title: Controlled cobalt doping in biogenic magnetite nanoparticles.
abstract: Cobalt-doped magnetite (CoxFe3 -xO4) nanoparticles have been produced through the microbial reduction of cobalt-iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe(2+) site with Co(2+), with up to 17 per cent Co substituted into tetrahedral sites.
authors.affiliation: School of Earth, Atmospheric and Environmental Sciences, Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester, UK. james.byrne@uni-tuebingen.de
authors.forename: J M
authors.initials: JM
authors.lastname: Byrne
authors.forename: V S
authors.initials: VS
authors.lastname: Coker
authors.forename: S
authors.initials: S
authors.lastname: Moise
authors.forename: P L
authors.initials: PL
authors.lastname: Wincott
authors.forename: D J
authors.initials: DJ
authors.lastname: Vaughan
authors.forename: F
authors.initials: F
authors.lastname: Tuna
authors.forename: E
authors.initials: E
authors.lastname: Arenholz
authors.forename: G
authors.initials: G
authors.lastname: van der Laan
authors.forename: R A D
authors.initials: RA
authors.lastname: Pattrick
authors.forename: J R
authors.initials: JR
authors.lastname: Lloyd
authors.forename: N D
authors.initials: ND
authors.lastname: Telling
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D045302:Geobacter / Q000378:metabolism; D008280:Magnetics; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods; D014961:X-Ray Diffraction
chemical_list: D058185:Magnetite Nanoparticles; D003035:Cobalt