NMR evidence of a sharp change in a measure of local order in deeply supercooled confined water

Using NMR, we measure the proton chemical shift δ, of supercooled nanoconfined water in the temperature range 195 K < T < 350 K. Because δ is directly connected to the magnetic shielding tensor, we discuss the data in terms of the local hydrogen bond geometry and order. We argue that the deriv...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 105; no. 35; pp. 12725 - 12729
Main Authors Mallamace, F, Corsaro, C, Broccio, M, Branca, C, González-Segredo, N, Spooren, J, Chen, S.-H, Stanley, H.E
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 02.09.2008
National Acad Sciences
Subjects
Chemical equilibrium
Correlation analysis
HDL lipoproteins
Heavy water
Hydrogen bonds
Liquids
Molecules
NMR
Nuclear magnetic resonance
Physical Sciences
Protons
Specific heat
Water
Water temperature
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Summary:Using NMR, we measure the proton chemical shift δ, of supercooled nanoconfined water in the temperature range 195 K < T < 350 K. Because δ is directly connected to the magnetic shielding tensor, we discuss the data in terms of the local hydrogen bond geometry and order. We argue that the derivative -([partial differential] ln δ/[partial differential]T)P should behave roughly as the constant pressure specific heat CP(T), and we confirm this argument by detailed comparisons with literature values of CP(T) in the range 290-370 K. We find that -([partial differential] ln δ/[partial differential]T)P displays a pronounced maximum upon crossing the locus of maximum correlation length at [almost equal to]240 K, consistent with the liquid-liquid critical point hypothesis for water, which predicts that CP(T) displays a maximum on crossing the Widom line.
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Present address: ETH Swiss Federal Institute of Technology Zurich, Computational Biophyics Lab, Universitaetstrasse 6, CAB E11, 8092 Zurich, Switzerland.
Author contributions: F.M., S.-H.C., and H.E.S. designed research; F.M., C.C., M.B., C.B., and J.S. performed research; F.M., C.C., M.B., C.B., N.G.-S., and J.S. analyzed data; and F.M., C.C., N.G.-S., and S.-H.C. wrote the paper.
Contributed by H. E. Stanley, May 30, 2008
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0805032105