LaF₃, LaVO₄ And LaCO₃OH Micro-/Nanostructures:Solutions-Phase Controllable Synthesis, Characterization And Fluorescence Properties

Rare-earth luminescence materials have enormuos potenial applications in photoelectric device and biomedicine due to its special phecial and chemical properties. Developing synthetic routes for rare-earth luminescence materials, exploring the formation mechanisms and investigating th relationship among the crystal structure, morphology and properties of nanomaterials have great significance. New solution-based manipulated synthetic straegies and flurescent properties of LaF3, LaVO4 and LaCO3OH micro/nanomaterials doped by Eu3+, Ce3+and Tb3+. Some new and intersting were achieve and listed as follows.Firstly, using La2O3,Tb4O7, HNO3, NH4F and Ce(NO3)3 as raw materials, LaF3:Tb3+,Ce3+nanocrystals have been successfully prepared via a facile hydrothermal method assisted by cetyltrimethyl ammonium bromide (CTAB). The as-prepared preducts were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), High-revolution transmission electron microscope (HRTEM), infrared spectroscopy (IR) and Photoluminescence (PL) as well as CIE chromaticity diagram. The results show that the LaF3:Tb3+,Ce3+ nanocrystals possess good green emission at 543 nm. As the the Ce3+/Tb3+ ratio increases, the flourescence intensities increase first and then weaken, and reach the strongest green emission at nce3+/nTb3+=4. Besides, the pH values have some influence on the colors and intensities of the LaF3:Tb3+,Ce3+ nanocrystals. The sample prepared at pH=9 presents the best color, while the one at pH=7 exhibits the strongest green emission.Secondly, using La2O3, Eu2O3, HNO3、NaOH, NaVO3, ethanol and diglycol as raw materials, LaVO4:Eu3+ nanocrystals have been successfully prepared via a facile hydrothermal method assisted by polyvinylpyrrolidone (PVP) and cetyltrimethyl ammonium bromide (CTAB). The as-prepared preducts were characterized by XRD, TEM, HRTEM, IR as well as PL. The results show that the LaVO4:Eu3+ nanocrystales possess good red emission at 620 nm. The pH values have some influence on the colors and intensities of the LaVO4:Eu3+ nanocrystals. The sample prepared at pH=5 presents the best color, while the one at pH=8 exhibits the strongest red emission.Finally, using La2O3,Eu2O3, concentrated nitric acid, HNO3, Di-ethylene glycol (DEG) and CO(NH2)2 as raw materials, LaCO3OH:Eu3+three-fold dendrites have been successfully prepared via a facile hydrothermal method assisted Polyvinylpyrrolidone (PVP). The as-prepared preducts were characterized by TD-TG, XRD, XPS, SEM and IR as well as PL. And the possible mechanism and growth process of LaCO3OH:Eu3+three-fold dendrites were investigated. The results show that PVP of the solution play key roles in the formation of product with three-fold dendrites. The FL results reveal that LaCO3OH:Eu3+three-fold dendrites excitated at 262 nm (CTB) possess very strong orange-red emission (616 nm,5D0�'7F2) when the optimum doping concentration of Eu3+ is determined to be 9mol.%. The Eu-doping concentration more than 9% will result in fluorescence quenching.