WJNSE  Vol.2 No.2 , June 2012
A Method to Improve the Up-Conversion Fluorescence of Polymer Modified NaYF4:Yb,Er(Tm) Nanocomposites
The modification of NaYF4:Yb,Er(Tm) nanoparticles synthesized in the presence of an ionic surfactant is critical to their application in biological fields for better solubility and biocompatibility. In this work, NaYF4:Yb,Er(Tm) was transformed from insoluble, inactive to hydrophilic, biocompatible via ligand exchange modification with polyacrylic acid (PAA). Ligand exchange was carried out at room temperature when a colloidal solution of NaYF4:Yb,Er(Tm) in tetrahydrofuran (THF) was treated with excess PAA. The PAA modified NaYF4:Yb,Er(Tm) nanoparticles got better surface properties but with declined inner up-conversion fluorescence. Generally, coating an analogous layer of material outside the core nanoparticles can improve the optical properties of the core. Accordingly, NaYF4:Yb,Er(Tm)/NaYF4 nanoparticles were synthesized before PAA modification to avoid the optical intensity decaying. The result of fluorescence test proved that the water soluble NaYF4:Yb,Er(Tm)/NaYF4/PAA nanocomposites had a sound up-conversion property compared with that of NaYF4:Yb,Er(Tm)/PAA. Furthermore, the up-conversion fluorescence property of the nanocomposite varied with the doping ratio of Er(Tm) to Yb and the possible mechanism for this change was also discussed.

Cite this paper
W. Cui, S. Ni, S. Shan and X. Zhou, "A Method to Improve the Up-Conversion Fluorescence of Polymer Modified NaYF4:Yb,Er(Tm) Nanocomposites," World Journal of Nano Science and Engineering, Vol. 2 No. 2, 2012, pp. 41-46. doi: 10.4236/wjnse.2012.22007.
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