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Lanthanum Silicate and Lanthanum Zirconate Nanoparticles Co-Doped with Ho 3+ and Yb 3+ : Matrix-Dependent Red and Green Upconversion Emissions

2009; American Chemical Society; Volume: 113; Issue: 33 Linguagem: Inglês

10.1021/jp904516s

1932-7455

Neralagatta M. Sangeetha, Frank C. J. M. van Veggel,

Glass properties and applications

Excitation of Ho3+ and Yb3+ co-doped lanthanum silicate and lanthanum zirconate nanoparticles with 980 nm diode laser light gave a red and green glow, respectively, observable by naked eye. Spectroscopic investigations on these materials revealed green (540 nm), red (660 nm), and near-infrared (750 nm) upconversion emissions with the green to red ratio varying with the matrix type and the dopant ion (Yb3+) concentration. The emission was predominantly red for Ho3+:Yb3+ (1:3) in lanthanum silicate nanoparticles, while it was predominantly green for Ho3+:Yb3+ (1:7) in lanthanum zirconate nanoparticles. A mechanism involving cross-relaxations and energy back transfer has been proposed to explain the observed behavior. The predominance of red emission has been attributed to a strong quenching of Ho3+ green emitting level mainly by energy back transfer from Ho3+ to Yb3+ on the basis of the near-infrared (NIR) emission spectral analysis.