title: Spectroscopic CW-EPR and HYSCORE investigations of Cu(2+) and O(2)(-) species in copper doped nanoporous calcium aluminate (12CaO.7Al(2)O(3)).
abstract: Continuous wave (CW) and pulse electron paramagnetic resonance in a variant of hyperfine sublevel correlation spectroscopy (HYSCORE) were used for obtaining structural information concerning speciation and local environment of alien Cu(2+) and native O(2)(-) ions encaged in copper doped nanoporous 12CaO.7Al(2)O(3) (mayenite). The samples were prepared by a solid-state reaction and characterized by means of XRD, SEM, and Raman techniques. X-Band CW-EPR spectra showed that three different Cu(2+) species together with paramagnetic extraframework O(2)(-) anions were present in the mayenite sample, whereas extraframework OH(-) anions were revealed by Raman spectroscopy. (27)Al HYSCORE provided evidence for the interaction of Cu(2+) ions with the mayenite framework. Superhyperfine interaction of the Cu(2+) ions with proximal (d(Cu-OH) = 2.4 A) and distal (d(Cu-OH) = 5.0 A) OH(-) anions, located in the same and the nearby cage, respectively, was resolved by means of (1)H HYSCORE spectra. A different situation held for the encaged O(2)(-) radicals found to be sitting on the Ca(2+) ions. They exhibited only a weak superhyperfine interaction of 1 MHz with the (27)Al(3+) framework ions.
authors.affiliation: Dipartimento di Chimica IFM, Università di Torino, and NIS Centre of Excellence, via P. Giuria 7, 10125 Torino, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Maurelli
authors.forename: Monika
authors.initials: M
authors.lastname: Ruszak
authors.forename: Stefan
authors.initials: S
authors.lastname: Witkowski
authors.forename: Piotr
authors.initials: P
authors.lastname: Pietrzyk
authors.forename: Mario
authors.initials: M
authors.lastname: Chiesa
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Sojka