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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 4 — Feb. 15, 2010
  • pp: 3364–3369
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Controllable energy transfer in fluorescence upconversion of NdF3 and NaNdF4 nanocrystals

M. Li, Z.-H. Hao, X.-N. Peng, J.-B. Li, X.-F. Yu, and Q.-Q. Wang  »View Author Affiliations


Optics Express, Vol. 18, Issue 4, pp. 3364-3369 (2010)
http://dx.doi.org/10.1364/OE.18.003364


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Abstract

The synthesized Nd fluoride nanocrystals exhibited different upconversion behaviors as dispersed and aggregated samples due to the different energy transfer mechanisms. When they were dispersed in water, the NaNdF4 nanocrystals exhibited ~400 times stronger upconversion fluorescence than the NdF3 nanocrystals. Remarkable upconversion behaviors were found when the nanocrystals were aggregated in the films. For the NdF3 nanocrystals, the energy transfer processes 4I13/24F3/24G7/2 in the films generated avalanche upconversion emissions with a high slope of ~12.0, which could be due to the large avalanche cross relaxation rates and spectral broadening effect. In contrast, the spectral broadening effect in the NaNdF4 NCs films increased the energy transfer 4I15/24F3/24G5/2 of the Nd3+ ions, and induced a new upconversion emission at ~680 nm with the slope increased from 1.0 to 3.2.

© 2010 OSA

1. Introduction

Frequency upconversion of infrared into visible light in rare-earth solid materials have received significant interest due to the possibility of infrared-pumped visible lasers and their potential applications in color display, optical storage, solar cells, and biological detection [1

1. H. X. Zhang, C. H. Kam, Y. Zhou, X. Q. Han, S. Buddhudu, Q. Xiang, Y. L. Lam, and Y. C. Chan, “Green upconversion luminescence in Er3+:BaTiO3 films,” Appl. Phys. Lett. 77(5), 609–611 (2000). [CrossRef]

6

6. D. K. Chatterjee, A. J. Rufaihah, and Y. Zhang, “Upconversion fluorescence imaging of cells and small animals using lanthanide doped nanocrystals,” Biomaterials 29(7), 937–943 (2008). [CrossRef]

]. Among rare-earth ions, neodymium has been recognized as one of the most efficient ions for solid-state lasers due to its intense emission at 1060 nm. In addition to the infrared emissions [7

7. A. A. Kaminskii, Laser Crystals, 2nd ed., Springer Series in Optical Sciences Vol. 14, edited by D. L. MacAdam (Springer-Verlag, Berlin, 1990).

,8

8. M. J. Weber, “Science and technology of laser glass,” J. Non-Cryst. Solids 123(1-3), 208–222 (1990). [CrossRef]

], Nd3+ ion can also be useful for upconversion fluorescence and lasers [9

9. S. Guy, M. F. Joubert, B. Jacquier, and M. Bouazaoui, “Excited-state absorption in BaY2F8:Nd3+,” Phys. Rev. B 47(17), 11001–11006 (1993). [CrossRef]

14

14. X. Wang, J. Song, H. Sun, Z. Xu, and J. Qiu, “Multiphoton-excited upconversion luminescence of Nd:YVO(4).,” Opt. Express 15(3), 1384–1389 (2007). [CrossRef] [PubMed]

]. In upconversion process, multi-phonon relaxation rates greatly decrease with the increased number of phonons involved in the transition between adjacent electronic levels [15

15. A. Mendioroz, R. Balda, M. Voda, M. Al-Saleh, and J. Fernández, “Infrared to visible and ultraviolet upconversion processes in Nd3+-doped potassium lead chloride crystal,” Opt. Mater. 26(4), 351–357 (2004). [CrossRef]

]. Consequently, investigation on low-energy phonon host materials is very important for obtaining upconversion fluorescence with high efficiency.

Fluoride compositions are currently being intensively investigated as suitable host materials for upconversion fluorescence of rare-earth ions [10

10. C. Jacinto, S. L. Oliveira, T. Catundab, A. A. Andrade, J. D. Myers, and M. J. Myers, “Upconversion effect on fluorescence quantum efficiency and heat generation in Nd3+-doped materials,” Opt. Express 13(6), 2040–2046 (2005). [CrossRef] [PubMed]

,16

16. O. S. Wenger, D. R. Gamelin, H. U. Güdel, A. V. Butashin, and A. A. Kaminskii, “Site-selective yellow to violet and near-infrared to green upconversion in BaLu2F8:Nd3+,” Phys. Rev. B 61(24), 16530–16537 (2000). [CrossRef]

19

19. L. de S. Menezes, C. B. de Araújo, G. S. Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70(6), 683–685 (1997). [CrossRef]

], because of their low phonon energies and adequate thermal and environmental stability [20

20. O. V. Kudryavtseva, L. S. Garashina, K. K. Rivkina, and B. P. Sobolev, “Solubility of LnF3 in lanthanum fluoride,” Sov. Phys. Crystallogr. 18, 531 (1974).

]. Among them, uniform rare-earth fluoride nanocrystals (NCs) with formula like ReF3 or NaReF4 (Re: rare-earth) are of new nanocrystalline phosphors due to their novel optical properties different from their bulk counterparts and common lanthanide-doped NCs in terms of luminescence efficiency, energy transfer behaviors, and concentration quenching effect, etc [21

21. N. O. Nuñez and M. Ocaña, “An ionic liquid based synthesis method for uniform luminescent lanthanide fluoride nanoparticles,” Nanotechnology 18(45), 455606 (2007). [CrossRef]

25

25. X. F. Yu, L. D. Chen, M. Li, M. Y. Xie, L. Zhou, Y. Li, and Q. Q. Wang, “Highly efficient fluorescence of NdF3/SiO2 Core/Shell nanoparticles and the applications for in vivo NIR detection,” Adv. Mater. 20(21), 4118–4123 (2008). [CrossRef]

]. Such uniform NCs can be incorporated into a broad range of materials and devices [24

24. R. B. Yu, K. H. Yu, W. Wei, X. Xu, X. Qiu, S. Liu, W. Huang, G. Tang, H. Ford, and B. Peng, “Nd2O3 nanoparticles modified with a silane coupling agent as a liquid laser medium,” Adv. Mater. 19(6), 838–842 (2007). [CrossRef]

,26

26. H. Yang, H. Wang, H. M. Luo, D. M. Feldmann, P. C. Dowden, R. F. DePaula, and Q. X. Jia, “Structural and dielectric properties of epitaxial Sm2O3 thin films,” Appl. Phys. Lett. 92(6), 062905 (2008). [CrossRef]

] and are also suitable for sensing at the molecular scale [3

3. S. Sivakumar, F. C. J. M. van Veggel, and P. S. May, “Near-infrared (NIR) to red and green up-conversion emission from silica sol-gel thin films made with La0.45Yb0.50Er0.05F3 nanoparticles, hetero-looping-enhanced energy transfer (Hetero-LEET): a new up-conversion process,” J. Am. Chem. Soc. 129(3), 620–625 (2007). [CrossRef] [PubMed]

]. However their upconversion properties have seldom been discussed. In this work, we synthesized hexagonal-phase uniform NdF3 and NaNdF4 NCs, and investigated their upconversion fluorescence properties and corresponding energy transfer mechanisms.

2. Synthesis and characterization

The NdF3 and NaNdF4 NCs were synthesized using the methods reported by our group previously [25

25. X. F. Yu, L. D. Chen, M. Li, M. Y. Xie, L. Zhou, Y. Li, and Q. Q. Wang, “Highly efficient fluorescence of NdF3/SiO2 Core/Shell nanoparticles and the applications for in vivo NIR detection,” Adv. Mater. 20(21), 4118–4123 (2008). [CrossRef]

, 27

27. M. Y. Xie, X. N. Peng, X. F. Fu, J. J. Zhang, G. L. Li, and X. F. Yu, “Synthesis of Yb3+/Er3+ co-doped MnF2 nanocrystals with bright red up-converted fluorescence,” Scr. Mater. 60(3), 190–193 (2009). [CrossRef]

].Transmission electron microscopy (TEM) images were measured with a JEOL 2010 HT transmission electron microscope (operated at 200 kV). XRD analyses were performed on a Bruker D8-advance X-ray diffractometer with Cu Kα irradiation (λ = 1.5406 Å). The excitation source was a mode-locked Ti: sapphire laser (Mira 900, Coherent) delivering ~3 ps pulses at a repetition rate of 76 MHz. The emission spectra were recorded by a monochromator (Spectrapro 2500i, Acton) with a liquid-nitrogen-cooled CCD detector (SPEC-10, Princeton).

3. Results and discussion

As shown in Fig. 1(a)
Fig. 1 TEM images (a, b) and XRD spectra (c) of NdF3 and NaNdF4 NCs.
and 1(b), the synthesized NdF3 NCs were of nearly spherical shape and had an average diameter of ~40 nm, while the NaNdF4 NCs were rodlike particles with an average diameter of ~12 nm and length of ~60 nm. As shown in the XRD spectra in Fig. 1(c), the peak positions and intensities of the NdF3 and NaNdF4 NCs could be well indexed in accord with hexagonal NdF3 crystals (JCPDS card 9-416), and hexagonal NaNdF4 crystals (JCPDS card 27-756), respectively.

Energy level diagram in Fig. 2(a)
Fig. 2 (a) Energy level diagram and corresponding ESA and ETU processes of Nd3+ involved in our studies. (b) Absorption spectra of NdF3 and NaNdF4 NCs dispersed in water with the same molar concentration of 180 mM.
exhibits the main energy levels and corresponding upconversion processes of Nd3+ ions. As known, upconversion fluorescence occurs via two basic mechanisms [28

28. W. F. Auzel, “Optical constants of the noble metals,” Proc. IEEE 61, 758–787 (1973). [CrossRef]

]. The simplest single ion upconversion mechanism is the ground-state absorption/excited-state absorption (GSA/ESA) mechanism. The second well-known mechanism is energy transfer upconversion (ETU), which is based on a non-radiative energy transfer between two or multiple ions. These two mechanisms determine the different upconversion processes, which would be discussed in the following sections.

Figure 2(b) shows the absorption spectra (500 – 900 nm) of the NdF3 and NaNdF4 NCs dispersed in water at the same molar concentration. The observed absorption bands were attributed to different transitions from the ground state 4I 9/2 to various excited states of electronic configuration of Nd3+ ion: 4 F 3 / 2 (~860 nm), 4 F 5 / 2 + 2 H 9 / 2 (~800 nm), 4 S 3 / 2 + 4 F 7 / 2 (~740 nm), 4 F 9 / 2 (~670 nm), 2 H 11 / 2 (~620 nm), 4 G 5 / 2 + 2 G 7 / 2 (~580 nm), and 2 K 13 / 2 + 4 G 7 / 2 (~525 nm). It could be found that the absorption peaks of the NaNdF4 NCs were slightly red-shifted and more distinguishable compared with those of the NdF3 NCs, probably due to their regular and anisotropic crystal structure.

Figure 3(a)
Fig. 3 (a) Upconversion fluorescence spectra of NdF3 and NaNdF4 NCs with λexc=800 nm and excitation power of 240 mW. (b) Excitation power dependences of upconversion emission intensities of NdF3 and NaNdF4 NCs. The above samples are all dispersed in water with the same molar concentration of 180 mM.
shows the upconversion fluorescence spectra (λexc = 800 nm) of the NdF3 and NaNdF4 NCs dispersed in water. The observed emission peaks at around 585 nm and 660 nm were attributed to the transitions 4 G 7/24 I 11/2 and 4 G 7/24 I 13/2 of Nd3+, respectively. The NaNdF4 NCs exhibited ~400 times stronger upconversion fluorescence than the NdF3 NCs under the same excitation power of 240 mW. Considering the NdF3 and NaNdF4 NCs were at the same concentration of 180 mM and had the similar absorption power at 800 nm, the results indicate that the NaNdF4 NCs have much higher upconversion fluorescence efficiency than the NdF3 NCs. As known, the NaReF4 NCs have very low phonon energy and have usually been regarded as the most efficient host materials for supporting upconversion fluorescence [29

29. F. Wang and X. Liu, “Recent advances in the chemistry of lanthanide-doped upconversion nanocrystals,” Chem. Soc. Rev. 38(4), 976–989 (2009). [CrossRef] [PubMed]

]. Additionally, compared with the NdF3 nanospheres, the more regular crystal structure of the NaNdF4 nanorods might also contribute to the lower nonradiative loss [14

14. X. Wang, J. Song, H. Sun, Z. Xu, and J. Qiu, “Multiphoton-excited upconversion luminescence of Nd:YVO(4).,” Opt. Express 15(3), 1384–1389 (2007). [CrossRef] [PubMed]

,30

30. G. A. Kumar, C. W. Chen, J. Ballato, and R. E. Riman, “Optical characterization of infrared emitting rare-earth-doped fluoride nanocrystals and their transparent nanocomposites,” Chem. Mater. 19(6), 1523–1528 (2007). [CrossRef]

]. We note that the upconversion efficiency of the NaNdF4 NCs in water was about an order of magnitude less than that of the commercial CdSe/ZnS core/shell quantum dots (Invitrogen Co., Ltd.) under 800 nm pulsed laser excitation. However, if a continuous wave laser was used as the excitation, the efficient upconversion fluorescence could only be found in the NaNdF4 NCs. Furthermore, the synthesis of core/shell structures would result in the great increase of the fluorescence efficiency [25

25. X. F. Yu, L. D. Chen, M. Li, M. Y. Xie, L. Zhou, Y. Li, and Q. Q. Wang, “Highly efficient fluorescence of NdF3/SiO2 Core/Shell nanoparticles and the applications for in vivo NIR detection,” Adv. Mater. 20(21), 4118–4123 (2008). [CrossRef]

,31

31. M.-Y. Xie, L. Yu, H. He, and X.-F. Yu, “Synthesis of highly fluorescent LaF3:Ln3+/LaF3 core/shell nanocrystals by a surfactant-free aqueous solution route,” J. Solid State Chem. 182(3), 597–601 (2009). [CrossRef]

]. Figure 3(b) shows the excitation power dependences of the peak emission intensities of these samples. In the excitation power region 170~300 mW, the slope (= ӘlogI emi/ӘlogI exc) values of the NdF3 and NaNdF4 NCs were 2.0 and 1.7, respectively. Since the particles were dispersed in water, the ETU process between different particles was very weak, thus the upconversion emissions were mainly induced by the ESA from the metastable state 4 F 3/2 to higher level 2 D 5/2 in single particle.

The upconversion behaviors were further investigated by preparing the films (thickness of ~10 μm) of the NdF3 and NaNdF4 NCs by using the method described previously [23

23. H. Deng, S. H. Yang, S. Xiao, H. M. Gong, and Q. Q. Wang, “Controlled synthesis and upconverted avalanche luminescence of cerium(III) and neodymium(III) orthovanadate nanocrystals with high uniformity of size and shape,” J. Am. Chem. Soc. 130(6), 2032–2040 (2008). [CrossRef] [PubMed]

]. Figure 4(a)
Fig. 4 (a, c) Upconversion emission spectra of NdF3 (a), and NaNdF4 (c) NCs films with λ exc=800 nm. (b, d) Excitation power dependences of upconversion emission intensities of NdF3 (b), and NaNdF4 (d) NCs films.
shows the upconversion fluorescence spectra of the aggregated NdF3 NCs in the film. As the excitation power increased from 190 to 350 mW, the nonlinearly increased emission peaks slightly red-shifted, and the emission bands were significantly broadened.

The excitation power dependences of the peak emission intensities of the NdF3 NCs film are shown in Fig. 4(b). When the excitation power was over the threshold of 270 mW, all the emissions at around 525, 585, and 640 nm exhibited avalanche increasing with the slope up to ~12.0. As is known, in bulk Nd crystals or Nd doped glasses, the Nd3+ upconversion was a two-photon (or three-photon) induced photoluminescence process [5

5. B. Ahrens, P. T. Miclea, and S. Schweizer, “Upconverted fluorescence in Nd3+-doped barium chloride single crystals,” J. Phys. Condens. Matter 21(12), 125501 (2009). [CrossRef] [PubMed]

,9

9. S. Guy, M. F. Joubert, B. Jacquier, and M. Bouazaoui, “Excited-state absorption in BaY2F8:Nd3+,” Phys. Rev. B 47(17), 11001–11006 (1993). [CrossRef]

11

11. R. Balda, M. Sanz, A. Mendioroz, J. Fernández, L. S. Griscom, and J. L. Adam, “Infrared-to-visible upconversion in Nd3+-doped chalcohalide glasses,” Phys. Rev. B 64(14), 144101 (2001). [CrossRef]

,15

15. A. Mendioroz, R. Balda, M. Voda, M. Al-Saleh, and J. Fernández, “Infrared to visible and ultraviolet upconversion processes in Nd3+-doped potassium lead chloride crystal,” Opt. Mater. 26(4), 351–357 (2004). [CrossRef]

,32

32. B. R. Reddy and P. Venkateswarlu, “Quenching, thermalisation and energy up-conversion in LaF3:Nd3+,” J. Phys. C Solid State Phys. 18(20), 3873–3879 (1985). [CrossRef]

], instead of the avalanche upconversion. In nanoscale materials, the avalanche upconversion with slope up to 3 was also observed in NdVO4 NCs films [23

23. H. Deng, S. H. Yang, S. Xiao, H. M. Gong, and Q. Q. Wang, “Controlled synthesis and upconverted avalanche luminescence of cerium(III) and neodymium(III) orthovanadate nanocrystals with high uniformity of size and shape,” J. Am. Chem. Soc. 130(6), 2032–2040 (2008). [CrossRef] [PubMed]

]. However, both the reported Nd doped NCs and our synthesized NdF3 NCs were still two-photon processes when they were dispersed insolutions [23

23. H. Deng, S. H. Yang, S. Xiao, H. M. Gong, and Q. Q. Wang, “Controlled synthesis and upconverted avalanche luminescence of cerium(III) and neodymium(III) orthovanadate nanocrystals with high uniformity of size and shape,” J. Am. Chem. Soc. 130(6), 2032–2040 (2008). [CrossRef] [PubMed]

], or as powder samples [5

5. B. Ahrens, P. T. Miclea, and S. Schweizer, “Upconverted fluorescence in Nd3+-doped barium chloride single crystals,” J. Phys. Condens. Matter 21(12), 125501 (2009). [CrossRef] [PubMed]

]. Based on these facts, we considered that the large extent of aggregation of the NCs in the films played an important role in the observed avalanche upconversion, which was probably ascribed to the following two mechanisms. Firstly, in general photon avalanche process, after the initial “seeding” process, efficient cross-relaxation is needed to populate the reservoir levels of neighboring ions to produce two ions in the key reservoir level. Followed by the cross-relaxation, a feedback cycle of energy transfer leads eventually to a substantial population of the reservoir level and, therefore, to strong upconversion fluorescence [3

3. S. Sivakumar, F. C. J. M. van Veggel, and P. S. May, “Near-infrared (NIR) to red and green up-conversion emission from silica sol-gel thin films made with La0.45Yb0.50Er0.05F3 nanoparticles, hetero-looping-enhanced energy transfer (Hetero-LEET): a new up-conversion process,” J. Am. Chem. Soc. 129(3), 620–625 (2007). [CrossRef] [PubMed]

]. In our experiments, the aggregated NdF3 NCs in the films can provide larger avalanche cross relaxation rates than the dispersed samples [23

23. H. Deng, S. H. Yang, S. Xiao, H. M. Gong, and Q. Q. Wang, “Controlled synthesis and upconverted avalanche luminescence of cerium(III) and neodymium(III) orthovanadate nanocrystals with high uniformity of size and shape,” J. Am. Chem. Soc. 130(6), 2032–2040 (2008). [CrossRef] [PubMed]

], due to the increased energy transfers and interactions between the aggregated NCs. Thus, the avalanche upconversion could be found in the NdF3 NCs films under the strong excitation power. Further experiments exhibited that the increased film thickness could greatly decrease the avalanche threshold excitation power, indicating a dramatically increasing of the avalanche cross relaxation rate with the increased film thickness. Secondly, a spectral broadening mechanism can also be considered in the avalanche upconversion. It was found that such avalanche upconversion emissions in the NdF3 NCs film could be attributed to the ETU processes 4 I 13/24 F 3/24 G 7/2 (labeled as ETU2 in Fig. 2). The emissions were very weak at low excitation power, due to the weak ESA and the small energy mismatching between the transitions (4 F 3/24 I 13/2) and (4 F 3/24 G 7/2). As the excitation power exceeded the threshold, the large excitation power led to the prominent broadening of the emission bands [see Fig. 4(a)], and the significant increase of the ETU2, thus the avalanche upconversion fluorescence could be observed.

It was interesting that different upconversion process was observed in the NaNdF4 NCs films. When the NaNdF4 NCs were aggregated in the film and excited with the excitation power of 2, 24, and 60 mW, the emissions at around 585 and 650 nm nonlinearly increased and the emissions energy significantly transferred between different transitions [Fig. 4(c)]. One new emission centered at ~680 nm (4 G 5/24 I 11/2 transition) appeared when the excitation power was increased. According to the energy level diagram of Nd3+, such new emission was induced by the ETU processes 4 I 15/24 F 3/24 G 5/2, which were labeled as ETU1 in Fig. 2(a).

Figure 4(d) exhibited the excitation power dependences of the emission intensities of the NaNdF4 film. Both the data recorded by increasing (solid marks) and decreasing (open marks) the excitation intensity showed that the emissions at around 585 and 650 nm had the slope of ~0.6. Considering their dispersed solution had the slope of 1.7 under the same testing condition, such very low slope value is probably due to the saturated populations of Nd3+ ions in the aggregated samples. The similar saturation behavior could also be found in the films made with La0.45Yb0.50Er0.05F3 NCs [3

3. S. Sivakumar, F. C. J. M. van Veggel, and P. S. May, “Near-infrared (NIR) to red and green up-conversion emission from silica sol-gel thin films made with La0.45Yb0.50Er0.05F3 nanoparticles, hetero-looping-enhanced energy transfer (Hetero-LEET): a new up-conversion process,” J. Am. Chem. Soc. 129(3), 620–625 (2007). [CrossRef] [PubMed]

]. Interestingly, the new emission at ~680 nm dramatically increased with the slope increased from 1.0 to 3.2. It was found that the emission bands were slightly broadened with the increased excitation power, which also played an important role in the new emission generation of the NaNdF4 NCs. Under the low excitation power, the slightly energy mismatching between the transitions (4 F 3/24 I 15/2) and (4 F 3/24 G 5/2) led to very weak ETU processes 4 I 15/24 F 3/24 G 5/2. As the excitation power increased, the spectral broadening effect reduced the energy mismatching, and thus improved the efficiency of the ETU1, resulting in the increased slope of the new emission. Further experiments found that the generated new emission could also been found in the aggregated NaYF4:Nd NCs film with higher Nd doping concentration.

4. Conclusion

In summary, we studied the upconversion behaviors of the typical Nd fluoride NCs as dispersed and aggregated samples. Unlike the dispersed NCs, the aggregation of the NdF3 and NaNdF4 NCs induced remarkable upconversion properties ascribed to the improved energy transfers and interactions between the aggregated NCs in the films, and the observed upconversion properties were quite different from the reported Nd bulk materials. We have also tried to compare the upconversion efficiency of the dispersed and aggregated samples quantitatively. When they were prepared with the same absorption power at the excitation wavelength, benefit from the elimination of the surface quenching, the aggregated NCs in the films exhibited over two orders of magnitude stronger upconversion fluorescence than the dispersed NCs under the low excitation power. Furthermore, the gap would be enlarged when the excitation power was over the avalanche threshold of the films. Our results draw attention to the importance of the proximity effects of the aggregated NCs on the upconversion properties of rare-earth materials, and our findings would help understanding the upconversion processes and corresponding energy transfer mechanisms of Nd nanoscale materials. Furthermore, the synthesized uniform Nd fluoride NCs with significant upconversion properties may find applicability in lasers, color display, and biological detection.

Acknowledgments

This work is supported by NSFC (NOs.10874134, 10904119), National Program on Key Science Research (2006CB921500), and Key Project of Ministry of Education (No. 708063).

References and links

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6.

D. K. Chatterjee, A. J. Rufaihah, and Y. Zhang, “Upconversion fluorescence imaging of cells and small animals using lanthanide doped nanocrystals,” Biomaterials 29(7), 937–943 (2008). [CrossRef]

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10.

C. Jacinto, S. L. Oliveira, T. Catundab, A. A. Andrade, J. D. Myers, and M. J. Myers, “Upconversion effect on fluorescence quantum efficiency and heat generation in Nd3+-doped materials,” Opt. Express 13(6), 2040–2046 (2005). [CrossRef] [PubMed]

11.

R. Balda, M. Sanz, A. Mendioroz, J. Fernández, L. S. Griscom, and J. L. Adam, “Infrared-to-visible upconversion in Nd3+-doped chalcohalide glasses,” Phys. Rev. B 64(14), 144101 (2001). [CrossRef]

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X. Wang, J. Song, H. Sun, Z. Xu, and J. Qiu, “Multiphoton-excited upconversion luminescence of Nd:YVO(4).,” Opt. Express 15(3), 1384–1389 (2007). [CrossRef] [PubMed]

15.

A. Mendioroz, R. Balda, M. Voda, M. Al-Saleh, and J. Fernández, “Infrared to visible and ultraviolet upconversion processes in Nd3+-doped potassium lead chloride crystal,” Opt. Mater. 26(4), 351–357 (2004). [CrossRef]

16.

O. S. Wenger, D. R. Gamelin, H. U. Güdel, A. V. Butashin, and A. A. Kaminskii, “Site-selective yellow to violet and near-infrared to green upconversion in BaLu2F8:Nd3+,” Phys. Rev. B 61(24), 16530–16537 (2000). [CrossRef]

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J. Fernández, R. Balda, A. Mendioroz, M. Sanz, and J. L. Adam, “Upconversion processes in Nd3+-doped fluorochloride glasses,” J. Non-Cryst. Solids 287(1-3), 437–443 (2001). [CrossRef]

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L. de S. Menezes, C. B. de Araújo, G. S. Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70(6), 683–685 (1997). [CrossRef]

20.

O. V. Kudryavtseva, L. S. Garashina, K. K. Rivkina, and B. P. Sobolev, “Solubility of LnF3 in lanthanum fluoride,” Sov. Phys. Crystallogr. 18, 531 (1974).

21.

N. O. Nuñez and M. Ocaña, “An ionic liquid based synthesis method for uniform luminescent lanthanide fluoride nanoparticles,” Nanotechnology 18(45), 455606 (2007). [CrossRef]

22.

L. Zhu, Q. Li, X. Liu, J. Li, Y. Zhang, J. Meng, and X. Cao, “Morphological Control and Luminescent Properties of CeF3 Nanocrystals,” J. Phys. Chem. C 111(16), 5898–5903 (2007). [CrossRef]

23.

H. Deng, S. H. Yang, S. Xiao, H. M. Gong, and Q. Q. Wang, “Controlled synthesis and upconverted avalanche luminescence of cerium(III) and neodymium(III) orthovanadate nanocrystals with high uniformity of size and shape,” J. Am. Chem. Soc. 130(6), 2032–2040 (2008). [CrossRef] [PubMed]

24.

R. B. Yu, K. H. Yu, W. Wei, X. Xu, X. Qiu, S. Liu, W. Huang, G. Tang, H. Ford, and B. Peng, “Nd2O3 nanoparticles modified with a silane coupling agent as a liquid laser medium,” Adv. Mater. 19(6), 838–842 (2007). [CrossRef]

25.

X. F. Yu, L. D. Chen, M. Li, M. Y. Xie, L. Zhou, Y. Li, and Q. Q. Wang, “Highly efficient fluorescence of NdF3/SiO2 Core/Shell nanoparticles and the applications for in vivo NIR detection,” Adv. Mater. 20(21), 4118–4123 (2008). [CrossRef]

26.

H. Yang, H. Wang, H. M. Luo, D. M. Feldmann, P. C. Dowden, R. F. DePaula, and Q. X. Jia, “Structural and dielectric properties of epitaxial Sm2O3 thin films,” Appl. Phys. Lett. 92(6), 062905 (2008). [CrossRef]

27.

M. Y. Xie, X. N. Peng, X. F. Fu, J. J. Zhang, G. L. Li, and X. F. Yu, “Synthesis of Yb3+/Er3+ co-doped MnF2 nanocrystals with bright red up-converted fluorescence,” Scr. Mater. 60(3), 190–193 (2009). [CrossRef]

28.

W. F. Auzel, “Optical constants of the noble metals,” Proc. IEEE 61, 758–787 (1973). [CrossRef]

29.

F. Wang and X. Liu, “Recent advances in the chemistry of lanthanide-doped upconversion nanocrystals,” Chem. Soc. Rev. 38(4), 976–989 (2009). [CrossRef] [PubMed]

30.

G. A. Kumar, C. W. Chen, J. Ballato, and R. E. Riman, “Optical characterization of infrared emitting rare-earth-doped fluoride nanocrystals and their transparent nanocomposites,” Chem. Mater. 19(6), 1523–1528 (2007). [CrossRef]

31.

M.-Y. Xie, L. Yu, H. He, and X.-F. Yu, “Synthesis of highly fluorescent LaF3:Ln3+/LaF3 core/shell nanocrystals by a surfactant-free aqueous solution route,” J. Solid State Chem. 182(3), 597–601 (2009). [CrossRef]

32.

B. R. Reddy and P. Venkateswarlu, “Quenching, thermalisation and energy up-conversion in LaF3:Nd3+,” J. Phys. C Solid State Phys. 18(20), 3873–3879 (1985). [CrossRef]

OCIS Codes
(190.7220) Nonlinear optics : Upconversion
(300.2530) Spectroscopy : Fluorescence, laser-induced
(160.4236) Materials : Nanomaterials

ToC Category:
Nonlinear Optics

History
Original Manuscript: November 23, 2009
Revised Manuscript: December 26, 2009
Manuscript Accepted: January 20, 2010
Published: February 2, 2010

Citation
M. Li, Z.-H. Hao, X.-N. Peng, J.-B. Li, X.-F. Yu, and Q.-Q. Wang, "Controllable energy transfer in fluorescence upconversion of NdF3 and NaNdF4 nanocrystals," Opt. Express 18, 3364-3369 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-4-3364


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References

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  11. R. Balda, M. Sanz, A. Mendioroz, J. Fernández, L. S. Griscom, and J. L. Adam, “Infrared-to-visible upconversion in Nd3+-doped chalcohalide glasses,” Phys. Rev. B 64(14), 144101 (2001). [CrossRef]
  12. Y. Guyot, H. Manaa, J. Y. Rivoire, R. Moncorgé, N. Garnier, E. Descroix, M. Bon, and P. Laporte, “Excited-state-absorption and upconversion studies of Nd3+-doped single crystals Y3Al5O12,YLiF4, and LaMgAl11O19,” Phys. Rev. B 51(2), 784–799 (1995). [CrossRef]
  13. T. Chuang and H. R. Verdún, “Energy-transfer up-conversion and excited-state absorption of laser-radiation in Nd:YLF laser crystals,” IEEE J. Quantum Electron. 32(1), 79–91 (1996). [CrossRef]
  14. X. Wang, J. Song, H. Sun, Z. Xu, and J. Qiu, “Multiphoton-excited upconversion luminescence of Nd:YVO(4).,” Opt. Express 15(3), 1384–1389 (2007). [CrossRef] [PubMed]
  15. A. Mendioroz, R. Balda, M. Voda, M. Al-Saleh, and J. Fernández, “Infrared to visible and ultraviolet upconversion processes in Nd3+-doped potassium lead chloride crystal,” Opt. Mater. 26(4), 351–357 (2004). [CrossRef]
  16. O. S. Wenger, D. R. Gamelin, H. U. Güdel, A. V. Butashin, and A. A. Kaminskii, “Site-selective yellow to violet and near-infrared to green upconversion in BaLu2F8:Nd3+,” Phys. Rev. B 61(24), 16530–16537 (2000). [CrossRef]
  17. J. Fernández, R. Balda, A. Mendioroz, M. Sanz, and J. L. Adam, “Upconversion processes in Nd3+-doped fluorochloride glasses,” J. Non-Cryst. Solids 287(1-3), 437–443 (2001). [CrossRef]
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  19. L. de S. Menezes, C. B. de Araújo, G. S. Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70(6), 683–685 (1997). [CrossRef]
  20. O. V. Kudryavtseva, L. S. Garashina, K. K. Rivkina, and B. P. Sobolev, “Solubility of LnF3 in lanthanum fluoride,” Sov. Phys. Crystallogr. 18, 531 (1974).
  21. N. O. Nuñez and M. Ocaña, “An ionic liquid based synthesis method for uniform luminescent lanthanide fluoride nanoparticles,” Nanotechnology 18(45), 455606 (2007). [CrossRef]
  22. L. Zhu, Q. Li, X. Liu, J. Li, Y. Zhang, J. Meng, and X. Cao, “Morphological Control and Luminescent Properties of CeF3 Nanocrystals,” J. Phys. Chem. C 111(16), 5898–5903 (2007). [CrossRef]
  23. H. Deng, S. H. Yang, S. Xiao, H. M. Gong, and Q. Q. Wang, “Controlled synthesis and upconverted avalanche luminescence of cerium(III) and neodymium(III) orthovanadate nanocrystals with high uniformity of size and shape,” J. Am. Chem. Soc. 130(6), 2032–2040 (2008). [CrossRef] [PubMed]
  24. R. B. Yu, K. H. Yu, W. Wei, X. Xu, X. Qiu, S. Liu, W. Huang, G. Tang, H. Ford, and B. Peng, “Nd2O3 nanoparticles modified with a silane coupling agent as a liquid laser medium,” Adv. Mater. 19(6), 838–842 (2007). [CrossRef]
  25. X. F. Yu, L. D. Chen, M. Li, M. Y. Xie, L. Zhou, Y. Li, and Q. Q. Wang, “Highly efficient fluorescence of NdF3/SiO2 Core/Shell nanoparticles and the applications for in vivo NIR detection,” Adv. Mater. 20(21), 4118–4123 (2008). [CrossRef]
  26. H. Yang, H. Wang, H. M. Luo, D. M. Feldmann, P. C. Dowden, R. F. DePaula, and Q. X. Jia, “Structural and dielectric properties of epitaxial Sm2O3 thin films,” Appl. Phys. Lett. 92(6), 062905 (2008). [CrossRef]
  27. M. Y. Xie, X. N. Peng, X. F. Fu, J. J. Zhang, G. L. Li, and X. F. Yu, “Synthesis of Yb3+/Er3+ co-doped MnF2 nanocrystals with bright red up-converted fluorescence,” Scr. Mater. 60(3), 190–193 (2009). [CrossRef]
  28. W. F. Auzel, “Optical constants of the noble metals,” Proc. IEEE 61, 758–787 (1973). [CrossRef]
  29. F. Wang and X. Liu, “Recent advances in the chemistry of lanthanide-doped upconversion nanocrystals,” Chem. Soc. Rev. 38(4), 976–989 (2009). [CrossRef] [PubMed]
  30. G. A. Kumar, C. W. Chen, J. Ballato, and R. E. Riman, “Optical characterization of infrared emitting rare-earth-doped fluoride nanocrystals and their transparent nanocomposites,” Chem. Mater. 19(6), 1523–1528 (2007). [CrossRef]
  31. M.-Y. Xie, L. Yu, H. He, and X.-F. Yu, “Synthesis of highly fluorescent LaF3:Ln3+/LaF3 core/shell nanocrystals by a surfactant-free aqueous solution route,” J. Solid State Chem. 182(3), 597–601 (2009). [CrossRef]
  32. B. R. Reddy and P. Venkateswarlu, “Quenching, thermalisation and energy up-conversion in LaF3:Nd3+,” J. Phys. C Solid State Phys. 18(20), 3873–3879 (1985). [CrossRef]

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