Luminescent properties of nanophosphors

The characteristics and luminescent properties of two nanophosphors, Y2SiO5:CeY2SiO5:Ce and Y2O3:TbY2O3:Tb, are reviewed and summarized in this work, with focus on the results obtained in our group. Hydrothermally prepared Y2SiO5:CeY2SiO5:Ce crystallizes in the P21/cP21/c structure rather than the B2/bB2/b structure observed in bulk material. Relative to bulk powder, Y2SiO5:CeY2SiO5:Ce nanophosphors of particle size ∼25∼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. Y2O3:TbY2O3: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+3Tb+3 ion. The maximum of the nanophosphor photoluminescence quenching curve occurs at Tb concentration three times higher than that in the bulk phosphor.