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Monodisperse upconversion GdF3:Yb, Er rhombi by microwave-assisted synthesis.

Wang H, Nann T - Nanoscale Res Lett (2011)

Bottom Line: We have synthesized a variety of monodisperse colloidal GdF3:Yb, Er upconversion nanocrystals with different shape, size, and dopants by microwave-assisted synthesis.Typical upconversion emission from Er3+ was observed.In addition to highly monodisperse spherical particles, we were able to prepare monodispersed rhombic-shaped slices that showed a tendency for self-assembly into stacks.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute Materials for Electronics and Energy Technology (I-MEET), Friedrich Alexander Universität Erlangen-Nürnberg, Marternsstraße 7, 91058, Erlangen, Germany. wang.hai-qiao@ww.uni-erlangen.de.

ABSTRACT
We have synthesized a variety of monodisperse colloidal GdF3:Yb, Er upconversion nanocrystals with different shape, size, and dopants by microwave-assisted synthesis. Typical upconversion emission from Er3+ was observed. In addition to highly monodisperse spherical particles, we were able to prepare monodispersed rhombic-shaped slices that showed a tendency for self-assembly into stacks.

No MeSH data available.


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TEMs of NaGdF4:Yb, Ho nanocrystals. (A) Five times standard concentration; (B) 25% standard concentration; (C) XRD pattern of NaGdF4:Yb, Ho nanocrystals; (D) Upconversion spectrum of NaGdF4:Yb, Ho nanocrystals under excitation of 980 nm.
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Figure 6: TEMs of NaGdF4:Yb, Ho nanocrystals. (A) Five times standard concentration; (B) 25% standard concentration; (C) XRD pattern of NaGdF4:Yb, Ho nanocrystals; (D) Upconversion spectrum of NaGdF4:Yb, Ho nanocrystals under excitation of 980 nm.

Mentions: In order to establish the reason for the strict rhombic shape of the nanocrystals, we replaced lithium with sodium in the above synthesis method. Yb/Ho codoped NaGdF4 nanocrystals were synthesized under the same conditions as above. Figure 6A shows the TEMs of the resulting particles with high and low reactant concentration, respectively. It can be seen that monodisperse, spherical particles were synthesized at low reactant concentration, and a bimodal distribution of monodisperse, spherical, and irregular larger nanocrystals at higher concentrations. Hence, these particles adopted a completely different morphology compared with GdF3. Figure 6C shows a XRD pattern of these particles, which confirms that the nanocrystals have crystallized in the cubic α-NaGdF4 phase (JCPDS 27-697). Therefore, we can conclude that the rhombic morphology of the GdF3 nanocrystals was primarily driven by the crystal lattice. Under the 980 nm excitation, mainly three emission bands were observed (Figure 6D). Predominantly green upconversion luminescence was observed at 542 nm, corresponding to the transition from the 5F4 and 5S2 to the 5I8 ground state. A weaker red and NIR upconversion luminescence was observed at 650 and 751 nm, which could be attributed to the transition from the 5F5 → 5I8 and 5F4, 5S2 → 5I7 states, respectively, which is in agreement with data from the literature.


Monodisperse upconversion GdF3:Yb, Er rhombi by microwave-assisted synthesis.

Wang H, Nann T - Nanoscale Res Lett (2011)

TEMs of NaGdF4:Yb, Ho nanocrystals. (A) Five times standard concentration; (B) 25% standard concentration; (C) XRD pattern of NaGdF4:Yb, Ho nanocrystals; (D) Upconversion spectrum of NaGdF4:Yb, Ho nanocrystals under excitation of 980 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211330&req=5

Figure 6: TEMs of NaGdF4:Yb, Ho nanocrystals. (A) Five times standard concentration; (B) 25% standard concentration; (C) XRD pattern of NaGdF4:Yb, Ho nanocrystals; (D) Upconversion spectrum of NaGdF4:Yb, Ho nanocrystals under excitation of 980 nm.
Mentions: In order to establish the reason for the strict rhombic shape of the nanocrystals, we replaced lithium with sodium in the above synthesis method. Yb/Ho codoped NaGdF4 nanocrystals were synthesized under the same conditions as above. Figure 6A shows the TEMs of the resulting particles with high and low reactant concentration, respectively. It can be seen that monodisperse, spherical particles were synthesized at low reactant concentration, and a bimodal distribution of monodisperse, spherical, and irregular larger nanocrystals at higher concentrations. Hence, these particles adopted a completely different morphology compared with GdF3. Figure 6C shows a XRD pattern of these particles, which confirms that the nanocrystals have crystallized in the cubic α-NaGdF4 phase (JCPDS 27-697). Therefore, we can conclude that the rhombic morphology of the GdF3 nanocrystals was primarily driven by the crystal lattice. Under the 980 nm excitation, mainly three emission bands were observed (Figure 6D). Predominantly green upconversion luminescence was observed at 542 nm, corresponding to the transition from the 5F4 and 5S2 to the 5I8 ground state. A weaker red and NIR upconversion luminescence was observed at 650 and 751 nm, which could be attributed to the transition from the 5F5 → 5I8 and 5F4, 5S2 → 5I7 states, respectively, which is in agreement with data from the literature.

Bottom Line: We have synthesized a variety of monodisperse colloidal GdF3:Yb, Er upconversion nanocrystals with different shape, size, and dopants by microwave-assisted synthesis.Typical upconversion emission from Er3+ was observed.In addition to highly monodisperse spherical particles, we were able to prepare monodispersed rhombic-shaped slices that showed a tendency for self-assembly into stacks.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute Materials for Electronics and Energy Technology (I-MEET), Friedrich Alexander Universität Erlangen-Nürnberg, Marternsstraße 7, 91058, Erlangen, Germany. wang.hai-qiao@ww.uni-erlangen.de.

ABSTRACT
We have synthesized a variety of monodisperse colloidal GdF3:Yb, Er upconversion nanocrystals with different shape, size, and dopants by microwave-assisted synthesis. Typical upconversion emission from Er3+ was observed. In addition to highly monodisperse spherical particles, we were able to prepare monodispersed rhombic-shaped slices that showed a tendency for self-assembly into stacks.

No MeSH data available.


Related in: MedlinePlus