Theoretical and experimental studies on the silica hollow spheres

The structures and properties of the silica hollow spheres have been studied by experimental and quantum chemical calculations. The structure of the silica hollow spheres was characterized by TEM, BET and XPS. According to the experimental results, a model of porous silica clusters has been proposed to represent the structure of the silica hollow spheres. The geometry of model was optimized by the semi-empirical PM3 method and the density of states for the model was calculated by ab initio methods at the level of 3-21G and 6-31G. Both the influences of model size and the effect of basis set are discussed. It is found that the calculated binding energies of O1s, Si2s and Si2p are in fairly good agreement with the experimental results. The studies indicate that the small cluster model can be used to reasonably analyzed the structure and properties of silica hollow spheres.