Surface Modification of ZrO2:Er3+ Nanoparticles to Attenuate Aggregation and Enhance Upconversion Fluorescence
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- 作者：Qiang Lü ; FengYun Guo ; Liang Sun ; Aihua Li ; LianCheng Zhao
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：February 28, 2008
- 年：2008
- 卷：112
- 期：8
- 页码：2836 - 2844
- 全文大小：394K
- 年卷期：v.112,no.8(February 28, 2008)
- ISSN：1932-7455
文摘
ZrO2:Er3+ nanoparticles are synthesized and further modified via a ligand-capped/ligand-exchanging methodwith TEOS, APTES, and SA. Antiaggregation investigations using TEM and FT-IR indicate that severeaggregation can be reduced by adhering ammonic or carboxylic functional groups to the nanoparticle surfaces.The upconversion fluorescence spectra of nonmodified and the modified nanoparticles with the same peaksplitting and positions show that local crystalline environments in which the Er3+ ions are embedded areidentical before and after modifying the surfaces. The remarkable upconversion fluorescence enhancementsof 4.7 and 1.5 times for amine- and carboxyl-modified nanoparticles are observed under the same excitationpower densities, respectively. An enhancement mechanism of upconversion luminescence, in which anasymmetric association crystalline field from both the degenerated crystalline field of the host interface anda complementary crystal field of the SiO2 shell can make the 'dormant' rare earth ions on nanoparticle surfacesbe activated, is presented. In addition, the improved spontaneous emission rate of Er3+ ions due to the enhancedlocal classical density of states and organic ligands with high vibrational energy on the nanoparticle surfacesare also considered. Thus, intense upconversion fluorescence and hydrophilicity via ammonic or carboxylicfunctional groups will provide the doped core-shell nanoparticles great potential as biolabels in the future.