Fe(3)O(4) synthesized by magnetotactic bacteria and α-Fe(2)O(3) synthesized via a microbial-mineralization-inspired process functioned as catalysts for the controlled cationic polymerization of a vinyl ether.

Iron-oxidizing bacteria produce trivalent iron oxides with the controlled crystal phases outside of their cells. Herein we have synthesized iron oxides with controlled oxidation states and crystal phases through a microbial-mineralization-inspired approach in an aqueous solution at low temperature. Trivalent iron oxides, such as lepidocrocite, ferrihydrite, goethite, and hematite, are selectively obtained from an aqueous solution containing divalent iron ions below 90 °C. The presence of a chelating agent facilitates the control of the oxidation states through the ligand-controlled approach because the precipitation of the divalent iron species is inhibited by the complexation between divalent iron ion and a chelating agent. The control of the crystal phases is achieved by the tuning of the synthetic conditions, such as the initial pH, the concentration of a chelating agent, and the reaction temperature. Furthermore, the resultant iron oxides have hierarchically organized structures consisting of nanoscale objects. The microbial-mineralization-inspired approach by using a chelating agent has potentials for the further morphological control of iron oxides and the further application to aqueous-solution syntheses of other metal oxides.

Of minerals and microbes: A microbial-mineralization-inspired approach was used to facilitate the syntheses of iron oxides with a high specific surface area, such as 253 m(2)g(-1) for maghemite (γ-Fe(2)O(3)) and 148 m(2)g(-1) for hematite (α-Fe(2)O(3)). These iron oxides can be applied to electrode material of lithium-ion batteries, adsorbents, and catalysts.

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-Fe2O3 and -Fe2O3 with BET surface areas of 253 and 148 m 2 /g, resp., are synthesized by thermal treatment of -FeOOH or -FeOOH precursors at 400 C for 2-3 min. The precursors are prepared by a microbial-mineralization-inspired approach from aqueous solutions containing Fe 2+ and EDTA at 25 C for 1 d. Changes in EDTA concentration, pH, and temperature control the formation of the crystalline phases. The obtained iron oxides may be applicable as electrode material for Li-ion batteries, adsorbents, and catalysts. -(YAGITA, N.; OAKI, Y.; IMAI*, H.; Chem. -Eur. J. 19 (2013) 14, 4419-4422, http://dx.