Scanning Polarization Force Microscopy Study of the Condensation and Wetting Properties of Glycerol on Mica

Abstract

The condensation of glycerol on mica surfaces in ambient air was studied with scanning polarization force microscopy (SPFM). Two different wetting regimes were found that depend on the state of the surface. On freshly cleaved mica, glycerol condenses, forming flat films. The films expand until a uniform layer is formed. The first molecular layer of glycerol was found to be more strongly bound to the surface than were subsequent layers. On contaminated mica (after 2 h of exposure to air) droplets in the shape of spherical caps form that partially wet the substrate. The droplets grow indefinitely in the saturated vapor. The contact angle of droplets with heights <20 nm was found to deviate from the macroscopic value found in large drops. The results are discussed in the context of the long-range forces in the liquid film.

Glycerol facilitates the disaggregation of recombinant adeno-associated virus serotype 2 on mica surface

“…Second, the influence of the substrate on the dispersion of particles would be considered. Xu and Salmeron found that a thickness of 1.5 nm inner glycerol layers strongly adhered to the mica through the spreading of droplet of water-glycerol deposited on bare mica [24]. The adhered glycerol layer may increase local concentration of glycerol, which may enhance the depletion effect of glycerol.…”

Wetting in the nanoscale: A continuum mechanics approach

“…However, at the nanometric level, it is quite difficult to observe the geometry of drops in full detail, including their contact angles. No optical instruments can obviously detect objects smaller than visible light wavelength, while only ESEM or probe microscope techniques (like SPFM) provide a good insight of nanodrops [40][41][42][43][44][45][46][47][48].…”

Scanning Polarization Force Microscopy: a Technique for Studies of Wetting Phenomena At the Nanometer Scale

“…The fact that the dielectric constant depends on the frequency (Xu and Salmeron, 1998a) gives SPFM an interesting spectroscopic character. Local dielectric spectroscopy, i.e., the study of ε(ω), can be performed by varying the frequency of the applied bias.…”

“…(b) A plot of the effective contact angle θ of the glycerol drops on contaminated mica vs. drop height e. A rapid increase occurs up to 200 Å (corresponding to a drop with a base diameter of ~ 2.2 µm), where it reaches a constant value θ 0 . Inset: Plot of (θ 2 0 -θ 2 ) / (1 + e/δ) vs. e. This plot shows that the potential due to the long-range forces depends exponentially on the distance (from Xu and Salmeron, 1998a).…”

“…It is clear that the effective contact angle is influenced by the disjoining pressure. We shall use this expression to determine P(e) from experiments with nanoscopic size droplets (Xu and Salmeron, 1998a).…”