Order and Orientation in Self-Assembled Long Chain Alkanephosphate Monolayers Adsorbed on Metal Oxide Surfaces

Octadecylphosphoric acid ester was employed to establish monolayers on various flat oxide substrates. The films were prepared via self-assembly from a heptane/propan-2-ol solution. The alkanephosphate was found to produce oriented, well-ordered films on titanium oxide, niobium oxide, and aluminum oxide surfaces. Contact-angle measurements and near-edge X-ray absorption fine structure spectroscopy (NEXAFS) indicate that these layers closely resemble those formed by a similar thiol−gold system, with respect to packing density, inclination, and molecular order. The preparation scheme appears to be rather universally applicable to a variety of metal oxide substrates. These systems show promise as an approach to functionalizing different oxide surfaces with well-ordered organic monolayers, with potential applications in the fields of corrosion protection, adhesion promotion, biochemical analysis, and sensors.