Good morning and thank you all for coming. I made sure to pick a nice room with lots of windows. I apologize, I believe my voice is a bit hoarse. If it were like this on some of my interviews I might have a job to go to. Thank you again for coming and I cannot express how valuable and maturing both scientifically and personally my time was here. Today I’m going to discuss a rather strange phenomenon. Ice at room temperature that remains ice. You may already have heard of it and I’m here to talk more on it today.
I hate outlines and think they’re useless.
Today’s talk is NMR intensive. So for those that aren’t NMR jocks in the audience, don’t worry. I’ll sum it up briefly and you’ll know everything I know about it in 5 minutes. This is the NMR periodic table of nuclear spins. Any nucleus with a spin angular momentum number greater than 0 is an NMR active isotope. In fact there are very few isotopes that are not NMR active. 12C, unfortunately is one. Those with spin ½ (in yellow) are of most interest to biological NMR spectroscopists, and synthetic chemists. However those in the green and blue (more than 2/3 of the table) are the nuclei we will be most interested in today, the quadrupolar nucleus. It is any nucleus with spin greater that ½. We will mainly focus on an isotope of hydrogen known as deuterium. It will soon become apparent why.
Nuclear magnetic resonance was first observed by Isidor Rabi in 1938 and later refined by Purcell and Bloch. You may have heard of the Bloch equations which classically describe the bulk motion of magnetization under the influence of external RF fields of certain flip angles. NMR is quite like a radio in that we may tune into our desired nucleus (given it has nuclear spin of course). Depending on our magnetic field strength we will have certain resonant frequencies to probe. For example, with a 7 Tesla magnet protons will resonate around 300 MHz, 13-C around 75 MHz and 15-N around 30 MHz. It is this low energy interaction that is the direct cause of the inherent sensitivity of NMR. We may do things to improve the sensitivity i.e. cryoprobes, etc, or making the sample very (of course this isn’t convenient for solution state chemists, and not very comfortable for MRI patients either. So we deal with the sensitivity issues as they come through several means. Even though NMR is plagued with low sensitivity it is still the most powerful technique known for characterization of molecular structure and dynamics
This is a picture of our 20 Tesla magnet in the basement. It’s quite an impressive sight but in reality is very similar to all of our other lower field magnets. Protons resonant at 850 MHz, while 13-C is at 212.5 MHz, and 15-N around 85 MHz. This gives us a large sensitivity increase coupled with our cryoprobe. I haven’t been able to use this instrument for any part of my research due to its arrival, but hope to be able to use it soon.
Me with Norbert and Dominique from Bruker Germany.
The angular momentum vector may point in any direction in space. Without a magnetic field there is no net alignment of the momenta, i.e. NMR /MR is not possible. With a magnetic field applied the momenta are still wandering randomly but with a bias towards the lower energy level (parallel to the magnetic field). The biased wandering leads to a stable anisotropic distribution of spin polarizations. This is thermal equilibrium and is exaggerated here for the sake of clarity.
NMR is an extremely valuable tool for all areas of science.
Those spins aligned against the magnetic field are a higher energy state than those aligned with the magnetic field. According to the Boltzmann statistics and field strength there are slightly more spins aligned with the field (lower energy) than against the magnetic field. This external magnetic field creates the Zeeman interaction, which is required for this spectroscopy.
Here are some cartoon examples of various NMR experiments described in the previous slide.
Here is a typical T1 inversion recovery experiment used to measure the longitudinal or spin lattice relaxation rates. From this type of experiment, conducted at multiple magnetic fields, we can make educated and logical statements of the type of motion that may be occuring whether that is in the liquid state or solid state makes no difference.
This is a typical phase diagram for water showing off some of the various forms of ice, including Ice IX, one of professor Anderson’s favorites. We are dealing with only atmospheric pressures ~ 101 kPa / 1 ATM. We hypothesize that an extended structure of solid water can exist at room temperature, and in fact well above in certain confined spaces we will describe.
In our research we have analyzed a number of materials. To mention a few is Na-Zeolite-A, Kanemite, a phyllosilicate (sheet like structure), tricalcium silicate (the main ingredient in Portland cement), and cellulosic, starch like structures, which we will not discuss here. I don’t want to steal Tanuj’s thunder.
Kanemite is a layered sheet structure known as a phyllosilicate and has an interlayer spacing of 10 angstroms, in which an extended solid water structure of up to 4 layers of water can form.
Zeolite-A is the first synthetic zeolite and is counterbalanced ionically in this case with Na. The surface area is very difficult to measure due to the gaseous size of the probe molecule for a BET type of analysis and the small pores of the zeolite-A. That said, the inner surface area is very large and the perfect size to hold all solid state water with no exchange of free bulk water. Unlike other zeolites such as Zeolite-Y or X.
Tricalcium silicate is the main ingredient in Portland cement and has been used as a model system for the more complex cement hydration for close to a century. It is thought to also be a layered type of structure and does indeed contain the same phenomenon we have observed in other materials.
Unfortunately, we are not the first to make the statement that there is an ice-like state of water at room temperature. It has been long known that solid water exists in certain crystalline hydrates. This is evident from the deuterium quadrupolar powder patterns. As well as found on the surfaces of Mica.
Among other techniques such as vicat needle strength test, an ASTM method. DSC and TGA.
There are various other reasons why 2H NMR is our choice. That will become clear very soon.
This is the main reason we used deuterated water for many of our relaxation experiments. Interactions such as J, chemical shift, ID, DD may be ignored because the qcc of the quadrupolar interaction is often an order of magnitude or more than any of the other interactions values. We used D2O also for the usefullness in determining various types of motion through VT-static 2H NMR lineshape analysis. E is the charge on the electron, q is the second derivative of the electric potential at the nucleus and Q is the quadrupole moment. The manifestation of the 2H lineshape depend on the product of the quadrupole moment and the electric field gradient at the 2H nucleus (qcc).
Powdered solids contain small crystallites of the material with all possible orientations present. Variable angles of the O-D covalent bonds will give variable frequencies as a signal. When all possible angles are accounted for there is a powder pattern.
As I said earlier. 2H NMR is very sensitive to motion!
Here are various types of motion, each of which yield distinctive powder patterns for the specific type of motion. Let’s run through a quick set of motions and their lineshapes.
Qcc ~ 187 kHz
qcc~ 31.2 kHz
Many of the results we have and will talk about have been published most recently in the following paper. The math is a bit hairy so we will quickly skim over that. There is the paper and a full appendix to refer to for the rigorous calculations.
We’ve now settled on such a simple model that I feel I must tell you the previous models that finally brought us to the most robust form.
Shows how much slower the tetrahedral jumps are than the C2 motion at low temps. At 222 and 232 the rigid component from the tet is gone due to its motion going into the intermediate range. By 251 we see an isotropic like peak, well below the freezing point of water. Now the tet jumps are much faster than the qcc as are the C2 motions but we see the high symmetry lineshape.
These are two trivially equivalent expressions. But the Eyring equation also yields entropic data not available from the Arrhenius eq. Moving to the next slide we can see this more clearly in the linear form of the Eyring equation.
These plots show the activation parameters of zeolite a from the lineshape simulation data, and the high temp T1 data. These are 2 independent sources that yield basically the same slopes and same entropic and enthalpic values for each source.
We have values of the T1 observed at multiple field strenghts. We know the value of free D2O liq to be 400msec and assume the solid T1 to be values consistent with what we found for kanemite and zeolite a at the specific fields. With this assumption we were able to solve for the fraction of solid and liq water at any point. Truly, this is NOT mathematically rigorous as we made an assumption. However we have tested the set of equations and their solutions with random values for the solid T1 and were not able to find any values that were physically meaningful or any values in which the 2 forms of water converge.
THIS IS THE PROOF. At the point in which the calorimetry shows the heat is given off (exothermic reaction) all other data intersects. The Vicat needle depression has its steepest slope as do the T1 values. It is all consistent with the increase of the solid fraction of the water providing some initial strenthening of the hydrate. Also notice the T1 field dependence increase as a function of time.
This shows the dramatic role that water plays in the hydration of C3S. If water were not a critical element of the hydration process there would be no isotope effect.
BVO Research Summary
Ice at Room Temperature: A NMR Investigation of H 2 O in Materials under Ambient Conditions Bernie O’Hare The Pennsylvania State University
Outline <ul><li>Introduction into NMR </li></ul><ul><li>Our Hypothesis </li></ul><ul><li>Our Work </li></ul><ul><li>Introduction to Deuterium NMR (brief) and Relaxation </li></ul><ul><li>Our Results </li></ul><ul><li>Our Conclusions </li></ul>
Nuclear Magnetic Resonance <ul><li>First Observed by Isidor Rabi in 1938, later refined by Felix Bloch and Edward Purcell in 1946. </li></ul><ul><li>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. </li></ul><ul><li>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. </li></ul><ul><li>Despite the above limitation, NMR is the one of the most powerful technique known for characterization of molecular structure and dynamics. </li></ul>
Modern NMR Spectrometer <ul><li>1 H Larmor frequency is 850 MHz </li></ul><ul><li>~ 20 Tesla Field </li></ul><ul><li>Used mainly for biological macromolecules and protein structure/function studies </li></ul>
SEE! The Germans would have never been this happy with me.
What is NMR No External B o Field External B o Field Applied in the Z direction. B o Net Magnetization
What Can NMR do? <ul><li>Molecular structure assignments for both small molecules and proteins up to 50 kDa in size in both the liquid and solid state. </li></ul><ul><li>Dynamic studies of molecular translational diffusion. </li></ul><ul><li>Dynamic studies of rotational diffusion via NMR relaxation. </li></ul><ul><li>Dynamics of solid state motion via NMR relaxation. </li></ul><ul><li>NMR can image the body or other objects given sufficient gradients in known directions. </li></ul><ul><li>Analytical work by “spin counting” to ascertain the amount of a given nuclei in a sample </li></ul>
NMR <ul><li>Nuclear spins are aligned with or against the main magnetic field axis. </li></ul><ul><ul><li>With the magnetic field is a low energy state. </li></ul></ul><ul><ul><li>Against the magnetic field is a high energy state. </li></ul></ul><ul><ul><li>Slightly more spins are aligned with the magnetic field in the lower energy state, but not many. </li></ul></ul>Magnetic Field Increasing ******** *********
Kanemite (NaHSi 2 O 5 •3H 2 O) <ul><li>Atomic view of the kanemite crystal </li></ul><ul><li>10 Å interlayer spacings </li></ul><ul><li>Can fit 3-4 layers of molecular H 2 O </li></ul><ul><li>Naturally occurring crystal </li></ul>GARVIE ET AL.: STRUCTURE OF NaHSi2O5·3H2O, Americ. Mineral 1999.
(Na) Zeolite-A (Na 12 Al 12 Si 12 O 48 • 27H 2 O) <ul><li>Atomic view of (Na) Zeolite A </li></ul><ul><li>Supercage ~ 14 Å </li></ul><ul><li>Sodalite cages ~ 9 Å </li></ul><ul><li>About 5 layers of molecular H 2 O can fit in the supercage. </li></ul><ul><li>About 3 layers of molecular H 2 O can fit in the sodalite cages. </li></ul><ul><li>Naturally occurring zeolite crystal. </li></ul>http://www.zeolitepure.co.uk/USERIMAGES/Zeolite(1).jpg
Tricalcium Silicate Ca 3 SiO 5 (C 3 S) <ul><li>Fully hydrated C-S-H </li></ul><ul><li>Pure synthesized C 3 S crystals </li></ul>
<ul><li>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 mica 1 , a hydrophilic aluminosilicate that can be used to “seed” clouds. </li></ul><ul><li>Room temperature solid state water is also commonly found in crystalline hydrates. 2 </li></ul><ul><li>At elevated pressure and temperatures slightly above the freezing point of pure water, solid state water is found as well in clathrate hydrates. 3 </li></ul>Previous evidence for solid state water at room temperature: <ul><li>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 . </li></ul><ul><li>(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. </li></ul><ul><li>(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. </li></ul>
We have used 2 H NMR techniques, isothermal calorimetry, and FT-IR to investigate water ( 2 H 2 O and 1 H 2 O) 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 published some 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 2 H Nuclei Detected in 2 H 2 O-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 2 H NMR T 1 Relaxation”, 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 2 H 2 O –Synthesized Kanemite and 2 H 2 O Hydrated Na + -Zeolite A”, Journal of Magnetic Resonance, 195, 85-102, 2008.
Why we use 2 H NMR? Because: We use 2 H 2 O to hydrate our samples…
2 H NMR well suited for studying molecular motion because: Quadrupolar interaction dominates, so other interactions can be ignored. “ Rigid” qcc = e 2 qQ/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 2 H spectral frequency and the orientation of the (quadrupolar PAS) covalent bond relative to the 2 H nucleus and the applied magnetic field. Because all possible angles are found in a powdered sample, this gives rise to the powder pattern. O 2 H B 0 Because of this sensitivity to motion, 2 H NMR can be used to characterize motions with frequencies ranging from ~1 x10 -2 s -1 < < 10 15 s -1 .
Deuterium NMR and Motion <ul><li>Deuterium NMR is very sensitive to motion </li></ul><ul><ul><li>Motions << Qcc are considered rigid </li></ul></ul><ul><ul><li>Motions ~ Qcc are considered intermediate </li></ul></ul><ul><ul><li>Motions >> Qcc are considered fast </li></ul></ul><ul><ul><li>Qcc ≡ e 2 qQ/h </li></ul></ul>
Types of Motion <ul><li>Low Symmetry </li></ul><ul><li>C2 rotations </li></ul><ul><li>C3 rotations </li></ul><ul><li>Diffusion in a cone </li></ul><ul><li>Tethered motion </li></ul><ul><li>High Symmetry </li></ul><ul><li>Octahedral jumps </li></ul><ul><li>Tetrahedral jumps </li></ul>
d5- Benzoic Acid -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) -The deuterons undergo 180 o rotations as the phenyl ring rotates -This is a common occurrence in proteins and other large molecules with phenyl groups
d18- HMB 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 motion 2 types of deuterons - fast 3 site jumps - slow 1 site motion Motion >> Qcc Motion << Qcc
Vertical Expansion of L-Alanine This expansions shows the static pattern more clearly Motion << Qcc
Frozen D2O The deuterons in ice slightly below its melting point exhibit highly symmetric, fast tetrahedral jumps which produce isotropic like lineshapes. Motion >~ Qcc
D 2 O ice, -120 C D 2 O ice, 0 C freezing pt. = 3.84 C, qcc D 2 O liquid, 21 C >> qcc qcc 2 H quadrupole echo spectra of 2 H 2 O (D 2 O): This is why everyone missed room temp solid state water
Earlier Models <ul><ul><li>Pure tetrahedral jumps. This model will work, but only at ONE given temperature, not very robust. </li></ul></ul><ul><ul><li>Tetrahedral jumps on an pseudo-isotropic sphere. These 2 motions were not in fast exchange, so simple addition of the spectral densities was incorrect. </li></ul></ul>
Our Relaxation Model is Simple and Robust <ul><li>( 1/T n ) Observed = X C2 (1/T n ) C2 + X tet (1/T n ) tet </li></ul><ul><li>The relaxation times are calculated using the conventions of Mehring and are based on the formalism developed by Torchia and Szabo </li></ul>The C2TET Relaxation Model
Spectral Densities Describing the Tetrahedral Relaxation
Spectral Densities Describing the C 2 Relaxation
Calculating Spectral Densities <ul><li>Using the appropriate jump matrix (i.e. C2 or tetrahedral), one can calculate the pertinent spectral densities for any type of motion </li></ul><ul><li>This is based on the formalism of Mehring but also heavily on Torchia and Szabo </li></ul>
T 1 Relaxation Model for Zeolite-A compared to experimental
Brief Comparison of the Arrhenius versus the Eyring Plot <ul><li>They are essentially equivalent </li></ul><ul><li>The Eyring plots Δ H ‡ is the Arrhenius E a. </li></ul><ul><li>The Δ S ‡ is entropic data not available from the Arrhenius equation </li></ul>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 T 1 experimental data 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.
Tricalcium Silicate <ul><li>We propose the C2TET model to also exist in this system. </li></ul><ul><li>At any given time we can calculate the fraction of solid water to the fraction of “free” liquid water. </li></ul>
<ul><li>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. </li></ul>
Isotope Effect on Setting of C 3 S Vicat Needle ASTM Test
Conclusions <ul><li>Deuterium NMR relaxation shows our C2TET solid state water model to be consistent and robust over a wide temperature range </li></ul><ul><li>VT- 2 H lineshape analysis is consistent with our C2TET model </li></ul><ul><li>Eyring plots show that we have activation parameter results consistent with the C2TET model </li></ul><ul><li>FT-IR gives us independent support of a solid state type of water in these materials </li></ul><ul><li>Solid state water is at least partially responsible for the initial strengthening of cement </li></ul>
High field Hardware <ul><li>All three instruments are equipped with four channels making the implementation of 2 H decoupling quite simple for biomolecules. </li></ul><ul><li>All three are equipped with the latest software, TopSpin 2.1.with patch level 4. </li></ul><ul><li>All three have the latest series cryoprobes and cryoplatforms (All CTI versions 5mm) </li></ul><ul><li>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. </li></ul>
Solid State NMR <ul><li>Varian – Chemagnetics Infinity Plus 500 spectrometer equipped with four channels and a high power gradient amplifier for solid state diffusion studies. </li></ul><ul><li>There are many probes for this system including DAS and static probes. </li></ul>
Solid State NMR <ul><li>The 500 Solid State spectrometer and work station. </li></ul><ul><li>VT capabilities as well as MAS and 19 F are available and used. </li></ul><ul><li>Triple resonance experiments, i.e. trapdor, etc… are conducted routinely. </li></ul>
Solid State NMR <ul><li>Tecmag, rebuilt from Chemagnetics 300 wide bore. </li></ul><ul><li>Multitude of probes exist. </li></ul><ul><li>Most of my deuterium relaxation work was done with this system. </li></ul>
Solid State NMR <ul><li>Bruker Avance 300 wide bore </li></ul><ul><li>Equipped with a double resonance 4mm MAS probe. </li></ul><ul><li>Capable of spin rates of 15 kHz. </li></ul><ul><li>Mostly 1H-13C CP is done here. </li></ul><ul><li>Also my homonuclear dipolar suppression work. </li></ul>
Solid State NMR <ul><li>Homebuilt 400 MHz widebore system. </li></ul><ul><li>Used specifically by Dr. Karl Mueller’s group. </li></ul><ul><li>Has limited capabilities. </li></ul>
13C-1H HSQC of 10% PEG <ul><li>Without BIRD filter the data is unintelligible. </li></ul><ul><li>Incorporating older NMR techniques with newer gradient selected pulse sequences gives us a great advantage when studying real samples. </li></ul>
Ubiquitin <ul><li>A small 76 amino acid protein </li></ul><ul><li>About 8.5 kDa </li></ul><ul><li>Perfect for acceptance test procedures in NMR </li></ul><ul><li>Usually doubly labeled with 15 N and 13 C isotopes </li></ul><ul><li>HSQC, TROSY-HSCQ, HNCO, HNCACO are all common experiments to verify structure via NMR </li></ul>