ABSTRACT
The light-induced antibacterial and antifungal properties of A2[M6I8L6] with M = Mo and W, A = organic cation, L = ligand have been studied. The photoactive compounds (TBA)2[W6I8(C7H7SO3)6] and (TBA)2[W6I8(COOCF3)6] have been incorporated into a permeable silicone matrix and were measured for their application in the decomposition of multi-resistant bioactive species (hospital germs) such as S. aureus and P. aeruginosa as well as fungi. In addition, we present a new high volume synthesis route for these types of cluster compounds departing from the soluble compound W6I22.
ABSTRACT
The photoluminescence and time-resolved emission for Eu(2+) in Sr4Al14O25 has been investigated in the temperature range 4 to 500 K. The Eu(2+) emission changes in a peculiar way with temperature. At low temperature two emission bands are observed at 490 and 425 nm, which are attributed to emission from Eu(2+) on the 7- and 10-coordinated sites. Upon raising the temperature, an unexpectedly large blue shift to 400 nm is observed for the 425 nm emission band. To explain these observations, the 400 and 425 nm emission bands are assigned to d-f and trapped exciton emission, for Eu(2+) on the 10-coordinated site. The trapped exciton emission is characterized by a short (0.5 µs) decay time. The temperature dependence of the emission is explained by a configurational coordinate diagram in which the Eu(2+) trapped exciton state is at a slightly lower energy than the lowest energy 4f(6)5d state. Upon raising the temperature, the 4f(6)5d state is thermally populated and emission from this state is observed, and because of the smaller lattice relaxation (smaller Stokes shift), a large blue shift from 425 to 400 nm is observed.
