The Preparation Of Rare-Earth Fluoride Nanocrystalline And The Research Of Optical Properties

The preparation of the rare-earth luminescence materials occupied a very importantposition in the field of research and application, with the development of rare-earthluminescence materials preparation technology, the study of new materials have made a greatprogress in the aspect of performance and application. The conversion luminescence materialsis a kind of rare-earth luminescence materials, which can issue visible light under theexcitation of the infrared radiation, it is also a class of photoluminescence materials withspecial properties. Fluoride is good matrix materials in the aspect of conversion luminescence,it can get polychromatic fluorescence at room temperature by dopping with different rareearth ions.To lanthanum elements and rare earth elements as the research object respectively,lanthanum fluoride nanocrystalline and rare earth fluoride nanocrystalline have beensynthesized via a thermal decomposition pathway with two different kinds of synthetic route,The phase, morphology, size, and photoluminescent properties and formation mechanismanalysis of as-prepared products were discussed, and the main contents are as follows:1. Three types of high-quality, monodisperse lanthanide fluoride colloidal nanocrystals (NCs)including LnF3(Ln=La–Pr), NaLnF4(Ln=Sm–Er), Na5Ln9F32(Ln=Tm–Lu) with two crystalphases (hexagonal and cubic) and a rich variety of morphologies have been synthesized inhigh boiling organic solvents oleic acid and1-octadecene, via a thermal decompositionpathway. The as-synthesized NCs were well characterized by X-ray diffraction (XRD),transmission electron microscopy (TEM), high resolution transmission electron microscopy(HRTEM), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL)spectra, respectively. It is found that the as-synthesized NCs consist of monodispersenanoparticles with diverse shapes and narrow size distribution, which can easily disperse innon-polar cyclohexane solvent. Additionally, possible mechanisms of NCs nucleation andgrowth, size and shape evolution have been presented. The results reveal that the formation ofmonodisperse NCs closely correlates with the inherent nature of lanthanide series from La toLu. Furthermore, the as-synthesized CeF3NCs show intensive down-conversion emissionsupon254nm ultraviolet (UV) excitation, and NaErF4and Na5Tm9F32NCs displayup-conversion (UC) fluorescence under980nm NIR excitation, which are promising forapplications in biolabels, bioimaging, displays and other optical technologies. 2. Monodisperse, high-quality rare-earth (RE) fluoride colloidal nanocrystals (NCs) includingREF3(RE=La, Pr, Nd), NaREF4(RE=Sm–Ho, Y), Na5RE9F32(RE=Er, Yb, Lu) have beensuccessfully synthesized by a facile method in a mixture of oleic acid and1-octadecence. Thephase, morphology, size, and photoluminescent properties of as-prepared products were wellinvestigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), andhigh-resolution transmission electron microscopy (HRTEM), Fourier transform infraredspectroscopy (FT-IR), and photoluminescence (PL) spectra, respectively. It is found that theas-synthesized NCs consist of monodisperse nanoparticles with diverse shapes and narrowsize distribution, which can easily disperse in non-polar cyclohexane solvent. The as-preparedNCs have a rich variety of morphologies and exhibit different crystal phases (hexagonal orcubic), which may be related with the inherent natures of different rare earth ions. Thepossible mechanism of NCs with diverse architectures has been presented. In addition,representative Yb/Er, Yb/Tm, and Yb/Ho co-doped NaGdF4and Na5Lu9F32NCs exhibitintensive multicolor up-conversion (UC) luminescence under a single980nm NIR excitation.Moreover, transparent and UC fluorescent NCs/polydimethylsiloxane (PDMS) compositeswith regular dimension were also prepared by an in situ polymerization route.