The Synthesis And Properties Of Rare Earth Fluoride Nano-materials

With abundant and unique energy level structures arising from4fninner shellconfigurations, rare earth doped materials have been the ideal photoelectric functionalmaterials, have attracted much attention in recent years owing to their wideapplications inmany fields, such as information technology,ptical storage, biologicallabels, bio-analyticalsensors, biological labels.As luminescent host matrix, rare earth fluorides is considered to beone of the efficient fluorescent materials, because they normally possess the relatively lowlattice phonon energy,the excellent optical performance,stable chemical properties,wide rangeof transparent,which leads to the low probability of non-radiative decay,improves thefluorescence lifetime and luminescence efficiency of the rare earth ions between themetastable energy levels in the middle. Consequently,preparation and properties ofLanthanide （Ln） doped fluoride nanomaterials have become one of the hot researches atpresent. This article main research content is as follows:（1） With polyacrylic acid（PAA） as complexing agent and surface activeagent,α-（β-）NaYF₄upconversion luminescent nano-materials were prepared through asimple hydrothermal process. Bovine serum albumin （BSA） protein was conjugated with freecarboxylic acid of samples by the amidation reation.The structure and properties ofas-prepared products were characterized by X-ray diffraction （XRD）, field emission scanningelectron microscopy （FE-SEM）, transmission electron microscope（TEM）, infrared （IR）spectrophotometer, ultraviolet （UV） spectrophotometer and photoluminescence spectroscopy（PL）.XRD results showed that pure α-NaYF₄:Yb³⁺,Er³⁺nanospheres could be obtained viaPAA assisted hydrothermal process at the pH value of4–5and160°C for1–4h. Theobtained product is a mixture of α and β phases NaYF₄:Yb³⁺,Er³⁺when the reaction timeincreased from more5h.When the solution was treated at160°C for more than24h at the pHvalue of8–9, pure β-NaYF₄:Yb³⁺,Er³⁺microspheres were obtained.When the solution wastreated at200°C for more8h at the pH value of8–9, pure β-NaYF₄:Yb³⁺,Er³⁺microsphereswere obtained.The above results revealed that pH values, reaction temperature and time ofhydrothermal treatment play important roles in the evolvement of crystalline phase andmorphology of the preparation of different crystal phase α-（β-）NaYF₄upconversionluminescent nano-materials.The FE-SEM esults showed that the morphology ofpureα-NaYF₄:Yb³⁺,Er³⁺was spherical nanoparticles with an average diameter of about70nmand the pureβ-NaYF₄:Yb³⁺,Er³⁺ was microsphere with an average diameter of about700nm,which is composed of spherical nanoparticles （30nm）.The FT-IR and UV spectra showed thatBSA had been conjugated with free carboxylic acid of samples by the amidation reaction.The luminescence properties of α-（β-） NaYF₄:Yb³⁺,Er³⁺phosphors were also studied. It was foundthe upconversion luminescence （UCL） intensity of β-NaYF₄:Yb³⁺,Er³⁺microspheres wasmuch stronger than that of α-NaYF₄:Yb³⁺,Er³⁺nanoparticles. Moreover, both red and greenupconversion were ascribed to the two-photon process.（2） With polyacrylic acid（PAA） as complexing agent and surface active agent, BaYF₅upconversion luminescent nano-materials with an average diameter of about4nm indiameter were prepared through a simple hydrothermal process. Bovine serum albumin （BSA）protein was conjugated with free carboxylic acid of samples by the amidation reation.Thestructure and properties of as-prepared products were characterized by X-ray diffraction（XRD）, field emission scanning electron microscopy （FE-SEM）, transmission electronmicroscope（TEM）, infrared （IR） spectrophotometer, ultraviolet （UV） spectrophotometer andphotoluminescence spectroscopy （PL）.（3）we firstly reported the synthesis of complex fluoride BaSiF₆:Eu²⁺downconversionluminescent materials in a hot oleic acid/1-octadecene solution, via a thermaldecomposition mathod.In the fluorescence spectra of as-prepared products,it was found theemission peak at358nm corresponded to f7→f7sharp line emission of Eu²⁺ions,this resultcouldn’t been found in BaSiF₆: Eu²⁺downconversionluminescent materials by otherwet-chemical methods.