Local water diffusivity as a molecular probe of surface hydrophilicity

The study of water’s functional role on hydrophilic surfaces of biological and soft materials benefits from experimental measurements that operate at finer length and time scales than contact-angle-measurement-derived surface wettability. We show that local translational diffusivity permits the empi...

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Bibliographic Details
Published in:MRS bulletin 2014-12, Vol.39 (12), p.1082-1088
Main Authors: Song, Jinsuk, Allison, Brendan, Han, Songi
Format: Article
Language:English
Subjects:
Applied and Technical Physics
Characterization and Evaluation of Materials
Diffusivity
Dynamics
Energy Materials
Hydrophilicity
Landscapes
Materials Engineering
Materials Science
Mathematical models
Nanotechnology
Surface chemistry
Surface water
Water at Functional Interfaces
Wettability
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Summary:The study of water’s functional role on hydrophilic surfaces of biological and soft materials benefits from experimental measurements that operate at finer length and time scales than contact-angle-measurement-derived surface wettability. We show that local translational diffusivity permits the empirical determination of local hydrophilicity by means of Overhauser dynamic nuclear polarization (ODNP) amplified 1H NMR relaxometry. Large unilamellar vesicles (LUVs) in dilute bulk water solution serve as good model hydrophilic surfaces, and their surface water diffusion was shown to be partially or entirely decoupled from the bulk water viscosity, with the extent of decoupling dependent on the surface activity of the particular viscogen chosen. The effective hydrophilicity of a hydrated LUV surface in solution was further shown to be tunable by specific ions or osmolytes dissolved in solution, and the chemical makeup of a surface can give rise to a heterogeneous hydration dynamics landscape, as demonstrated on protein surfaces. ODNP-derived surface water diffusivity is suggested to be a unique tool for the site-specific mapping of the interaction landscape of a wide range of functional materials operating in aqueous solution, from wet adhesives to fuel cell membranes.
ISSN:0883-7694
1938-1425
DOI:10.1557/mrs.2014.254