Structure and Dynamics of Confined Alcohol–Water Mixtures

Abstract

The effect of confinement between mica and graphene on the structure and dynamics of alcohol-water mixtures has been studied in situ and in real time at the molecular level by atomic force microscopy (AFM) at room temperature. AFM images reveal that the adsorbed molecules are segregated into faceted alcohol-rich islands on top of an ice layer on mica, surrounded by a pre-existing multilayer water-rich film. These faceted islands are in direct contact with the graphene surface, revealing a preferred adsorption site. Moreover, alcohol adsorption at low relative humidity (RH) reveals a strong preference of the alcohol molecules for the ordered ice interface. The growth dynamics of the alcohol islands is governed by supersaturation, temperature, the free energy of attachment of molecules to the island edge and two-dimensional (2D) diffusion. The measured diffusion coefficients display a size dependence on the molecular size of the alcohols, and are about 6 orders of magnitude smaller than the bulk diffusion coefficients, demonstrating the effect of confinement on the behavior of the alcohols. These experimental results provide new insights into the behavior of multicomponent fluids in confined geometries, which is of paramount importance in nanofluidics and biology.

Wettability and Applications of Nanochannels

“…Reduced nanochannels dimensions could provide a stronger capillary force, which induced a high driving force for the fast Li confinement. Besides confinement of metal in 2D nanochannels, Bampoulis et al studied the real‐time confined behavior of various alcohol molecules, including ethanol, methanol, 2‐butanol, and 2‐propanol, between mica and graphene surface with an atomic force microscopy (AFM), and showed the alcohol molecules formed islands with both liquid‐like and crystal‐like behavior on the top of ice layers . It was also demonstrated the alcohol molecules prefer wetting at the graphene/ice interface, but water molecules prefer wetting the mica surface.…”

“…The explorations of 1D nanochannels wettability include CNTs, boron nitride nanotubes (BNNTs), polymeric nanochannels, alumina nanochannels, and silicon nitride nanochannels . 2D nanochannels comprised of graphene, mica, gold, reduced graphene oxide (rGO), and graphene oxide are studied to understand the confined 2D nanochannels wettability. The utilization of 3D nanochannels for wettability research contains porous carbon, porous metal, mesoporous silica, porous titanium dioxide, shale nanopores, and metal‐organic frameworks (MOFs) .…”

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

“…In the 2D nanofluidics, the charge density and membrane structure asymmetry could be influenced by confined adsorbates between 2D materials, resulting in enhanced ionic current rectification. Similarly, volatile small organic molecules can also be confined between 2D materials and substrate to form atomically thin films, which showed quite different properties from their bulk counterparts [24,28,[31][32][33]. For instance, tetrahydrofuran (THF) molecules formed atomically thin films in a layerby-layer manner and exhibited both liquid and solid properties, which were confirmed by atomic force microscopy (AFM) [24].…”

Insight into the wetting of a graphene-mica slit pore with a monolayer of water

“…It has been extensively used to investigate rheological properties of liquids squeezed between its surface and another solid surface [7][8][9]. High-resolution SFM imaging of graphene replicating the topography of thin-fluid films on a mica surface can potentially provide further insight into the properties of thin films, particularly of water films confined in this soft slit pore [10][11][12][13][14]. However, the properties of these water films remain controversial, not the least because of the limited information accessible so far.…”