The Controllable Preparation Of Rare Earth Micro-Fluoride Nanocrystals With Luminous Performance

Rare earth fluoride luminescent materials contain wide application in optics, display, medical science and other fields because of their narrow emission peaks, high color purity, rich of the 4 f level, high emission brightness, high refractive index, tunable emission wavelength, no radiation, and low phonon energy etc. How to controll synthesize the rare earth fluoride luminescent materials with excellent performance and high luminescence efficiency is one of the current research focuses. In recent years, graphene, a typical two-dimensional material, with high specific surface area and high anisotropy, has become a hot research topic. Graphene with the special two-dimensional structure plays a guiding role and can be used as a template or the morphology inducing agent for synthesizing micro/nanomaterials, which will provide a new way for the synthesis of rare earth fluoride.In this paper, graphene were used as the morphology-control agent and template to synthesize rare earth fluoride micro/nanomaterials with special morphology by hydrothermal method. The structure and morphology of products have been characterized by X ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM). Growth behavior of rare earth fluoride micro-nanocrystalline has been studied and its possible mechanism has been proposed. Their optical properties have been analyzed through steady-state fluorescence spectrometer. The details are summarized as follows:1. Synthesis and characterization of graphene oxide. Graphene oxide with bright yellow and good quality was prepared by modified Hummers method. The structure and morphology of Graphene oxide have been characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM).2.Spherical EuF3 and bulk ErF3 micro/nanocrystals were successfully prepared by graphene assisted hydrothermal method. The XRD, TEM and FE-SEM were used to characterize the structure and morphology of the samples. The crystal morphology can be controlled by changing the reaction conditions. The effect of the initial concentration ratio, reaction temperature and reaction time on the morphology of the samples has been discusses and the possible growth mechanism were proposed. The luminescence spectram show that spherical EuF3 emit relatively bright orange-red light when excited with 393 nm, while, under 980 nm excitation, ErF3 will exist strong red, sharp line emission peak at 680 nm, which can be used as probes and will have potential application in field of biological optical imaging3.NaDyF4 microrod and NaYF4:Eu3+microflake crystals were successfully prepared by graphene assisted hydrothermal method. The growth kinetics of the products under different reaction conditions were studied, and the possible mechanism of growth was proposed. The luminescence spectram show that NaDyF4 microrod emit strong yellow-green emission peak at 583nm and 621 nm when excited with 393 nm. The luminescence spectrum at room temperature show that, in addition to the characteristic red emission peaks of Eu3+, an intense blue emission band originating from the 4f65d to 4f7 configuration in Eu2+is also observed when excited at 392 nm.