Figure 3. TEM characterization.

(a–c), TEM images of the bacteria-supported, hierarchical, porous-Co₃O₄ superstructures. Low- (a) and high-magnification micrographs (b). The images shown in (b) and (c) are open triangle (yellow line) and square (red line) regions, respectively, located in (a). The highly porous, hierarchical structures can be identified by the assembly of Co₃O₄ nanocrystals grown on the bacterial template. (d), HR-TEM image of ~ 2–10-nm nanocrystalline Co₃O₄ grains in the obtained hierarchical, porous-Co₃O₄/bacteria product. (e), The SAED pattern for the polycrystalline Co₃O₄ in the hierarchical, porous-Co₃O₄/bacteria sample. (f), An individual TEM image of the bacteria-supported, hierarchical, porous-Co₃O₄ sample. The inset shows a 3D-hierarchical Co₃O₄ layer grown on a bacterial surface (scale bar represents 50 nm). (g–j), The HAADF STEM image (g) and the EDS elemental mapping analysis (h–j) for an individual sample of the bacteria-supported, hierarchical, porous-Co₃O₄ sample shown in (f), showing the uniform distribution of Co₃O₄ nanostructures and the biosorption of cobalt ions onto a phosphate functional group associated with the negative charge of glycopolymers (see figure 1b, TA and LTA) in a bacterial cell wall.