NMR and EPR

Molecular systems important to biology, environmental remediation and sustainability are studied using a suite of nuclear magnetic resonance (NMR) spectrometers with frequencies ranging from 300 to 850 MHz. A pair of electron paramagnetic resonance (EPR) spectrometers complement the capability. See a complete list of NMR and EPR instruments.

Description

Interfacial and in situ biology—Innovative NMR instrumentation and techniques for probing properties of macromolecular cellular assemblies and in situ and ex situ metabolic processes, as well as for exploring biological membrane proteins in the solid state. Unique EPR and variable-temperature NMR approaches to explore structure and properties of redox metal centers critical catalysis, environmental chemistry and cell biology.

Environmental chemistry— EMSL offers a unique NMR system for radiological studies. Users can perform magic angle spinning of highly radioactive samples with a novel hermetically sealed 3.2mm NMR probe. These tools allow users to apply NMR techniques to critical areas of radiological research, including the study of radioactive waste processing and storage.

Interfacial and in situ chemistry—Leading-edge solid-state NMR probe technology to analyze and quantify properties of advanced energy materials, fuel cells and real-time catalytic processes. High power pulsed field gradient diffusion capabilities for liquid and solid samples.

EMSL offers unique and custom NMR and EPR tools, including probes for specialized studies.

  • NMR spectrometers, ranging from 300 MHz to 850 MHz for high-field liquid-state, solid-state and micro-imaging techniques
  • W- and X-band pulsed EPR spectremeter for probing metal centers in biological and materials systems
  • NMR metabolomics capabilities
  • Extreme-temperature probes, both high and low temperatures
  • Virtual NMR tools for remote access to spectrometer systems.

Instruments

Highlighted Research Applications Structural biology Protein structure and dynamics Nuclei acid structure and dynamics. Metabolomics Eukaryotic and...
Custodian(s): Sarah D Burton, David Hoyt
Highlighted Research Applications Structural biology Protein structure and dynamics Nuclei acid structure and dynamics Metabolomics Eukaryotic and...
Custodian(s): David Hoyt, Nancy Isern
Highlighted Research Applications Characterization of quadrupolar nuclei for materials and biological samples In situ catalysis investigations via...
Research applications Samples containing paramagnetics Soils (SOM and NOM) Metal oxide materials for catalysis applications Researchers may operate...
Custodian(s): Nancy Washton, Sarah D Burton
Highlighted Research Applications Characterization of natural and soil organic matter (NOM and SOM) CO2 sequestration investigations via high-...
Custodian(s): Sarah D Burton, David Hoyt

Publications

Sources, optical properties, and chemical composition of atmospheric brown carbon (BrC) aerosol are uncertain, making it challenging to estimate its...
Catalysis by single isolated atoms of precious metals has attracted much recent interest since it promises the ultimate economy in atom efficiency....
Ferrocene (Fc) and N-(ferrocenylmethyl)-N,N-dimethyl-N-ethylammonium bistrifluoromethyl-sulfonimide (Fc1N112-TFSI) were dissolved in carbonate...
We recently discovered that MgAl2O4 spinel {111} nano-facets optimally stabilize the small sizes of platinum nanoparticles even after severe high...
Complementary methods of high-resolution mass spectrometry and micro-spectroscopy were utilized for molecular analysis of secondary organic aerosol (...

Science Highlights

Posted: January 15, 2015
A team of scientists with Pacific Northwest National Laboratory, EMSL, Marine Biological Laboratory and The Pennsylvania State University grew two...
Posted: November 21, 2014
The Science Carbon dioxide (CO2) sequestration in deep subsurface environments has received significant attention and investment as a way to reduce...
Posted: August 14, 2014
Industry uses zeolites as an ion exchange material and solid acid to catalyze a broad range of chemical reactions. Zeolites are also promising...
Posted: June 23, 2014
Congratulations to Pacific Northwest National Laboratory and EMSL researchers on being named highly cited authors for 2012-2013 by the Journal of...
Posted: November 12, 2013
Tiny electrical wires protrude from some bacteria and contribute to rock and dirt formation. Researchers studying the protein that makes up one such...

Molecular systems important to biology, environmental remediation and sustainability are studied using a suite of nuclear magnetic resonance (NMR) spectrometers with frequencies ranging from 300 to 850 MHz. A pair of electron paramagnetic resonance (EPR) spectrometers complement the capability. See a complete list of NMR and EPR instruments.

Diffusional Motion of Redox Centers in Carbonate Electrolytes .

Abstract: 

Ferrocene (Fc) and N-(ferrocenylmethyl)-N,N-dimethyl-N-ethylammonium bistrifluoromethyl-sulfonimide (Fc1N112-TFSI) were dissolved in carbonate solvents and self diffusion coefficents (D) of solutes and solvents were measured by 1H and 19F pulsed field gradient (PFG) nuclear magnetic resonance (NMR) spectroscopy. The organic solvents were propylene carbonate (PC), ethyl methyl carbonate (EMC) and a ternary mixture that also includes ethylene carbonate (EC). Results from NMR studies over the temperature range of 0-50 °C and for various concentrations (0.25 - 1.7 M) of Fc1N112-TFSI are compared to values of D simulated with classical molecular dynamics (MD). The measured self-diffusion coefficients gradually decreased as the Fc1N112-TFSI concentration increased in all solvents. Since the peaks for the two ions (Fc1N212 and TFSI) are separated in one-dimensional NMR spectra, separate diffusion coefficients could be measured and DTFSI is larger than DFc1N112 in all samples measured. The EC, PC and EMC have the same D in the neat solvent mixture and when Fc is dissolved in EC/PC/EMC at a concentration of 0.2 M, probably due to the interactions between common carbonyl structures within EC, PC and EMC. A difference in D (DPC < DEC < DEMC), and both a higher Ea for translational motion and higher effective viscosity for PC in the mixture containing Fc1N112-TFSI reflect the interaction between PC and Fc1N112+, which is a relatively stronger interaction than that between Fc1N112+ and other solvent species. In the EC/PC/EMC solution that is saturated with Fc1N112-TFSI, we find that DPC = DEC = DEMC and Fc1N112+ and all components of the EC/PC/EMC solution have the same Ea for translational motion, while the ratio DEC/PC/EMC/DFc1N112+ is approximately 3. These results reflect the lack of available free volume for independent diffusion in the saturated solution. The Fc1N112+ transference numbers lie around 0.4 and increases slightly as the temperature is increased in the PC and EMC solvents. The trends observed for D from simulations are in good agreement with experimental results and provide molecular level understanding of the solvation structure of Fc1N112-TFSI dissolved in EC/PC/EMC.

Citation: 
Han KS, NN Rajput, X Wei, W Wang, JZ Hu, KA Persson, and KT Mueller.2014."Diffusional Motion of Redox Centers in Carbonate Electrolytes ."Journal of Chemical Physics 141(10):104509. doi:10.1063/1.4894481
Authors: 
KS Han
NN Rajput
X Wei
W Wang
JZ Hu
KA Persson
KT Mueller
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2014

Low-Temperature Carbon Monoxide Oxidation Catalysed by Regenerable Atomically Dispersed Palladium on Alumina.

Abstract: 

Catalysis by single isolated atoms of precious metals has attracted much recent interest since it promises the ultimate economy in atom efficiency. Previous reports have been confined to reducible oxide supports such as FeOx, TiO2 or CeO2. Here we show that isolated Pd atoms can be stabilized on industrially relevant gamma-alumina supports. At low Pd loadings (≤0.5 wt%) these catalysts contain exclusively atomically dispersed Pd species. The addition of lanthanum-oxide to the alumina, long known for its ability to improve alumina stability, is found to also help in the stabilization of isolated Pd atoms. Aberration-corrected scanning transmission electron microscopy (AC-STEM) confirms the presence of intermingled Pd and La on the gamma-alumina surface. Operando X-ray absorption spectroscopy, performed on Pd/La-alumina and Pd/gamma-alumina (0.5 wt% Pd) demonstrates the presence of catalytically active atomically dispersed ionic Pd in the Pd/La-doped gamma-alumina system. CO oxidation reactivity measurements show onset of catalytic activity at 40 ˚C, indicating that the ionic Pd species are not poisoned by CO. The reaction order in CO and O2 is positive, suggesting a reaction mechanism that is different from that on metallic Pd. The catalyst activity is lost if the Pd species are reduced to their metallic form, but the activity can be regenerated by oxidation at 700 ˚C in air. The high-temperature stability of these ionic Pd species on commercial alumina supports makes this catalyst system of potential interest for low-temperature exhaust treatment catalysts.

Citation: 
Peterson E, A DelaRiva, S Lin, RS Johnson, H Guo, J Miller, JH Kwak, CHF Peden, B Kiefer, LF Allard, F Ribeiro, and AK Datye.2014."Low-Temperature Carbon Monoxide Oxidation Catalysed by Regenerable Atomically Dispersed Palladium on Alumina."Nature Communications 5:Article No. 4885. doi:10.1038/ncomms5885
Authors: 
E Peterson
A DelaRiva
S Lin
RS Johnson
H Guo
J Miller
JH Kwak
CHF Peden
B Kiefer
LF Allard
F Ribeiro
AK Datye
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0
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0
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0
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2014

Effect of Solar Radiation on the Optical Properties and Molecular Composition of Laboratory Proxies of Atmospheric Brown Carbon

Abstract: 

Sources, optical properties, and chemical composition of atmospheric brown carbon (BrC) aerosol are uncertain, making it challenging to estimate its contribution to radiative forcing. Furthermore, optical properties of BrC may change significantly during its atmospheric aging. We examined the effect of solar photolysis on the molecular composition, mass absorption coefficient, and fluorescence of secondary organic aerosol prepared by high-NOx photooxidation of naphthalene (NAP SOA). The aqueous solutions of NAP SOA was observed to photobleach with an effective half-time of 15 hours (with sun in its zenith) for the loss of the near-UV (300 -400 nm) absorbance. The molecular composition of NAP SOA was significantly modified by photolysis, with the average SOA formula changing from C14.1H14.5O5.1N0.08 to C11.8H14.9O4.5N0.02 after 4 hours of irradiation. The average O/C ratio did not change significantly, however, suggesting that it is not a good metric for assessing the extent of photolysis-driven aging in NAP SOA (and in BrC in general). In contrast to NAP SOA, the photolysis of BrC material produced by aqueous reaction of limonene+O3 SOA (LIM/O3 SOA) with ammonium sulfate was much faster, but it did not result in a significant change in the molecular level composition. The characteristic absorbance of the aged LIM/O3 SOA in the 450-600 nm range decayed with an effective half-time of <0.5 hour. This result emphasizes the highly variable and dynamic nature of different types of atmospheric BrC.

Citation: 
Lee HJ, PK Aiona, A Laskin, J Laskin, and S Nizkorodov.2014."Effect of Solar Radiation on the Optical Properties and Molecular Composition of Laboratory Proxies of Atmospheric Brown Carbon ."Environmental Science & Technology 48(17):10217-10226. doi:10.1021/es502515r
Authors: 
HJ Lee
PK Aiona
A Laskin
J Laskin
S Nizkorodov
Volume: 
48
Issue: 
17
Pages: 
10217-10226
Publication year: 
2014

A general mechanism for stabilizing the small sizes of precious metal nanoparticles on oxide supports.

Abstract: 

We recently discovered that MgAl2O4 spinel {111} nano-facets optimally stabilize the small sizes of platinum nanoparticles even after severe high temperature aging treatments. Here we report the thermal stabilities of other precious metals with various physical and chemical properties on the MgAl2O4 spinel {111} facets, providing important new insights into the stabilization mechanisms. Besides Pt, Rh and Ir can also be successfully stabilized as small (1-3 nm) nanoparticles and even as single atomic species after extremely severe (800 °C, 1 week) oxidative aging. However, other metals either aggregate (Ru, Pd, Ag, and Au) or sublimate (Os) even during initial catalyst synthesis. On the basis of ab initio theoretical calculations and experimental observations, we rationalize that the exceptional stabilization originates from lattice matching, and the correspondingly strong attractive interactions at interfaces between the spinel {111} surface oxygens and epitaxial metals\metal oxides. On this basis, design principles for catalyst support oxide materials that are capable in stabilizing precious metals are proposed.

Citation: 
Li WZ, L Kovarik, D Mei, MH Engelhard, F Gao, J Liu, Y Wang, and CHF Peden.2014."A general mechanism for stabilizing the small sizes of precious metal nanoparticles on oxide supports."Chemistry of Materials 26(19):5475-5481. doi:10.1021/cm5013203
Authors: 
Li WZ
L Kovarik
D Mei
MH Engelhard
F Gao
J Liu
Y Wang
CHF Peden
Volume: 
26
Issue: 
19
Pages: 
5475-5481
Publication year: 
2014

Molecular Selectivity of Brown Carbon Chromophores.

Abstract: 

Complementary methods of high-resolution mass spectrometry and micro-spectroscopy were utilized for molecular analysis of secondary organic aerosol (SOA) generated from ozonolysis of two structural monoterpene isomers: D-limonene (LSOA) and a-pinene (PSOA). Laboratory simulated aging of LSOA and PSOA, through conversion of carbonyls into imines mediated by NH3 vapors in humid air, resulted in selective browning of the LSOA sample, while the PSOA sample remained white. Comparative analysis of the reaction products in the aged LSOA and PSOA samples provided insights into chemistry relevant to formation of brown carbon chromophores. A significant fraction of carbonyl-imine conversion products with identical molecular formulas were detected in both samples. This reflects the high level of similarity in the molecular composition of these two closely related SOA materials. Several highly conjugated products were detected exclusively in the brown LSOA sample and were identified as potential chromophores responsible for the observed color change. The majority of the unique products in the aged LSOA sample with the highest number of double bonds contain two nitrogen atoms. We conclude that chromophores characteristic of the carbonyl- imine chemistry in LSOA are highly conjugated oligomers of secondary imines (Schiff bases) present at relatively low concentrations. Formation of this type of conjugated compounds in PSOA is hindered by the structural rigidity of the a-pinene oxidation products. Our results suggest that the overall light-absorbing properties of SOA may be determined by trace amounts of strong brown carbon chromophores.

Citation: 
Laskin J, A Laskin, S Nizkorodov, PJ Roach, PA Eckert, MK Gilles, B Wang, HJ Lee, and Q Hu.2014."Molecular Selectivity of Brown Carbon Chromophores."Environmental Science & Technology 48(20):12047-12055. doi:10.1021/es503432r
Authors: 
J Laskin
A Laskin
S Nizkorodov
PJ Roach
PA Eckert
MK Gilles
B Wang
HJ Lee
Q Hu
Volume: 
48
Issue: 
20
Pages: 
12047-12055
Publication year: 
2014

Fe/SSZ-13 as an NH3-SCR Catalyst: A Reaction Kinetics and FTIR/Mössbauer Spectroscopic Study.

Abstract: 

Using a traditional aqueous solution ion-exchange method under a protecting atmosphere of N2, an Fe/SSZ-13 catalyst active in NH3-SCR was synthesized. Mössbauer and FTIR spectroscopies were used to probe the nature of the Fe sites. In the fresh sample, the majority of Fe species are extra-framework cations. The likely monomeric and dimeric ferric ions in hydrated form are [Fe(OH)2]+ and [HO-Fe-O-Fe-OH]2+, based on Mössbauer measurements. During the severe hydrothermal aging (HTA) applied in this study, a majority of cationic Fe species convert to FeAlOx and clustered FeOx species, accompanied by severe dealumination of the SSZ-13 framework. The clustered FeOx species do not give a sextet Mössbauer spectrum, indicating that these are highly disordered. However, some Fe species in cationic positions remain after aging as determined from Mössbauer measurements and CO/NO FTIR titrations. NO/NH3 oxidation reaction tests reveal that dehydrated cationic Fe are substantially more active in catalyzing oxidation reactions than the hydrated ones. For NH3-SCR, enhancement of NO oxidation under ‘dry’ conditions promotes SCR rates below ~300 C. This is due mainly to contribution from the “fast” SCR channel. Above ~300 C, enhancement of NH3 oxidation under ‘dry’ conditions, however, becomes detrimental to NOx conversions. The HTA sample loses much of the SCR activity below ~300 C; however, above ~400 C much of the activity remains. This may suggest that the FeAlOx and FeOx species become active at such elevated temperatures. Alternatively, the high-temperature activity may be maintained by the remaining extra-framework cationic species. For potential practical applications, Fe/SSZ-13 may be used as a co-catalyst for Cu/CHA as integral aftertreatment SCR catalysts on the basis of the stable high temperature activity after hydrothermal aging. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

Citation: 
Gao F, M Kollar, RK Kukkadapu, NM Washton, Y Wang, J Szanyi, and CHF Peden.2015."Fe/SSZ-13 as an NH3-SCR Catalyst: A Reaction Kinetics and FTIR/Mössbauer Spectroscopic Study."Applied Catalysis. B, Environmental 164:407-419. doi:10.1016/j.apcatb.2014.09.031
Authors: 
F Gao
M Kollar
RK Kukkadapu
NM Washton
Y Wang
J Szanyi
CHF Peden
Volume: 
Issue: 
Pages: 
Publication year: 
2015

Fe(II)-catalyzed Recrystallization of Goethite Revisited.

Abstract: 

Results from enriched 57Fe isotope tracer experiments have shown that atom exchange can occur between structural Fe in Fe(III) oxides and aqueous Fe(II) with no formation of secondary minerals or change in particle size or shape. Here we derive a mass balance model to quantify the extent of Fe atom exchange between goethite and aqueous Fe(II) that accounts for different Fe pool sizes. We use this model to reinterpret our previous work and to quantify the influence of particle size and pH on extent of goethite exchange with aqueous Fe(II). Consistent with our previous interpretation, substantial exchange of goethite occurred at pH 7.5 (≈ 90%) and we observed little effect of particle size between nanogoethite (81 x 11 nm) and microgoethite (590 x 42 nm). Despite ≈ 90% of the bulk goethite exchanging at pH 7.5, we found no change in mineral phase, particle size, crystallinity, or reactivity after reaction with aqueous Fe(II). At a lower pH of 5.0, no net sorption of Fe(II) was observed and significantly less exchange occurred accounting for less than the estimated proportion of surface Fe atoms in the particles. Particle size appears to influence the amount of exchange at pH 5.0 and we suggest that aggregation and surface area may play a role. Results from sequential chemical extractions indicate that 57Fe accumulates in extracted Fe(III) goethite components. Isotopic compositions of the extracts indicate that a gradient of 57Fe develops within the goethite with more accumulation of 57Fe occurring in the more easily extracted Fe(III) that may be nearer to the surface. We interpret our particle size, pH, and sequential extraction findings as consistent with the mechanism of interfacial electron transfer and bulk conduction previously proposed to explain the substantial Fe atom exchange observed in goethite in contact with aqueous Fe(II).

Citation: 
Handler R, AJ Frierdich, C Johnson, KM Rosso, B Beard, CM Wang, D Latta, A Neumann, TS Pasakarnis, WAPJ Premaratne, and M Scherer.2014."Fe(II)-catalyzed Recrystallization of Goethite Revisited."Environmental Science & Technology 48(19):11302-11311. doi:10.1021/es503084u
Authors: 
R Hler
AJ Frierdich
C Johnson
KM Rosso
B Beard
CM Wang
D Latta
A Neumann
TS Pasakarnis
WAPJ Premaratne
M Scherer
Volume: 
48
Issue: 
19
Pages: 
11302-11311
Publication year: 
2014

In-Situ Transmission Electron Microscopy Probing of Native Oxide and Artificial Layers on Silicon Nanoparticles for Lithium Ion

Abstract: 

Surface modification of silicon nanoparticle via molecular layer deposition (MLD) has been recently proved to be an effective way for dramatically enhancing the cyclic performance in lithium ion batteries. However, the fundamental mechanism as how this thin layer of coating function is not known, which is even complicated by the inevitable presence of native oxide of several nanometers on the silicon nanoparticle. Using in-situ TEM, we probed in detail the structural and chemical evolution of both uncoated and coated silicon particles upon cyclic lithiation/delithation. We discovered that upon initial lithiation, the native oxide layer converts to crystalline Li2O islands, which essentially increases the impedance on the particle, resulting in ineffective lithiation/delithiation, and therefore low coulombic efficiency. In contrast, the alucone MLD coated particles show extremely fast, thorough and highly reversible lithiation behaviors, which are clarified to be associated with the mechanical flexibility and fast Li+/e- conductivity of the alucone coating. Surprisingly, the alucone MLD coating process chemically changes the silicon surface, essentially removing the native oxide layer and therefore mitigates side reaction and detrimental effects of the native oxide. This study provides a vivid picture of how the MLD coating works to enhance the coulombic efficiency and preserve capacity and clarifies the role of the native oxide on silicon nanoparticles during cyclic lithiation and delithiation. More broadly, this work also demonstrated that the effect of the subtle chemical modification of the surface during the coating process may be of equal importance as the coating layer itself.

Citation: 
He Y, DM Piper, M Gu, JJ Travis, SM George, SH Lee, A Genc, L Pullan, J Liu, SX Mao, J Zhang, C Ban, and CM Wang.2014."In-Situ Transmission Electron Microscopy Probing of Native Oxide and Artificial Layers on Silicon Nanoparticles for Lithium Ion Batteries."ACS Nano 8(11):11816-11823. doi:10.1021/nn505523c
Authors: 
He Y
DM Piper
M Gu
JJ Travis
SM George
SH Lee
A Genc
L Pullan
J Liu
SX Mao
J Zhang
C Ban
CM Wang
Volume: 
8
Issue: 
11
Pages: 
11816-11823
Publication year: 
2014

Enhancing the Lithiation Rate of Silicon Nanowires by the Inclusion of Tin.

Abstract: 

Silicon (Si) has a very high lithium storage capacity and is being explored as a negative electrode material in lithium-ion batteries (LIBs). Si nanowires can exhibit relatively stable performance for many cycles of charging; however, conductive carbon must often be added to the electrode layer to improve the rate capability due to the relatively low electrical conductivity of Si. The added carbon lowers the capacity of the electrode. Here, we show that the rate capability of Si in LIBs can be substantially enhanced by incorporating tin (Sn) into Si nanowires. The solubility of Sn in Si is very low (0.015 at%); yet, Sn used as a seed for supercritical fluid–liquid–solid (SFLS) growth can be trapped in Si nanowires with relatively high concentration (10 at%). Such Sn-containing Si nanowires and no added conductive carbon in the electrode layer, could be cycled in LIBs with high capacity (*1000 mA h g*1 over 100 cycles) at a current density of 2.8 A g*1 (1 C). Capacities exceeding that of graphite could still be reached at cycle rates as high as 2 C. Real-time in situ transmission electron microscopy (TEM) revealed that lithiation occurs five times faster in Si nanowires with significant amounts of Sn than in the Si nanowires without Sn, and twice as fast as in nanowires that were coated with carbon.

Citation: 
Bogart TD, X Lu, M Gu, CM Wang, and BA Korgel.2014."Enhancing the Lithiation Rate of Silicon Nanowires by the Inclusion of Tin."RSC Advances 4(79):42022-42028. doi:10.1039/c4ra07418a
Authors: 
TD Bogart
X Lu
M Gu
CM Wang
BA Korgel
Volume: 
4
Issue: 
79
Pages: 
42022-42028
Publication year: 
2014

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