Graphene Assisted Synthesis And Luminescent Of Rare-Earth Fluoride Materials

Rare earth fluorides luminescent materials have excellent properties, and have been widely applicated in the field of biology, medicine,microelectronic devices and other fields.Over the years, to meet the social needs, tremendous research effort has been made to develop reliable, environmentally-friendly and cost-effective technologies for controlled synthesis of rare-earth fluorides luminescence nanomaterials with high performance and high luminous efficiency. However, the synthesis and properties of rare earth fluorides luminescent materials both for materials science or physical science are still an urgent issue in depth. Meanwhile, with the increasing miniaturization and small size of devices, low-dimensional luminescent rare earth fluoride nanocrystals become particularly important for the development and performance of photovoltaic devices. Graphene is a kind of high specific surface area and a highly anisotropic two-dimensional material. The 2D dimensions and special band gap structural make Grapheme shows a lot of extraordinary features.Recently, researchers found that graphene plays a structure-directing role in the synthesis of metal-organic framework nanowires. This resuits will provide a new synthesis method for the preparation of nano materials, with graphene as a template, the growth of nanomaterials on the graphene surface by physical or chemical methods.In this paper, we try to employ graphene as the morphology-control agent, taking advantage of their special 2D surface structure and structure-directing effect, to synthesize two-dimensional rare earth fluoride nanomaterials with special morphology(truncated octahedron YF3:Eu3+、flaky NdF3, regular-hexagonal rod NaErF4 and hexagonal columnar NaNdF4). The structure and morphology of products have been characterized by Transmission electron microscopy (TEM). Growth behavior of two-dimensional rare earth fluoride micro-nanocrystalline 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、Preparation and characterization of graphene oxide. Graphene oxide prepared by an improved Hummers method. The structure and morphology of Graphene oxide have been characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM).According to the Bragg equation can be drawn, the interlayer spacing of graphite oxide is 0.83nm and the layer spacing of graphite is 0.34nm.Compared to graphite, the spacing of GO has a substantial increase which shows that on graphene oxide carbon plane introduces a number of oxygen-containing functional groups.2、Controlled synthesis and luminescence of binary rare earth fluoride (REF3) micro/nanocrystals. Truncated octahedron YF3:Eu3+and flaky NdF3 nanocrystals were prepared by the use of chemical liquid phase method with graphene assisted synthesis. The structure and morphology of products have been characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Transmission electron microscopy (TEM). The effect of reaction conditions on the crystal morphology have been stuied and the possible growth mechanism was proposed. We found that the crystal morphology can be controlled by changing the reaction conditions. The luminescence spectram show that truncated octahedron YF3:Eu3+ nanocrystals emit relatively bright orange-red light when excited with 393nm, and flaky NdF3 nanocrystals have great infrared luminescence propertie under the excitation of 850nm. So it has a potential application prospect in laser and biological detection.3、Controlled synthesis and luminescence of ternary rare earth fluoride (NaREF4) micro/nanocrystals. Regular-hexagonal rod NaErF4 and hexagonal columnar NaNdF4 micro-nanocrystals were prepared by graphene-assisted hydrotheremal synthesis method. The luminescence spectram show that when regular-hexagonal NaErF4 nanorods were excited at 980nm, a strong red emission peak at 672 nm will be obtained. While when excited at 850 nm, NdF3 and NaNdF4 samples shows the strong emission peak in near infrared region, which will have potential application prospect in the field of solid lasers.