Figure 1
Schematics of the bacteria used and the design of the 3D-hierarchical Co3O4 superstructure.
(a), FE-SEM image of the original Micrococcus lylae bacteria used as biotemplates. The diameter characteristic of Micrococcus lylae is around 800 nm to 1 μm. (b), Detailed depiction of the Micrococcus cell envelope. The cell wall of Micrococcus, as a Gram-positive bacterium, has generally well-known structures (thick peptidoglycan and S-layer) and glycopolymers (teichoic acid; TA or lipoteichoic acid; LTA). (c), Zeta-potential (ζ) for Micrococcus bacteria suspended in distilled water (pH 6.5) was −38 mV, indicating the net negatively charged surface of the bacteria. (d), Schematic showing the one-pot synthesis of 3D-hierarchical Co3O4 structures through cobalt oxides (green) directly assembled onto bacterial surface at room temperature. The hierarchical cobalt oxides are produced by the biosorption of Co2+ onto the cell surfaces of Micrococcus and subsequent reduction and oxidation reactions (reaction time was 12 h). FE-SEM image was taken by H.-W. Shim. The simplified illustration of the cell wall of micrococcus was drawn by J.-C. Kim. The zeta-potential was taken by H.-W. Shim. The experimental concept was drawn by J.-C. Kim.
