Representative transmission electron (TEM) images of the mesoporous
silica on a GO substrate prior to magnesiothermic reduction
are displayed in Figures 2a and 2b and those of the resulting silicon nanoparticles are shown in Figures 2c and 2d. In these images, bright
and dark areas correspond to the GO substrate and thin walls of the
silica channels, respectively. As can be seen, the cylindrical mesoporous
silica channels are vertically aligned with respect to the GO
substrate (Figure 2a and see Supplementary Fig. S1 online).