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Complex dynamics of partially freezable confined water revealed by combined experimental and computational studies

Title data

Steinrücken, Elisa ; Weigler, Max ; Kloth, Sebastian ; Vogel, Michael:
Complex dynamics of partially freezable confined water revealed by combined experimental and computational studies.
In: The Journal of Chemical Physics. Vol. 161 (2024) . - 014706.
ISSN 0021-9606
DOI: https://doi.org/10.1063/5.0215451

Official URL: Volltext

Abstract in another language

We investigate water dynamics in mesoporous silica across partial crystallization by combining broadband dielectric spectroscopy (BDS), nuclear magnetic resonance (NMR), and molecular dynamics simulations (MDS). Exploiting the fact that not only BDS but also NMR field- cycling relaxometry and stimulated-echo experiments provide access to dynamical susceptibilities in broad frequency and temperature ranges, we study both the fully liquid state above the melting point Tm and the dynamics of coexisting water and ice phases below this temperature. It is found that partial crystallization leads to a change in the temperature dependence of rotational correlation times τ, which occurs in addition to previously reported dynamical crossovers of confined water and depends on the pore diameter. Furthermore, we observe that dynamical susceptibilities of water are strongly asymmetric in the fully liquid state, whereas they are much broader and nearly symmetric in the partially frozen state. Finally, water in the nonfreezable interfacial layer below Tm does not exhibit a much debated dynamical crossover at ∼220 K. We argue that its dynamics is governed by a static energy landscape, which results from the interaction with the bordering silica and ice surfaces and features a Gaussian-like barrier distribution. Consistently, our MDS analysis of the motional mechanism reveals a hopping motion of water in thin interfacial layers. The rotational correlation times of the confined ice phases follow Arrhenius laws. While the values of τ depend on the pore diameter, freezable water in various types of confinements and mixtures shows similar activation energies of Ea ≈ 0.43 eV.

Further data

Item Type: Article in a journal
Refereed: No
Institutions of the University: Research Institutions
Research Institutions > Collaborative Research Centers, Research Unit
Research Institutions > Collaborative Research Centers, Research Unit > SFB 1585 - MultiTrans – Structured functional materials for multiple transport in nanoscale confinements
Result of work at the UBT: No
DDC Subjects: 500 Science > 530 Physics
500 Science > 540 Chemistry
Date Deposited: 15 Oct 2024 06:25
Last Modified: 15 Oct 2024 06:25
URI: https://eref.uni-bayreuth.de/id/eprint/90681