Near-Infrared-to-Near-Infrared Downshifting and Near-Infrared-to-Visible Upconverting Luminescence of Er3+-Doped In2O3 Nanocrystals
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- 作者：Qingbo Xiao ; Haomiao Zhu ; Datao Tu ; En Ma ; Xueyuan Chen
- 刊名：The Journal of Physical Chemistry C
- 出版年：2013
- 出版时间：May 23, 2013
- 年：2013
- 卷：117
- 期：20
- 页码：10834-10841
- 全文大小：423K
- 年卷期：v.117,no.20(May 23, 2013)
- ISSN：1932-7455
文摘
Luminescent lanthanide-doped nanoparticles (NPs) excitable in the near-infrared (NIR) spectral region are highly desired as new optical bioprobes in the fields of biological assays and medical imaging. Er3+-doped In2O3 NPs, synthesized via a facile sol鈥揼el solvothermal method, exhibit intense and well-resolved NIR-to-NIR downshifting (DS) and NIR-to-visible upconversion (UC) dual-mode luminescence upon NIR excitation at 808 and 980 nm, respectively. Forty-one crystal-field levels below 23鈥?00 cm鈥? were identified for Er3+ at a single lattice site of C2 symmetry in In2O3 NPs by means of high-resolution site-selective NIR spectroscopy at 10 K and room temperature. Furthermore, the luminescence dynamics for the UC emissions were systematically investigated, and various UC processes were clearly distinguished based on excited state dynamics and rate equation analysis. Mediated by the long-lived intermediate states of 4I11/2 and 4I13/2, the decay times of 4F9/2 (or 4S3/2) due to energy transfer upconversion (ETU) were found to be approximately 1 order of magnitude larger than that of DS luminescence, namely, increasing from 20 渭s to 0.51 ms (or 0.24 ms). It was revealed that the contribution from the ETU process to the UC luminescence of 4S3/2 and 4F9/2 increased significantly along with the increase of the ETU probability of Er3+ at high doping concentration.