title: Morphology, structural properties and reducibility of size-selected CeO2- x nanoparticle films.
abstract: Non-stoichiometric ceria nanoparticles (NPs) were obtained by a gas aggregation source with a magnetron and were mass-selected with a quadrupole mass filter. By varying magnetron power, Ar gas flow, and the length of the aggregation tube, NPs with an average diameter of 6, 9, and 14 nm were synthesized and deposited onto a substrate, thus obtaining NP films. The morphology of the films was studied with scanning electron microscopy, while high resolution transmission electron microscopy was used to gain a deeper insight into the atomic structure of individual NPs. By using X-ray photoelectron spectroscopy we analyzed the degree of reduction of the NPs of different diameters, before and after thermal treatments in vacuum (reduction cycle) and in O2 atmosphere (oxidation cycle) at different temperatures. From this analysis we inferred that the size is an important parameter only at intermediate temperatures. As a comparison, we evaluated the reducibility of an ultra-thin ceria film with the same surface to volume ratio as the 9 nm diameter NPs film, observing that NPs are more reducible than the ceria film.
authors: CNR-NANO, Centro di Ricerca S3, via G. Campi 213/a, Modena, Italy ; Dipartimento FIM, Università di Modena e Reggio Emilia, Via G. Campi 213/a, Modena, Italy.
authors: Maria Chiara
authors: MC
authors: Spadaro
authors: CNR-NANO, Centro di Ricerca S3, via G. Campi 213/a, Modena, Italy ; Dipartimento FIM, Università di Modena e Reggio Emilia, Via G. Campi 213/a, Modena, Italy.
authors: Sergio
authors: S
authors: D'Addato
authors: CNR-NANO, Centro di Ricerca S3, via G. Campi 213/a, Modena, Italy ; Dipartimento FIM, Università di Modena e Reggio Emilia, Via G. Campi 213/a, Modena, Italy.
authors: Gabriele
authors: G
authors: Gasperi
authors: CNR-NANO, Centro di Ricerca S3, via G. Campi 213/a, Modena, Italy ; Dipartimento FIM, Università di Modena e Reggio Emilia, Via G. Campi 213/a, Modena, Italy.
authors: Francesco
authors: F
authors: Benedetti
authors: CNR-NANO, Centro di Ricerca S3, via G. Campi 213/a, Modena, Italy.
authors: Paola
authors: P
authors: Luches
authors: CNR-NANO, Centro di Ricerca S3, via G. Campi 213/a, Modena, Italy ; CNR-IMEM, Parco Area delle Scienze 37/A - 43124 Parma, Italy.
authors: Vincenzo
authors: V
authors: Grillo
authors: CNR-IMEM, Parco Area delle Scienze 37/A - 43124 Parma, Italy.
authors: Giovanni
authors: G
authors: Bertoni
authors: CNR-NANO, Centro di Ricerca S3, via G. Campi 213/a, Modena, Italy ; Dipartimento FIM, Università di Modena e Reggio Emilia, Via G. Campi 213/a, Modena, Italy.
authors: Sergio
authors: S
authors: Valeri
keywords: CeO2 ultra-thin films; X-ray photoelectron spectroscopy; ceria nanoparticles; magnetron sputtering; reduction and oxidation; size-dependent properties; size-selected nanoparticles