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Nanostructured Pt-Doped Tin Oxide Films: Sol−Gel Preparation, Spectroscopic and Electrical Characterization

2001; American Chemical Society; Volume: 13; Issue: 11 Linguagem: Inglês

10.1021/cm001228o

1520-5002

Franca Morazzoni, Carmen Canevali, N. Chiodini, C.M. Mari, Riccardo Ruffο, Roberto Scotti, Lidia Armelao, E. Tondello, Laura E. Depero, Elza Bontempi,

Transition Metal Oxide Nanomaterials

Nanostructured (3−6 nm) thin films (80 nm) of SnO2 and Pt-doped SnO2 were obtained by a new sol−gel route using tetra(tert-butoxy)tin(IV) and bis(acetylacetonato)platinum(II) as metal precursors. The results of glancing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS) investigations demonstrated that platinum substituted for tin(IV) in the cassiterite structure. Electron paramagnetic resonance (EPR) and XPS analyses showed that singly ionized paramagnetic oxygen vacancies (VO•) were formed on pure SnO2 thin films by interaction with CO atmosphere; in Pt-doped SnO2 films, the same defects VO• fully transferred their electrons to the noble metal so that Pt(IV) became Pt(II) and Pt(0). Such samples successively exposed to air, at room temperature, reduced O2 to O2-. The behavior was well-detected by EPR measurements, which showed on thin films the presence of Sn(IV)−O2- species. The surface reactivity agrees with the results of the electrical measurements.