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Journal of Nanomaterials
Volume 2014, Article ID 821706, 7 pages
http://dx.doi.org/10.1155/2014/821706
Research Article

Controlled Synthesis of Water-Soluble NaYF4:Yb3+, Er3+ Nanoparticles with Surfactant Dependent Properties

1Department of Materials Science and Engineering, Luoyang Institute of Science and Technology, Luoyang 471023, China
2State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China

Received 31 December 2013; Revised 5 March 2014; Accepted 6 March 2014; Published 31 March 2014

Academic Editor: Marinella Striccoli

Copyright © 2014 Junwei Zhao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Water-soluble NaYF4:Yb3+, Er3+ nanoparticles (NPs) are successfully prepared by a solvothermal reaction using branched polyethylenimine (PEI) with different chain lengths as the surfactants in a water/diethylene glycol (DEG) mixed solution. It is shown that the size of NaYF4 NPs prepared with high molecular weight PEI (HPEI) is smaller than that of the NPs prepared with low molecular weight (LPEI), while small-sized NPs exhibit more intense upconversion luminescence intensities than large-sized NPs in the same excitation power of 980 nm. It is found that HPEI is conducive to the formation of smaller NP with high crystallinity. Small-sized NaYF4:Yb3+, Er3+ NPs with intense upconversion luminescence and improved crystallinity were related to their growth process. A possible growth mechanism of the samples is proposed. The results of this study can provide new insights into the controlled synthesis of novel NPs.