Investigation of the surface structure of colloidal platinum by infrared spectroscopy of adsorbed CO

The infrared spectra of (CO)-C-12 and of (CO)-C-12-(CO)-C-13 mixtures adsor bed on poly(vinylpyrrolidone)-stabilized colloidal platinum in liquid dispe rsion are reported. Comparison with the vibrational spectra reported for an alogous supported Pt particles shows the absence of detectable terrace site s on the colloidal particles. Spectral features resulting from vibrational coupling between the adsorbed CO molecules are analysed in terms of the str ucture and sizes of the metal particles and the adsorption sites available for CO.