Affiliation: | a Departamento de Química, Universidad de las Islas Baleares, 07071, Palma de Mallorca, Spain b Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali, Via Pietro Giuria 7, 10125, Torino, Italy c CSELT, Centro Studi e Laboratorio Telecomunicazioni, Via Reiss Romoli 274, 10148, Torino, Italy |
Abstract: | The monolayer of CO molecules adsorbed at low temperature on highly sintered nickel oxide, gives rise to a very symmetric IR absorption band at 2136 cm−1 (θmax) with a full-width at half-maximum (FWHM) of 3.7 cm−1. This band shifts to higher frequenc upon decreasing the coverage, reaching the 2152 cm−1 value for θ→0. The observed shift is due to changes in the lateral interactions (dynamic and static) among the adsorbed molecules. The observed spectral simplicity implies that most of the adsorbed CO molecules occupy crystallographically identical sites with a similar environment. Moreover, the remarkably small half-width indicates that inhomogeneous broadening effects, due to surface defects, are very small and that NiO microcrystals behave as single crystals. The morphology of microcrystals has been studied by SEM, AFM and HRTEM techniques: it was concluded that the surface termination of the sample is mainly represented by the (100) and (111) faces. |