Quasi-elastic Neutron Scattering Studies on Dynamics of Water Confined in Nanoporous Copper Rubeanate Hydrates

Published

October 14, 2011

Author(s)

Takeshi Yamada, Ryo Yonaimine, Teppei Yamada, Hiroshi Kitagawa, Madhu Sudan Tyagi, Michihiro Nagao, Osamu Yamamuro

Abstract

We have investigated the mechanism of the first order transition and proton conductivity in copper rubeanate hydrates from microscopic and dynamical points of view. Three different types of neutron spectrometer, time of flight, back scattering and neutron spin echo, were used to cover wide dynamic range (1 ps ¿ 100 ns). We found that the water molecules adsorbed in the pore is divided into the ¿free water¿ having diffusion coefficients similar to those of bulk water and the ¿condensed water¿ which is about 10 times slower than bulk water owing to the interaction with the pore wall. The hydrogen atoms in the pore wall exhibited no relaxation. The neutron spin echo measurement revealed that the first order transition is a kind of liquid-liquid transition at which the free water is condensed on the pore surface in the low temperature phase. On cooling the condensed water, the relaxation time starts to deviate from the VFT equation around 200 K as previously observed in the water confined in nano-porous silicates. The free water plays an important role as the proton carrier but the proton conductivity is mainly governed by the number of protons provided from the pore wall.

Citation

Journal of Physical Chemistry B

Volume

115

Pub Type

Journals

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Keywords

Dynamics, Neutron Scattering, Confinement, Water

Citation

Yamada, T. , Yonaimine, R. , Yamada, T. , Kitagawa, H. , Tyagi, M. , Nagao, M. and Yamamuro, O. (2011), Quasi-elastic Neutron Scattering Studies on Dynamics of Water Confined in Nanoporous Copper Rubeanate Hydrates, Journal of Physical Chemistry B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908310 (Accessed April 20, 2024)