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  • Title: Interaction of Rh with Rh nanoparticles encapsulated by ordered ultrathin TiO(1+x) film on TiO2(110) surface.
    Author: Berkó A, Gubó R, Ovári L, Bugyi L, Szenti I, Kónya Z.
    Journal: Langmuir; 2013 Dec 23; 29(51):15868-77. PubMed ID: 24299464.
    Abstract:
    Rh films of 5-50 monolayers (ML) were grown on TiO2(110)-(1 × 1) surface by physical vapor deposition (PVD) at 300 K followed by annealing at max. 1050 K. In the coverage range of 5-15 ML, separated stripe-like Rh nanoparticles of approximately 30 × 150 nm lateral size and 10-20 layer thickness with a flat top (111) facet were formed. At higher coverages (15-50 ML), the Rh film sustained its continuity at least up to 950 K. For both cases, the Rh(111) top facets were completely covered by a long-range ordered hexagonal "wagon-wheel" TiO(1+x) ultrathin oxide (hw-TiO-UTO) film. STM-STS, XPS, LEIS, and TDS methods were used for morphologic and electronic characterization of surfaces prepared in this way. The main part of this study is devoted to the study of postdeposition of Rh on the hw-TiO-UTO layer at different temperatures (230 K, 310 K, 500 K) and to the effect of subsequent annealing. It was found that 2D nanoparticles of 0.2-0.3 nm height and 1-2 nm diameter are formed at RT and their average lateral size increases gradually in the range of 300-900 K. The LEIS intensity data and the CO TDS titration of the particles have shown that an exchange of the postdeposited Rh atoms with the hw-TiO-UTO layer proceeds to an extent of around 50% at 230 K and this value increases up to 80-90% in the range of 300-500 K. The total disappearance of the characteristic LEIS signal for Rh takes place at around 900 K where a complete hw-TiO-UTO adlayer forms on top of the postdeposited metal (100% exchange).
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