Water on surface studied by scanning probe microscopies

Abstract

The wetting properties of a surface exposed to water determine crucial phenomena in biology, chemistry and material sciences. Scanning Probe Microscopies have recently opened new ways to study water films and droplets on surfaces allowing the study of the wetting properties of surfaces at molecular level. Several approaches providing different information on the phenomena have been developed. Scanning Tunneling Microscopy is being used to study the structure of water clusters and water monolayers, but unfortunately these studies are limited to low temperatures and conductive substrates. Atomic Force Microscopy working in non-contact electrostatic modes has become a powerful tool to investigate wetting in ambient conditions. This technique is being used to study the structure of water films beyond the first monolayer, imaging droplets at the nanometer range to study hydrophobicity and hydrophillicity at molecular level, studying chemical processes within adsorbed water films or probing the impermeability of molecular coatings used in nanotechnology. A selection of illustrative Scanning Probe Microscopy studies covering different scientific and technologically relevant aspects related to water and surfaces on water is presented in this review.