title: Extracellular synthesis of magnetite and metal-substituted magnetite nanoparticles.
abstract: We have developed a novel microbial process that exploits the ability of Fe(III)-reducing microorganisms to produce copious amounts of extracellular magentites and metal-substituted magnetite nanoparticles. The Fe(III)-reducing bacteria (Theroanaerobacter ethanolicus and Shewanella sp.) have the ability to reduce Fe(III) and various metals in aqueous media and form various sized magnetite and metal-substituted magnetite nano-crystals. The Fe(III)-reducing bacteria formed metalsubstituted magnetites using iron oxide plus metals (e.g., Co, Cr, Mn, Ni) under conditions of relatively low temperature (<70 degrees C), ambient pressure, and pH values near neutral to slightly basic (pH = 6.5 to 9). Precise biological control over activation and regulation of the biosolid-state processes can produce magnetite particles of well-defined size (typically tens of nanometers) and crystallographic morphology, containing selected dopant metals into the magnetite (Fe(3-y)XyO4) structure (where X = Co, Cr, Mn, Ni). Magnetite yields of up to 20 g/L per day have been observed in 20-L vessels. Water-based ferrofluids were formed with the nanometer sized, magnetite, and metal-substituted biomagnetite particles.
authors.affiliation: Faculty of Earth Systems and Environmental Sciences, Chonnam National University, Gwangju, 500-757, Korea.
authors.forename: Y
authors.initials: Y
authors.lastname: Roh
authors.forename: H
authors.initials: H
authors.lastname: Vali
authors.forename: T J
authors.initials: TJ
authors.lastname: Phelps
authors.forename: J W
authors.initials: JW
authors.lastname: Moon
mesh_terms: D001419:Bacteria / Q000378:metabolism; D005290:Ferric Compounds / Q000737:chemistry; D052203:Ferrosoferric Oxide / Q000138:chemical synthesis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry; D020592:Shewanella / Q000378:metabolism; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; C001215:ferrite; D007501:Iron; D052203:Ferrosoferric Oxide