Linda Reven

McGill University, Chemistry, Department Member

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Address: Montréal, Québec, Canada

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2H NMR Studies of Polymer Multilayer Capsules, Films, and Complexes

Macromolecules, 2009

17O nuclear-magnetic-resonance spin-lattice relaxation and Knight-shift behavior in bismuthate, plumbate, and cuprate superconductors

Physical Review B, 1991

We have measured the 17 O nuclear-magnetic-resonance spin-lattice relaxation times (T 1 ) as a fu... more

Magic-angle spinning carbon-13 NMR spectroscopy of transition-metal carbonyl clusters

The Journal of Physical Chemistry, 1989

A variety of I3C-enriched metal carbonyl clusters (Fe3(CO)12, R U~( C O )~~, O S~( C O )~~, Rhs(C... more A variety of I3C-enriched metal carbonyl clusters (Fe3(CO)12, R U~( C O )~~, O S~( C O )~~, Rhs(C0)16, and Ir4(CO)12) have been examined by magic-angle spinning 13C nuclear magnetic resonance spectroscopy. The results yield both the isotropic chemical shifts and the principal components of the chemical shift tensor for each crystallographically distinct carbonyl site, as well as their spin-lattice relaxation times. With the 0.25-ppm resolution obtained at high field (8.45 T), effects from I3C-I3C and I3C-' O3RRh J coupling, as well as incompletely averaged 13C-1911r/1931r dipolar coupling, can be discerned. The chemical shift tensor components, obtained from analysis of spinning sideband intensities, are shown to be in generally good agreement with values previously obtained from broad-line spectra. The motionally averaged chemical shift tensor components for Fe3(CO)12, which is fluxional at room temperature, are shown to be consistent with a previously proposed exchange process.

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NMR of optically pumped xenon thin films

Chemical Physics Letters, 1992

ABSTRACT NMR of 129Xe has been observed in thin films of xenon frozen onto the surfaces of glass ... more ABSTRACT NMR of 129Xe has been observed in thin films of xenon frozen onto the surfaces of glass sample cells with various geometries. The 129Xe polarization was enhanced by optical pumping, and the xenon was then transferred to a high-field pulsed NMR spectrometer allowing the observation of strong signals from xenon films of approximately 1 μm thickness. The line shape depends on the film geometry because of the bulk diamagnetic susceptibility χD of solid xenon. The spectral line shape and resonance frequency also depend on temperature.

17O nuclear-magnetic-resonance spectroscopic study of high-Tc superconductors

Physical Review B, 1989

We have obtained solid-state Â¹â·O NMR spectra of a number of Â¹â·O-enriched oxides and high-te... more We have obtained solid-state Â¹â·O NMR spectra of a number of Â¹â·O-enriched oxides and high-temperature oxide superconductors, including Cuâ{sup I}O, Cu{sup II}O, KCu{sup III}Oâ, BiâOâ, TlâOâ, La{sub 1.85}Sr{sub 0.15}CuOâ, YBaâCuâO{sub 7-{ital x}}, BiâSrâCaCuâO{sub 8+{ital x}}, TlâBaâCaCuâO{sub 8+{ital x}}, and Ba{sub 0.6}K{sub 0.4}BiOâ. Spectra of all of the simple diamagnetic oxides contain relatively sharp resonances in a diamagnetic&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#x27;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#x27; region of {similar

High-field cross polarization NMR from laser-polarized xenon to a polymer surface

Journal of The American Chemical Society, 1993

We report the use of laser-polarized xenon as the source of magnetization for a high-field cross ... more We report the use of laser-polarized xenon as the source of magnetization for a high-field cross polarization experiment, obtaining surface-selective magnetization transfer. Contact between laser-polarized xenon and surface spins was achieved in high field by Hartmann-Hahn matching of the energy levels in the rotating frame with direct NMR detection of the polarized species. Proton spins are observed due to their

Spin-polarized xenon-129 NMR study of a polymer surface

The Journal of Physical Chemistry, 1993

A method for NMR studies of low surface area materials using optically pumped xenon gas is descri... more A method for NMR studies of low surface area materials using optically pumped xenon gas is described. The method has been used to investigate spin-polarized xenon adsorbed onto poly(acry1ic acid). The temperature dependence of the xenon-surface interaction, as measured by the xenon chemical shifts extrapolated to zero pressure, is shown to be consistent with a simple model of chemical exchange between the gas and adsorbed phases. The magnitude of the surface contribution to the 129Xe chemical shift indicates a relatively strong interaction between xenon and poly(acry1ic acid), possibly due to the polar carboxylic acid functional groups at the polymer surface. From the pressure dependence of the It9Xe shift, the diffusion coefficient of xenon on poly(acry1ic acid) is estimated to be 3.3 X lo-' cm2/s. (0 1993 American Chemical Society

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High-field NMR of adsorbed xenon polarized by laser pumping

Physical Review Letters, 1991

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Phosphonic and Sulfonic Acid-Functionalized Gold Nanoparticles: A Solid-State NMR Study

Langmuir, 2007

Gold nanoparticles capped with 11-mercaptoundecanylphosphonic acid (MUP) and sodium 10-mercaptode... more Gold nanoparticles capped with 11-mercaptoundecanylphosphonic acid (MUP) and sodium 10-mercaptodecanesulfonic acid (MDS) were characterized by a range of techniques which included solid-state 31 P and 13 C NMR spectroscopies. Despite similar core sizes and alkyl chain lengths, the conformational and dynamic properties of the capping ligands are very different for the two types of nanoparticles. Whereas MDS produces disordered monolayers on planar gold surfaces, the MDS-capped nanoparticles show a high degree of chain order with the onset of reversible chain disordering occurring just above room temperature. The alkyl chains of MUP adsorbed on the gold nanoparticles are more ordered and motionally restricted than the unbound solid surfactant due to strong intramonolayer and interparticle hydrogen bonds. This conformational order is thermally stable, and disordering only occurs upon decomposition and desorption of MUP from the gold core. Solid-state 31 P NMR has been demonstrated to be a sensitive probe of the interactions of the PO 3 H 2 terminal groups.

format_quoteThe study measures chemical shift anisotropy parameters of phosphonic acids on gold nanoparticles, revealing sensitivity to hydrogen-bonding interactions.format_quote

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Particle−Particle Interactions and Chain Dynamics of Fluorocarbon and Hydrocarbon Functionalized ZrO 2 Nanoparticles

Langmuir, 2008

The chain conformation and dynamics of hydrocarbon and perfluorocarbon fatty acids adsorbed on 4 ... more The chain conformation and dynamics of hydrocarbon and perfluorocarbon fatty acids adsorbed on 4 nm ZrO2 particles were characterized by solid-state 13C chemical shift and 19F NMR relaxation measurements, respectively, and compared to those from previous studies on lower surface area fumed metal oxide powders. The interdigitation of chains between neighboring particles, which increases with chain length, can be detected from the splitting of the 13C NMR and 19F NMR signals of the CH3 and CF3 groups, respectively. Similar to the case of alkanethiol self-assembled monolayers (SAMs) on gold nanoparticles, this interdigitation allows for efficient chain packing despite the high surface curvature. The hydrocarbon chains on the ZrO2 nanoparticles are more ordered, and the reversible chain length dependent order-disorder transition temperatures are elevated relative to those of the same fatty acids adsorbed on fumed ZrO2 powder. Likewise, the 19F spin lattice relaxation times of the fluorocarbon chains approach those of the bulk acids with increasing chain length and interdigitation, indicating densely packed chains.

Conformation of Adsorbed Random Copolymers: A Solid-State NMR and FTIR-PAS Study

Macromolecules, 2001

The properties of bulk and adsorbed polyethylene-co-acrylic acid (PEA) random copolymers were cha... more The properties of bulk and adsorbed polyethylene-co-acrylic acid (PEA) random copolymers were characterized by solid-state NMR and vibrational spectroscopy. FTIR-PAS (Fourier transform infrared photoacoustic spectroscopy) measurements show that the copolymers are chemisorbed to zirconia surfaces via the carboxylic acid sticker groups. The chain mobility, conformation, and morphology of bulk and adsorbed PEA were studied by 13 C CP-MAS, 2D WISE, and 1 H spin diffusion NMR experiments. The effect of the copolymer loading and acrylic acid content on these properties was examined. Whereas adsorbed PEA with a 5% w/w acrylic acid content contain transoid chain segments at all loadings, samples with higher acrylic acid contents (15 % w/w) only display an all-trans component at higher loadings where unbound acid groups are present.

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A Dynamic View of Self-Assembled Monolayers

Accounts of Chemical Research, 2000

In this Account, we discuss the dynamic features of self-assembled monolayers (SAMs) on both plan... more In this Account, we discuss the dynamic features of self-assembled monolayers (SAMs) on both planar and nonplanar substrates. Our focus is on organothiol and organic acid-based monolayers. Results from variable-temperature electrochemical, calorimetric, vibrational, and solid-state NMR spectroscopic measurements lead to a convergent description of SAM dynamics.

Gold−Sulfur Interactions in Alkylthiol Self-Assembled Monolayers Formed on Gold Nanoparticles Studied by Solid-State NMR

Journal of The American Chemical Society, 1997

... 8) (a) Whetten, RL; Khoury, JT; Alvarez, MM; Murphy, S.; Vezmar, I.; Wang, ZL; Stephens, PW; ... more

Self-Assembly of Carboxyalkylphosphonic Acids on Metal Oxide Powders

Langmuir, 2002

... Shane Pawsey, Kimberly Yach, and Linda Reven*. Department of Chemistry, McGill University, 80... more

19 F Fast Magic-Angle Spinning NMR Studies of Perfluoroalkanoic Acid Self-Assembled Monolayers

Langmuir, 2006

The bonding and dynamic properties of perfluoroalkanoic acid self-assembled monolayers (SAMs) on ... more The bonding and dynamic properties of perfluoroalkanoic acid self-assembled monolayers (SAMs) on zirconia and titania powders were characterized by Fourier transform infrared and solid-state 19F magic-angle spinning NMR spectroscopy. The perfluoro fatty acids investigated included C(n)F(2n+1)CO2H, n = 7, 13, 15 and 17. The acids bind to both metal oxides via ionic carboxylate bonds, but complete monolayers are only formed on the zirconia. The shift of the CF3 group from -83 ppm in the bulk state to -85 ppm for the adsorbed monolayers is assigned to CF3 groups located at the air/monolayer interface. With the exception of the perfluorooctanoic acid, 19F spin lattice relaxation measurements indicate that the fluorocarbon chains of the adsorbed acids, even in the case of densely packed monolayers, are significantly more mobile than those in the bulk state. The motions associated with the enhanced mobility of the adsorbed acids are proposed to involve reorientations along the long chain axes. No evidence for chain melting in the fluorocarbon SAMs is found for temperatures well above the melting temperature of the bulk acids.

Structure and Chain Dynamics of Alkanethiol-Capped Gold Colloids

Langmuir, 1996

ABSTRACT The structure and dynamical behavior of short and long chain alkanethiols, CH3(CH2)7SH a... more ABSTRACT The structure and dynamical behavior of short and long chain alkanethiols, CH3(CH2)7SH and CH3(CH)17SH, and of a hydroxyalkanethiol, HO(CH2)16SH, adsorbed onto gold nanoparticles were studied by variable temperature solid-state 13C NMR spectroscopy. In both the solution and solid state, the resonances of the first three carbons next to the sulfur headgroup disappear upon binding to the gold, indicating a strong interaction with the surface. A 13C-enriched sample, CH3(CH2)12*CH2SH/gold, displays a broad resonance centered at 42 ppm for the carbon next to the sulfur headgroup. Whereas the solid-state 13C shifts of CH3(CH2)7SH/gold are essentially the same as in solution, the methylene carbons of CH3(CH2)17SH and HO(CH2)16SH/gold shift downfield by 4.5 ppm in the solid state, indicating that the chains crystallize into an extended all-trans conformation. The high conformational order, along with reduced methylene proton line widths in the CH3(CH)17SH/gold sample, indicates that the chains are undergoing large-amplitude motions about their long axes. Molecular mobility increases toward the unbound ends which have a higher population of gauche conformers. Relaxation measurements show the coexistence of motionally restricted all-trans chains and a smaller population of liquid-like conformationally disordered chains in CH3(CH2)17SH/gold at room temperature. The two types of chains are proposed to arise from close packing of the gold colloidal spheres, resulting in interstitial spaces and regions where chains of neighboring colloids can interdigitate to produce ordered domains. Phase transitions of the thiol-capped gold nanocrystals, which are detected by differential scanning calorimetry, are shown to involve a reversible disordering of the alkyl chains.

The Effect of Terminal Hydrogen Bonding on the Structure and Dynamics of Nanoparticle Self-Assembled Monolayers (SAMs): An NMR Dynamics Study

Advanced Materials, 1998

... The Effect of Terminal Hydrogen Bonding on the Structure and Dynamics of Nanoparticle Self-As... more

Self-Assembled Monolayers of Alkylphosphonic Acids on Metal Oxides

Langmuir, 1996

Density-functional based calculations have been used to investigate self-assembled monolayers of ... more Density-functional based calculations have been used to investigate self-assembled monolayers of different alkylphosphonic acids on corundum α-Al 2 O 3 (0001), bayerite β-Al(OH) 3 (001) and boehmite γ-AlOOH (010) surface models. Mono-, bi-, and tridentate adsorption modes have been considered. In addition, the organization of single adsorbed molecules has been compared to the organization at full surface coverage. The height (thickness) of the self-assembled monolayers is always shorter than the length of the phosphonic acid molecules due to tilting of the alkyl chains. Tilt angles at full surface coverage are very similar to the tilt angle of a single adsorbed molecule, indicating that the density of the self-assembled monolayers is limited by the density of adsorption sites. The lateral interactions between alkyl chains are evidenced by small torsions of the adsorbed molecules, which may serve to minimize the repulsion forces between interchain hydrogen atoms. Similar tilt angles have been obtained for mono-, bi-, and tridentate adsorptions. Hence, the coordination mode cannot be characterized by the molecule tilting.

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Solid-State NMR Studies of Self-Assembled Monolayers

Langmuir, 1995

Phase Transitions in Lamellar Alkylphosphonate Salts

Chemistry of Materials, 1997

The thermal behavior of lamellar metal alkylphosphonate salts is sensitive to the valency of the ... more The thermal behavior of lamellar metal alkylphosphonate salts is sensitive to the valency of the metal cation. Sodium alkylphosphonates are similar to metal alkanoates, manifesting a small enthalpy transition from a crystalline solid phase to a dynamically disordered solid phase and then a large enthalpy transition to a fluid mesophase. Solid-state 13 C and 31 P NMR spectroscopies show that the large enthalpy transition is associated with melting of the hydrocarbon chains and mobilizing of the phosphonic acid headgroups. The smaller transition, involving the onset of mobility of the all-trans hydrocarbon chains and not the phosphonate headgroups which remain rigid, is detected by DSC and NMR. Above the melting transition, the sample becomes strongly birefringent, indicating the formation of an ordered fluid phase that persists up to the temperature at which the sample begins to lose lattice water. In the case of a divalent metal cation, Zn II (O 3 PC n H 2n+1 ), n ) 8, 14, 18, the enthalpies of the main transitions are much smaller and the transition temperatures are higher than the sodium alkylphosphonates. Variable-temperature 13 C and 31 P NMR spectra reveal that there is disordering of the hydrocarbon chains at the main transition temperature, but the metal phosphonate network remains intact.

$Figure 1. X-ray powder diffraction pattern of sodium octa- decylphosphonate (a) heated to 160 °C and then cooled to room temperature and (b) virgin sample. The intensity scales are the same in (a) and (b).$

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Linda Reven

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