Anomalously low dielectric constant of confined water

The dielectric constant ε of interfacial water has been predicted to be smaller than that of bulk water (ε ≈ 80) because the rotational freedom of water dipoles is expected to decrease near surfaces, yet experimental evidence is lacking. We report local capacitance measurements for water confined be...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2018-06, Vol.360 (6395), p.1339-1342
Main Authors: Fumagalli, L, Esfandiar, A, Fabregas, R, Hu, S, Ares, P, Janardanan, A, Yang, Q, Radha, B, Taniguchi, T, Watanabe, K, Gomila, G, Novoselov, K S, Geim, A K
Format: Article
Language:English
Subjects:
Atomic force microscopy
Boron
Boron nitride
Capacitance
Channels
Computational fluid dynamics
Constants físiques
Dielectric constant
Dielectric properties
Electrical properties
Molecular chains
Permittivity
Physical constants
Química de l'aigua
Rotation
Water
Water chemistry
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Summary:The dielectric constant ε of interfacial water has been predicted to be smaller than that of bulk water (ε ≈ 80) because the rotational freedom of water dipoles is expected to decrease near surfaces, yet experimental evidence is lacking. We report local capacitance measurements for water confined between two atomically flat walls separated by various distances down to 1 nanometer. Our experiments reveal the presence of an interfacial layer with vanishingly small polarization such that its out-of-plane ε is only ~2. The electrically dead layer is found to be two to three molecules thick. These results provide much-needed feedback for theories describing water-mediated surface interactions and the behavior of interfacial water, and show a way to investigate the dielectric properties of other fluids and solids under extreme confinement.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.aat4191