Relaxation dynamics of surface-adsorbed water molecules in nanoporous silica probed by terahertz spectroscopy

Yu Ru Huang, Kao Hsiang Liu, Chung Yuan Mou, Chi Kuang Sun

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Relaxation dynamics of an exclusively adsorbed water molecule in mesoporous silica MCM-41-S was studied by using terahertz spectroscopy. With the temperature controlled from 0 to 50°C, we observed strongly frequency- and temperature-dependent dielectric relaxation responses, implying that, unlike ice, surface-adsorbed water molecules retained flourishing picosecond dynamics. Based on the Debye relaxation model, a relaxation time constant was found to increase from 1.77 to 4.83 ps when the water molecule was cooled from 50 to 0°C. An activation energy of ∼15 kJ/mol, which was in close agreement with a hydrogen-bonding energy, was further extracted from the Arrhenius analysis. Combined with previous molecular dynamics simulations, our results indicate that the reorientation relaxation originated from the "flip-flop" rotation of a three hydrogen-bonded surface-adsorbed water molecule.

Original languageEnglish
Article number081607
JournalApplied Physics Letters
Volume107
Issue number8
DOIs
Publication statusPublished - Aug 24 2015
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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