environments. Generally speaking, the selection mechanism is based on one property, which renders it suitable to only those domains with that given property. As a result, several experiments are required to study all the structural domains present in the material. The newly developed, Discrimination Induced by Variable-Amplitude Minipulses (DIVAM) filter sequence selects on the basis of the spin-spin relaxation rate and the Chemical Shielding Anisotropy interaction, simultaneously. By adjusting its pulse spacing and excitation angles, its sensitivity can be tuned to either or both effects. Using this tunability it is possible to obtain spectra from both crystalline and amorphous domains using the same experiment.Experimental and theoretical studies that demonstrate and explain this tunable selectivity behavior will be presented. For example, the 19F spectra of both the crystalline and amorphous domain in ploy(vinylidenefluoride) were obtained by tuning the DIVAM filter using different excitation angles. These measurements were made either, directly, by applying the DIVAM filter on the 19F nucleus, or indirectly, by applying it on the 1H nucleus with subsequent cross polarization to 19F. The direct and indirect approach were used to obtain the 19F, 1H, 31P and 13C NMR spectra of the crystalline and amorphous domains in poly[bis(trifluoroethoxy)phosphazene]. For the first time it was demonstrated that 13C {19F,1H} MAS NMR spectra contained detailed structural features representing several of its crystalline phases. By contrast the 19F, 1H and 31P spectra show only one signal for the crystalline domain.
9:00 PM - MM7.15
NMR Analysis of Group 14 Nanocluster and Molecular Materials.
Jason Giuliani 1 , Steven Harley 1 , Ray Carter 1 , Matthew Augustine 1
1 chemistry, ucdavis, Davis, California, United States
Show AbstractThe diversity amongst various group 14 elements make them vital components of our economy, playing key roles in the semiconductor, solar power, and biomedical industry. [1] Group 14 elements also link the properties of nonmetals, metalloids and metals making an understanding of their basic physics and chemistry essential for future applications. Since each element in the group is NMR active and four of the five members have at least one spin-1/2 isotope, NMR spectroscopy can provide information necessary for understanding such systems. The characterization of novel compounds having 29Si and 117/119Sn isotopes by solid state NMR will be presented. Particular attention will be directed at studying nanoparticulate silicon material synthesized by novel electrochemical techniques as well as the characterization of nanoclusters with functional capping groups. [2-4] In addition to these materials molecular and nanoparticulate material from solution phase reduction synthesis will be analyzed. 1. Stix, et al. Sci. Amer. 2001, Sept., 32. 2. Carter, et al. Chem. Mater. 2005, 17, 2932.3. Giuliani, et al. J. Non-Cryst. Solids In press.4. Spikes, et al. Inorg. Chem. In press.
9:00 PM - MM7.17
Multinuclear NMR Study of Phosphine Stabilized Gold Nanoparticles.
Ramesh Sharma 1 , Jeff Yarger 1 , Daniel Buttry 2 , Gregory Holland 1 , Virgil Solomon 1 , Samrat Amin 2 , Steven Schiffenhaus 1
1 Chemistry, Arizona State University, Tempe, Arizona, United States, 2 Chemistry, University of Wyoming, Larmie, Wyoming, United States
Show AbstractUsing ligands that are chemically bound to gold nanoparticles is an important feature in the stability and catalytic property of these materials. Phosphine stabilized gold nanoparticles are investigated to understand their surface capping chemistry by using multinuclear Nuclear Magnetic Resonance (NMR) spectroscopy. In our current work, we exploit NMR to elucidate the binding and stability of triphenyl phosphine (TPP) stabilized gold nanoparticles. 1H solution NMR of these nanoparticles shows substantial broadening of the phenyl ring resonance and the associated protons. This broadening is attributed to the reduction in motion of the ligand due to binding gold surface. Both solution and solid state 31P NMR were taken for surface bound and free ligands at room temperature. There are distinct differences in 31P peak position and peak widths between the two. This further demonstrates that there is a difference between ligand mobility and the chemical environment of free and chemically bound ligands. Interestingly, 31P peak position and peak width changes with time when nanoparticles are stored in solution for several days. By doing ligand exchange, variable temperature (VT) and variable field NMR, the origin of this behavior is being investigated. A conventional 1H=>31P Cross Polarization Magic Angle Spinning (CP-MAS) experiment was used to probe the CP kinetics of near-surface phosphorous. Information about particle size and dispersity were obtained by high resolution transmission electron microscopy (TEM). These nanoparticles have size ranging from 1 to 5 nm, are very crystalline and highly dispersed. Further characterization of these nanoparticles was facilitated by TGA, UV-Vis, AFM and XRD experiments. These results show the potential of NMR spectroscopy to characterize metal nanoparticles and determine various aspects of surface chemistry and ligand binding properties.
9:00 PM - MM7.18
Electron Spin Resonance of Vanadium Oxide Nanotubes.
Kyu Won Lee 1 , Eunmo Lee 1 , Hyocheon Kweon 1 , Jitae Park 1 , Cheol Eui Lee 1
1 Physics, Korea University, Seoul Korea (the Republic of)
Show AbstractVanadium oxide nanotubes, synthesized through hydrothermal treatment of vanadium oxide-alkylamine composite, were studied by means of electron spin resonance (ESR). The ESR spectra were composed of a broad Lorentzian line superposed by a hyperfine structure, from which uniaxial g-tensor and hyperfine coupling tensor were obtained. The eight-line hyperfine structure appears to indicate that the 3d electrons of the V4+ nuclei interact with only one vanadium nucleus and thus are strongly localized. The Lorentzian line appears to arise from dipolar broadening and exchange narrowing rather than motional narrowing. The ESR intensity of the Lorentzian line follows the Curie-Weiss law with a negative Weiss temperature indicating an antiferromagnetic interaction.
9:00 PM - MM7.19
NMR and Spin Relaxation in Systems with Magnetic Nanoparticles.
Tracee Weaver 1 , Marsha King 1 , Natalia Noginova 1
1 , NSU, Norfolk, Virginia, United States
Show AbstractTo better understand the effects of magnetic nanoparticles to nuclear spectra and spin relaxation in different systems, we have studied proton NMR spectra and spin dynamics of the host system in liquid and solid suspensions of γ-Fe2O3 nanoparticles. Significant line broadening of proton NMR spectra and growing relaxation rates were observed with increased concentration of nanoparticles in the liquid systems, with the relation T1/T2 depending on the particular host. Solid systems demonstrate inhomogeneous broadening of the spectra and practically no dependence of the spin-lattice relaxation rate upon the nanoparticle concentration. We explain the experimental results taking into account predomination of diffusion as a source of the relaxation, and estimate effective parameters of relaxation in the systems in study.
9:00 PM - MM7.2
NMR Investigation of Fuel Cell Membranes Electrolytes Based on Ionic Liquid.
Cristina Iojoiu 2 , Jean-Yves Sanchez 2 , Patrick Judeinstein 1
2 LEPMI, Laboratoire d'Electrochimie et de Physicochimie des Matériaux et Interfaces, CNRS-INPG-UJF, Saint Martin d'Hères Cedex France, 1 RMN en Milieu Orienté, ICMMO, CNRS, Orsay France
Show AbstractProton Exchange Membrane Fuel Cells (PEMFC) operating above 120°C are nowadays expected as the best candidates for electric and hybrid vehicles. In this context, perfluorinated proton conducting membranes such as Nafion® which is the reference ionomer in PEFMC are inadequate, because high protonic conductivity require high backpressures and the control of high relative humidity inside the membranes. To overpass these limitations, critical need in fuel cell development requires a proton conducting membrane that can be operated on a wide temperature range (-20°C/160°C) in anhydrous conditions or at very low relative humidity. Our approach to overpass these limitations is to investigate new proton-conducting ionic liquids. New families of ionic liquids, based on perfluorinated sulfate anion (XfSO3-) and on an ammonium cation (HxNR4-x+, x=1 or 2) were investigated. These ionic liquids present satisfactory ionic conductivity (10-2 S.cm-1) but impedance spectroscopy does not probe the nature of the most efficient charge carriers and NMR experiments are required to obtain very complementary results. In this study, we will focus on specific techniques to probe the structure and the dynamic of the different species from the molecular to the macroscopic scale, more specifically - equilibrium and proximity between the different species (anion, amine, proton, ammonium) could be obtained from the measurement of homo and heteronuclear NOE effects (1H-1H, 1H-19F, 1H-2H) ; - diffusion coeffcient of cations and anions by 1H and 19F Pulsed Field Gradient NMR spectroscopy.;- local motions from relaxation T1 and T2 measurements.Such experiments allow to decipher different aspects of the conductivity mechanisms and to forecast the influence of the molecular architecture on the dissociation equilibrium inside these complex ionic liquids.
9:00 PM - MM7.20
Solid State Carbon-13 NMR Studies of Lead(II) Thiourea Materials.
Cecil Dybowski 1 , Alicia Glatfelter 1 , Shi Bai 1 , Dale Perry 2
1 Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract9:00 PM - MM7.21
Solid State NMR Investigation of LDPE/Silica Dispersions Obtained by Photo-Grafting Reaction.
Marco Geppi 1 , Silvia Borsacchi 1 , Lucia Ricci 1 , Giacomo Ruggeri 1 , Carlo Veracini 1
1 Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Pisa Italy
Show AbstractMaterials with enhanced properties, such as higher strength, better barrier toward gases, increased solvent and heat resistance and decreased flammability, are commonly obtained by filling polymers with inorganic fillers. To this regard, an important role is played by the dispersion of the filler into the polymer matrix and, consequently, by the occurrence of interphase filler-polymer interactions, which are particularly scarce in the case of apolar polymers as polyolefins. In this study we investigated the possibility of enhancing the compatibility between polyolefins and inorganic fillers by directly grafting the latter to the polymer matrix. To this aim, a TSPM-modified silica has been prepared and employed as filler in LDPE films, in which a photo-grafting reaction between polymerizable groups present on the functionalized filler and the polymer has been performed. Besides FT-IR, TGA and SEM characterizations, both the TSPM-modified silica and the polymer-filler blends have been extensively investigated by means of solid state NMR, through a combined analysis of several 29Si, 1H and 13C mono- and bi-dimensional high-resolution techniques, as well as 1H low-resolution FID analysis and spin-lattice relaxation times measurements. This allowed us to obtain detailed and quantitative information on the silica functionalization reaction, to characterize the silica-TSPM interface, and to get insights into the change of the dynamic properties of LDPE due to the presence of the filler. The NMR results and several macroscopic properties of the blend LDPE/silica-TSPM, such as Young’s modulus and oxygen permeability, were compared with those of the same blend prepared with unfunctionalized silica and of the pristine polymer.
9:00 PM - MM7.22
Dynamics of Amorphous Polymers Through a Unified Analysis of Multi Frequency 1H and 13C Spin-Lattice Relaxation Times.
Giulia Mollica 1 , Marco Geppi 1 , Claudia Forte 2 , Marco Malvaldi 1 , Carlo Alberto Veracini 1
1 Chimica e Chimica Industriale, Università di Pisa, Pisa Italy, 2 Area della Ricerca-CNR, Istituto per i Processi Chimico Fisici, Pisa Italy
Show Abstract9:00 PM - MM7.3
51V and 133Cs MAS NMR Investigation of Crystalline Trivanadate and Hexavanadate Phases. Probing the Interlamellar Space by 1H-133Cs CP MAS HETCOR Experiments.
Olivier Durupthy 1 , Jocelyne Maquet 1 , Nathalie Steunou 1 , Christian Bonhomme 1 , Thibaud Coradin 1 , Jacques Livage 1
1 Université Paris 6, Chimie de la Matière Condensée de Paris, Paris France
Show Abstract9:00 PM - MM7.4
Lanthanum Sulfate Hydrates: A Solid-State 139La NMR Investigation.
Silvia Borsacchi 1 , Kirk Feindel 2 , Kristopher Ooms 2 , Roderick Wasylishen 2 , Marco Geppi 1
1 Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Pisa Italy, 2 Department of Chemistry-Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta, Canada
Show AbstractThe dehydration and subsequent decomposition process of the rare earth metal sulfate hydrates has previously been studied. Lanthanide sulfates and their decomposition products are involved in applications including metallurgical industrial processes, storage of solar energy and nuclear heat, and fuel gas purification [1-3]. Most of the research on the dehydration process has been performed using thermal analysis techniques. Unfortunately, such techniques do not provide structural information on the sulfate hydrate intermediates making it impossible to obtain a clear picture of the dehydration process. In this study, we have used solid-state 139La NMR spectroscopy to gain insight into the dehydration process of the lanthanum (III) sulfate, La2(SO4)3●9H2O. 139La is a quadrupolar nucleus (I = 7/2) with natural isotopic abundance of 99.9% and a moderate nuclear quadrupole moment (Q = +20 fm2). Recent solid-state 139La NMR investigations of the lanthanum halides and oxo-coordinate lanthanum complexes demonstrate the value of this technique in characterizing La-containing materials [4, 5]. Various hydrates were prepared by heating commercial samples of La2(SO4)3●xH2O at different temperatures. The water content for each sample was determined by means of thermogravimetric analysis (TGA) and the effects of hydration on molecular structure were observed via acquisition of solid-state 139La NMR spectra. Simulation of the NMR spectra enabled the 139La electric field gradient and chemical shift tensor parameters to be obtained for several La sites in lanthanum sulfate nona-hydrate, different intermediate hydrates, and anhydrous lanthanum sulfate.[1] W. W. Wendlandt, J. Inorg. Nucl. Chem. 7 (1958) 51-54.[2] W. W. Wendlandt, T. D. George, J. Inorg. Nucl. Chem. 19 (1961) 245-250.[3] J. A. Poston Jr., R. V. Siriwardane, E. P. Fisher, A. L. Miltz, Appl. Surf. Sci. 214 (2003) 83-102.[4] K. J. Ooms, K. W. Feindel, M. J. Willans, R. E. Wasylishen et al., Solid State Nucl. Magn. Reson. 28 (2005) 125-134.[5] M. J. Willans, K. W. Feindel, K. J. Ooms, R. E. Wasylishen, Chem. Eur. J. 12 (2006) 159-168.
9:00 PM - MM7.5
Pulse Field Gradient NMR Investigation of Diffusion along Hexagonally Packed Rods in a Polymeric Barrier Matrix for Fuel Cell Membrane Applications.
Marcus Giotto 1 , Guoxing Lin 1 , Alana Canfield 1 , Alan Jones(*) 1
1 Chemistry Department, Clark University, Worcester, Massachusetts, United States
Show Abstract9:00 PM - MM7.6
NMR Studies of Capacity Degradation of Lithium Rechargeable Batteries.
Riqiang Fu 1 , Jim Zheng 2
1 , National High Magnetic Field Laboratory, Tallahassee, Florida, United States, 2 , Florida A&M, Tallahassee, Florida, United States
Show Abstract9:00 PM - MM7.7
Membrane Gas Diffusion Measurements with MRI.
Ziheng Zhang 1 , Bruce Balcom 1 , Alexei Ouriadov 1 , Chris Willson 2
1 MRI Centre, Department of Physics, University of New Brunswick, Fredericton, New Brunswick, Canada, 2 ElectraStor, 333 West Street, Pittsfield, Massachusetts, United States
Show Abstract9:00 PM - MM7.8
EPR Study of Electron-Donor Surface Sites on Modified Alumina Catalysts.
Dmitriy Medvedev 1 , Alexander Volodin 1 , Alexander Bedilo 1
1 , Boreskov Institute of Catalysis, Novosibirsk Russian Federation
Show Abstract9:00 PM - MM7.9
Study on the Magnetic Property of Permanent Magnet by γ-ray Irradiation.
Song Lee 1 , Young Soo Kang 1
1 Chemistry, Pukyong National Univ., Pusan Korea (the Republic of)
Show AbstractWe report how γ-ray irradiation affects magnetic properties of permanent magnets. Due to the accumulated high energy, γ-ray irradiation was used to change the magnetic properties of permanent magnets. Before and after the irradiations, the total magnetic properties were measured by using superconducting quantum interference device (SQUID). The experimental results show that the γ-ray irradiation affected the properties of permanent magnet. And the characterization was done by XRD, FE-SEM images, and VSM, etc.
Symposium Organizers
Julie Herberg Lawrence Livermore National Laboratory
Yue Wu University of North Carolina-Chapel Hill
Phil Grandinetti The Ohio State University
Sophia Hayes Washington University
Ian Farnan University of Cambridge
MM8: Magnetic Resonance Studies on Semiconductors
Session Chairs
Wednesday AM, November 29, 2006
Liberty (Sheraton)
9:30 AM - **MM8.1
Probing Semiconductor/Insulator Heterostructures Through Electron Spin Resonance of Point Defects: Interfaces, Interlayers, and Stress.
Andre Stesmans 1 , V. Afanas'ev 1
1 Physics, University of Leuven, Leuven Belgium
Show AbstractThe presentation addresses the value of electron spin resonance (ESR) spectroscopy in the atomic-scale investigation of structural, and correlated, electrical properties of actual semiconductor/insulator heterostructures. As known, the “classical” thermal (100)Si/SiO
2 unit still constitutes the foremost basic building bloc of current metal-oxide-silicon (MOS) based integrated circuits (ICs). A categorical must for realization of any device-grade MOS entity is the absolute control, i.e., elimination to subcritical levels, of charge traps, i.e., structural faults both at critical interfaces and in the bulk of insulating layers. As known from the hallmark Si/SiO
2 case, point defects were demonstrated or hinted as the origin of virtually all electrical imperfections. A notorious class here are the ESR-detected Si dangling bond type interface defects (Pb centers) occurring naturally in thermally grown Si/SiO
2, admittedly because of interface mismatch. They were shown electrically to be detrimental charge traps. Yet, as a “positive” attribute, being naturally incorporated right at the interface, they may serve as probes utmost sensitive to the local environment –a unique criterion of the (electrical) quality of the interface and its behavior during thermal treatments. The relentless scaling in IC technology projects drastic changes. A most challenging one dictates replacement of the conventional SiO
2 gate by an alternative dielectric of higher dielectric constant κ. This raises formidable new technological issues, not the least the control of detrimental charges traps in crucial interfacial layers. Basic insight here may appear essential, for which ESR has proven indispensable. So, in a first part, partly based on the Pb fingerprint, an overview will be presented of ESR results on stacks of (100)Si with nm-thin layers of high-κ insulators (Al
2O
3, HfO
2, ZrO
2, LaAlO
3) grown using various deposition methods, with particular emphasis on occurring defects in interlayers. Examples will be given of exquisite mapping of the evolution of the nature of the interfacial under thermal treatment through ESR monitoring of incorporated point defects. Next, as unique ESR probing, the impact of in situ applied in-plane mechanical stress during thermal oxidation of (111)Si will be discussed, showing the properties of the inherent Pbs at the Si/SiO
2 interface to be distinctly affected. Stepping from this basis, investigation of biaxially tensile strained (100)Si/SiO
2 entities reveals a drastic reduction in detrimental point defects in interfacial layers. Touching fundamental properties such as carrier mobility enhancement, 1/f noise, etc., it exposes one more basic aspect of the beneficial influence of prestraining Si, a route taken to enhance channel carrier mobility in Si-based ICs. A final part will address ESR identification of critical impurity related defects.
1International Technology Roadmap for Semiconductors, 2003 ed. (SIA, Austin, TX)
10:00 AM - MM8.2
Multifrequency ESR Investigations of the Point Defects in Superhard, Diamond-like Cubic Boron Nitride Crystalline Powders.
Vasile Nistor 1 , Daniela Ghica 1 , Mariana Stefan 1 , Etienne Goovaerts 2 , Auguste Bouwen 2
1 Lab. Microstructure of Defects in Solid Materials, National Institute for Materials Physics, Magurele-Bucuresti Romania, 2 Department of Physics, University of Antwerp, Antwerp Belgium
Show Abstract10:15 AM - MM8.3
Electrically Detected Magnetic Resonance Study of High-κ/Semiconductor Interfaces.
Marco Fanciulli 1 , Silvia Baldovino 1 , Gabriele Seguini 1 , Sabina Spiga 1
1 MDM National Laboratory, CNR-INFM, Agrate Brianza (MI) Italy
Show AbstractThe scaling down of modern nano-electronic devices, based on a MOS structure, has motivated an intense activity on high-κ dielectrics. Although a large number of materials have been investigated, candidates suitable for the scaling down to the 32 nm node and beyond have not been identified yet. Among the several parameters which must be optimized we have the dielectric constant (around 25-35), the band offsets (CBO > 1 eV), the thermo dynamical stability, and the interface control. Not only silicon, but also high-mobility substrates such as Ge, despite the lower junction breakdown voltage and difficulties in the etching steps, and GaAs are now reconsidered for MOSFET applications due to the availability of a variety of insulating materials [1]. Among the most important deposition methods we find atomic layer deposition (ALD) and molecular beam epitaxy (MBE).Defects at the semiconductor/high-k interface and in the dielectric layers play a crucial role in determining the device performance. There is a need to identify the microscopic structure of electrically active point defects in the dielectric and at its interface with the semiconductor.Conventional electron spin resonance spectroscopy (ESR), one of the most powerful spectroscopy techniques for the investigation of point defects in semiconductors and insulators, suffers from sensitivity problems when dealing with state-of-the-art test devices due to their total area as well as low density of defects, both in the bulk as well as at the interface. Electrically detected magnetic resonance (EDMR) spectroscopy, in its various implementations, provides higher sensitivity and has also the intrinsic advantage of the selectivity for electrically active defects. These techniques rely on the detection of a certain electrical parameter (photo-current, capacitance, and tunneling current) of the device under investigation in spin resonance conditions [2, 3]. Experimental results obtained by different versions of EDMR on the semiconductor/dielectric interface will be presented and discussed. The EDMR results will be also compared with those obtained with conventional electrical techniques (C-V, G-V). The investigated systems will be high-k dielectrics (Al2O3, HfO2, Lu2O3, STO) grown by ALD or MBE on different semiconductor substrates (Si, SiGe, Ge, GaAs). Results on the oxidation mechanism(s) on the semiconductor surface will be also presented. [1] M. Fanciulli, S. Spiga, G. Scarel, G. Tallarida, C. Wiemer, G. Seguini, Mat. Res. Symp. Proc. Vol. 786, E6.14 (2004).[2] S. Baldovino, S. Nokhrin, G. Scarel, M. Fanciulli, T. Graf, and M.S. Brandt, J. of Non-Cryst. Solids, 322, 168 (2003).[3] M. Fanciulli, O. Costa, S. Baldovino, S. Cocco, G. Seguini, E. Prati, and G. Scarel, NATO Series book on "Defects in High-k Gate Dielectric Stacks", Vol. 220, p. 263 (2005).
MM9: Magnetic Resonance Studies on Polymers
Session Chairs
Wednesday PM, November 29, 2006
Liberty (Sheraton)
10:45 AM - **MM9.1
Low-Field NMR Approaches for the Characterization of Polymer Materials.
Kay Saalwachter 1
1 Fachbereich Physik, Martin-Luther Universitaet Halle-Wittenberg, Halle Germany
Show AbstractWe have recently established proton multiple-quantum NMR at low field as a reliable and quantitative method to study elastomer microstructure, structural heterogeneities, and chain dynamics [1]. Recent work includes quantitative relationships between the NMR observables and the cross-link density of diene rubbers [2] and the analysis of chain dynamics in the same type of systems [3]. Some of our findings are in marked contrast to earlier observations, and suggest that a number of models commonly used to analyze chain motion in elastomers (and ultimately to explain their mechanical behavior) are in need of revision. In this contribution, I will further demonstrate the application of MQ-NMR to gel-point determination and the quantitative analysis of systems that gel in dilute solution and in the bulk. New low-field developments include robust and reliable approaches to determine the crystallinity and monitor the crystallization kinetics as well as the mobile-phase mobility in semicrystalline polymers [4], as well as spin-diffusion studies of the domain size in block copolymers.[1] KS, J. Am. Chem. Soc. 125 (2003) 14684.[2] KS, B. Herrero, M. A. López-Manchado, Macromolecules 38 (2005) 9650-9660.[3] KS, A. Heuer, Macromolecules 39 (2006) 3291-3303.[4] A. Maus, C. Hertlein, KS, Macromol. Chem. Phys. 207 (2006) 1150-1158.
11:15 AM - MM9.2
Probing the Dynamics of Polymers in Nanolayered Films Via Solid State NMR.
Christopher Klug 1 , Eric Baer 2 , Anne Hiltner 2
1 Chemistry Division, Naval Research Laboratory, Washington , District of Columbia, United States, 2 Department of Macromolecular Science, Case Western Reserve University, Cleveland, Ohio, United States
Show Abstract11:30 AM - **MM9.3
Characterization of Polymer Fluids Using Distant Dipolar Field Effects.
Marcel Utz 1 , Priyanga Bandara 2 3
1 Department of Mechanical And Aerospace Engineering, University of Virginia, Charlottesville, Virginia, United States, 2 Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 3 Department of Physics, University of Connecticut, Storrs, Connecticut, United States
Show AbstractThe quantitative observation of distant dipolar field (DDF) echoes in polymer melts is reported. Distant dipolar field effects, also referred to as intermolecular multiple-quantum coherences (iMQC), have been shown to contain structural information on the spatial distribution of the spin density in the sample. So far, such effects have been explored mainly in the context of liquids composed of small molecules. In these systems, the spin-spin relaxation times are typically comparable to the buildup times for DDF echoes. However, the achievable resolution is limited by self-diffusion to approximately 10 µm. As our work demonstrates, DDF echoes can be observed and quantified also in polymer melts, where the T2 relaxation times are of the order of only a few ms. This requires the use of very strong gradient pulses, which must be carefully calibrated. Due to the slower self-diffusion in polymers, much smaller length scales can be probed. This makes the approach promising for the structural characterization of block copolymers, phase transition processes, and polymer nano-composites.As a proof of principle, we have studied the DDF response from suspensions of poly(tetrafluoro ethylene) (PTFE) beads of various sizes in poly(isobutylene) (PIB). The resulting spin-density autocorrelation functions are compared to those expected from random packings of uniform spheres. In addition, theoretical considerations of the use of DDF experiments to study phase transitions in polymer fluids are discussed.
12:00 PM - MM9.4
NMR Multi-Scale Description of Ionic Conductivity Mechanisms in Polymer Electrolytes.
Patrick Judeinstein 1 , Tito Bonagamba 2 , Eduardo Ribeiro de Azevedo 2 , Detlef Reichert 3 , Thomas Brauniger 3 , Terry Gullion 4
1 RMN en Milieu Orienté, ICMMO, CNRS, Orsay France, 2 Instuto de Fisica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos, SP, Brazil, 3 Department of Physics, University of Halle, Halle Germany, 4 Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States
Show Abstract12:15 PM - MM9.5
Diffusive Diffraction in a Porous Polymer Material by NMR Using a Radio-frequency Field Gradient (B1 gradient).
Pierre Mutzenhardt 1 , Daniel Canet 1 , Gregory Trausch 1 , Jean-François Kuntz 2 , Pascal Palmas 2
1 , Université Henri Poincaré, Vandoeuvre les Nancy France, 2 , Commissariat à l’Energie Atomique , Monts France
Show Abstract12:30 PM - MM9.6
Introduction to SWIFT (Sweep Imaging with Fourier Transformation) for Magnetic Resonance Imaging of Materials.
Curtis Corum 1 , Djaudat Idiyatullin 1 , Jang-Yeon Park 1 , Michael Garwood 1
1 Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States
Show Abstract12:45 PM - MM9.7
Penetrant Diffusion in Triblock Polymer by Pulse-field-gradient NMR Measurements and Lattice Model Simulation.
Xueqian Kong 1 , Tabitha Hargrove 1 , Sara Ouellette 1 , Darryl Aucoin 1 , Guoxing Lin 1 , Alan Jones* 1
1 Carlson School of Chemistry and Biochemistry, Clark University, Worcester, Massachusetts, United States
Show AbstractMM10/OO10: Joint Session: Magnetic Resonance Studies on Actinides
Session Chairs
Julie Herberg
Bruce McNamara
Wednesday PM, November 29, 2006
Liberty (Sheraton)
2:30 PM - **MM10.1/OO10.1
NMR Spectroscopy and the Testing of Ab Initio Relativistic Electronic Structure Theory: Recent Results for Uranyl Salts.
Herman Cho 1 , Wibe de Jong 2 , Chuck Soderquist 3 , Bruce McNamara 3
1 Fundamental Science Directorate, Pacific Northwest National Laboratory, Richland, Washington, United States, 2 Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, United States, 3 Environmental Technology Directorate, Pacific Northwest National Laboratory, Richland, Washington, United States
Show Abstract3:00 PM - **MM10.2/OO10.2
A 23Na and 133Cs MAS NMR Study of the Structural Transformations of Microcrystalline MxWO3+x/2.ZH2O Hexagonal Tungsten Bronze and NaW2O6.2H2O Cubic Tungsten Pyrochlore Systems.
John Hanna 1 , Victor Luca 1 , Christopher Griffith 1 , Kevin Pike 1 , Andrew Howes 2 , Mark Smith 2 , Thibault Charpentier 3
1 Institute of Materials Science & Engineering, ANSTO, Menai, New South Wales, Australia, 2 Dept. of Physics, University of Warwick, Coventry , Warwickshire, United Kingdom, 3 Laboratoire de Structure et Dynamique par Résonance Magnétique, Commissariat à l’Energie Atomique , Saclay France
Show AbstractLow temperature (25-600 oC) thermal transformation in hydrothermally-prepared microcrystalline hexagonal tungsten bronze compounds (AxWO3.2H2O where A is an exchangeable cation located in hexagonal channels of the structure) are studied as a function the exchangeable tunnel cation composition. Thermal treatments in air were studied using conventional laboratory-based X-ray diffraction while vacuum heating was studied by synchrotron X-ray diffraction and neutron diffraction. For the sodium form of the bronze, cell volume contraction occurs from room temperature to about 350 oC; this is the regime in which water is squeezed from the tunnel sites. This is followed by a cell volume expansion throughout the 350–600 oC temperature range. Over this entire temperature range studied a net thermal contraction in cell volume is observed due to anisotropic variations in the cell dimensions in which the c-dimension contracts more than the concomitant expansion in the a-direction. These changes explain why Cs+ ions are locked into tunnel positions at temperatures as low as 400 oC resulting in a significant reduction in extractability in nitric acid. While similar effects are observed for the as-prepared Na+-exchanged sample, the smaller radius of this cation causes it to be relatively easily removed under corresponding acidic conditions. 23Na MAS and MQMAS NMR have been used to investigate the sodium speciation and local order/disorder phenomena induced in the channel sites of the unsubstituted Na-tungsten bronze via a dynamic equilibrium with intercalated H2O and OH-. The speciation changes with thermal transformation and eventual phase transition over the 25-600 oC temperature range reported. Similarly, 23Na and 133Cs MAS NMR has been used to investigate the same phenomena in the Cs-substituted Na-tungsten bronze. These results corroborate the observations from quantitative Cs uptake measurements that the theoretical maximum Cs uptake in these systems is never achieved, and that the residual Na speciation after Cs incorporation demonstrates significantly increased short-range positional order. Low temperature thermal transformations in the hydrothermally-prepared microcrystalline defect pyrochlore system NaW2O6.2H2O have also been studied. In contrast, the zig-zag pseudo-tetrahedral channel sites of this structure afford very little discernable order with respect to Na speciation within these channels. 23Na MAS and MQMAS NMR studies show that some dynamic equilibrium between Na+ and H2O/OH- channel species also exists in similar fashion to the hexagonal W-bronze system, however, the overall complexion of the Na speciation is quite different from that of the hexagonal W-bronze. Preliminary investigations of Cs uptake and retention in the thermally treated defect pyrochlore (~600 oC) showed that very favourable Cs leach characteristics can be achieved with this system.
4:00 PM - MM10/OO10
BREAK
4:30 PM - **MM10.4/OO10.4
Identifying and Quantifying Actinide Radiation Damage in Ceramics with Radiological Magic-Angle Spinning Nuclear Magnetic Resonance.
Ian Farnan 1 , Herman Cho 2 , William Weber 2
1 Earth Sciences, Cambridge University, Cambridge United Kingdom, 2 EMSL, Pacific Northwest National Laboratory, Richland, Washington, United States
Show AbstractIn the characterisation of amorphisation or local disordering due to actinide radiation damage, nuclear magnetic resonance (NMR) spectroscopy is attractive because it is element specific and equally sensitive to local structure in crystalline and amorphous materials. We have applied high-resolution solid-state NMR spectroscopy (magic-angle spinning) to radiation damaged natural minerals containing 238U/232Th to determine the ‘number fraction’ of amorphous material (fa) through spin-counting techniques. In samples with a known alpha dose, the number of atoms displaced per alpha decay may be determined from an integration of the spectrum. We have developed a protocol for performing similar magic-angle spinning experiments on plutonium containing ceramic samples with an activity of > 5 GBq. Results obtained have allowed data from ancient, radiation damaged mineral samples of ZrSiO4 (238U/232Th) to be compared with modern 238/239Pu doped ceramic ZrSiO4 samples. The number of atomic displacements per alpha particle from 239Pu is similar to that for 238U/232Th (4980 ± 300/α). At lower α-doses there are significant differences in the amorphous volume fraction (observed by density and x-ray diffraction) and the number fraction of displaced atoms (as measured by NMR) as a function of cumulative dose. These differences arise from local density considerations that manifest themselves in the local structure of the amorphous and crystalline phases. Using ab initio simulations of the damaged crystalline and amorphous regions, the magnetic response of these structures and hence the NMR shifts can be compared with experiment to reveal the nature of radiation induced changes occurring at the local scale.
5:00 PM - **MM10.5/OO10.5
A Review of the Contributions of Electron Paramagnetic Resonance Spectroscopy to Actinide Science.
Lynn Boatner 1
1 MSTD, Oak Ridge National Lab., Oak Ridge, Tennessee, United States
Show Abstract5:30 PM - **MM10.6/OO10.6
Rotating Microdetectors for Nuclear Magnetic Studies of Radioactive Materials.
Dimitris Sakellariou 1
1 DSM/DRECAM/SCM/LSDRM, CEA-Saclay, Gif-sur-Yvette France
Show Abstract
Symposium Organizers
Julie Herberg Lawrence Livermore National Laboratory
Yue Wu University of North Carolina-Chapel Hill
Phil Grandinetti The Ohio State University
Sophia Hayes Washington University
Ian Farnan University of Cambridge
MM11: Magnetic Resonance Studies on Dielectrics, Thin Films, and Spintronics
Session Chairs
Thursday AM, November 30, 2006
Liberty (Sheraton)
9:30 AM - **MM11.1
NMR and OPNMR Studies of Semiconductor Thin Films and Quantum Wells.
Sean Barrett 1
1 Physics Dept., Yale University, New Haven, Connecticut, United States
Show Abstract10:00 AM - MM11.2
Current Induced g-factor Shift in Modulation Doped Si Quantum Wells.
Hans Malissa 1 , Wolfgang Jantsch 1 , Zbyslaw Wilamowski 2
1 Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Linz Austria, 2 Institute of Physics, Polish Academy of Sciences, Warsaw Poland
Show Abstract10:15 AM - **MM11.3
Dynamic Nuclear Polarization and NMR Spectroscopy in GaAs/AlGaAs Quantum Wells in the Quantum Hall Regime.
Clifford Bowers 1
1 Chemistry, Unversity of Florida, Gainesville, Florida, United States
Show Abstract10:45 AM - MM11.4
Properties of the Two-Dimensional Electron Gas Confined in GaN/AlGaN Interface Studied by Electron Spin Resonance.
Agnieszka Wolos 1 , W. Jantsch 1 , K. Dybko 2 , Z. Wilamowski 2 1 , Cz. Skierbiszewski 3
1 Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Linz Austria, 2 Institute of Physics, Polish Academy of Sciences, Warsaw Poland, 3 High Pressure Research Center, Unipress, Polish Academy of Sciences, Warsaw Poland
Show AbstractGaN-AlGaN heterostructures, apart from their well known potential in blue optoelectronics and high-frequency electronics might offer also attractive features in the context of spintronics. In particular, owing to the low spin-orbit interaction, they may offer long electron spin coherence times, highly desired to maintain the information stored in electron spins. In addition, transition metal doped GaN is one of the predicted candidates for room temperature ferromagnetism. In order to establish GaN-AlGaN heterostructures in spintronics the spin properties of conduction electrons in these materials need to be investigated. In this communication we report results of electron spin resonance (ESR) investigations of the two-dimensional (2D) electron gas in GaN/AlGaN quantum wells. The samples used in our studies have been grown by plasma-assisted molecular beam epitaxy on bulk GaN substrates. The two-dimensional electron gas formed at the GaN/AlGaN interface exhibits mobility values of up to 70.000 cm2/Vs at 2 K owing to the high quality and low dislocation density of the bulk substrates used. The high mobility value is an essential prerequisite for investigations of free electrons by ESR techniques.The ESR measurements of high-mobility GaN/AlGaN heterostructures show simultaneously spin resonance, Shubnikov-de Haas oscillations and a coupled plasmon-cyclotron resonance due to the 2D electron gas at the GaN/AlGaN interface. Shubnikov-de Haas oscillations allow to determine the sheet carrier density in our samples of typically 2*1012 cm-2. The spin resonance is seen as an extraordinarily narrow resonance line (peak-to-peak width of 0.5 G) which is characteristic for delocalized carriers and their motional narrowing. This ESR line allows to determine the g-factor and its anisotropy, which appear to be strongly temperature-dependent. The observed effects are discussed in terms of Bychkov-Rashba and Dresselhaus spin-orbit coupling mechanisms. We have also investigated the electron spin relaxation time T1 in GaN/AlGaN, which is of the order of 10-5 s.
11:00 AM - MM11.5
Molecular Insights on Mesostructured Inorganic-Organic Materials Processing for Optical Applications.
Chris Steinbeck 1 3 , Matthias Ernst 2 , Beat Meier 2 , Brad Chmelka 1
1 Department of Chemical Engineering, University of California, Santa Barbara, California, United States, 3 Department of Biochemistry, Brandeis University, Waltham, Massachusetts, United States, 2 Physical Chemistry, ETH, Zurich Switzerland
Show AbstractInorganic-organic hybrid materials exhibiting mesostructural ordering are attractive host matrices for the inclusion of optically responsive guest species. These materials combine the beneficial properties of both the structure-directing block copolymer species (high organic dye solubilities) and inorganic components (mechanical and thermal stability).
1 In addition, long-range alignment of the mesostructured host matrix, such as obtained by spin coating, can orient included chromophores and yield composite materials with anisotropic optical properties.
One of the challenges in designing such systems and optimizing synthesis conditions is determining where specific guest species are localized in the composite material and how different conditions affect their locations, which may crucially affect the performance of the final device. Molecular-level design and processing insights can be obtained from powerful solution- and solid-state nuclear magnetic resonance (NMR) spectroscopy measurements, especially when correlated with macroscopic material properties. In particular, heteronuclear correlation experiments and pulsed-field-gradient diffusion NMR measurements, in combination with Hadamard-encoding for rapid signal acquisition,2 elucidate important interactions among molecular species present under different processing conditions. Specifically, for example, interactions between optically responsive porphyrin dye species and structure-directing block-copolymer species are shown to be highly composition- and temperature-dependent in precursor solutions.3 In addition, solid-state NMR experiments conducted under ultra-fast magic-angle-spinning conditions (45 kHz) establish that the dilute (~5 wt%) dye guest species associate principally with the hydrophilic copolymer moieties in the final mesostructured inorganic-organic host product. Such information is typically not obtainable from optical absorption spectra or conventional NMR experiments, for which spectral resolution is usually poor or signal sensitivity weak, respectively. The resulting molecular insights are specifically correlated with the macroscopic optical properties for aligned mesostructured poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer-silica composites containing optical limiting tetra(4-sulfonatophenyl)porphyrin dye species.
It is thus shown that modern NMR experiments can provide the molecular level information required for rationally improving the synthesis conditions and performance characteristics of complex mesostructured iorganic-organic materials.
1 N.A. Melosh, C.A. Steinbeck, B.J. Scott, R.C. Hayward, P. Davidson, G.D. Stucky, B.F. Chmelka, J. Phys. Chem. B, 108(32):11909-11914 (2004)
2 C.A. Steinbeck, B.F. Chmelka, J. Am. Chem. Soc, 127(33):11624-11635 (2005)
3 C.A. Steinbeck, N. Hedin, B.F. Chmelka, Langmuir, 20(24):10399-10412 (2004)
MM12: Magnetic Resonance Studies on Glasses, Ceramics, Sol-gel, and Colloids I
Session Chairs
Thursday PM, November 30, 2006
Liberty (Sheraton)
11:30 AM - **MM12.1
Solid State NMR as a probe of Inorganic Materials:Examples from Glasses, Catalytic Materials and Nanoparticles.
Mark Smith 1
1 Physics, University of Warwick, Coventry United Kingdom
Show Abstract12:00 PM - MM12.2
Measuring Correlated Structure Distributions in Amorphous Solids.
Philip Grandinetti 1
1 Chemistry, Ohio State University, Columbus , Ohio, United States
Show AbstractThe T-O-T bond angle distribution is often considered to be one of the first structural distinction between amorphous and crystalline forms of tetrahedral oxide glasses and is an important criterion for any proposed non-crystalline structural model of these materials.Over the years we and others have established and uantified strong correlations between O-17 quadrupolar coupling parameters and first coordination sphere structural features in tetrahedral oxide materials such as the T-O-T bridging bond angle, the T-O distance, and the number of coordinating modifier cations. Using the two- dimensional isotropic-anisotropic interaction separation of Dynamic- Angle Spinning(DAS) we have measured the distribution of O-17 quadrupolar coupling constants, asymmetry parameters, and isotropic chemical shifts for the bridging oxygen in a number of O-17 enriched glasses produced from the melt. In an analysis of the O-17 DAS results of a number of inorganic oxide glasses, we have obtained not only the T-O-T bond angle distribution but also the T-O and T-T distance distributions as well as the two dimensional distribution of T-O-T angles and T-O distances. The implication of these measured distribution on the glass structure will be discussed.
12:15 PM - MM12.3
Structure and Phase Development in Glass-Ceramics and Their Base Glasses.
Randall Youngman 1 , Bruce Aitken 1 , Carrie Hogue 1 , Matthew Dejneka 1
1 Science & Technology, Corning Incorporated, Corning, New York, United States
Show AbstractSince their discovery in the 1950’s, glass-ceramics have become an important material for many different applications. Classic examples of commercial glass-ceramics include CorningWare®, Macor®, Keraglas® and Visions® cookware. The key attribute of glass-ceramics such as these is the ability to combine the properties of conventional sintered ceramics with the favorable processing and other characteristics of glasses. These materials are typically formed from a base glass by controlled crystallization of at least one crystal phase. Therefore an understanding of glass structure and compositional effects on the resulting glass-ceramic are key to development of new materials.Self-nucleating glass-ceramics can be fabricated from binary SiO2-P2O5 glasses, the resulting material consisting of a fine-grained SiP2O7 glass-ceramic with a silica-rich glassy phase. These SiP2O7 crystals are one of the few phases stable at atmospheric pressure in which Si is octahedrally coordinated by O. Despite the fact that Si is almost invariably four-fold coordinated by O in oxide glasses, the SiP2O7 crystalline phase can be easily formed in this system. 29Si NMR data show small quantities of SiV and SiVI in the binary base glasses, although their concentrations depend greatly on composition. Upon heat treatment, the SiV (SiVI) fraction decreases (increases) and all SiV groups are eventually depleted. Moreover, the residual glass gives rise to a 29Si NMR resonance which is less shielded than the tetrahedral Si resonance in the base glass, indicating a gradual depletion in P next-nearest neighbors. 31P NMR spectroscopy of these materials shows the precursor and nucleated glasses to contain tetrahedral O=PO3/2 species, while the spectra of the crystallized glass-ceramics are characterized by both a broad “glassy” peak and at least 7 sharp “crystalline” peaks with chemical shifts ranging from -50 to -75 ppm. The latter are diagnostic of the cubic polymorph of SiP2O7, in agreement with results from X-ray diffraction.Multinuclear NMR spectroscopy has also been invaluable in understanding the growth of LaF3 crystallites in heat-treated aluminosilicate glasses. 19F NMR confirms the LaF3 crystalline phase and shows changes in LaF3 content with both heat treatment and base glass composition. These results also reveal that only a portion of the total F is used to form LaF3, with some F remaining in the glassy matrix, where further study shows both Si-F and Al-F bonding, depending on the type of network modifier.NMR studies of glass-ceramics are complementary to X-ray diffraction in that these data typically identify the crystalline phases, but of particular importance, NMR also allows us to understand the base glass and any residual glassy matrix that may exist in the final material. NMR results on the base glasses may also contain details on precursor structural environments related to these crystalline phases which are often undetected with X-ray diffraction.
12:30 PM - MM12.4
Solid-state NMR Investigation of Metal Oxide Nanomaterials.
Gregory Holland 1 , Ramesh Sharma 1 , Daniel Grohol 2 , Jacob Angola 2 , Virgil Solomon 1 , Samrat Amin 2 , Daniel Buttry 2 , Jeff Yarger 1
1 Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, United States, 2 Department of Chemistry, University of Wyoming , Laramie, Wyoming, United States
Show Abstract12:45 PM - MM12.5
Oxide Glass Structure: New Insights from High-Resolution Oxygen-17 NMR.
Jonathan Stebbins 1
1 Geological and Environmental Sciences, Stanford University, Stanford, California, United States
Show AbstractHigh-resolution solid-state NMR of oxygen-17 has proven to be an especially useful method to address fundamental questions about the network structure of oxide glasses, providing an “anionic” perspective that complements more common views of short-range cationic environments. One-dimensional magic-angle spinning (MAS) NMR at relatively high fields and high sample spinning speeds, and, especially, two-dimensional triple-quantum MAS NMR (3QMAS), have thus opened new doorways to understanding glass structure and its links to macroscopic glass and liquid properties.Examples of new types of information gained from this approach include recent studies of the ordering and network connectivity in borosilicate, aluminoborate, aluminosilicate and more complex glasses, where in many cases O-17 3QMAS NMR can be used to count the relative fractions of various oxygen bridges directly, such as Si-O-Si, B-O-Si, B-O-B, Al-O-Al, Al-O-Si, etc. Such results often reveal significant cation ordering, for example that related to the energetic unfavorability of oxygen coordination by two tetrahedral, trivalent cations. When such ordering is present at the glass transition temperature (as sampled by spectroscopy on glasses at ambient temperature), it allows the possibility of increased disorder at higher temperatures, which can have major effects on properties of glass-forming liquids (viscosity, phase equilibria, etc.) Temperature effects on network ordering have now been quantified in glasses prepared with different quench rates and thus different fictive temperatures, in aluminosilicates, borosilicates, oxyfluorides, and multicomponent compositions. Recent work on aluminosilicate and borosilicate glasses quenched from melts at pressures up to 10 GPa provides new insights into structural mechanisms of densification, where increase in coordination of network cations (B, Al, Si) are often accompanied by reduction in content of non-bridging oxygen (NBO).In new studies of alkali germanate glasses, O-17 3QMAS NMR reveals changes in non-bridging oxygen content with composition, thus directly confirming the “classical” picture of delay in NBO formation until about 18% alkali oxide content is reached. Data on crystalline model compounds have defined separate ranges of chemical shift for oxygens bridging between various combinations of 4- and 6-coordinated Ge. Application of these systematics to glasses confirms as well the necessary complement to delayed NBO formation, that the mean coordination number of Ge must increase above 4.
MM13: Magnetic Resonance Studies on Semiconductors
Session Chairs
Thursday PM, November 30, 2006
Liberty (Sheraton)
2:30 PM - **MM13.1
Magnetic Resonance Studies of MOSFETs Based on Alternative Materials.
Patrick Lenahan 1
1 Engineering Science and Mechanics, Penn State University, University Park, Pennsylvania, United States
Show AbstractMetal oxide semiconductor (MOS) field effect transistors (MOSFETs) have dominated solid state electronics for more than thirty years. Until very recently, the oxide in these devices has been silicon dioxide, the semiconductor silicon. During the past few years great progress has been made in developing MOSFET technology with alternative materials, that is, different insulators and semiconductors. As the gate insulator, hafnium oxide offers considerable potential advantages due to a dielectric constant much higher than that of SiO2. Several semiconductors offer potential advantages over silicon under certain circumstances, among them are silicon carbide, germanium, and some III-V compounds. This presentation will deal with both electrically detected magnetic resonance (EDMR) and conventional electron spin resonance (ESR) studies of MOS devices based on alternative materials. The EDMR measurements have bee made via spin dependent recombination (SDR) in fully processed transistors. The SDR/EDMR measurements achieve sensitivities of order one thousand paramagnetic sites, thus allowing measurements on fully processed devices of reasonably high quality. The presentation will focus primarily upon HfO2/Si and SiO2/SiC based devices.
3:00 PM - MM13.2
High 29Si Nuclear Spin Polarization Using Low Temperature DNP in Silicon Powder and Crystal Samples.
Anatoly Dementyev 1 , Chandrasekhar Ramanathan 2 , David Cory 1 2
1 Francis Bitter Magnet Lab, MIT, Cambridge, Massachusetts, United States, 2 Department of Nuclear Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractWe will present our recent DNP and ESR measurements in silicon powder (particle size 1-5 microns) and doped silicon crystals. We have extended earlier DNP experiments in silicon to low temperatures (~1.1 Kelvin) and higher magnetic field (2.35 Tesla) and have achieved 29Si nuclear spin polarization of about 5 %, higher than any previously reported results. Our ESR measurements and DNP microwave frequency dependence have suggested that unpaired electrons in silicon powder are due to dangling bonds on the surface of the particles. Nuclei close to the surface become polarized by forced electron-nucleus spin flips driven by off-resonant microwave radiation (“solid effect”) while nuclei in the center of the particles are polarized by spin diffusion.The dramatic changes in the NMR lineshape as a function of microwave irradiation time provide additional information about distribution of dangling bonds in the particles. For the very long microwave irradiation times (> 1hour) the NMR line consists of a broad line from nuclei close to impurities and a sharp line from nuclei in the center of the particles. Using multipulse NMR sequences, we have effectively separated inhomogeneous and homogeneous contributions to the lineshape.
3:15 PM - MM13.3
Electron Paramagnetic Resonance Study of Silicon Nano-crystal Memory Structures.
Jason Ryan 1 , Patrick Lenahan 1 , Edward Macdonald 1
1 , The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractThe use of very small silicon crystals (mean diameter <10 nanometers) has great potential advantages with regard to trap assisted tunneling problems in flash memories. The trap assisted tunneling process, which likely proceeds through silicon dioxide E’ centers, limits the period of time during which the memory devices can retain information. We will present results of electron paramagnetic resonance (EPR) measurements on flash memory structures silicon/silicon dioxide/silicon nano-crystal/silicon dioxide. EPR measurements have been made before and after the structures have been subjected to flooding with electrons and with holes and also before and after the structures have been subjected to very high electric field stressing. The densities of several paramagnetic centers are greatly altered by the various charge injection and stressing sequences. A comparison of EPR and “electronic” measurements provides some physical insight into the roles several paramagnetic point defects play in the operation of these potentially important nano-crystal devices.
MM14: Magnetic Resonance Studies on Glasses, Ceramics, Sol-gel, and Colloids II
Session Chairs
Thursday PM, November 30, 2006
Liberty (Sheraton)
4:00 PM - MM14.1
17O Solid-state NMR Study of Phosphate Glasses: Methodology and Applications.
Laurent Delevoye 1 , Lionel Montagne 1 , Gregory Tricot 1 , Jean-Paul Amoureux 1 , Gérard Palavit 1
1 , UCCS, Villeneuve d'Ascq France
Show Abstract4:15 PM - MM14.2
Solid-State NMR studies of Rare Earth Aluminosilicate Glasses.
Joseph Sachleben 1 , Alexanne Holcombe 1
1 Department of Chemistry and Biochemistry, Otterbein College, Westerville, Ohio, United States
Show AbstractRare earth aluminosilicate glasses are important optical materials and are models of radioactive waste storage systems. We are using fluorescence resonance energy transfer (FRET) and one- and two-dimensional solid-state nuclear magnetic resonance (NMR) spectroscopy to characterize these glasses. FRET provides us with the average distance between the rare earth metals as a function of their mole percentage. 29Si and 27Al NMR of mixed Y and Sm aluminosilicate glasses is sensitive to the distance between the nucleus and the paramagnetic Sm3+. The magnetic field created by the unpaired electrons of the Sm3+ broadens the 29Si NMR resonance and leads to a powder pattern that is similar to that caused by the chemical shift anisotropy (CSA). The paramagnetic anisotropy, δpara, is related to the distance between the Sm3+ and the 29Si nucleus, while the paramagnetic asymmetry parameter, ηpara, is related to both the distance and the symmetry of the distribution of the Sm3+ atoms around the silicon site. We will present 2D-PASS experiments (a 2-D experiment that correlates the infinite spinning frequency MAS spectrum with the spinning sideband patterns) of 29Si in Y, Sm, and mixed aluminosilicate glasses. These spectra provide information about the distribution of Sm3+ ions around the 29Si in these important glasses.
4:30 PM - MM14.3
93Nb Solid State NMR of High Surface Area Niobium Oxides.
Xuefeng Wang 1 , Luis Smith 1
1 Chemistry, Clark University, Worcester, Massachusetts, United States
Show Abstract4:45 PM - MM14.4
Ferromagnetic Resonance in Metallic Glasses.
Mircea Chipara 1 , Monica Sorescu 2 , Septimiu Balascuta 3 , Jeffrey Zaleski 3
1 Physics and Geology, University of Texas Pan-American, Edinburg, Texas, United States, 2 Physics, Duquesne University, Pittsburgh, Pennsylvania, United States, 3 Chemistry, Indiana University , Bloomington, Indiana, United States
Show Abstract5:00 PM - MM14.5
Dipolar and J- Derived Solid State NMR Techniques and First Principles Calculations Applied to the Structure of Silicophosphates and to the Characterization of Phosphonate Grafting on Silica Nanoparticles.
Christian Bonhomme 1 , Cristina Coelho 1 , Nadia Benyarbah 1 , Christel Gervais 1 , Thierry Azais 1 , Laure Bonhomme Coury 1
1 , Universite P et M Curie, Paris France
Show AbstractSilicophosphate gels and derivatives can act as useful biocompatible materials in various medical fields such as bone repair. Solid state NMR appears as a valuable tool of investigation for establishing connectivities in both crystalline and amorphous phases. 2D correlations experiments are based on dipolar and J-coupling interactions.We present full assignments of complex mixtures of silicophosphate phases through 2D 31P/29Si HETCOR MAS experiments [1]. Model compounds such as Si5P6O25 or SiP2O7 were used for the set up of J-derived sequences such as 31P/29Si J-HMQC-MAS experiment [2] and 31P/29Si INEPT-MAS experiment. In the case of the HMQC experiment, a spectacular gain in resolution in the 29Si dimension was observed, as well as potentialities in spectral edition. The 2J31P-29Si coupling constants have been precisely measured by using full 31P/29Si INEPT evolution curves taking into account complex SI4 and SI6 spin systems for 4-fold and 6-fold coordinated Si atoms, respectively. In the case of SI6 systems, two different J coupling constants were measured, corresponding to crystallographic inequivalent J-pathways.All experiments were extended to the precise study of amorphous silicophosphate gels by using 31P/29Si double and triple 1H/31P/29Si CP MAS experiments [3-4]. Dynamical processes leading to a partial reduction of the CP transfer under MAS were encountered.Finally, experimental assignments were compared to first principles calculations of NMR parameters, including CSA and Q (17O) interactions for all nuclei and using the PAW and GIPAW approach (first developed by Mauri et al.) [5-6]. Excellent agreement between calculations and experimental data was obtained for both 29Si and 31P nuclei (delta iso and CSA). 29Si CSA tensors were carefully measured by 31P/29Si CP static experiments.The solid state NMR techniques presented above were consequently applied to the characterization of covalent grafting of phosphonate moieties on silica nanoparticles obtained by the Stauber process. J-derived techniques are valuable tools of investigation for Si-O-P covalent bonds at the surface: such bonds are often evoked in the literature but rarely characterized unambiguously from a spectroscopic point of view.[1] C. Lejeune, C. Coelho et al., Solid State NMR 27 (2005) 242-246.[2] C. Coelho, T. Azais et al., J. Magn. Reson., 179 (2006) 106-111.[3] C. Coelho, T. Azais et al., Comptes-Rendus Chimie 9 (2006) 472-477.[4] C. Coelho, F. Babonneau et al., invited article, J. Sol Gel Sc. Technol., in press.[5] C.J. Pickard, F. Mauri, Phys. Rev. B 63 (2001) 245101.[6] C. Gervais, M. Profeta et al., Magn. Reson. Chem. 42 (2004) 445-452.
5:15 PM - MM14.6
NMR Characterisation of the Silica-surfactant Interfaces in Templated Materials.
Niki Baccile 1 , Guillaume Laurent 1 , Florence Babonneau 1 , Thierry Azais 1
1 Chimie de la Matiere Condensee, Universite Pierre et Marie Curie/Paris6, Paris France
Show AbstractThursday 11/30New Presenter - MM14.6 @ 4:15 pmNMR Characterisation of the Silica-surfactant Interfaces in Templated Materials. Thierry Azais
5:30 PM - MM14.7
Solution NMR Spectroscopy as a Useful Tool to Investigate Colloidal Nanocrystal Dispersions from the Capping Ligand's Point of View.
Jose Martins 1 , Iwan Moreels 2 , Zeger Hens 2
1 Department of Organic Chemistry, Universiteit Gent, Gent Belgium, 2 Department of Inorganic and Physical Chemistry, Universiteit Gent, Gent Belgium
Show Abstract5:45 PM - MM14.8
Solid State NMR Studies of Functionalized Zeolites and Mesoporous Silica Catalysts.
Sarah Larsen 1 , Weiguo Song 1 , Ramasubramanian Kanthasamy 1 , James Woodworth 1 , Isa Mbaraka 2 , Brent Shanks 2
1 Department of Chemistry, University of Iowa, Iowa City, Iowa, United States, 2 Department of Chemical Engineering, Iowa State University, Stony Brook, New York, United States
Show AbstractMM15: Poster Session II
Session Chairs
Friday AM, December 01, 2006
Exhibition Hall D (Hynes)
9:00 PM - MM15.1
ESR Study Of Graphite-Like Amorphous Carbon Thin Film In The 20 – 340 K Temperature Range.
Gustavo Viana 1 , Ana Champi 1 , Francisco Marques 1
1 DFA, UNICAMP, Campinas, SP, Brazil
Show AbstractAlong the last years a large amount of research about electron spin resonance (ESR) of amorphous carbon (a-C) have been carried out using room temperature X-band to investigate the paramagnetic centers density and the lineshape of the ESR signal. The majority of these works revealed a featureless Lorenztian line [1 – 2] without any kind of g-anisotropy and no resolvable hyperfine structure, which could be expected due to exchange interactions. In order to get more information concerning the paramagnetic centers in a-C many authors have performed ESR measurements using a more energetic band (Q / W – Band) and/or varying the temperature of measurement [3, 4]. A recent review reported by Barklie [5] shows an inversely proportional behavior relating the density of paramagnetic centers with the optical band gap of a-C films in the 1.0 eV up to 4.5 eV gap range deposited by various different techniques. In this work we investigate ESR of a-C with smaller than 1.0 eV band gap in the 20 K up to 340 K temperature range. Graphite-like a-C thin films with sp2 concentration around 90% (determined by electron energy loss spectroscopy - EELS) were prepared by dual-ion-beam-assisted deposition (DIBAD). The results revealed an unexpected low paramagnetic centers density, ascribed to itinerant states (conduction electrons) and not to localized states usually reported for a-C with band gap higher than 1.0 eV. A paramagnetic-diamagnetic transition, due to spin pairing, is observed as the band gap decreases to values smaller than 1.0 eV. [1] H. J. Bardeleben, J. L. Cantin, A. Zeinert, B. Racine et al. Appl. Phys. Lett 78, 2843 (2001).[2] M. Hoinkis, E. D. Tober, R. L. White, M. S. Crowder et al. Appl. Phys. Lett. 61, 2653 (1992).[3] B. J. Jones, R. C. Barklie, G. Smith, H. El Mkami et al., Diam. Rel. Mater. 12, 116 (2003).[4] H. J. Bardeleben, J. L. Cantin, K. Zellama and A. Zeinert, Diam. Rel. Mater. 12, 124 (2003). [5] R.C. Barklie, Diam. Rel. Mater. 10 (2001) 174 – 181.
9:00 PM - MM15.10
13C and 15N CP-MAS NMR of Isotopically Labeled Nephila clavipes Spider Silk from the Major and Minor Ampullate Glands.
Janelle Jenkins 1 , Jeff Yarger 1 , Melinda Creager 2 , Randolph Lewis 2 , Gregory Holland 1
1 Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, United States, 2 Deparment of Molecular Biology, University of Wyoming, Laramie, Wyoming, United States
Show AbstractDue to immense strength and intriguing mechanical properties spider silk has captured the imagination and interest of researchers for decades. With a tensile strength exceeding that of KEVLAR® and an elasticity comparable to Nylon, spider silk has countless potential applications. It has long been speculated that the silk fiber’s mechanical properties are related to the secondary structure of the highly conserved amino acid sequence. Most recently structural characterization has been performed on spider silk utilizing solid-state nuclear magnetic resonance spectroscopy (ssNMR).1-3 The majority of ssNMR has been performed on dragline silk, which is produced by the major ampullate gland. The dragline silk of Nephila clavipes (N. clavipes) consists of two main proteins, spidroin 1 (MaSp1) and spidroin 2 (MaSp2).2 NMR and X-ray have shown that the polyalanine portion of the proteins form β-sheets3 while, NMR indicates a 3-fold helical structure for the glycine-rich region.1 13C ssNMR has focused primarily on glycine and alanine, which comprise only 45% of the protein. The focus of the present research is to label the less abundant amino acids. Although they contribute to the structure in lower percentages, focusing on these will eventually give a more complete picture of the protein molecular structure. One such amino acid is tyrosine. Until recently, labeling tyrosine in natural silk has been problematic. Preliminary cross polarization magic angle spinning (CP-MAS) data will be presented on 13C-labeled tyrosine major ampullate silk. 15N CP-MAS has been exploited to study labeled silkworm silk, but has been applied to a much lesser extent in spider silk.4 Additional 15N CP-MAS results on labeled spider silk will be presented. Comparisons will be made to 13C and 15N CP-MAS data of natural abundant silk to determine the extent of isotope labeling. Compared to major ampullate silk, minor ampullate silk is four times weaker, less elastic, and much more difficult to collect. The minor silk protein structure varies from major silk, most greatly in that it contains twice as much alanine and only trace proline. These major differences are believed to contribute to its different mechanical properties. A minimal number of NMR studies have been performed on minor ampullate silk, because of difficulty in collection and small sample size. Preliminary 13C and 15N CP-MAS data will be presented on minor ampullate silk. 1. van Beek, J. B.; Hess, S.; Vollrath, F.; Meier, B. H. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 10266.2. Simmons, A.; Ray, E.; Jelinski, L. W. Macromolecules 1994, 27, 5235.3. Lewis, R. V. Acc. Chem. Res. 1992, 25, 395.4. Michal, C.; Jelinski, L. J. Biomol. NMR 1998, 12, 231.
9:00 PM - MM15.11
Ceramic Host Materials for the Encapsulation of Radioactive Waste: 89Y (I = 1/2) NMR.
Sharon Ashbrook 1 2 , Karl Whittle 1 3 , Elizabeth Harvey 1 , Simon Redfern 1 , Ian Farnan 1 , Gregory Lumpkin 1 4
1 Department of Earth Sciences, University of Cambridge, Cambridge United Kingdom, 2 Department of Chemistry, University of St Andrews, St Andrews United Kingdom, 3 Engineering Materials, University of Sheffield, Sheffield United Kingdom, 4 Institute of Materials and Engineering Science, Australian Nuclear Science and Technology Organisation (ANSTO), Sydney, New South Wales, Australia
Show Abstract9:00 PM - MM15.12
NMR Spectroscopy at AWE.
Jenny Cunningham 1
1 , AWE, Berkshire United Kingdom
Show Abstract9:00 PM - MM15.13
Multiple Quantum NMR Investigations of Structure-Property Relationships in Synthetic and Aged Silicones and Nanocomposites.
Sarah Chinn 1 , Erica Gjersing 1 , Robert Maxwell 1 , Naida Lacevic 1 , Richard Gee 1 , Eric Eastwood 2 , Dan Bowen 2 , Tom Stephens 3
1 , Lawrence Livermore National Laboratory, Livermore, California, United States, 2 , Honeywell FM&T Kansas City Plant, Kansas City, Missouri, United States, 3 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractInorganic fillers have been used as thixotropic and reinforcing agents in elastomeric systems for decades, and an understanding of the role of the filler-polymer interface in material behavior is a key step in developing rational structure-property relationships and predictive models for lifetime performance. 1H relaxation and multiple quantum NMR methods are proving to be versatile and sensitive tools for assessing not only changes in molecular level speciation, but also in the network structure. We have combined these methods with molecular dynamic computations to understand the changes that occur at the polymer-filler interface in a class of silica filled polydimethylsiloxane (PDMS) based elastomers and a series of novel nanocomposite fillers. These experiments have proven capable of separating time-dependent changes in the mobility of both the bulk polymer network and the surface associated chains and have provided in depth insight into potentially life limiting aging phenomena for these materials. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract # W-7405-ENG-48.
9:00 PM - MM15.14
A Multinuclear Solid State NMR Characterization of Polyorganophosphazenes Employed as Supports for Catalytically Active Palladium Nanoparticles.
Silvia Borsacchi 1 , Marco Geppi 1 , Nicoletta Panziera 1 , Paolo Pertici 1 , Carlo Alberto Veracini 1
1 Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Pisa Italy
Show AbstractPolyorganophosphazenes, -[N=PR2]n-, are polymers constituted by an inorganic backbone formed by alternating nitrogen and phosphorus atoms, with two organic side groups bonded to each phosphorus atom. They are known to exhibit interesting physical and chemical properties, as stability against strong acids, bases and aggressive chemicals, high thermal stability, flame resistance, unusual flexibility, biocompatibility and photosensitivity [1]. Recently, the basic properties of the backbone nitrogen atoms, which make them able to coordinate metal atoms and cations, have been exploited in the synthesis of polyorganophosphazene supported metal nanoparticle catalysts [2], found to be active in the hydrogenation of a wide range of organic compounds. Quite few Solid State NMR studies of polyorganophosphazenes have been reported, mostly concerning the polymers structural and dynamic properties [3-7]. Here we present a multinuclear Solid State NMR study of two different polyorganophosphazenes (polydimethylphosphazene and poly[bis(phenoxy)]phosphazene), both employed as supports for palladium nanoparticle catalysts. By means of 31P, 13C and 15N high resolution and 1H low resolution techniques , the different coexistent polymer phases have been detected and characterized, and interesting differences have been observed as a consequence of the presence of Pd nanoparticles. In this sense, the employment of a multinuclear and comparative Solid State NMR approach and the analysis of two different polymers have turned out to be very useful to understand the modification of the polymer properties induced by the supported metal nanoparticles, as well as their mutual interaction mechanism.[1] R. De Jaeger, M. Gleria, Prog. Polym. Sci. 23 (1998) 179.[2] A. Spitaleri, P. Pertici, N. Scalera, G. Vitulli, M. Hoang, T.W. Turney, M. Gleria, Inorg. Chim. Acta 352 (2003) 61.[3] H. Tanaka, M. A. Gomez, A. E. Tonelli, S. V. Chichester-Hicks, R. C. Haddon, Macromolecules 21 (1988) 2301.[4] H. Tanaka, M. A. Gomez, A. E. Tonelli, S. V. Chichester-Hicks, and R. C. Haddon, Macromolecules 22 (1989) 1031. [5] K. Takegoshi, I. Tanaka, K. Hikichi, S. Higashida, Macromolecules 25 (1992), 3392.[6] R. Simonutti, A. Comotti, P. Sozzani, J. Inorg. Organomet. Polym. 6 (1996) 313. [7] R. Simonutti, W. S. Veeman, F. C. Ruhnau, M. C. Gallazzi, P. Sozzani, Macromolecules 29 (1996) 4958.
9:00 PM - MM15.15
Cotton Fibers Encapsulated with Homo- and Block- Copolymers by means of ATRP Grafting-From Technique: A Solid State NMR Study.
Giulia Mollica 1 , Valter Castelvetro 1 , Marco Geppi 1 , Simone Giaiacopi 1
1 Chimica e Chimica Industriale, Università di Pisa, Pisa Italy
Show Abstract9:00 PM - MM15.2
FMR Effects on Integrated Ferromagnetic Thin-film RF Inductors.
Weiping Ni 1
1 , Cornell University, Ithaca, New York, United States
Show Abstract9:00 PM - MM15.3
Order Parameters in Fluorinated Liquid Crystals by 13C NMR.
Marco Geppi 1 , Alberto Marini 1 , Donata Catalano 1 , Joanna Czub 2 , Roman Dabrowski 3 , Wojciech Kuczynski 4 , Stanislaw Urban 2 , Carlo Veracini 1
1 Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Pisa Italy, 2 Institute of Physics, Jagiellonian University, Krakow Poland, 3 Institute of Chemistry, Military University of Technology, Warsawa Poland, 4 Institute of Molecular Physics, Polish Academy of Sciences, Poznan Poland
Show Abstract9:00 PM - MM15.4
Local Structure and Motion in Fluorite Oxide Ionic Conductors: High Temperature 17O MAS NMR Studies.
Namjun Kim 1 , Jonathan Stebbins 1
1 Dept. of Geological & Environmental Sciences, Stanford University, Stanford, California, United States
Show AbstractPolycrystalline oxide ionic conductors have long been of great interest due to their usefulness in various applications that require rapid oxygen diffusion, such as electrolytes in solid oxide fuel cell and oxygen sensors. One of the most important classes of oxide ionic conductors is based on the fluorite structure. Stabilized zirconias such as commercially used YSZ (yttrium stabilized zirconia) are among the most well known in this class. In addition, doped ceria and doped bismuth oxide also adopt the cubic fluorite structure. In order to establish the relationship between structure and property of these materials and thus to improve their properties, information on local structure around dopant cations and oxygen vacancies is essential. NMR is one of the most powerful methods to investigate the local structure around the specific nuclei. However, most NMR studies have been carried out only at room temperature or moderately high temperature range (up to 250 oC) especially under magic angle spinning conditions, although the data at high temperatures, where the materials are employed in actual applications, would be very useful.Here we report high temperature (up to 700 oC) 17O MAS NMR results of various fluorite oxide ionic conductors including calcium and scandium stabilized zirconia, yttrium doped ceria, and yttrium doped bismuth oxide with various dopant concentrations. Oxygens in different local environments were identified at room temperature and dynamics between sites was studied at high temperature. Most of the compounds show line narrowing or coalescences at high temperatures. Oxygen hopping frequencies were estimated by lineshape analyses with variable temperatures. The activation energies for jumps were also estimated from Arrhenius plots and compared with those from bulk conductivity measurements. In addition, the local structures around dopant cations, such as Sc3+ or Y3+, were also studied using 45Sc and 89Y MAS NMR and provide new information on cation and/or vacancy ordering.
9:00 PM - MM15.5
Spin Resonance Investigations of the Composition, Shape, and Orientation of Ferromagnetic Precipitates in GaFeN.
Agnieszka Wolos 1 , H. Przybylinska 2 1 , C. Simbrunner 1 , A. Bonanni 1 , Li Tian 1 , F. Schäffler 1 , W. Jantsch 1
1 Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Linz Austria, 2 Institute of Physics, Polish Academy of Sciences, Warsaw Poland
Show AbstractSince the predictions of room-temperature ferromagnetism of the Zener-type in wide band gap semiconductors substantial technological effort has been devoted to investigations of transition metal-doped oxides and nitrides (GaMnN, GaFeN, AlCrN, ZnVO, ZnCoO). Numerous reports were published on the ferromagnetic response of the fabricated materials, with Curie temperatures ranging from a few up to several hundred Kelvin. In some cases, the presence of ferromagnetic precipitates or transition metal-rich regions inside the semiconductor matrix has been reported, to which the spontaneous magnetic moment of the sample could be assigned. In other cases the formation of ferromagnetic precipitates has been excluded as the origin of the sample magnetization, basing on results of high resolution transmission electron microscopy, X-ray diffraction or extended X-ray absorption fine structure investigations. These techniques, however, are insensitive to the presence of a small number of nano-sized inclusions and bear rather limited information. Here we show that ferromagnetic resonance (FMR) is a powerful tool to study the inhomogeneities in magnetic properties of semiconductors. In particular, using this technique we can immediately distinguish different ferromagnetic phases within a sample (both intrinsic and extrinsic precipitates). The composition, shape and orientation of ferromagnetic inclusions can be easily identified. The nanometer-size of the precipitates is not an obstacle here (in contrast to many other structural characterization techniques), as long as the precipitates are well oriented in the host semiconductor matrix.We have investigated a series of MOVPE grown GaN:Fe samples, obtained with different growth parameters. In samples obtained at the highest Fe fluxes we observe, apart from the paramagnetic resonance of substitutional Fe3+ ions, additional signals related to three different magnetically ordered phases. The angular dependence does not reveal any shape anisotropy (indicating that the precipitates are spherical in shape) but pronounced magnetocrystalline anisotropy of cubic symmetry. One of the FMR signals can be ascribed to magnetite (Fe3O4), on behalf of the similarity of its g-factor at 300 K, the saturation magnetization, Ms, and the first order magnetocrystalline anisotropy constant, K1, as well as the temperature dependence of the latter. The <001> hard axes of this kind of precipitate are tilted by 12° from the [0001], [1-100], and [1-210] crystallographic axes of GaN. The second kind grows with its [110] axis almost along the c-axis or, in another sample, perpendicular to it. The parameters obtained are close to literature values for iron nitride. The third type of signal can be explained satisfactorily in terms of bcc iron nano-precipitates, showing size effects. The presence of such spheroidal precipitates and their crystal symmetry is corroborated with transmission electron microscopy.
9:00 PM - MM15.6
Flow Imaging of Fluids in Porous Materials by means of Time-of-Flight Remote Detection NMR and MRI.
Ville-Veikko Telkki 1 2 , Christian Hilty 1 2 , Sandra Garcia 1 2 , Elad Harel 1 2 , Alexander Pines 1 2
1 Chemistry, University of Berkeley, Berkeley, California, United States, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract9:00 PM - MM15.8
Functional Study of an Aluminum Nitride Encapsulated Auditory Brainstem Implant.
Brian Murphy 1 , Jinsheng Zhang 2 , Gregory Auner 3
1 Biomedical Engineering, Wayne State University, Detroit, Michigan, United States, 2 Wayne State University School of Medicine , Wayne State, Detroit, Michigan, United States, 3 Electrical and Computer Engineering, Wayne State University, Detroit, Michigan, United States
Show Abstract9:00 PM - MM15.9
Using Magnetic Resonance Microscopy to Assess the Osteogenesis in Porous Hydrogels.
Prasanna Mishra 1 , Mahrokh Dadsetan 1 , Srinivasan Rajagopalan 1 , Theresa Hefferan 1 , Michael Yaszemski 1 , Slobodan Macura 1
1 , Mayo Foundation, Rochester, Minnesota, United States
Show AbstractHydrogels are multifunctional and can be used as scaffolds in bone tissue engineering. The pore architecture of the scaffolds is a significant factor in bone cell function. In this work, polyethylene glycol fumarate (OPF) hydrogel is used in the fabrication of porous scaffolds, and the effect of hydrogel porosity on bone formation is evaluated using an in vitro bone marrow stromal cell model. The porous hydrogels consist of copious amounts of water (90% or more by volume), and their structure is very similar to soft tissues. The characterization of porosity and interconnectivity in a typical OPF hydrogel scaffold and the bone formation inside the scaffold are assessed using magnetic resonance microscopy (MRM) techniques and are shown to be very useful in micro structural studies of such water-rich materials. A Bruker Avance 7 Tesla (proton 300 MHz) spectrometer equipped with a Micro Imaging 2.5 accessory is used in these studies. By optimizing the acquisition parameters such as relaxation recovery time (TR), echo time (TE), pulse flip angle (TA), and using solvent relaxation-enhancing media, the pores and bone formations are clearly observed at an in-plane resolution of 29 μm/ pixel in various scaffold materials. Analysis of our MRM images data shows that the pores are highly interconnected, and the porosity computed from the images correlate quite well with the experimental porosity parameters such as porogen size and percentage. In addition, the quantitative alkaline phosphatase activity, alizarin red staining as marker of osteoblastic differentiation, and the mineralization capacity of marrow stromal cells are in good agreement with the bone formation seen in the MRM images.
Symposium Organizers
Julie Herberg Lawrence Livermore National Laboratory
Yue Wu University of North Carolina-Chapel Hill
Phil Grandinetti The Ohio State University
Sophia Hayes Washington University
Ian Farnan University of Cambridge
MM16: Magnetic Resonance Studies on Fuel Cells, Batteries, and Other Energy Related Materials II
Session Chairs
Friday AM, December 01, 2006
Liberty (Sheraton)
9:30 AM - **MM16.1
Coverage Dependence of CO Surface Diffusion on Pt Nanoparticles – an EC-NMR Study.
Andrzej Wieckowski 1 , Takeshi Kobayashi 1 , Panakkattu Babu 1 , Jong Ho Chung 1 , Eric Oldfield 1
1 Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show Abstract10:00 AM - MM16.2
Phosphine Ligand Protected Pt Nanoclusters Observed by Solution and Solid State NMR.
Brian Zelakiewicz 1 , Christopher Klug 1 , Cynthia Kostelansky 1 , Terry Schull 1
1 Code 6122, U.S. Naval Research Laboratory, Washington, District of Columbia, United States
Show Abstract10:15 AM - **MM16.3
Self-assembly of Asphaltenes: Enthalpy, Entropy of Depletion and Dynamics at the Crossover.
Natalia Lisitza 1 , Denise Freed 1 , Pabitra Sen 1 , Kosta Ladavac 1 , Andrew Pomerantz 1 , Yi-Qiao Song 1
1 , Schlumberger, Ridgefield, Connecticut, United States
Show AbstractThe continuous rise of global demand for energy and the difficulty of significantly increasing production capacity have driven the petroleum industry to develop much more difficult oil reservoirs, such as deep-water fields. Asphaltenes, naturally-occurring large aromatic molecules in crude oils, are known to be the ``cholesterol'' of petroleum, because they self-associate to form solid aggregates and eventually clog the production pipes and the rocks. An extraordinary amount of work using many analytical techniques has been applied to elucidate the properties of asphaltenes. However, many fundamental issues, e.g. the molecular architecture and the aggregation mechanisms, are still in debate. Here we use NMR to detect asphaltene aggregation and to obtain the binding energy and entropy of aggregation. We observe an abrupt drop of the asphaltene diffusion constant indicative of a molecular conformation (shape) change that is intimately related to or possibly a prerequisite of the aggregation. The entropy was found to exhibit a positive contribution from the excluded volume during aggregation, reminiscent of the depletion entropy force found to be the driving force for the aggregation of much larger artificial nanoparticles. This depletion entropy might be important for many other molecular mixtures from nature, e.g. biological fluids in cells and tissues.
10:45 AM - MM16.4
The Effect of Co-doping on the Conductivity and Local structure of Yttria-Stabilized Zirconia from High Resolution Solid-State 89Y NMR.
Luke Henson 2 , Richard Darby 2 , R. Kumar 2 , Ian Farnan 1
2 Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom, 1 Earth Sciences, Cambridge University, Cambridge United Kingdom
Show AbstractMM17: Calculation and Simulation on Magnetic Resonance Data
Session Chairs
Friday PM, December 01, 2006
Liberty (Sheraton)
11:30 AM - **MM17.1
Pressure and Stress on Materials Assessed by NMR.
Josef Zwanziger 1 2
1 Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada, 2 Institute for Research in Materials, Dalhousie University, Halifax, Nova Scotia, Canada
Show AbstractPressure and stress in materials may result both from the external environment and from internal inhomogeneities. Measuring and controlling stress and pressure are important both for material characterization and applications. We will show results from several studies that combine NMR with first-principles calculations to determine stress and pressure in different systems. In a photo-thermo-refractive glass ceramic we will show how subtle chemical shifts in the nanoparticles that appear upon ceramming may be interpreted using computations to determine the stress field under which the particles form. We will also show how NMR data of both unstressed and stressed samples coupled with calculations indicate the mechanism responsible for photoelastic effects, that is, the relationship between refractive index change and applied anisotropic stress.
12:15 PM - MM17.3
DFT Calculations : A Tool To Assign And Understand 6,7Li NMR Shifts In Paramagnetic Materials.
Dany Carlier-Larregaray 1 , M. Menetrier 1 , C. Delmas 1
1 Institute de Chimie de la Matiere Condensee de Bordeaux - CNRS, University of Bordeaux, Pessac France
Show AbstractThe number of NMR studies of battery materials has increased dramatically over the last few years. In particular, the lithium NMR spectra of systems with an increasingly large number of transition metal ions, oxidation states, and structural types have now been investigated. The aim of the work presented in this paper is to attempt to provide a rational basis for the interpretation of the shifts as a function of the electronic configuration and geometric environment of the transition metal ion and of the lithium local environment.The 6,7Li MAS NMR spectra are sensitive to the presence of paramagnetic cations in its environment, which leads to a certain spin density on the lithium nucleus. In order to understand the spin density transfer mechanism from the transition metal ion to the lithium nucleus, we performed Density Functional Theory calculations using a pseudopotential method (VASP code). We the study of layered transition metal oxides, LiMO2, LiMyCo1-yO2 (α-NaFeO2 structure), and La4LiMO8 (K2NiF4 structure), we understand the effect of eg or t2g electronic spins on neighboring Li. More recently, we focus on other paramagnetic compounds that exhibit more complex interactions: Li6CoO4 et LiNi2O4 as well as LiMPO4 olivine-compounds.For each compound, we calculate the spin densities values on the transition metal, oxygen and lithium ions and map the spin density in the M-O-Li plan. Predictions of the calculations are in good agreement for several experimental results. We show that DFT calculations are a useful tool to interpret the observed paramagnetic shifts in layered oxides and allow us to figure out the major transfer processes. We can therefore use this information to predict the magnitudes and signs of the Li hyperfine shifts for different Li local environments and t2g vs. eg electrons in other compounds.
12:30 PM - MM17.4
Fitting of Deuterium Quadrupole Echo Spectra with Multiple Motional Models.
Margaret Eastman 1 , Mark Nanny 2 3
1 Chemistry, Oklahoma State University, Stillwater, Oklahoma, United States, 2 School of Engineering and Environmental Science, University of Oklahoma, Norman, Oklahoma, United States, 3 Institute for Energy and the Environment, University of Oklahoma, Norman, Oklahoma, United States
Show AbstractDeuterium quadrupole echo spectra have been used to study dynamics of macromolecular materials, and dynamics of small molecules in association with materials such as zeolites. The shape of the quadrupole echo spectrum is generally sensitive to motions with a range of rates from 10e3 to10e7 Hz. These rates may be estimated by calculating spectra for a proposed motional model and matching a calculated spectrum to the experimental spectrum, a comparison that is often done by eye. In some situations an experimental spectrum suggests the presence of more than one motional model. The main goal of this work has been to facilitate and partially automate the fitting of calculated spectra with multiple (or single) motional models to experimental spectra. We also try to establish a goodness of fit parameter that can be used to evaluate and compare different fits. Our method is to calculate series of spectra for particular motional models, called libraries, and fit combinations of spectra from different libraries to an experimental spectrum with the fitting program DFP. DFP fits with calculated spectra from one to five libraries, either by a systematic method in which all possible combinations of one spectrum from each library are made, or by using simulated annealing. We find that the systematic method is most useful for fits requiring one or two motional models, but for fits requiring three or more models simulated annealing is more expeditious. Our goodness of fit parameter is quite stringent, and we find that it may frequently judge experimental spectra to be poorly fit, suggesting that established methods of theoretical calculation of spectra are not capable of reproducing experimental spectra well in every detail. Despite this, parameters such as the percentage of each motional model may be extracted in favorable cases with a moderate level of error.