Enhanced Upconversion Luminescence in Yb3+/Tm3+-Codoped Fluoride Active Core/Active Shell/Inert Shell Nanoparticles through Directed Energy Migration
"> Figure 1
<p>Transmission electron images (TEM) of: (<b>a</b>) The core NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup> nanoparticles; (<b>b</b>) The active core/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYF<sub>4</sub> nanoparticles; (<b>c</b>) The active core/active shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub> nanoparticles; and (<b>d</b>) The active core/active shell/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>/NaYF<sub>4</sub> nanoparticles. Histogram of size distribution of (<b>e</b>) The core NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup> nanoparticles; (<b>f</b>) The active core/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYF<sub>4</sub> nanoparticles; (<b>g</b>) The active core/active shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub> nanoparticles; and (<b>h</b>) The active core/active shell/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>/NaYF<sub>4</sub> nanoparticles. The size was evaluated according to TEM images of corresponding nanoparticles dispersed in hexane at a concentration of 0.1 wt.%.</p> "> Figure 2
<p>X-ray diffraction patterns of the core NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup> nanoparticles, the active core/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYF<sub>4</sub> nanoparticles, the active core/active shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub> nanoparticles, and the active core/active shell/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>/NaYF<sub>4</sub> nanoparticles, contrasted with the standard cubic NaYF<sub>4</sub> structure of JCPDS 06-0342.</p> "> Figure 3
<p>(<b>a</b>) Compared upconversion luminescence of colloidal nanoparticles (hexane dispersion, 1 wt.%) of the core NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>, the active core/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYF<sub>4</sub>, and the active core/active shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>. The peaks at ~690 and ~720 nm marked by asterisk correspond to the second order of the peaks at 345 and 360 nm; (<b>b</b>) Compared upconversion luminescence of colloidal nanoparticles (hexane dispersion, 1 wt.%) of the active core/active shell/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>/NaYF<sub>4</sub> and the active core/active shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>. The same batch of the core nanoparticles is utilized to grow the active core/inert shell, the active core/active shell, and the active core/active shell/inert shell nanoparticles. The excitation is performed with a diode laser at ~980 nm of about 50 W/cm<sup>2</sup>. All the spectra have been calibrated by the spectral sensitivity of the utilized spectrophotometer system.</p> "> Figure 4
<p>(<b>a</b>) A log-log plot of the dependence of various luminescence intensities from the active core/active shell/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>/NaYF<sub>4</sub> nanoparticles on the excitation density; (<b>b</b>) Energy level diagrams of Yb<sup>3+</sup> and Tm<sup>3+</sup> ions as well as the involved mechanisms for upconversion luminescence from different energy states of Tm<sup>3+</sup> ions.</p> "> Figure 5
<p>Decays of upconversion luminescence at 802 nm from the core NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>, the active core/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYF<sub>4</sub>, the active core/active shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>, and the active core/active shell/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>/NaYF<sub>4</sub> nanoparticles.</p> "> Figure 6
<p>Schematic illustration of the luminescence quenching mechanism in: (<b>a</b>) The core NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup> nanoparticles, as well as the luminescence enhancement mechanism in (<b>b</b>) The active core/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYF<sub>4</sub> nanoparticles; (<b>c</b>) The active core/active shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub> nanoparticles; and (<b>d</b>) The active core/active shell/inert shell (NaYF<sub>4</sub>: 30%Yb<sup>3+</sup>, 0.5%Tm<sup>3+</sup>)/NaYbF<sub>4</sub>/NaYF<sub>4</sub> nanoparticles.</p> ">
Abstract
:1. Introduction
2. Results and Discussion
2.1. Characterizations of Morphology and Crystal Structure
2.2. Upconversion Luminescence
2.3. Upconversion Mechanism
2.4. Decay of Upconversion Luminescence
2.5. Quenching and Enhancing Mechanisms
3. Experimental Section
3.1. Synthesis of NaYF4: Yb3+30%/Tm3+0.5% Core Nanoparticles
3.2. Synthesis of (NaYF4: Yb3+30%/Tm3+0.5%)/NaYbF4 Active Core/Active Shell Nanoparticles
3.3. Synthesis of (NaYF4: Yb3+30%/Tm3+0.5%)/NaYF4 Active Core/Inert Shell Nanoparticles
3.4. Synthesis of (NaYF4: Yb3+30%/Tm3+0.5%)/NaYbF4/NaYF4 Active Core/Active Shell/Inert Shell Nanoparticles
3.5. Instruments
4. Conclusions
Acknowledgments
Conflicts of Interest
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Qiu, H.; Yang, C.; Shao, W.; Damasco, J.; Wang, X.; Ågren, H.; Prasad, P.N.; Chen, G. Enhanced Upconversion Luminescence in Yb3+/Tm3+-Codoped Fluoride Active Core/Active Shell/Inert Shell Nanoparticles through Directed Energy Migration. Nanomaterials 2014, 4, 55-68. https://doi.org/10.3390/nano4010055
Qiu H, Yang C, Shao W, Damasco J, Wang X, Ågren H, Prasad PN, Chen G. Enhanced Upconversion Luminescence in Yb3+/Tm3+-Codoped Fluoride Active Core/Active Shell/Inert Shell Nanoparticles through Directed Energy Migration. Nanomaterials. 2014; 4(1):55-68. https://doi.org/10.3390/nano4010055
Chicago/Turabian StyleQiu, Hailong, Chunhui Yang, Wei Shao, Jossana Damasco, Xianliang Wang, Hans Ågren, Paras N. Prasad, and Guanying Chen. 2014. "Enhanced Upconversion Luminescence in Yb3+/Tm3+-Codoped Fluoride Active Core/Active Shell/Inert Shell Nanoparticles through Directed Energy Migration" Nanomaterials 4, no. 1: 55-68. https://doi.org/10.3390/nano4010055