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Abstract: Phosphor powders of Yb3+ co-doped BaZrO3:Er3+ have been prepared by the urea combustion route. The formation of single-phase BaZrO3:Er3+ and BaZrO3:Er3+,Yb3+ was confirmed by X-ray powder diffraction (XRD). Green and red luminescence along with a weaker blue emission is observed upon excitation at ∼978nm with a diode laser. These emissions are caused by frequency upconversion in the Er3+-doped BaZrO3 (BZO) phosphor. Both the green and red upconversion emissions of the Er3+ are enhanced by about ∼3 and ∼43 times respectively when triply ionized ytterbium is incorporated as a co-dopant. The frequency upconversion processes responsible for the blue, green and red emissions are discussed on the basis of the experimental data. [Copyright &y& Elsevier]

Abstract: The adsorption of CO on well-defined Co–Pt alloy surfaces prepared by physical vapour deposition in ultra-high vacuum was studied by Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS) and temperature-programmed desorption (TPD) spectroscopy. The adsorption behaviour was found to depend strongly on the composition of the surface and the first subsurface atomic layer. In the case of low Co concentrations at the surface CO adsorbs preferentially on Pt sites, however with an enthalpy of adsorption which is substantially lowered when compared to CO adsorption on Pt single crystals. TPD shifts of ∼60K were found. When Co dominates the surface composition, CO adsorbs preferentially on Co sites, however with an enthalpy of adsorption leading to a TPD shift by ∼80K to higher temperatures with respect to monometallic single crystals. This behaviour can be explained by ligand effects, i.e., by an electronic influence of the presence of a second metal in the chemical environment of a given adsorption center. The experimental findings were compared with theoretical calculations. [Copyright &y& Elsevier]