Luminescent properties of nanophosphors

Abstract

The characteristics and luminescent properties of two nanophosphors, Y 2 SiO 5 : Ce and Y 2 O 3 : Tb , are reviewed and summarized in this work, with focus on the results obtained in our group. Hydrothermally prepared Y 2 SiO 5 : Ce crystallizes in the P 2 1 / c structure rather than the B 2 / b structure observed in bulk material. Relative to bulk powder, Y 2 SiO 5 : Ce nanophosphors of particle size ∼ 25 –100 nm diameter exhibit red shifts of the photoluminescence excitation and emission spectra, reduced self absorption, enhanced light output, and a medium-dependent radiative lifetime. Perturbation of the Ce ion electric field due to reduced dimensionality of the nanocrystals is responsible for the variable lifetime. Y 2 O 3 : Tb nanophosphors prepared by the solution combustion method exhibit nanocrystals within the 30–70 nm range comprising cubic structure. Photoluminescence emission and excitation measurements show a complex behavior comprised of several sharp lines in the visible spectrum associated with electronic transitions of the Tb + 3 ion. The maximum of the nanophosphor photoluminescence quenching curve occurs at Tb concentration three times higher than that in the bulk phosphor.