Possible pore size effects on the state of tris(8-quinolinato)aluminum(iii) (Alq₃) adsorbed in mesoporous silicas and their temperature dependence

The states of tris(8-quinolinato)aluminum(iii) (Alq₃) adsorbed in mesoporous silicas with different pore sizes (2.5, 3.1 and 5.0 nm) were investigated. Alq₃ was successfully occluded into the mesoporous silicas from solution and the adsorbed amount of Alq₃ per BET surface area was effectively controlled by changing the added amount Alq₃ to the solution. The state of Alq₃ in the mesopore varied depending on the pore size as well as the adsorbed amount of Alq₃ as revealed by variation of the photoluminescence spectra. The luminescence of the adsorbed Alq₃ was found to be temperature-dependent, indicating the mobility of the adsorbed Alq₃ to temperature variations. The temperature-dependence also depended on the pore size. The guest-guest interactions between Alq₃ molecules as well as the host-guest interactions between Alq₃ and the mesopore were controlled by the pore size.