FIG. 1.

(A) Transmission electron micrograph showing an amorphous silicon dioxide aggregate particle (gray structure) together with numerous supported silver metal particles (dark spots). (B) Scanning transmission electron micrograph of the structure shown in panel A, providing better contrast between the silica structure (gray) and the silver metal particles (bright spots). (C) Higher magnification of the region in panel B enclosed in a box. The silver metal particles are typically between 1 and 10 nm in diameter. Transmission electron microscope and scanning transmission electron microscope images were obtained using an FEI Tecnai F30 FEG microscope operated at 300 kV.