| With the development of nanotechnology, rare-earth doped luminescent nanomaterials have been widely used in many applications, such as phosphors, three-dimensional displays, optical devices, biolabeling and therapeutics. Among various rare-earth doped luminescent nanomaterials. fluorides have received great attention due to their lower phonon energy, which leads to smaller relaxation rates and higher fluorescence quantum yields. Meanwhile, rare-earth doped borates are also ideal nanomaterials owning to their high chemical stability, thermal stability, non-toxic, and excellent color purity. As is well-known, the sizes and morphologies of rare-earth doped luminescent nanomaterials have much to do with their luminescent properties. In the past decades, much efforts have been made to control the size and morphology to obtain excellent luminescent properties. And the surface chemical modification is an efficient method to obtain high luminescence efficiency by improving the appearances and reducing the surface quenching centers of nanomaterials. Very recently, the incorporation of noble metal NCs with nanomaterials has received great attention because of the plasmon-enhanced luminescence properties.In this paper, the present status of lanthanide-doped fluoride and borate nanomaterials are reviewed for their preparation methods and property investigation. Due to problems of nonuniform morphologies, poor dispersion, poor biocompatibility and low luminescence efficiency, we prospect the research work in the near future. Here. lanthanide-doped fluoride and borate nanomaterials with various morphologies have been synthesized by different surface modifications. The preparation conditions and luminescent properties have been characterized by XRD, FE-SEM. TEM. FT-IR. Abs and PL analyses. The main contents are as follows:(1) Uniform and morphology controllable Ba-B-O:Eu3+ nanorods. nanowires. and flowerlike assemblies have been successfully synthesized via a hydrothermal method for the first time. Many factors, including the amount of OA. reaction time, and pH values, influenced the formation and growth of the Eu3+-doped Ba-B-O NCs. Based on the experimental results, we conclude that OA is a crucial factor acting as a capping reagent which has a effect on the growth of the NCs. By adjusting pH. we have controlled the absorptions of OA on the surfaces of NCs and modulated the growth rates along different crystallographic directions. The anisotropic growth and the process of Ostwald ripening determined the morphologies of the NCs. Furthermore, the I(5D0→7F2)/I(5D0→7F1) is about 2.01.1.89. and 2.29, respectively. The luminescent investigation indicates that the Ba-B-O:Eu3+ nanocrystals. especially the flower-like assemblies, can emit intense fluorescence with excellent color purity, which will promise the efficient photoluminescence in applications of displays and nanodevices.(2) Europium (Eu3+) doped BaF2 nanocubes have been synthesized successfully through one-step precipitation reaction, using OA as a capping agent. XRD analysis indicated that the products were cubic BaF2, SEM analysis indicated that the products exhibited nanocubic morphology with a side length of～150 nm. Furthermore, the luminescent investigation indicates that the emission intensity of the BaF2:Eu3+ nanocubes have been enhanced greatly after modified with proper amount of OA. which is promising for new optical technologies in the future.(3) NaYF4:Yb3+,Tm3+(Er3+) nanocrystals (NCs) have been synthesized by a hydrothermal method using trisodium citrate as a surfactant. XRD and TEM indicate that we have obtained well-dispersedβ-NaYF4: Yb3+,Tm3+(Er3+) NCs with the diameter of about 150 nm. Many factors, including the amount of trisodium citrate and reaction time influenced the formation and growth of theβ-NaYF4: Yb3+,Tm3+(Er3+) NCs. The optimal reaction condition is 4 mmol of trisodium citrate, 12 h. The influence of the concentration of dopants inβ-NaYF4 NCs on the upconversion emission intensities has been discussed, and 0.5% Tm3+ and 1.5% Er3+ and were chosen as the optimal condition.(4) we synthesized Au@β-NaYF4:Yb,Tm(Er) hybrid nanostructures and achieved enhanced multicolour UC emissions and decreased pumping threshold. Under low NIR pumping power of～50 mW. the enhancement for 5-photon UC emissions located at 291 and 345 nm have been enhanced most suggests that ANNCs are excellent UC nanomaterials especially for high-order photon UC. The prolonged lifetimes of Yb3+,Tm3+ and Er3+excited states suggest a new evidence that the enhanced UC emissions are induced by the plasmon field enhancement of attached Au NCs. This work provides a novel strategy to study how Au NCs improved efficiency for UC emissions and indicates the Au@β-NaYF4:Yb,Tm(Er) hybrid nanostructures exhibit great potential in a broad range of photonic, medical, therapeutic, and biological applications. In addition, we initially investigated the UC emissions of Au@SiO2@NaYF4:Yb,Tm NCs, and found that the UV UC emissions were enhanced most when 0.3 ml tetraethyl orthosilicate was added. |
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