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The structure and formation mechanisms of 3-aminopropyltrimethoxysilane (3-APTS) films deposited on wet-chemically grown silicon dioxide over n-Si(100) wafer have been examined systematically using x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The asymmetric N 1s XPS spectrum for the anchored 3-APTS was fitted for -NH 2 (399.6 ± 0.3 eV) and -NH 3 + (401.1 ± 0.3 eV). Rougher surfaces are obtained by deposition from toluene solutions than from the gaseous phase. Over the 3-APTS layer was deposited the [FeTIM(CH 3 CN) 2 ]2+ complex, where TIM is 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene. The adsorption occurs by acetonitrile replacement for the-NH 2 -grafted group with the equatorial plane parallel to the organomodified surface. Once FeTIM can bind a CO, NO or N-heterocycle, a built-on Si wafer sensor device could be envisaged for these molecules.

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The activity of solid niobic acid treated with sulfuric acid and with phosphoric acid was tested in the catalytic esterification of oleic acid and in transesterification of soybean oil with methanol. X-ray diffraction studies revealed niobic acid treated with sulfuric acid to be an amorphous solid, while niobic acid treated with phosphoric acid presented a crystalline phase, probably due to the formation of hydrogen niobium phosphate. Among the characterization methods employed here, XPS was particularly instrumental in showing that niobium dihydrogen phosphate and niobium hydrogen sulfate moieties are the acidic active sites responsible for the catalytic effect. The latter is more active according to ammonia TPD studies. Yields as high as 78% in the esterification of oleic acid with methanol and 40% in the transesterification of soybean oil catalyzed by NbSO 4 were recorded.

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