title: Local coordination of Fe3+ in ZnO nanoparticles: multi-frequency electron paramagnetic resonance (EPR) and Newman superposition model analysis.
abstract: Iron-doped ZnO nanoparticles have been synthesized through high-energy ball milling of powders produced by the co-precipitation method. Fine particles with an average size down to 40 nm have been obtained after 15 min of milling. Fe(3+) cations have been incorporated into the ZnO lattice within the limits of the solubility. By using multi-frequency and high-field electron paramagnetic resonance (EPR) we have resolved all electronic transitions for the S = 5/2 high-spin system and have accurately determined the EPR spin-Hamiltonian parameters. By combining data from crystallographic x-ray diffraction and EPR with the semi-empirical Newman superposition model we have found the local configurational position of Fe(3+) and have confirmed the symmetry of the lattice. Results presented in this paper indicate that Fe cations most probably substitute at Zn-sites in ZnO. At nanosizes the effect of Fe(3+) cations on the surface becomes remarkable: additional size effects can be observed in the EPR spectrum, which are different from the spectrum of bulk.
authors.affiliation: Albert-Ludwigs Universität Freiburg, Institut für Physikalische Chemie, Albertstraße 21, 79104 Freiburg, Germany.
authors.forename: Muhammed
authors.initials: M
authors.lastname: Açıkgöz
authors.forename: Michael D
authors.initials: MD
authors.lastname: Drahus
authors.forename: Andrew
authors.initials: A
authors.lastname: Ozarowski
authors.forename: Johan
authors.initials: J
authors.lastname: van Tol
authors.forename: Stefan
authors.initials: S
authors.lastname: Weber
authors.forename: Emre
authors.initials: E
authors.lastname: Erdem
mesh_terms: D000465:Algorithms; D056831:Coordination Complexes / Q000737:chemistry*; D003460:Crystallization; D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D015233:Models, Statistical; D053758:Nanoparticles / Q000737:chemistry*; D014961:X-Ray Diffraction; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D007501:Iron; D015034:Zinc Oxide