Ice at Room Temperature: A NMR Investigation of H2O in Materials

under Ambient Conditions

Bernie O’Hare

The Pennsylvania State University

Outline

• Introduction into NMR• Our Hypothesis• Our Work• Introduction to Deuterium NMR

(brief) and Relaxation• Our Results• Our Conclusions

NMR Active Nuclei

Nuclear Magnetic Resonance

• First Observed by Isidor Rabi in 1938, later refined by Felix Bloch and Edward Purcell in 1946.

• NMR allows one to “tune in to” the desired nucleus by choosing the correct frequency (1-1000 MHz), because each nucleus has a specific Larmor frequency at a given magnetic field.

• NMR is not a sensitive technique. NMR requires a minimum concentration of ~1mM and a minimum sample volume of ~1 ml. Because of this, we need large surface area samples to study molecules at interfaces.

• Despite the above limitation, NMR is the one of the most powerful technique known for characterization of molecular structure and dynamics.

Modern NMR Spectrometer

• 1H Larmor frequency is 850 MHz

• ~ 20 Tesla Field• Used mainly for

biological macromolecules and protein structure/function studies

I Had Nothing to do with the Second Quench

SEE!

The Germans would have never been this happy with me.

What is NMR

No External Bo FieldExternal Bo Field Applied in the Z direction.

Bo

Net Magnetization

What Can NMR do?

• Molecular structure assignments for both small molecules and proteins up to 50 kDa in size in both the liquid and solid state.

• Dynamic studies of molecular translational diffusion.• Dynamic studies of rotational diffusion via NMR

relaxation.• Dynamics of solid state motion via NMR relaxation.• NMR can image the body or other objects given

sufficient gradients in known directions.• Analytical work by “spin counting” to ascertain the

amount of a given nuclei in a sample

NMR• Nuclear spins are aligned with or against the main magnetic field

axis.– With the magnetic field is a low energy state.– Against the magnetic field is a high energy state.– Slightly more spins are aligned with the magnetic field in the

lower energy state, but not many.

Magnetic Field Increasing

********

*********

Examples of NMR

The focus of this work utilizes NMR relaxation.

T1 NMR experiment of the 2H in 2H2O

1.bp.blogspot.com/.../y1gg-u9u2rM/s400/t1.jpg

Phase Diagram of H2O

http://www.lsbu.ac.uk/water/images/phase.gif

Materials Research with NMR

Kanemite (NaHSi2O5•3H2O)

• Atomic view of the kanemite crystal

• 10 Å interlayer spacings

• Can fit 3-4 layers of molecular H2O

• Naturally occurring crystal

GARVIE ET AL.: STRUCTURE OF NaHSi2O5·3H2O, Americ. Mineral 1999.

(Na) Zeolite-A (Na12Al12Si12O48•27H2O)

• Atomic view of (Na) Zeolite A• Supercage ~ 14 Å• Sodalite cages ~ 9 Å

• About 5 layers of molecular H2O can fit in the supercage.

• About 3 layers of molecular H2O can fit in the sodalite cages.

• Naturally occurring zeolite crystal.

http://www.zeolitepure.co.uk/USERIMAGES/Zeolite(1).jpg

Tricalcium Silicate Ca3SiO5 (C3S)

• Fully hydrated C-S-H

• Pure synthesized C3S crystals

1. Molecular dynamics simulations, scanning polarization force microscopy (SPFM), and sum frequency generation spectroscopy have shown the formation of room temperature “ice-like bilayers” on the surface of muscovite mica1, a hydrophilic aluminosilicate that can be used to “seed” clouds.

2. Room temperature solid state water is also commonly found in crystalline hydrates.2

3. At elevated pressure and temperatures slightly above the freezing point of pure water, solid state water is found as well in clathrate hydrates.3

Previous evidence for solid state water at room temperature:

1. (a) Hu, J; Xiao, X.-d.; Ogletree, D. F.; Salmeron, M. Surf. Sci. 1995, 344, 221-236. (b) Hu, J; Xiao, X.-d.; Ogletree, D. F.; Salmeron, M. Science 1995, 268, 267-269. (c) Odelius, M.; Bernasconi, M.; Parrinello, M. Phys. Rev. Lett. 1997,

78, 2855-2858. (d) Salmeron, M.; Bluhm, H. Surf. Rev. and Lett. 1999, 6, 1275-1281. 2. (a) Weiss, A.; Weiden, N. In Advances in Nuclear Quadrupole Resonance, Smith, J. A. S., Ed. Heyden: 1980, Vol. 4,

pp. 149-248. (b) Reeves, L. W. In Progress in NMR Spectroscopy, Emsley, J. W.; Feeney, J.; Sutcliffe, L. H. Eds. Pergamon:1969, Vol. 4, pp. 193-234.

3. (a) Bach-Verges, M.; Kitchin, S. J.; Harris, K. D. M.; Zugic, M.; Koh, C. A. J. Phys. Chem. B 2001, 105, 2699-2706. (b) Kirschgen, T. M.; Zeidler, M. D.; Geil, B.; Fujara, F. Phys. Chem. Chem. Phys. 2003, 5, 5247-5252.

We have used 2H NMR techniques, isothermal calorimetry, and FT-IR to investigate water (2H2O and 1H2O) in a variety of hydrated materials:

Kanemite, Zeolite A, Silicalite, Montmorillonite, Silica Gel, Porous Glass, Hydrated Tricalcium Silicate (cement), Hydroxyapatite, Cellulose, Nafion, and Sulfonimide substituted polyphosphazenes

We have found room temperature solid state water in all of these samples! We have publishedsome of the work in the papers below:

A. J. Benesi, M. W. Grutzeck, B. O’Hare, and J. W. Phair, “Room Temperature Solid Surface Water with Tetrahedral Jumps of 2H Nuclei Detected in 2H2O-Hydrated Porous Silicates”, J. Phys. Chem. B, 108, 17783-17790, 2004.

A. J. Benesi, M. W. Grutzeck, B. O’Hare, and J. W. Phair, “Room Temperature Ice-Like Water in Kanemite Detected by 2H NMR T1Relaxation”, Langmuir, 21, 527-529, 2005.

B. O’Hare, M.W. Grutzeck, D.B. Asay, S.H. Kim, and Alan J. Benesi “Solid State Water Motions Revealed by Deuterium Relaxation in 2H2O –Synthesized Kanemite and 2H2O Hydrated Na+ -Zeolite A”, Journal of Magnetic Resonance, 195, 85-102, 2008.

Why we use 2H NMR?

Because: We use 2H2O to hydrate our samples…

2H NMR well suited for studying molecular motion because:

Quadrupolar interaction dominates, so other interactionscan be ignored.

“Rigid” qcc = e2qQ/h = 160-300 kHz gives rise to characteristic powder pattern in spectrum (shown below for :

3/2 qcc

¾ qcc

There is a direct link between the observed 2H spectral frequency and the orientation of the (quadrupolar PAS) covalent bond relative

to the 2H nucleus and the applied magnetic field. Because all possible angles are found in a powdered sample, this gives rise to the powder pattern.

O

2H

B0

Because of this sensitivity

to motion, 2H NMR can be used to

characterize motions with frequencies ranging from ~1 x10-2 s-1 < < 1015 s-1.

Deuterium NMR and Motion

• Deuterium NMR is very sensitive to motion

– Motions << Qcc are considered rigid– Motions ~ Qcc are considered intermediate– Motions >> Qcc are considered fast

Qcc ≡ e2qQ/h

Types of Motion

• Low Symmetry• C2 rotations• C3 rotations• Diffusion in a cone• Tethered motion

• High Symmetry• Octahedral jumps• Tetrahedral jumps

Deuterium Motion Examples

d5- Benzoic Acid

COOH

DD

D D

D -At 22 deg C the phenyl ring flips are not apparent.

-All that is observed is a static powder pattern.

-Motion << Qcc

Phenyl Ring Flips (Calculated)

-200000 -100000 100000 200000

100

200

300

400

500

600

700

D D

DD

R

X -The deuterons undergo 180o rotations as the phenyl ring rotates

-This is a common occurrence in proteins and other large molecules with phenyl groups

d18- HMB

CD3

CD3

CD3D3C

D3C

D3C

Methyl groups experience fast 3 site jumps and produce a “mini” powder pattern as do other low symmetry fast motions.

Motion >> Qcc

d4-L-Alanine (Slow Pulse)

2 types of motion2 types of deuterons -fast 3 site jumps -slow 1 site motion

Motion >> Qcc Motion << Qcc

D3C COOH

H2N D

Vertical Expansion of L-Alanine

This expansions showsthe static pattern moreclearly

Motion << Qcc

D3C COOH

H2N D

Frozen D2O

The deuterons in ice slightly below its melting point exhibit highly symmetric, fast tetrahedral jumps which produce isotropic like lineshapes.

Motion >~ Qcc

D2O ice, -120 C

D2O ice, 0 Cfreezing pt. = 3.84 C,qcc

D2O liquid, 21 C >> qcc

qcc

2H quadrupole echo spectra of 2H2O (D2O):

This is why everyonemissed room tempsolid state water

Earlier Models

– Pure tetrahedral jumps. This model will work, but only at ONE given temperature, not very robust.

– Tetrahedral jumps on an pseudo-isotropic sphere. These 2 motions were not in fast exchange, so simple addition of the spectral densities was incorrect.

Our Relaxation Model is Simple and Robust

(1/Tn) Observed = XC2 (1/Tn )C2 + Xtet (1/Tn )tet

The relaxation times are calculated using the conventions of Mehring and are based on the formalism developed by Torchia and Szabo

The C2TET Relaxation Model

Spectral Densities Describing the Tetrahedral Relaxation

Spectral Densities Describing the C2 Relaxation

Calculating Spectral Densities

• Using the appropriate jump matrix (i.e. C2 or tetrahedral), one can calculate the pertinent spectral densities for any type of motion

• This is based on the formalism of Mehring but also heavily on Torchia and Szabo

T1 Relaxation Model for Zeolite-A compared to experimental

Low Temperature T1 Data

T1 Data for kanemite

Additional Evidence

Brief Comparison of the Arrhenius versus the Eyring Plot

GB RTk T

k eh

‡aE

RTk Ae

•They are essentially equivalent

•The Eyring plots ΔH‡ is the Arrhenius Ea.

•The ΔS‡ is entropic data not available from the Arrhenius equation

Arrhenius Equation Eyring Equation

Eyring Plots of Zeolite-A

Activation parameters are determined from the dynamic lineshape simulation data

Activation parameters are determined by high temperature T1 experimental data

1ln ln Bkk H S

T R T h R

‡ ‡

The plot of ln k/T versus 1/T gives a straight line with slope of

from which the enthalpy of activation can be derived and with intercept

from which the entropy of activation is derived.

H

R

‡

ln Bk S

h R

‡

FT-IR Support

Tricalcium Silicate • We propose the C2TET model to also exist in this system.• At any given time we can calculate the fraction of solid water to the

fraction of “free” liquid water.

• We propose that the initial strength in cement is due to the hydrogen bridges formed during the acceleratory period facilitating a phase change of bulk water to solid state water.

Isotope Effect on Setting of C3S

Vicat Needle ASTM Test

Conclusions• Deuterium NMR relaxation shows our C2TET solid state

water model to be consistent and robust over a wide temperature range

• VT-2H lineshape analysis is consistent with our C2TET model

• Eyring plots show that we have activation parameter results consistent with the C2TET model

• FT-IR gives us independent support of a solid state type of water in these materials

• Solid state water is at least partially responsible for the initial strengthening of cement

NMR at Penn State

The Bruker Biospin Lloyd Jackman Highfield NMR Facility

AV-III-600

AV-III-500

High field Hardware• All three instruments are equipped with four

channels making the implementation of 2H decoupling quite simple for biomolecules.

• All three are equipped with the latest software, TopSpin 2.1.with patch level 4.

• All three have the latest series cryoprobes and cryoplatforms (All CTI versions 5mm)

• The 850 has microimaging capabilities as well as a fast MAS probe included with the CTI probe and a BCU-Xtreme for low temperature solid state NMR.

The Open User’s Facility

Solid State NMR• Varian – Chemagnetics

Infinity Plus 500 spectrometer equipped with four channels and a high power gradient amplifier for solid state diffusion studies.

• There are many probes for this system including DAS and static probes.

Solid State NMR

• The 500 Solid State spectrometer and work station.

• VT capabilities as well as MAS and 19F are available and used.

• Triple resonance experiments, i.e. trapdor, etc… are conducted routinely.

Solid State NMR

• Tecmag, rebuilt from Chemagnetics 300 wide bore.

• Multitude of probes exist.

• Most of my deuterium relaxation work was done with this system.

Solid State NMR

• Bruker Avance 300 wide bore

• Equipped with a double resonance 4mm MAS probe.

• Capable of spin rates of 15 kHz.

• Mostly 1H-13C CP is done here.

• Also my homonuclear dipolar suppression work.

Solid State NMR

• Homebuilt 400 MHz widebore system.

• Used specifically by Dr. Karl Mueller’s group.

• Has limited capabilities.

Electronics Work and Probe Repair

My Collaborative Work at PSU

OLD MEETS NEW

13C-1H HSQC of 10% PEG

• Without BIRD filter the data is unintelligible.

• Incorporating older NMR techniques with newer gradient selected pulse sequences gives us a great advantage when studying real samples.

15N-1H HSQCNo BIRD Flipped the BIRD

Stereochemical determination via 2D Homonuclear NOE Spectroscopy

Distance determination of RNA via 2D Excitation Sculpted NOE

10 oC with 30 msec mixing time 1 oC with 200 msec mixing time

Standard Small Molecule Analysis

• Adiabatic, signal enhanced HMQC

Ionic Liquid Diffusion NMR

Industrial NMR

Impurity Analysis

6-Hexadecenoic Acid

Small Molecule Assignments

Energetic Materials Analysis

Ubiquitin

• A small 76 amino acid protein

• About 8.5 kDa• Perfect for acceptance

test procedures in NMR• Usually doubly labeled

with 15N and 13C isotopes• HSQC, TROSY-HSCQ,

HNCO, HNCACO are all common experiments to verify structure via NMR

15N-1H HSQC of Ubiquitin

13C-1H HSQC of Ubiquitin

How can we deal with spectral overlap?The HNCO 3D Experiment

Ubiquitin HNCO (3D-NMR)

3D-HNCO

TROSY-HSQC 50 kDa Protein

Solid State NMR at PSU

1H SS MAS of Sucrose 4 kHz

Can we make that better?

Spinning at 12 kHz helps a great deal, but the resolution is still poor.

My Time Averaged Magic Angle Spinning Echo Sequence

Comparison

Thank You All

Very Much!