Phase Transition of Nanoconfined Water in Clay: Positron Annihilation, Nuclear Magnetic Resonance, and Dielectric Relaxation Studies

• Published in: Journal of physical chemistry. C 2013-07, Vol.117 (27), p.14313-14324
• Main Authors: Maheshwari, Priya, Pujari, P. K, Sharma, S. K, Dutta, D, Sudarshan, K, Mithu, V. S, Madhu, P. K, Deshpande, S. K, Patil, P. N, Raje, N
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Physics; Specific phase transitions; Structural transitions in nanoscale materials; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp403212c

The structural and dynamical features associated with the phase behavior of water confined in clay nanopores (2D confined water) are studied using positron annihilation spectroscopy, nuclear magnetic resonance, and dielectric relaxation spectroscopy techniques. We report the experimental evidence of a new phase transition (above the bulk freezing point of water) in nanoconfined water, in addition to a low-temperature transition in supercooled water. The study reveals it to be a structural rearrangement of water molecules associated with modification of hydrogen-bonded network. Evidence also suggests the dynamical arrest/immobilization of water layer near the clay platelet surface (bound water molecules) to be associated with this transition. This transition is a manifestation of the role of surface interaction on the phase behavior of confined liquids.