Adsorption geometry and reactivity of the phosphonic acid linker group on cerium oxide thin films

Spontaneously adsorbed organic monolayers have recently received a great deal of attention for their enormous potential in tailoring surface properties of materials for catalysts, sensors, nonlinear optics and memory devices. Chemical functionalization of metal oxide surfaces by covalent attachment of organic molecules offers one of the most general strategies for synthesis of new materials for nanotechnology. In organic/inorganic hybrid materials the organic part is introduced through a linker group, such as thiol for gold or trichlorosilane for silicon surfaces. The phosphonate group (-PO(OH)₂) has been shown to be a promising linker on various oxide surfaces, but no surface science studies exist for ceria surfaces so far. Phosphonic acids are known to bind strong to oxide surfaces and they are expected to be more temperature-stable than carboxylic acid groups. To fully understand the interactions between the linker group and the surface we propose to study the adsorption geometry and reactivity of a small model molecule, for instance phenylphosphonic acid, alkanephosphonic acid, etc. on cerium oxide films of different stoichiometry and morphology. The system will be studied by combining lab-source and synchrotron-radiation X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, atomic force microscopy and scanning electron microscopy.