On determining the entrance size of cage-like pores in mesoporous silica films by positron annihilation lifetime spectroscopy

- Porous silica films were studied by positron annihilation lifetime spectroscopy.
- Almost no o-Ps annihilates in the entrance channels of cages in the porous films.
- After trimethylsilylation, an appreciable fraction of Ps is trapped in the entrance.
- It is possible to estimate the pore entrance size from the trapped o-Ps lifetime.