Fabrication And Photoluminescent Properties Of One-dimensional Nanosized Luminescent Materials Doped With Rare Earth

The studies on one-dimensional (1D) luminescent materials doped with rare earth have been focus of luminescent sciences. In this paper, the 1D nanostructures of LaPO₄: Eu³⁺, LaPO₄: Ce³⁺, LaPO₄: Tb³⁺, and La₂O₃: Eu³⁺ were prepared by a hydrothermal method and investigated the influences of shape anisotropy and surface on local environment surrounding rare earth and electronic transition process. The energy transfer (ET) was compared between nano- and micrometer system. The main results were listed as follow:(1) The dependence of space dimensionality on local symmetry surrounding rare earth ions were observed for the first time. In LaPO₄: Eu³⁺ nanoparticles and micrometer particles, Eu³⁺ occupied only site, A. In nanowires and micrometer rods, Eu³⁺ occupied a same site, A, and an additional site, B. Moreover, the relative intensity of Eu³⁺ at site B linearly increased with the increase of the ratio of the length to diameter.(2) The radiative transition rate of ⁵D₁-Σ⁷F_J and ⁵D₀- Σ⁷F_J and internalquantum efficiency in nanowires greatly increased in comparison with nanoparticles and bulk materials for the first time. This indicated that one-dimensional nanostructures as one of effective ways can increase luminescent efficiency of rare earth ions. In LaPO₄: Ce³⁺ , LaPO₄: Tb³⁺ and La₂O₃: Eu³⁺ nanowires, the radiative transition rate of Ce³⁺ , Tb³⁺ and Eu³⁺ do not increase in contrast to bulk mamterials, which indicated that the increase of electronic radiative transition rate was dependent of space dimensionality, the matrix and rare earth.(3) In La₂O₃: Eu³⁺ nanowires, the exciton band blue-shifted greatly with the decrease of size due confinement effect, relative intensity of exciton decreased incomparison charge transfer band, which can be contributed to the more energy transfer from exciton transition to defects at the surface.(4) InLaPO4.- Ce3+,Tb3+ nanowires, the decrease of the energy transfer efficiency and rate between Ce and Tb, and between Ce,Tb to defect state, was observed due boundary effect for the firsi! time. Thus the quenching concentration increased in comparison with bulk materials, and brightness of Tb3+ greatly increased.