1. Troyer et al SolStNMR 28(2005),238 -Topic of the paper: strange liquid states of water in nano-pores -Tool used: nuclear magnetic resoance (NMR) spin-spin relaxation - Main message: proton spins make good local probe for determination of amount of water in surface and in bulk-like state Message talk: Let’s understand the field, the method, and then let’s evaluate the paper.

2. Condensed Matter Physics – Phase Transitions The problem of water The problem of liquids in confined geometries Traditionally, three phases of matter: gas, liquid, solid Every material changes between these phases as function of:pressure temperature volume p,V,T dep. are described in thermodynamics 

3. Phase diagram Ice/Water http://www.lsbu.ac.uk/water/phase.html Reality isn’t quite as nice: The case of water closeup

4. The problem: For water the hydrogen bond is delicate Liquid water consists of a mixture of short, straight and strong hydrogen bonds and long, weak and bent hydrogen bonds with many intermediate between these extremes. 

5. A whole different animal: Pores, nano-pores and water in (nano)pores The problem is very relevant for many unsolved issues In biophysical fields, technical issues like crude oil harvesting, or academic problems like flow in nano confinements. Question: What happens to the phase diagram of water in pores? What happens when other phases or solutes are present? The present paper is cutting-edge in this incomplete story. IE don’t confuse it with textbook knowledge. And: How does one measure these properties and processes?  a local probe is necessary

6. NMR is such a probe:

7. Left to right: 3mm slices, 6mm spaced Influence T 1 2s (above), 0.5s (below)

8. Influence of shuffling on water dis.

10. Motion in pores Influence of local environment on relaxation. Influence of changed dynamics. In nano-pores the ‘moveability’ of a water molecule changes by two Orders of magnitude between surface and pseudo-bulk water!

11. Influence of local structure/geometry on susceptibility, hence line position.

12. Evaluating the paper: Three principle ways of water filling for nano-pores. (1)All pores contain water but small pores fill faster (2) All pores filled completely (3) Not all pores contain water Thus the understanding of the ‘virgin’ state of the sample is very important (dry weight, cleaning, checking for traces of molecular water)

13. What does the statement mean: ‘At higher hydration levels, the decay curves exhibited bi-exponential behavior’? It means there are two phases. But how well can such data be separated? Note, these are not raw data but separated curves! So what would the actual raw data have looked like? 

14. Puddle model: Plug model: pores hydrated via filling of surface layer followed by growth in thickness ‘the plug’ – this is in agreement with one phase being present Details not very accessible (published as thesis) Dimensionless puddle size Study shows no clear indication which water filling model applies.  Same eqn

15. Troyer et al SolStNMR 28(2005),238