Novel chelating ligands are very significant for preparing nanocrystals with different morphologies and applications. In this paper, we directly introduced amine groups onto UCNPs by choosing a new chelating ligand tetraethylene pentamine (TEPA) to synthesis
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:Yb, Er through hydrothermal method. The influences of rare earth concentration, the ratio of RE/TEPA, solvent composition, and reaction time on the morphology and fluorescence intensity of the as-prepared
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:Yb, Er samples were systematically investigated and discussed. Field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), and upconversion luminescence spectroscopy were used to characterize the product. It was found that rare earth concentration, ratio of RE/TEPA, solvent composition, and reaction time were all responsible for the luminescent intensity and morphology.
Li Na,Tan Haihu,Xie Shaowen,Liu Simin,Tong Chao,Ouyang Min,Xu Lijian
Upconversion nanocrystals with uniform size and hydrophilic surface have potential applications in biological medical engineering. In this study, hydrophilic NaYF4:Yb, Er nanospheres were synthesized via hexadecylpyridinium chloride (CPC) mediated hydrothermal process. The
synthesized NaYF4:Yb, Er upconversion nanospheres (UCNSs) were characterized by various characterization methods. Results showed that the synthesized UCNSs exhibited a uniform sphere-like structure with average diameter of ~250 nm. The surface of UCNSs was captured by CPC molecule
indicating hydrophilic properties of UCNSs. The spherical UCNSs composed of mixed phase (α+β) NaYF4 nanocrystals. This is the novel study for synthesis of NaYF4:Ln3+ crystal employing CPC as ligand. Moreover, the effect of CPC concentration on
synthesis of UCNSs was investigated by comparatively studying morphology, crystal phase and luminescent properties of desired sample prepared under different experimental conditions. It was found that high concentrations of CPC ligands were more favorable for forming NaYF4 crystal
nanospheres with morphology that is more regular, have smoother surface, with higher crystallinity and better upconversion fluorescent properties. The possible growing mechanism was proposed and growing of NaYF4:Yb, Er nanospheres followed the classical Ostwald ripening process.
Graphene oxide/NaYF 4 : Yb, Er nanocomposites have been synthesized via hydrothermal synthesis, in which spherical cubic phase NaYF 4 : Yb, Er nanocrystals with uniformity are implanted onto the surface of graphene oxide (GO). Using a near infrared laser set to 980 nm, the light-to-heat energy transfer efficiency of GO/NaYF 4 : Yb, Er is 13.9% higher than GO by itself, revealing that the photothermal conversion efficiency of GO could be enhanced by doping NaYF 4 : Yb, Er nanocrystals. This phenomenon can be attributed to the energy transfer between the NaYF 4 : Yb, Er nanocrystals to the energy receptor in the GO substrate.
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