Variable Interfacial Water Nanosized Arrangements Measured by Atomic Force Microscopy

While there seems to be broad agreement that cluster formation does exist near solid surfaces, its presence at the liquid/vapor interface is controversial. We report experimental studies we have carried out on interfacial water attached on hydrophobic and hydrophilic surfaces. Nanosized steps in the measured force vs distance to the surface curves characterize water cluster profiles. An expansion of the interfacial structure with time is observed; the initial profile extent is typically similar to 1 nm, and for longer times expanded structures of similar to 70 nm are observed. Our previous results showed that the interfacial water structure has a relative permittivity of epsilon asymptotic to 3 at the air/water interface homogeneously increasing to epsilon 80 at 300 nm inside the bulk, but here we have shown that the interfacial dielectric permittivity may have an oscillating profile describing the spatial steps in the force vs distance curves. This low dielectric permittivity arrangements of clusters extend the region with epsilon asymptotic to 3 inside bulk water and exhibit a behavior similar to that of water networks that expand in time.