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Energy dissipation of nanoconfined hydration layer: long-range hydration on the hydrophilic solid surface.

ABSTRACT: The hydration water layer (HWL), a ubiquitous form of water on the hydrophilic surfaces, exhibits anomalous characteristics different from bulk water and plays an important role in interfacial interactions. Despite extensive studies on the mechanical properties of HWL, one still lacks holistic understanding of its energy dissipation, which is critical to characterization of viscoelastic materials as well as identification of nanoscale dissipation processes. Here we address energy dissipation of nanoconfined HWL between two atomically flat hydrophilic solid surfaces (area of ~120 nm(2)) by small amplitude-modulation, noncontact atomic force microscopy. Based on the viscoelastic hydration-force model, the average dissipation energy is ~1 eV at the tapping amplitude (~0.1 nm) of the tip. In particular, we determine the accurate HWL thickness of ~6 layers of water molecules, as similarly observed on biological surfaces. Such a long-range interaction of HWL should be considered in the nanoscale phenomena such as friction, collision and self-assembly.

SUBMITTER: Kim B

PROVIDER: S-EPMC4179125 | biostudies-other | 2014

REPOSITORIES: biostudies-other

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Energy dissipation of nanoconfined hydration layer: long-range hydration on the hydrophilic solid surface.

Kim Bongsu B Kwon Soyoung S Mun Hyosik H An Sangmin S Jhe Wonho W

Scientific reports 20140930

The hydration water layer (HWL), a ubiquitous form of water on the hydrophilic surfaces, exhibits anomalous characteristics different from bulk water and plays an important role in interfacial interactions. Despite extensive studies on the mechanical properties of HWL, one still lacks holistic understanding of its energy dissipation, which is critical to characterization of viscoelastic materials as well as identification of nanoscale dissipation processes. Here we address energy dissipation of ...[more]

PMID: 25267426

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Project description:Many different molecular species have been observed in the interstellar medium. These range from simple diatomic species to saturated organic molecules with several carbon atoms. The latter molecules are assumed to be formed predominantely on the surface of interstellar dust grains. All surface reactions that can proceed under the low interstellar temperatures are exothermic. Their exothermicity can be as high as a few electron volts, which is considerable compared to the thermal energy of the molecules at 10 K. It is postulated that this exothermicity can be used for the desorption of reaction products from the grain. In previous studies, we have shown that translational excitation can lead to desorption, whereas vibrational and rotational excitations are much less efficient in the desorption of surface products. Vibrational excitation is however much more likely upon bond formation than translational excitation. The present study follows energy dissipation upon translational, vibrational, or rotational excitation of admolecules on a surface and its conversion, or lack thereof, to different energy contributions. To this end, thousands of molecular dynamics simulations were performed with an admolecule on top of a surface that received a fixed amount of energy, vibrational, rotational, or translational. Three different surface species have been considered, CO2, H2O, and CH4, spanning a range in binding energies, the number of internal degrees of freedom, and molecular weights. A fast exchange of energy between vibrational stretches is observed, but only very limited exchange to rotational or translation excitation has been found. For the dissipation of energy to the surface, excitation of the surface-admolecule bond is critical. Astrochemical models often assume instantaneous equipartition of energy after a reaction process to estimate the amount of available energy for chemical desorption. Based on the present study, we conclude that this assumption is not justified.

Dataset Information

Energy dissipation of nanoconfined hydration layer: long-range hydration on the hydrophilic solid surface.

Publications

Energy dissipation of nanoconfined hydration layer: long-range hydration on the hydrophilic solid surface.

Similar Datasets

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