Preparation and luminescence properties of organically modified silicate composite phosphors doped with an europium(III) beta-diketonate complex

The phenanthroline adduct of the tris(2 -thenoyltrifluoroaceto-O,O')europiu m(III) complex, Eu(TTA)(3)phen, was doped into organically modified silicat e (ORMOSIL) matrixes via the sol-gel process, and the luminescence properti es of the resultant ORMOSIL composite phosphors (ORMOSIL:Eu(TTA)(3)phen) we re characterized. The emission intensity of the composite phosphors maximiz ed at similar to 50% vs the commercially available lamp phosphor Y(P,V)O-4: Eu, and transparent ORMOSIL:Eu(TTA)(3)phen composite phosphor disks (45 mm in diameter by 1.5 mm) were obtained under appropriate complex concentratio n and matrix composition. Moreover, the emission intensity of the composite phosphors was found to be maintained at the same level even after standing for up to 180 days in air, but lowered after heat treatments (100-300 degr ees C), possibly due to the transformation of the beta-diketonate ligand fl om the photoactive pi electron-conjugated enolate to the corresponding non photoactive ketone form. In particular, the ORMOSIL:Eu(TTA)(3)phen composit e phosphor powders treated with (CH3)(3)SiNHSi(CH3)(3) (hexamethyldisilazan e, HMDS) showed a remarkable increase in emission intensity, owing to the i mproved water repellency resulting from the implantation of the -OSi(CH3)(3 ) (trimethylsilyl substituent: TMS) in the ORMOSIL composites and the favor able reconversion of the ligand from the nonconjugated beta-diketone to the photoactive conjugated enolate form as induced by the NH3 evolved during t he TMS modification process. A composite phosphor with high emission intens ity (similar to 70% vs Y(P,V)O-4:Eu) was obtained after the modification.