Phosphate Nano Preparation And Characterization Of Luminescent Materials

Luminescence materials take phosphate as hosts have been widely applied in various lighting and displaying instruments for their excellent thermal and chemical stability. With the rapid development of nanotechnology, nanomaterials have drawn much attention and been the hot topic for their high luminescence intensity and high quantum efficiency. In this paper, we have utilized different methods to synthesize various nanomaterials take phosphate as hosts and investigated their luminescence properties doped with different ions.The main content is as follows:1. We have synthesized haloapatites nanocrystals by a precipitation method and first investigated their luminescence properties of Ce³⁺ ions doped-Ba₅ (PO₄)₃X (X = F,Cl) and Ni²⁺ ions doped-Sr₅(PO₄)₃Cl nanocrystals.Three broad emission peaks located at 345, 376 and 404 nm have been found in Ce³⁺ ions doped-Ba₅(PO₄)₃Cl nanocrystals, which are correspond to the splitting of Ce³⁺ ions ground state 4f due to the spin-orbit coupling. The concentration quenching of Ce³⁺ ions is 0. 4mol%, which is due to excitation energy migration to the quenching centers. The luminescence properties of Ce³⁺ ions in Ba₅(PO₄)₃F and Ba₅(PO₄)₃Cl have much difference for their different crystal field.620 nm broad emission band has been found in Ni²⁺ ions doped-Sr₅(PO₄)₃Cl nanocrystals, which is correspond to ¹T₂(¹D)-³T₂(³F) transition of Ni²⁺ ions. The concentration quenching of Ni²⁺ ions is 2mol%, which is also due to excitation energy migration to the quenching centers.2. We have synthesized rare earth-based orthophosphate nanomaterials by a combustion method using urea as a fuel and first investigated theirluminescence properties of Dy3+^doped YPO4 and Eu+^doped LaP04 nanocrystals.Two emission peaks at 486 nm (blue) and 575 run (yellow) have been found in Dy3+-doped YPO4 nanocrystals calcined at 600°C. Dy3+ can easily enter into the eight-fold coordination Y3^ sites of D2d point symmetry (without an inversion center). Therefore the yellow emission is prominent in the emission spectrum. Because the increase in Dy3+ concentration will cause cross-relaxation between the transitions 4F9/2— 6F3/2 and eHi5/2—6Fu/2, the quenching of Dy3+ luminescence occurs at low concentration lmol%. The optimum quantity of urea exceeds its theoretical value because urea is easily decomposed or reacted with surrounding oxygen at high temperatures.Four emission peaks, which are at 593, 622, 652 and 686 nm, are due to the 5D0-7Fi,2,3,4 transitions of Eu3+, respectively, have been found in Eu3+-doped LaP04 nanocrystals calcined at 7OCTC. Since the 5D0-7Fi transition, which is a magnetic dipole transition, is by far the most intense, indicating a centro-symraetrical environment for Eu3" ions. The concentration quenching is due to Eu3+ ions exchange interactions. The optimum quantity of urea also exceeds its theoretical value, which is the same as the former experiment.3. We have synthesized PbHAsO4, Pb5(P04)30H, Pb9(P04)6 nanocrystals using different surfactants as templates.Monoclinic lead hydrogen arsenate (LHA) nanocrystals have been prepared successfully by a soft template synthesis method in the presence of sodium dodecylbenzenesulfonate (SDBS) or polyvinylpyrrolidone (PVP). SDBS has little influence on the crystallization morphology of LHA while it can greatly decrease its crystallite sizes. However, the polymer PVP can not only decrease the crystallite sizes greatly but also affect crystallization morphologies.Lead phosphate hydroxyapatite (PbHA) nanoparticles were prepared with a cat ionic surfactant (celyltrimethylammonium bromide (CTAB))-assisted method at different temperatures (25°C, 100°C and 150°C). The surfactant CTAB could well control the final shape and size of PbHA.Rod-like lead phosphate Pb9(P04)6 nanocrystals were prepared by a surfactant SDBS-assisted chemical precipitation method in the presence of ethylenediaminetetraacetic acid (EDTA). EDTA as a multidentate ligand is effective to control the formation of rod-like Pb9(P04)6 nanocrystals. The surfactant SDBS plays an important role in the formation of Pb9(P04)6 nanorods by preventing the nanoparticles from the aggregation into large ones. The 350 nm emission of the Pb9(P04)6 nanorods is ascribed to the 3P]-'So transition of Pb2+ ions.4. Barium hydroxyapatite (BaHAP) nanoparticles have been synthesized by citric acid sol-gel combustion method using citric acid as a reductant/fuel and nitrate as an oxidant. A drastic combustion reaction around 540 °C could be seen from the TG/DTA curves. The obtained nanoparticles are fine and nearly spherical with some agglomeration and their sizes are in the range of 40⁵0nm.