Atomic-Scale Structure of Biogenic Materials by Total X-ray Diffraction: A Study of Bacterial and Fungal MnO x V. Petkov, †, * Y. Ren, ‡ I. Saratovsky, § P. Paste ´ n,  S. J. Gurr, ¶ M. A. Hayward, § K. R. Poeppelmeier, # and J.-F. Gaillard p † Department of Physics, 203 Dow Science, Central Michigan University, Mt. Pleasant, Michigan 48859, ‡ Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, § Inorganic Chemistry Laboratory, University of Oxford, Oxford, U.K. OX1 3QR,  Pontificia Universidad Cato ´lica de Chile, Santiago, Co ´digo Postal 690441, Chile, ¶ Department of Plant Sciences, Oxford University, Oxford, U.K. OX1 3RB, # Department of Chemistry, Northwestern University, Evanston, Illinois 60202, and p Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois 60208 C urrently, technology is looking for smaller scale, ordered materials with well-defined properties. Nanophase materials are, therefore, being manufactured in increasing numbers. 1-3 Nature is also a prolific producer of nanophase materials. A typical example of this is the microorganism assisted, or bio- genic, oxidation of water-soluble metal ions into insoluble oxides. 4 Indeed this process has been taking place for millions of years leaving its signature all around: in the sedi- ments on the ocean floor and in the soil on land. Nature‘s evident success is inspiring and scientists are trying to employ its tools for applications including manufacturing of magnetic nanoparticles 5 and capturing of contaminant metal ions. 6-8 Thus under- standing the way living microorganisms produce materials, in particular nanophase metal oxides, is becoming important not only for the advance of today’s technology but also for remediating some of its un- wanted consequences such as metal pollution. One of the most important prerequi- sites to understanding a physicochemical process, such as the formation of a nanophase material, is the knowledge of the atomic-scale structure of its product. Re- cently, good progress has been made in de- termining the structure of synthetic (i.e., man-made) nanophase materials by em- ploying total X-ray diffraction (XRD) involv- ing a combination of high-energy XRD and atomic pair distribution function (PDF) analysis. 9-11 This nontraditional approach has also been applied to nanophase materi- als of geological interest, such as ores. 12 The approach can also be applied to mate- rials freshly produced by living microorgan- isms. As an example we consider MnO x pro- duced by bacteria and fungi. These biogenic materials show a length of struc- tural coherence of about 2-3 nm only and, in this sense, are in a nanophase state. Nev- ertheless, their atomic-scale structure is pe- riodic and can be described in simple crys- tallographic terms. Surprisingly the crystal structures of fungal and bacterial MnO x turn out to be substantially different indicating that biogenic materials are inherently struc- turally diverse. Manganese oxides are ubiquitous in na- ture 13 and have been used by mankind for many thousands of yearsOfirst as pigments and today as catalysts and battery materi- als. This has generated a long-lasting inter- est in their genesis. Several studies on MnO x produced by microorganisms have been carried out but no complete structural de- termination has yet been performed. The studies have only suggested that bacterial MnO x is likely to possess a layered-type structure of the type found in the mineral birnessite. 14,15 Even less is known about fun- gal MnO x . 16,17 *Address correspondence to petkov@phy.cmich.edu. Received for review October 3, 2008 and accepted December 30, 2008. Published online January 13, 2009. 10.1021/nn800653a CCC: $40.75 © 2009 American Chemical Society ABSTRACT Biogenic materials are produced by microorganisms and are typically found in a nanophase state. As such, they are difficult to characterize structurally. In this report, we demonstrate how high-energy X-ray diffraction and atomic pair distribution function analysis can be used to determine the atomic-scale structures of MnO x produced by bacteria and fungi. These structures are well-defined, periodic, and species-specific, built of MnO 6 octahedra forming birnessite-type layers and todorokite-type tunnels, respectively. The inherent structural diversity of biogenic material may offer opportunities for practical applications. KEYWORDS: biogenic materials · structure determination · X-ray diffraction · manganese oxides ARTICLE www.acsnano.org VOL. 3 ▪ NO. 2 ▪ 441–445 ▪ 2009 441