Plasmon energy shift in mesoporous and double length-scale ordered nanoporous silica

Electron energy-loss spectroscopy studies are reported on three different types of structures: solid silica spheres, mesoporous silica, and the double length-scale ordered (DLSO) porous silica. The mesoporous silica has porosity at the length scale of nanometers. The DLSO porous silica has an additional ordering on submicron hollows created by the template polystyrene spheres. The plasmon energy of the porous silica shows a significant shift in comparison to that of the bulk, suggesting that the local density of the bound electrons in the porous structures is lower than that in the bulk. This gives the possibility of tuning the electronic structure of silica by varying its porosity, leading to even lower dielectric loss.