Positronium time-of-flight Measurements of Mesoporous Silica Films

Mesoporous silica films were synthesized with various concentrations of cetyltrimethylammonium bromide (CTAB) in precursor sols through the method of electro-assisted self-assembly (EASA). Oriented pore channels were observed in the films prepared with more CTAB in the precursor sols. Positronium time-of-flight (Ps-TOF) measurements were performed for the silica films with different porous structures. It is demonstrated that the Ps emission intensity and energies are well correlated to the apparent porosity, pore interconnectivity and possibly pore channel orientation. The results indicate that Ps-TOF can be a useful technique for probing the structures of porous films.