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Author: search.filters.author.Coluccia, Salvatore

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    Infrared Study of Carbon Monoxide Adsorption on Calcium and Strontium Oxides
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (05), 1981) Coluccia, Salvatore; Garrone, Edoardo; Guglielminotti, Eugenio
    CO adsorption on CaO and SrO takes place, as on MgO, via a disproportionation reaction leading to both surface carbonates and unusual surface species with a complex vibrational spectrum in the low-frequency range. These are thought to be negatively charged CO polymers, the simplest ones being (CO)2–2. A strong electrostatic interaction between negative species and surface cations accounts for the marked dependence of the infrared signal on the lattice parameter of the solids. The increasing basicity along the series MgO, CaO, SrO causes: (i) a marked increase in the total adsorptive capacity; (ii) an increase in the relative population of polymers with respect to dimers; (iii) an increase in the importance of a Boudouart-like reaction upon desorption.
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    I.r. Spectroscopic Study of CO2 Adsorption onto q-Al2O3
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (10), 1977) Morterra, Claudio; Zecchina, Adriano; Coluccia, Salvatore; Chiorino, Anna
    The adsorption of CO2 at room temperature onto η–Al2O3 dehydrated at various temperatures between 25 and 800°C was studied by i.r. and microgravimetric techniques. The following surface species are formed; three σ-coordinated linear structures, two bicarbonates that can be interconverted, several “organic” carbonates and minor amounts of mono- and bi-dentate carbonates. Relative concentrations of these species depend strictly on pretreatment conditions, while the nature of the species is primarily determined by the coordination of surface cations. The overall coverage is quite small, (θ⩽ 10 %) and nearly the same as in all transition aluminas. A cooperative mechanism for CO2 adsorption is thus invoked to account for this and other features. The interaction between CO2 adsorption and catalytic activity is considered, and the probable nature of the centres responsible for exchange and equilibration reactions is suggested.
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    Photoluminescent Spectra of Surface States in Alkaline Earth Oxides
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Coluccia, Salvatore; Deane, A. Michael; Tench, Anthony J.
    Photoluminescence has been observed from high surface area alkaline earth oxides with exciting light of a much lower frequency than that expected from the band gaps of the bulk oxides. This luminescence can be quenched by oxygen and hydrogen and the quenching is reversible under some conditions. It seems probable that both the excitation and the luminescence spectra observed arise from excitons in the surface region. The different behaviour towards oxygen and hydrogen has been used to develop a model in which the excitation site, where absorption of light occurs, is thought to be associated with anions on the surface in states of unusually low coordination such as might be found at step, edge or corner sites on the surface. The luminescence is thought to be associated with a cation on the surface in a similar state of coordination.
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    Luminescence and Other Spectroscopic Studies of the Reaction of Pyridine and Oxygen with Thermally Activated SrO
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Coluccia, Salvatore; Hemidy, Jean F.; Tench, Anthony J.
    The reaction of pyridine and O2 on SrO powder has been studied using several different spectroscopic techniques to characterise the intermediate and the final products. Reflectance spectroscopy has been used to demonstrate the formation of the 4,4′-bipyridyl negative ion when pyridine is adsorbed on SrO. Subsequent adsorption of oxygen leads to the formation of the O–2 ion by a one-to-one electron transfer process from the organic ion and photoluminescence studies confirm that the 4,4′-bipyridyl molecule is also formed on the surface when the electron transfer occurs.