Preparation and Luminescence Properties of Organically Modified Silicate Composite Phosphors Doped with an Europium(III) β-Diketonate Complex

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Abstract

The phenanthroline adduct of the tris(2-thenoyltrifluoroaceto-O,O‘)europium(III) complex, Eu(TTA)3phen, was doped into organically modified silicate (ORMOSIL) matrixes via the sol−gel process, and the luminescence properties of the resultant ORMOSIL composite phosphors (ORMOSIL:Eu(TTA)3phen) were characterized. The emission intensity of the composite phosphors maximized at ∼50% vs the commercially available lamp phosphor Y(P,V)O4:Eu, and transparent ORMOSIL:Eu(TTA)3phen composite phosphor disks (45 mm in diameter by 1.5 mm) were obtained under appropriate complex concentration 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 °C), possibly due to the transformation of the β-diketonate ligand from the photoactive π electron-conjugated enolate to the corresponding nonphotoactive ketone form. In particular, the ORMOSIL:Eu(TTA)3phen composite phosphor powders treated with (CH3)3SiNHSi(CH3)3 (hexamethyldisilazane, HMDS) showed a remarkable increase in emission intensity, owing to the improved water repellency resulting from the implantation of the −OSi(CH3)3 (trimethylsilyl substituent: TMS) in the ORMOSIL composites and the favorable reconversion of the ligand from the nonconjugated β-diketone to the photoactive conjugated enolate form as induced by the NH3 evolved during the TMS modification process. A composite phosphor with high emission intensity (∼70% vs Y(P,V)O4:Eu) was obtained after the modification.

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