title: Biogenic nanosized iron oxides obtained from cultivation of iron bacteria from the genus Leptothrix.
abstract: A detailed investigation of nanostructured iron oxides/(oxy)hydroxides gathered after cultivation of bacteria from the genus Leptothrix as iron (II) oxidizers is presented. A specific type of medium is selected for the cultivation of the bacteria. Results for sediment powder and bio-film on glass substrate samples from the same media are discussed. XRD, Raman spectroscopy, SEM, and TEM images and PPMS measurements are used to prove the exact composition of the biogenic products and to interpret the oxidation process. Analysis of the data collected shows that around 80 % of the iron (II) from the growth medium has been transformed into iron (III) in the form of different (oxy)hydroxides, with the rest found to be in a mixed 2,5 valence in magnetite. Our investigation shows that the bio-film sample has a phase content different from that of the powdered biomass and that lepidocrocite (γ-FeOOH) is the predominant and the initial biogenic phase in both samples. Magnetite nanoparticles are a secondary product in the bio-film, part of which possesses a defective quasi-maghemite surface layer. In the powdered biomass, the oxidation steps are not fully completed. The initial products are non-stoichiometric and due to the mixed ferric and ferrous ions present, they develop into: (i) lepidocrocite (γ-FeOOH) as a basic sediment, (ii) magnetite (Fe3O4) and (iii) goethite (α-FeOOH) in small quantities. The average size of all iron-bearing particles is found to be below 30 nm. The magnetic measurements performed show a superparamagnetic behavior of the material at room temperature.
authors: Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee Blvd, 1784, Sofia, Bulgaria.
authors: I
authors: I
authors: Nedkov
authors: Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee Blvd, 1784, Sofia, Bulgaria.
authors: L
authors: L
authors: Slavov
authors: Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee Blvd, 1784, Sofia, Bulgaria. raly_angelova@abv.bg.|Faculty of Biology, St. Kliment Ohrdiski University of Sofia, 8, Dragan Tsankov Blvd, 1164, Sofia, Bulgaria. raly_angelova@abv.bg.
authors: R
authors: R
authors: Angelova
authors: Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee Blvd, 1784, Sofia, Bulgaria.
authors: B
authors: B
authors: Blagoev
authors: Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, bl. 11 Acad. Georgi Bonchev Str., 1113, Sofia, Bulgaria.
authors: D
authors: D
authors: Kovacheva
authors: Faculty of Physics, Sofia University, 5 James Bourchier Blvd, 1164, Sofia, Bulgaria.
authors: M V
authors: MV
authors: Abrashev
authors: Faculty of Biology, St. Kliment Ohrdiski University of Sofia, 8, Dragan Tsankov Blvd, 1164, Sofia, Bulgaria.
authors: M
authors: M
authors: Iliev
authors: Faculty of Biology, St. Kliment Ohrdiski University of Sofia, 8, Dragan Tsankov Blvd, 1164, Sofia, Bulgaria.
authors: V
authors: V
authors: Groudeva
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism*; D042743:Leptothrix / Q000254:growth & development* / Q000378:metabolism*; D049329:Nanostructures; D010084:Oxidation-Reduction
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide
keywords: Bio-coatings; Goethite (α-FeOOH); Laboratory cultivated Leptothrix sp., Nanosized biogenic iron oxides/(oxy)hydroxides; Lepidocrocite (ɣ-FeOOH); Magnetite (Fe3O4)