Figure 1.
Electron microscopy of metallized cells of E. coli MC4100. (a) TEM of cells of E. coli MC4100 following the sequential reduction of Pd(II) and Au(III) (5%/5% Pd–Au on biomass w/w); untreated cells are shown in inset (b). Scale bars are 500 nm. (c) EDX mapping of two Pd–Au particles showing superimposed Au and Pd distributions: yellow, X-ray signal intensity from the characteristic Lα transitions of Au; blue, the characteristic Lα transitions of Pd. The particle on the right-hand side has segregation between Pd and Au with a clearly observed Pd-rich region. The particle on the left-hand side shows homogeneous mixing between Pd and Au. Regions of Pd are apparent at the surface of the nanoparticles (arrowed) and some areas between the NPs also indicated the presence of Pd (circled). Individual distributions of Au and Pd, together with complementary high-angle annular dark field microscopy, which provides atomic number contrast, were described previously [21].