A facile and productive method has been developed to synthesize uniform LaF3 nanocrystals with controllable shapes, including polyhedrons, nanorods and nanoplates. By tuning the amount of NaOH and ligands (oleic acid and octadecylamine), we can finely tailor the shapes and sizes of LaF3 nanocrystals. Three prepared LaF3 nanostructures were well characterized, followed by a series of control experiments to propose a mechanism for the shape control. Based on the success in materials synthesis, controlled patterning of LaF3 nanoplates on substrates has also been achieved. After Yb/Er or Yb/Tm was co-doped in these LaF3 nanostructures, they could serve as nanoparticulate host matrices to give strong upconversion luminescence, showing great potential in biomedical applications considering their small sizes and well-defined shapes.
Synthesis of well-defined sodium yttrium fluoride (NaYF 4 ) nanocrystals has been achieved in nonpolar solvents, but these nanocrystals possess a hydrophobic surface and need to be surfacemodified for various biological applications. Development of facile aqueous solution method to synthesize one-dimensional NaYF 4 with a hydrophilic surface still remains challenging. Herein, we demonstrate a simple route to prepare hydrophilic NaYF 4 nanorods by using hydrophobic NaYF 4 nanospheres as precursor. It is interesting to find that hydrothermal treatment of oleic acid-capped NaYF 4 nanocrystals can not only induce anisotropic growth of these nanocrystals but also change their surface properties. The hydrophilic NaYF 4 nanorods synthesized in this work has been well characterized and possible formation mechanism has also been discussed.
Uniform and assembled LaBO3 nanocrystals have been successfully synthesized via a facile hydrothermal method. These assemblies exhibit a rod-shape morphology and each of them consists of small LaBO3 nanocrystals which are tightly attached together. The phase, surface and morphology of these assemblies have been characterized. A possible assembly mechanism of such morphology is also proposed through investigation on the formation process. Photoluminescent spectra suggest that these assemblies doped with Eu3+ can give stronger red emissions than the orange one due to its aragonite structure. Such emission has been explained by the Judd-Ofelt theory. It is expected that these well-defined LaBO3 assemblies could find applications in future luminescent displays and lamps.
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