The study of the entrapment of glucose oxidase (GOD) and horseradish peroxidase (HRP) enzymes on different solid-state substrates has been carried out. By using conventional methods, these enzymes have been immobilized on the following substrates: commercial Si wafers, thin films of nanostructured TiO 2 and gold nanotubes grown on polycarbonate membranes. Surface chemical composition and morphology of the samples have been investigated by means of X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Peak-fitting analysis of the main XPS signals permitted identification of the fingerprints of GOD and HRP enzymes and comparison of their entrapment on different substrates. The highest amount of attached enzymes was registered on the nanostructured TiO 2 films prepared by using the sol-gel technique. Moreover, the surface impurities, remaining on the samples after the immobilization of the phosphate buffer solution, were identified, and their removability by sample washing in deionized water was demonstrated.
Zirconium-stannate titanate Zr 1−x Sn x TiO 4 (ZTS) thin films, undoped and doped with Sb, Ta and Nb, were prepared by a polymeric precursor technique. The ZTS films were deposited on the multilayered substrates (Pt/Ti/SiO 2 /Si) by means of multiple spin-coating. After this deposition, the samples were heated at different temperatures (300-700• C). The chemical composition of these films and bulk ZTS samples was investigated by using x-ray photoelectron spectroscopy and selected-area XPS depth profiling. A partial surface segregation of Sn IV and the presence of Sn 0 , Ti II and Ti III species in the films were revealed from XPS depth profiles. An optimized ZTS deposition process, where an oxidizing agent (H 2 O 2 ) is added to the gel, is proposed.
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