Bacteria-mediated synthesis of free-standing cobalt oxide rods

We demonstrate the simple room-temperature preparation of rod-type, oxide nanostructures derived from the Bacillus subtilis templates. Specifically, free-standing, cobalt oxide rods were produced via the following systematic processes: incubation of the bacteria templates in aqueous cobalt chloride solution, reduction with sodium borohydride (NaBH4), and subsequent oxidation in water at room temperature. We observed that single nanocrystals or small clusters approximately 3 to 5 nm in diameter were uniformly distributed on the as-prepared individual rods. Additionally, thermogravimetric (TG) analysis and field emission electron scanning microscopy (FESEM) observation revealed the important role played by the concentration of the reductant, NaBH4, in anchoring the cobalt oxide nanocrystals on the bacterial cell surface. Our proposed strategy facilitates the economic and easy construction of other oxide nanostructures and assemblies for applications in nanoelectronics, photonics, sensing, catalysis, and energy storages.