This paper presents a strategy for immobilizing biomolecules on a photoactivable surface. A self-assembled monolayer is prepared by adsorbing an ω-functionalized dialkyl disulfide on gold. Functional groups of this monolayer are converted in two steps into a benzophenone derivative with an overall yield of 50 ± 10%. Several independent techniques (ellipsometry, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, radiolabel assay, and autoradiography) characterize the reaction and photoimmobilization of antibodies on this surface. The photoimmobilized antibodies cover the surface as a homogeneous and dense monolayer that could not be disrupted by vigorous washing with the detergent Tween 20. Immunoassays demonstrated specific recognition of the immobilized immunoglobulins as measured by their complexation with alkaline phosphatase-linked antibodies. The method of photoimmobilization used here leads to a homogeneous single layer of IgGs, in which the proteins maximize their contact with the surface. Residual adsorption of IgG on the nonirradiated surface of benzophenone remains one limitation of this approach. Progressively higher coverages of IgGs on the surface did not lead to strictly proportional changes of the biological activity of these surfaces, probably because of interactions between the IgGs in the film. This method of photoimmobilization is nonetheless useful as an experimental system to immobilize other proteins because it is simple, flexible, and efficient.

The nature and the role of 1 to 5 nm thick TiO 2 seed layers for the growth of textured PbTiO 3 and Pb(Zr,Ti)O 3 thin films on textured Pt(111) thin film substrates have been studied. Under otherwise identical in situ sputter deposition process conditions, the PbTiO 3 texture could be turned from (100) to (111) orientation by adding the seed layer. This is demonstrated by patterning the TiO 2 film. Auger electron spectroscopy and x-ray photoemission spectroscopy showed that the seed layer was a continuous TiO 2 film. X-ray photoelectron diffraction measurements revealed epitaxial ordering in the seed layer. As there is no azimuthal order among the Pt grains, the reduced information of azimuthally averaged polar cuts is obtained. These give strong evidence for a strained rutile (110) structure. Various deposition experiments indicated that the TiO 2 is effective only when it is ordered before the PbTiO 3 nucleation starts. The epitaxial relationship between PbTiO 3 (111) and Pt(111) is thus mediated by the intermediate, epitaxial TiO 2 film, which is dissolved or transformed to PbTiO 3 afterwards. The observed growth behavior is discussed in terms of surface and interface energies.

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