Heterogeneity of surface colour centres on alkaline earth metal oxides as revealed through EPR/ENDOR spectroscopy

Purnell, Ian J., Chiesa, Mario, Farley, Robert D., Murphy, Damien Martin ORCID: https://orcid.org/0000-0002-5941-4879, Rowlands, Christopher C., Paganini, Maria Cristina and Giamello, Elio 2002. Heterogeneity of surface colour centres on alkaline earth metal oxides as revealed through EPR/ENDOR spectroscopy. Magnetic Resonance in Chemistry 40 (6) , pp. 381-386. 10.1002/mrc.1028

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Abstract

A variety of surface anion vacancies, or point defects, are created by high-temperature activation of a series of polycrystalline alkaline earth metal oxides (MgO, CaO and SrO). Subsequent UV irradiation of the activated oxide under a hydrogen atmosphere results in the generation of surface colour centres [FS +(H)], by electron trapping at these anion vacancies. The paramagnetic properties of these colour centres were studied by EPR and ENDOR spectroscopy. 1H ENDOR spectroscopy revealed that a well defined heterogeneity of trapped electron species exists on each oxide surface, as characterized by the different superhyperfine couplings between the trapped electron and the nearby proton of the FS + (H) centre. On MgO and CaO two dominant FS + (H) centres were identified (labelled sites I and II) whereas on SrO three FS + (H) species were found (sites I, II and III). The possible surface sites responsible for electron stabilization are discussed, and include a 3Ccornermono-vacancy, a 4Cmono-vacancy and an anion–cation di-vacancy. The results indicate that regardless of the oxide used, a common degree of morphological similarities exists on each oxide.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	Wiley-Blackwell
ISSN:	0749-1581
Last Modified:	24 Oct 2022 11:32
URI:	https://orca.cardiff.ac.uk/id/eprint/48501

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