Abstract

Hexagonal NaYF4 nanocrystals (NCs) have been prepared by core-mediated hetero-shell growth process using polyvinylpyrrolidone (PVP) as chelating agents and cubic CaF2 as core. It is found that the NaYF4 NCs prepared by this strategy have narrow size distribution, small particle size and well water-soluble property, can be easily dispersed in water. Besides, by increasing the doping concentration of Tm3+ ions in Er3+-Yb3+ codoping system, the upconversion (UC) liminescence of CaF2@NaYF4: Yb/Er/Tm NCs was modulated from green to red by the naked eye. These NCs with red upconversion luminescence (UCL) and good water solubility show potential applications in biological labeling field.

© 2015 Optical Society of America

1. Introduction

Recently, upconversion luminescence of lanthanide-doped nanocrystals has attracted extensive research attention. Because these nanocrystals have unique optical properties and potential applications in fields such as color display, temperature sensors, UC lasers, DNA detection, photodynamic therapy and biological labeling [1–9 ]. As a kind of biological fluorescence label, the “optical windows” of biological tissue is an important influencing factor to be considered, its range is from 600 nm to 1100 nm [8,10–12 ]. When the wavelength of light locates in this region, the tissue absorption is minimum, and the penetration depth is maximum. As we know, fluorescent emissions of many ions or ion pairs locate in this range, but Yb3+ - Er3+ ion pairs are still the best choice because of their excellent UC efficiency. When Yb3+ - Er3+ ion pairs were excited by 980 nm laser, we can observe two strong emission peaks: green emission (550 nm) and red emission (660 nm). Obviously, the emission in green region is not conducive to biological probes. Therefore, avoiding the green emission and achieving strengthened red emission from the Yb3+ - Er3+ ion pairs are essential for the deep tissue imaging by fluorescent label [13,14 ].

Up to now, many methods have been reported to increase the luminescence intensity ratio of red/green UC emissions in Yb3+- Er3+ codoped system. As the particle size of Y2O3:Yb3+, Er3+ NCs decreases, the relative luminescence intensity ratio of red to green increases gradually which is induced by surface effects [15]. Bai et al. has modified the UC luminescence from green to red in Er3+/Yb3+ doped zeolites by tuning the concentration of Yb3+ ions [16]. Recently, some dopants, such as Mn2+ [12, 17,18 ], Au+ [19], Li+ ions [20], have been recognized as effective elements which can enhance the ratio of red/green. However, few papers have been found on tuning output color from green to red by increasing the doping concentration of Tm3+ ions in Yb3+ - Er3+ co-doping system. Although Yb/Er/Tm tridoped La2O3, NaYF4, BaYF5 and YF3 have been reported in some literatures, they focused on white light emission [21–24 ].

Herein, we have prepared a kind of water dispersed and small particle size hexagonal NaYF4 NCs with red upconversion fluorescence by a heterogeneous core-shell strategy. With the increase of doped Tm3+ ions concentration from 0 to 4 mol%, the intensity ratio of red/green UC emission increases dramatically from 0.1 to 6.2 in CaF2@NaYF4: Yb/Er/Tm Core-Shell NCs.

2. Experimental

2.1 Materials

All chemicals were analytical grade and used without further purification. Y(NO3)3·6H2O (99.999%), Yb(NO3)3·6H2O (99.999%), Er(NO3)3·6H2O (99.999%), Tm(NO3)3·6H2O (99.999%), were supplied by Yutai Qingda Chemical Technology Co., Ltd. China. Polyvinylpyrrolidone K-30 (PVP, 58000 g/mol), Ca(NO3)2·4H2O (AR), NaCl (AR), NaNO3 (AR), KF·2H2O (AR), NaF (AR) and ethylene glycol (EG, AR) were supplied by Beijing Fine Chemical Company.

2.2 Synthesis of the cubic CaF2 core

Polyvinylpyrrolidone K-30 (PVP, 0.5 g) was dissolved in EG (5 mL) to form transparent solution. Then, 1 mmol Ca(NO3)2 were added into PVP solution under strong stirring, KF (3 mmol) was dissolved in 2 ml EG and dropwise into above solution. Subsequently, the above solution was transferred into a polytetrafluoroethylene autoclave, and then heated at 180 °C for 2 hours. The content was taken out at room temperature and retained as core for next procedure.

2.3 Synthesis of the CaF2@NaYF4 core-shell hybrid nanocrystals

For synthesis of CaF2@NaYF4:20 mol%Yb, 2 mol%Er hybrid nanocrystals (HNCs), PVP (0.5 g) was dissolved in the above CaF2 core solution. Then 0.8 mmol Y(NO3)3, 0.18 mmol Yb(NO3)3, 0.02 mmol Er(NO3)3 and 1 mmol NaNO3 were added into above core solution respectively under strong stirring. 5 mmol KF was dissolved in 2 ml EG, and subsequently was added dropwise into above mixture. All the solution was then transferred into a polytetrafluoroethylene autoclave and reacted at 180 °C for 12 hours. The final product was obtained by centrifugation and washed with ethanol for several times. The other samples CaF2@NaYF4:20 mol%Yb, 2 mol%Er, x mol%Tm (x = 0, 0.5, 1, 1.5, 2, 2.5, 3, 4) were prepared by the similar process as described above.

2.4 Characterization

The crystal structures and phase purities were analyzed by a Rigaku RU-200b X-ray powder diffractometer (XRD) using nickel-filtered Cu-Kα radiation (λ = 1.5406 Å). The sizes and morphologies of the samples were investigated by transmission electron microscopy (TEM, Hitachi H-600). UC luminescence spectra were recorded using a Hitachi F-4500 fluorescence spectrophotometer which was equipped with a power-controllable 980 nm CW diode laser (Maximum power 2W).

3. Results and discussion

The CaF2 core NCs and the resulting CaF2@NaYF4 core-shell HNCs were synthesized by a facile solvothermal method using an amphiphilic surfactant, polyvinylpyrrolidone (PVP) as the chelating agent. To illustrate the corresponding crystalline phases of the core precursors and core-shell NCs, all these samples were examined by X-ray powder diffraction (XRD) to determine their crystal structures. As is shown in the Fig. 1(a) , all the diffraction peaks of the precursor can be well indexed to pure cubic phase CaF2 (JCPDS NO. 35-816), no other impurity peaks can be detected from this XRD pattern, indicating that the obtained precursor is cubic phase CaF2. In the further step, the CaF2 NCs, adopted as the precursors, together with the sodium and yttrium sources, to induce the growth of the hexagonal NaYF4 NCs. As evidenced by XRD pattern in Fig. 1(b), pure hexagonal NaYF4 NCs (JCPDS NO. 16-334) are fabricated.

 

Fig. 1 XRD patterns (a) CaF2 core; (b) CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs; (c) CaF2 (JCPDS NO. 35-816); (d) β-NaYF4 (JCPDS NO. 16-334)

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Compare with forming a new nanoparticle, reaction ions depositing on the surface of pre-existing particles has the less surface tension and less energy barrier to overcome, the formation of core-shell NCs is more advantageous [25–27 ]. Therefore, in the 12h shell growth process, very less new nanocrystals formed and most of the ions were coated on CaF2 core to forming the NaYF4 shell. This was demonstrated in Fig. 2 . After a 12 h growth process, Ca element, Na element and Y element can be observed by EDS analysis [Fig. 2(e)] and the mean size of NCs increased from 27 nm [Fig. 2(c)] to 33 nm [Fig. 2(d)]. In addition, the size distribution becomes narrower, this means core-shell growth process is successful, a 6 nm shell has been coated on the CaF2 core. Combine to the result of the Fig. 1, it demonstrates that the cubic phase CaF2 NCs can induce the growth of hexagonal phase NaYF4 shell, forming the core-shell hetero structure. Moreover, from the Fig. 2(e), we also can see strong O element and K element peaks. The O element may come from the PVP which was on the surface of the NCs. This can also be an indirect proof that PVP has been successfully modified to surface of NCs. The K element may come from the fluorine source KF.

 

Fig. 2 (a) TEM images of CaF2 core NCs; (b) TEM image of CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs; (c) Size distribution of CaF2 core NCs; (d) Size distribution of CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs; (e) EDX analysis of elemental composition of CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs.

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To further study the growth process of the CaF2@NaYF4 hetero structure, we replaced some reaction material or changed the reaction sequence to prepare the CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs. The details of the reaction process and product crystallographic phase are shown in Table 1 . In addition, the corresponding XRD patterns, UC photographic and UCL spectra are shown in Fig. 3 . As shown in XRD patterns (left of Fig. 3), the sample (a) and sample (b) which were prepared with Sodium source NaNO3 or NaCl, together with Fluorine source KF can be induced by CaF2 NCs successfully and get the hexagonal phase NaYF4 shell. But the samples (c) and (d) are pure cubic phase NaYF4, which was synthesized with NaF as Sodium source and Fluorine source in the shell growth. The sample (e) was prepared by a non-core induce process, directly mixing all the reaction material of sample (a) in a one-step reaction process. The result product is cubic phase NaYF4. Therefore, CaF2 core NCs induce and KF as the fluorine source are two necessary conditions for this core-mediated hetero-shell process. In this growth process, α-NaYF4 and CaF2 have similar lattice Cell parameters (CaF2: a = 0.546 nm, α-NaYF4: a = 0.545 nm) and similar crystal structure, α-NaYF4 is very easy to continue to grow on the surface of CaF2 core NCs. When K+ ions exists in reaction solution, K+ ions replaced some Na+ ions lattice sites in the NaYF4 crystal, the ionic radius difference between K+ ions (0.138 nm) and Na+ ions (0.102 nm) cause the lattice distortion of the hetero interface, forming a low symmetric structure. Therefore, the subsequently deposited NaYF4 shell can epitaxial grow in hexagonal phase. As a result, K+ ions and CaF2 core are two necessary conditions in forming β-NaYF4 NCs [27–30 ]. Moreover, UCL spectra (right-top of Fig. 3) and the UC photographic (right-bottom of Fig. 3) of these samples are also shown that the product prepared with Fluorine source KF [sample (a) and sample (b)], exhibited enhanced UC luminescence intensity as compared to the other three products. The upconversion luminescence intensity of sample (a) or sample (b) is 23 times larger than that of sample (c) at 550 nm. This is more than the previously reported that green UC luminescence efficiency in hexagonal phase NaYF4: Yb, Er NCs is approximately 10 times stronger than that in the cubic phase form [31,32 ]. The reason to explain this phenomenon is that KF not only served as Fluorine source in NaYF4 shell growth process, but also a part of K+ was doped into NaYF4 crystal lattice, occupy the Na+ ions lattice sites in the crystal. A small amount of non-fluorescent dopant ions in the asymmetric crystal, the crystal symmetry around Er3+ ions were lower. It is generally favorable for higher UC emission luminescence intensity [33–36 ].

Tables Icon

Table 1. The detail of reaction process and the Crystallographic phase of product.

View Table
 

Fig. 3 XRD patterns (left), UCL spectra excited by a 80 mW 980 nm laser (right-top) and corresponding UC photographic (right-bottom) of HNCs samples prepared with different reaction material or different reaction sequence: (a) NaCl as Sodium source, KF as Fluorine source; (b) NaNO3 as Sodium source, KF as Fluorine source; (c) NaF as Sodium source and KF as Fluorine source; (d) KF as Fluorine source in the core growth, NaF as Sodium source and Fluorine source in the shell growth; (e) All the reaction materials of sample (a) was mixed directly (non-core induce).

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As shown in Fig. 4 , the XRD patterns of shell growth time increased from 6h to 24h, the diffraction peak intensities of the hexagonal phase increased as the reaction time longer. This evolution of diffraction peaks is also indicated the growth of hexagonal phase NaYF4 NCs.

 

Fig. 4 XRD patterns of CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs. with shell growth time of (a) 6h; (b) 12h; (c) 24h.

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Figure 5(a) is the UCL spectra of CaF2@NaYF4:20 mol%Yb, 2 mol%Er, x mol%Tm (x = 0, 0.5, 1, 1.5, 2, 2.5, 3, 4) nanocrystals excited by 980 nm laser respectively. As shown in Fig. 5(a), with the increase of Tm3+ concentration from 0 mol% to 4 mol%, red emission (650 nm, 4F9/2 → 4I15/2) was enhanced remarkably, green emission (525 nm, 540 nm, 2S3/2, 2H11/2 → 2I15/2) was quenched. Figure 5(b) shows the intensity ratio of red/green UC emission and the total luminescence integrated intensity. The ratio increases dramatically from 0.1 to 6.2 with the increase of doped Tm3+ ion concentrations, but the total luminescence integrated intensity did not reduce. This result indicates that the enhanced red UC fluorescence arises from the effective energy transfer between Er3+ ions and Tm3+ ions, not in the expense of a lower PLQY. Figure 5(c) is photostability of CaF2@NaYF4:20 mol%Yb, 2 mol%Er, 2 mol%Tm NCs. The sample was excited by 980 nm and its luminescence emission was collected by a 652 nm channel. The exposure time for imaging data collection is 0.5 s. As is shown in picture, the NCs exhibited neither blinking nor photobleaching over 30 min continuous laser excitation. And the UC photographic of CaF2@NaYF4:20 mol%Yb, 2 mol%Er, x mol%Tm (x = 0, 0.5, 1, 1.5, 2, 2.5, 3, 4) nanocrystals solution excited by 980 nm laser are shown in Fig. 5(d), the UC color output of emission was gradually modulated from green to yellow, then to red by the naked eye.

 

Fig. 5 (a) The UCL spectra of CaF2@NaYF4:20 mol%Yb, 2 mol%Er, x mol%Tm (x = 0, 0.5, 1, 1.5, 2, 2.5, 3, 4) nanocrystals excited by a 80 mW 980 nm laser; (b) Corresponding UC emission red/green intensity ratio and total luminescence integrated intensity; (c) Photostability of CaF2@NaYF4:20 mol%Yb, 2 mol%Er, 2 mol%Tm NCs. Emission was collected by a 652 nm channel. Time interval of imaging data collection = 0.5 s; (d) UC photographic of nanocrystals water solution excited by a 80 mW 980 nm laser.

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Figure 6 describes schematically energy level diagrams of Er3+ and Tm3+ ions and possible UC processes excited by 980 nm. When NCs were excited by 980 nm, compared with Er3+, Yb3+ has the larger doping concentration and a much larger absorption cross section around 980 nm, therefore, the main pathway to populate the excited states of Er3+ is the energy transfer (ET) from Yb3+ to Er3+. As pictured in Fig. 6, two ET processes from Yb3+ to Er3+ ion excite the 4I15/2 level to 4I11/2 and 4F7/2 levels. Then two nonradiative relaxations processes:4F7/2→2H11/2 and 4F7/2→4S3/2 populate the 2H11/2 and 4S3/2 levels respectively. Subsequent back to ground level 4I15/2, green (525 nm, 540 nm 2S3/2, 2H11/2 → 2I15/2) emission can be observed. Moreover, when it stays at 4I11/2 level, it could nonradiative relaxations to 4I13/2 level, then another ET process excite the 4I13/2 level to 4F9/2 level. Then back to ground level, and emit red (660nm, 4F9/2 → 4I15/2) fluorescence. In addition, there are two non-resonant energy transfer (ET) processes between Tm3+ and Er3+ ions, (ET1) 3F4 → 3H6 (Tm3+) 4I11/2 → 4F9/2 (Er3+), (ET2): 4I13/2 → 4I15/2 (Er3+):3H6 → 3F4 (Tm3+). The color tuning of upconversion emission from green to red is achieved by these non-resonant energy transfer (ET) processes.

 

Fig. 6 Energy level diagrams of Er3+ and Tm3+ ions and possible energy transfer mechanism under 980 nm excitation.

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4. Conclusions

In conclusion, a kind of water dispersed and small particle size hexagonal NaYF4 NCs are prepared by a new strategy. In this strategy, we use cubic CaF2 to induce heterogeneous growth of hexagonal phase shells NaYF4 and using an amphiphilic surfactant, polyvinylpyrrolidone (PVP) as the chelating agent to make our core-shell NC material have good water solubility and small particle size. In addition, we tune the doping concentration of Tm3+ ions to modulate the UC color output from green to yellow, then to red by the naked eye. The above features may make our NCs have a good prospect about the applications of lanthanide-based luminescent bioprobes.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (NSFC) (grants 61405016, 11274139, 61275189), China Scholarship Council, Jilin Province Education Department (2015107) and Natural Science Foundation of Jilin Province (2016).

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References

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  1. A. Sedlmeier and H. H. Gorris, “Surface modification and characterization of photon-upconverting nanoparticles for bioanalytical applications,” Chem. Soc. Rev. 44(6), 1526–1560 (2015).
    [Crossref] [PubMed]
  2. X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
    [Crossref] [PubMed]
  3. D. Chen and P. Huang, “Highly intense upconversion luminescence in Yb/Er:NaGdF4@NaYF4 core-shell nanocrystals with complete shell enclosure of the core,” Dalton Trans. 43(29), 11299–11304 (2014).
    [Crossref] [PubMed]
  4. C. Zhang and J. Y. Lee, “Prevalence of anisotropic shell growth in rare earth core-shell upconversion nanocrystals,” ACS Nano 7(5), 4393–4402 (2013).
    [Crossref] [PubMed]
  5. X. Xue, M. Liao, R. Tiwari, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Intense ultraviolet and blue upconverison emissions in Tb3+/Yb3+ codoped KY3F10 nanocrystals,” Appl. Phys. Express 5(9), 092601 (2012).
    [Crossref]
  6. X. Xue, S. Uechi, R. N. Tiwari, Z. Duan, M. Liao, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Size-dependent upconversion luminescence and quenching mechanism of LiYF4: Er3+/Yb3+ nanocrystals with oleate ligand adsorbed,” Opt. Mater. Express 3(7), 989–999 (2013).
    [Crossref]
  7. X. Xue, Z. Duan, T. Suzuki, R. N. Tiwari, M. Yoshimura, and Y. Ohishi, “Luminescence properties of α-NaYF4:Nd3+ nanocrystals dispersed in liquid: local field effect investigation,” J. Phys. Chem. C 116(42), 22545–22551 (2012).
    [Crossref]
  8. M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
    [Crossref] [PubMed]
  9. Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
    [Crossref] [PubMed]
  10. H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
    [Crossref] [PubMed]
  11. H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
    [Crossref] [PubMed]
  12. G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
    [Crossref] [PubMed]
  13. Y. Liu, D. Tu, H. Zhu, and X. Chen, “Lanthanide-doped luminescent nanoprobes: controlled synthesis, optical spectroscopy, and bioapplications,” Chem. Soc. Rev. 42(16), 6924–6958 (2013).
    [Crossref] [PubMed]
  14. G. Chen, H. Ågren, T. Y. Ohulchanskyy, and P. N. Prasad, “Light upconverting core-shell nanostructures: nanophotonic control for emerging applications,” Chem. Soc. Rev. 44(6), 1680–1713 (2015).
    [Crossref] [PubMed]
  15. X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
    [Crossref]
  16. Z. Bai, M. Fujii, K. Imakita, and S. Hayashi, “Green to red tunable upconversion fluorescence from Bi–Er–Yb codoped zeolites,” Microporous Mesoporous Mater. 173, 43–46 (2013).
    [Crossref]
  17. M. Liu, Y. Ye, C. Yao, W. Zhao, and X. Huang, “Mn2+-doped NaYF4:Yb/Er upconversion nanoparticles with amplified electrogenerated chemiluminescence for tumor biomarker detection,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6626–6633 (2014).
    [Crossref]
  18. L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
    [Crossref]
  19. Z. Li, L. Wang, Z. Wang, X. Liu, and Y. Xiong, “Modification of NaYF4:Yb,Er@SiO2 nanoparticles with gold nanocrystals for tunable green-to-red upconversion emissions,” J. Phys. Chem. C 115(8), 3291–3296 (2011).
    [Crossref]
  20. W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
    [Crossref] [PubMed]
  21. G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
    [Crossref]
  22. J. Li, L. Yang, Y. Zhang, J. Zhong, C. Q. Sun, and P. K. Chu, “Pump-power tunable white upconversion emission in lanthanide-doped hexagonal NaYF4 nanorods,” Opt. Mater. 33(6), 882–887 (2011).
    [Crossref]
  23. C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
    [Crossref]
  24. D. Chen, Y. Wang, K. Zheng, T. Guo, and Y. Yu, “Bright upconversion white light emission in transparent glass ceramic embedding Tm3+/Er3+/Yb3+: beta-YF3 nanocrystals,” Appl. Phys. Lett. 92, 1903 (2007).
  25. Q. Dou, N. M. Idris, and Y. Zhang, “Sandwich-structured upconversion nanoparticles with tunable color for multiplexed cell labeling,” Biomaterials 34(6), 1722–1731 (2013).
    [Crossref] [PubMed]
  26. K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
    [Crossref] [PubMed]
  27. N. J. J. Johnson and F. C. J. M. van Veggel, “Sodium lanthanide fluoride core-shell nanocrystals: a general perspective on epitaxial shell growth,” Nano Res. 6(8), 547–561 (2013).
    [Crossref]
  28. D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
    [Crossref]
  29. D. Gao, X. Zhang, H. Zheng, P. Shi, L. Li, and Y. Ling, “Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+ nanorods,” Dalton Trans. 42(5), 1834–1841 (2013).
    [Crossref] [PubMed]
  30. D. Gao, X. Zhang, and J. Zhang, “The effects of structural characterization on the luminescence of Eu3+-doped fluoride nano/microcrystals,” CrystEngComm 16(48), 11115–11121 (2014).
    [Crossref]
  31. W. Yu, W. Xu, H. Song, and S. Zhang, “Temperature-dependent upconversion luminescence and dynamics of NaYF4:Yb3+/Er3+ nanocrystals: influence of particle size and crystalline phase,” Dalton Trans. 43(16), 6139–6147 (2014).
    [Crossref] [PubMed]
  32. S. Song, Y. Kuang, J. Liu, Q. Yang, L. Luo, and X. Sun, “Separation and phase transition investigation of Yb3+/Er3+ co-doped NaYF4 nanoparticles,” Dalton Trans. 42(37), 13315–13318 (2013).
    [Crossref] [PubMed]
  33. M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
    [Crossref] [PubMed]
  34. C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
    [Crossref] [PubMed]
  35. L. Lei, D. Chen, J. Xu, R. Zhang, and Y. Wang, “Highly intensified upconversion luminescence of Ca2+ -doped Yb/Er:NaGdF4 nanocrystals prepared by a solvothermal route,” Chem. Asian J. 9(3), 728–733 (2014).
    [Crossref] [PubMed]
  36. L. Lei, D. Chen, P. Huang, J. Xu, R. Zhang, and Y. Wang, “Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping,” Nanoscale 5(22), 11298–11305 (2013).
    [Crossref] [PubMed]

2015 (4)

A. Sedlmeier and H. H. Gorris, “Surface modification and characterization of photon-upconverting nanoparticles for bioanalytical applications,” Chem. Soc. Rev. 44(6), 1526–1560 (2015).
[Crossref] [PubMed]

X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
[Crossref] [PubMed]

G. Chen, H. Ågren, T. Y. Ohulchanskyy, and P. N. Prasad, “Light upconverting core-shell nanostructures: nanophotonic control for emerging applications,” Chem. Soc. Rev. 44(6), 1680–1713 (2015).
[Crossref] [PubMed]

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

2014 (10)

D. Gao, X. Zhang, and J. Zhang, “The effects of structural characterization on the luminescence of Eu3+-doped fluoride nano/microcrystals,” CrystEngComm 16(48), 11115–11121 (2014).
[Crossref]

W. Yu, W. Xu, H. Song, and S. Zhang, “Temperature-dependent upconversion luminescence and dynamics of NaYF4:Yb3+/Er3+ nanocrystals: influence of particle size and crystalline phase,” Dalton Trans. 43(16), 6139–6147 (2014).
[Crossref] [PubMed]

L. Lei, D. Chen, J. Xu, R. Zhang, and Y. Wang, “Highly intensified upconversion luminescence of Ca2+ -doped Yb/Er:NaGdF4 nanocrystals prepared by a solvothermal route,” Chem. Asian J. 9(3), 728–733 (2014).
[Crossref] [PubMed]

K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
[Crossref] [PubMed]

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
[Crossref] [PubMed]

M. Liu, Y. Ye, C. Yao, W. Zhao, and X. Huang, “Mn2+-doped NaYF4:Yb/Er upconversion nanoparticles with amplified electrogenerated chemiluminescence for tumor biomarker detection,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6626–6633 (2014).
[Crossref]

L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
[Crossref]

D. Chen and P. Huang, “Highly intense upconversion luminescence in Yb/Er:NaGdF4@NaYF4 core-shell nanocrystals with complete shell enclosure of the core,” Dalton Trans. 43(29), 11299–11304 (2014).
[Crossref] [PubMed]

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

2013 (12)

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

X. Xue, S. Uechi, R. N. Tiwari, Z. Duan, M. Liao, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Size-dependent upconversion luminescence and quenching mechanism of LiYF4: Er3+/Yb3+ nanocrystals with oleate ligand adsorbed,” Opt. Mater. Express 3(7), 989–999 (2013).
[Crossref]

C. Zhang and J. Y. Lee, “Prevalence of anisotropic shell growth in rare earth core-shell upconversion nanocrystals,” ACS Nano 7(5), 4393–4402 (2013).
[Crossref] [PubMed]

Y. Liu, D. Tu, H. Zhu, and X. Chen, “Lanthanide-doped luminescent nanoprobes: controlled synthesis, optical spectroscopy, and bioapplications,” Chem. Soc. Rev. 42(16), 6924–6958 (2013).
[Crossref] [PubMed]

Z. Bai, M. Fujii, K. Imakita, and S. Hayashi, “Green to red tunable upconversion fluorescence from Bi–Er–Yb codoped zeolites,” Microporous Mesoporous Mater. 173, 43–46 (2013).
[Crossref]

H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
[Crossref] [PubMed]

D. Gao, X. Zhang, H. Zheng, P. Shi, L. Li, and Y. Ling, “Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+ nanorods,” Dalton Trans. 42(5), 1834–1841 (2013).
[Crossref] [PubMed]

N. J. J. Johnson and F. C. J. M. van Veggel, “Sodium lanthanide fluoride core-shell nanocrystals: a general perspective on epitaxial shell growth,” Nano Res. 6(8), 547–561 (2013).
[Crossref]

L. Lei, D. Chen, P. Huang, J. Xu, R. Zhang, and Y. Wang, “Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping,” Nanoscale 5(22), 11298–11305 (2013).
[Crossref] [PubMed]

Q. Dou, N. M. Idris, and Y. Zhang, “Sandwich-structured upconversion nanoparticles with tunable color for multiplexed cell labeling,” Biomaterials 34(6), 1722–1731 (2013).
[Crossref] [PubMed]

S. Song, Y. Kuang, J. Liu, Q. Yang, L. Luo, and X. Sun, “Separation and phase transition investigation of Yb3+/Er3+ co-doped NaYF4 nanoparticles,” Dalton Trans. 42(37), 13315–13318 (2013).
[Crossref] [PubMed]

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

2012 (5)

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
[Crossref]

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

X. Xue, M. Liao, R. Tiwari, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Intense ultraviolet and blue upconverison emissions in Tb3+/Yb3+ codoped KY3F10 nanocrystals,” Appl. Phys. Express 5(9), 092601 (2012).
[Crossref]

X. Xue, Z. Duan, T. Suzuki, R. N. Tiwari, M. Yoshimura, and Y. Ohishi, “Luminescence properties of α-NaYF4:Nd3+ nanocrystals dispersed in liquid: local field effect investigation,” J. Phys. Chem. C 116(42), 22545–22551 (2012).
[Crossref]

2011 (3)

Z. Li, L. Wang, Z. Wang, X. Liu, and Y. Xiong, “Modification of NaYF4:Yb,Er@SiO2 nanoparticles with gold nanocrystals for tunable green-to-red upconversion emissions,” J. Phys. Chem. C 115(8), 3291–3296 (2011).
[Crossref]

J. Li, L. Yang, Y. Zhang, J. Zhong, C. Q. Sun, and P. K. Chu, “Pump-power tunable white upconversion emission in lanthanide-doped hexagonal NaYF4 nanorods,” Opt. Mater. 33(6), 882–887 (2011).
[Crossref]

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

2007 (2)

D. Chen, Y. Wang, K. Zheng, T. Guo, and Y. Yu, “Bright upconversion white light emission in transparent glass ceramic embedding Tm3+/Er3+/Yb3+: beta-YF3 nanocrystals,” Appl. Phys. Lett. 92, 1903 (2007).

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Ågren, H.

G. Chen, H. Ågren, T. Y. Ohulchanskyy, and P. N. Prasad, “Light upconverting core-shell nanostructures: nanophotonic control for emerging applications,” Chem. Soc. Rev. 44(6), 1680–1713 (2015).
[Crossref] [PubMed]

Bai, X.

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Bai, Z.

Z. Bai, M. Fujii, K. Imakita, and S. Hayashi, “Green to red tunable upconversion fluorescence from Bi–Er–Yb codoped zeolites,” Microporous Mesoporous Mater. 173, 43–46 (2013).
[Crossref]

Bednarkiewicz, A.

K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
[Crossref] [PubMed]

Chang, H.

X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
[Crossref] [PubMed]

Chen, D.

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

L. Lei, D. Chen, J. Xu, R. Zhang, and Y. Wang, “Highly intensified upconversion luminescence of Ca2+ -doped Yb/Er:NaGdF4 nanocrystals prepared by a solvothermal route,” Chem. Asian J. 9(3), 728–733 (2014).
[Crossref] [PubMed]

D. Chen and P. Huang, “Highly intense upconversion luminescence in Yb/Er:NaGdF4@NaYF4 core-shell nanocrystals with complete shell enclosure of the core,” Dalton Trans. 43(29), 11299–11304 (2014).
[Crossref] [PubMed]

L. Lei, D. Chen, P. Huang, J. Xu, R. Zhang, and Y. Wang, “Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping,” Nanoscale 5(22), 11298–11305 (2013).
[Crossref] [PubMed]

D. Chen, Y. Wang, K. Zheng, T. Guo, and Y. Yu, “Bright upconversion white light emission in transparent glass ceramic embedding Tm3+/Er3+/Yb3+: beta-YF3 nanocrystals,” Appl. Phys. Lett. 92, 1903 (2007).

Chen, G.

G. Chen, H. Ågren, T. Y. Ohulchanskyy, and P. N. Prasad, “Light upconverting core-shell nanostructures: nanophotonic control for emerging applications,” Chem. Soc. Rev. 44(6), 1680–1713 (2015).
[Crossref] [PubMed]

Chen, H.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Chen, X.

Y. Liu, D. Tu, H. Zhu, and X. Chen, “Lanthanide-doped luminescent nanoprobes: controlled synthesis, optical spectroscopy, and bioapplications,” Chem. Soc. Rev. 42(16), 6924–6958 (2013).
[Crossref] [PubMed]

Cheng, Z.

G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
[Crossref]

Chu, P. K.

J. Li, L. Yang, Y. Zhang, J. Zhong, C. Q. Sun, and P. K. Chu, “Pump-power tunable white upconversion emission in lanthanide-doped hexagonal NaYF4 nanorods,” Opt. Mater. 33(6), 882–887 (2011).
[Crossref]

Chuai, X.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Cichy, B.

K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
[Crossref] [PubMed]

Dai, Q.

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Deng, R.

X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
[Crossref] [PubMed]

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

Di, W.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Ding, M.

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

Dong, B.

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Dou, Q.

Q. Dou, N. M. Idris, and Y. Zhang, “Sandwich-structured upconversion nanoparticles with tunable color for multiplexed cell labeling,” Biomaterials 34(6), 1722–1731 (2013).
[Crossref] [PubMed]

Duan, Z.

X. Xue, S. Uechi, R. N. Tiwari, Z. Duan, M. Liao, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Size-dependent upconversion luminescence and quenching mechanism of LiYF4: Er3+/Yb3+ nanocrystals with oleate ligand adsorbed,” Opt. Mater. Express 3(7), 989–999 (2013).
[Crossref]

X. Xue, Z. Duan, T. Suzuki, R. N. Tiwari, M. Yoshimura, and Y. Ohishi, “Luminescence properties of α-NaYF4:Nd3+ nanocrystals dispersed in liquid: local field effect investigation,” J. Phys. Chem. C 116(42), 22545–22551 (2012).
[Crossref]

Fan, L.

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Feng, J.

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

Feng, L.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

Fu, H.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
[Crossref] [PubMed]

Fujii, M.

Z. Bai, M. Fujii, K. Imakita, and S. Hayashi, “Green to red tunable upconversion fluorescence from Bi–Er–Yb codoped zeolites,” Microporous Mesoporous Mater. 173, 43–46 (2013).
[Crossref]

Gai, S.

H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
[Crossref] [PubMed]

Gao, D.

D. Gao, X. Zhang, and J. Zhang, “The effects of structural characterization on the luminescence of Eu3+-doped fluoride nano/microcrystals,” CrystEngComm 16(48), 11115–11121 (2014).
[Crossref]

D. Gao, X. Zhang, H. Zheng, P. Shi, L. Li, and Y. Ling, “Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+ nanorods,” Dalton Trans. 42(5), 1834–1841 (2013).
[Crossref] [PubMed]

Ge, X.

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

Geng, D.

G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
[Crossref]

Gnach, A.

K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
[Crossref] [PubMed]

Gorris, H. H.

A. Sedlmeier and H. H. Gorris, “Surface modification and characterization of photon-upconverting nanoparticles for bioanalytical applications,” Chem. Soc. Rev. 44(6), 1526–1560 (2015).
[Crossref] [PubMed]

Gu, Z.

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

Guo, T.

D. Chen, Y. Wang, K. Zheng, T. Guo, and Y. Yu, “Bright upconversion white light emission in transparent glass ceramic embedding Tm3+/Er3+/Yb3+: beta-YF3 nanocrystals,” Appl. Phys. Lett. 92, 1903 (2007).

Hayashi, S.

Z. Bai, M. Fujii, K. Imakita, and S. Hayashi, “Green to red tunable upconversion fluorescence from Bi–Er–Yb codoped zeolites,” Microporous Mesoporous Mater. 173, 43–46 (2013).
[Crossref]

He, F.

H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
[Crossref] [PubMed]

Huang, L.

X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
[Crossref] [PubMed]

Huang, P.

D. Chen and P. Huang, “Highly intense upconversion luminescence in Yb/Er:NaGdF4@NaYF4 core-shell nanocrystals with complete shell enclosure of the core,” Dalton Trans. 43(29), 11299–11304 (2014).
[Crossref] [PubMed]

L. Lei, D. Chen, P. Huang, J. Xu, R. Zhang, and Y. Wang, “Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping,” Nanoscale 5(22), 11298–11305 (2013).
[Crossref] [PubMed]

Huang, S.

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

Huang, X.

M. Liu, Y. Ye, C. Yao, W. Zhao, and X. Huang, “Mn2+-doped NaYF4:Yb/Er upconversion nanoparticles with amplified electrogenerated chemiluminescence for tumor biomarker detection,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6626–6633 (2014).
[Crossref]

Idris, N. M.

Q. Dou, N. M. Idris, and Y. Zhang, “Sandwich-structured upconversion nanoparticles with tunable color for multiplexed cell labeling,” Biomaterials 34(6), 1722–1731 (2013).
[Crossref] [PubMed]

Imakita, K.

Z. Bai, M. Fujii, K. Imakita, and S. Hayashi, “Green to red tunable upconversion fluorescence from Bi–Er–Yb codoped zeolites,” Microporous Mesoporous Mater. 173, 43–46 (2013).
[Crossref]

Ji, Z.

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

Jiang, B.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

Jin, S.

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

Johnson, N. J. J.

N. J. J. Johnson and F. C. J. M. van Veggel, “Sodium lanthanide fluoride core-shell nanocrystals: a general perspective on epitaxial shell growth,” Nano Res. 6(8), 547–561 (2013).
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Kang, X.

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

Kong, X.

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

Kuang, Y.

S. Song, Y. Kuang, J. Liu, Q. Yang, L. Luo, and X. Sun, “Separation and phase transition investigation of Yb3+/Er3+ co-doped NaYF4 nanoparticles,” Dalton Trans. 42(37), 13315–13318 (2013).
[Crossref] [PubMed]

Lee, J. Y.

C. Zhang and J. Y. Lee, “Prevalence of anisotropic shell growth in rare earth core-shell upconversion nanocrystals,” ACS Nano 7(5), 4393–4402 (2013).
[Crossref] [PubMed]

Lei, L.

L. Lei, D. Chen, J. Xu, R. Zhang, and Y. Wang, “Highly intensified upconversion luminescence of Ca2+ -doped Yb/Er:NaGdF4 nanocrystals prepared by a solvothermal route,” Chem. Asian J. 9(3), 728–733 (2014).
[Crossref] [PubMed]

L. Lei, D. Chen, P. Huang, J. Xu, R. Zhang, and Y. Wang, “Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping,” Nanoscale 5(22), 11298–11305 (2013).
[Crossref] [PubMed]

Lei, Y.

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Li, C.

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

Li, G.

G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
[Crossref]

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

Li, H.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Li, J.

J. Li, L. Yang, Y. Zhang, J. Zhong, C. Q. Sun, and P. K. Chu, “Pump-power tunable white upconversion emission in lanthanide-doped hexagonal NaYF4 nanorods,” Opt. Mater. 33(6), 882–887 (2011).
[Crossref]

Li, L.

D. Gao, X. Zhang, H. Zheng, P. Shi, L. Li, and Y. Ling, “Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+ nanorods,” Dalton Trans. 42(5), 1834–1841 (2013).
[Crossref] [PubMed]

Li, S.

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

Li, Y.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

Li, Z.

Z. Li, L. Wang, Z. Wang, X. Liu, and Y. Xiong, “Modification of NaYF4:Yb,Er@SiO2 nanoparticles with gold nanocrystals for tunable green-to-red upconversion emissions,” J. Phys. Chem. C 115(8), 3291–3296 (2011).
[Crossref]

Liao, M.

X. Xue, S. Uechi, R. N. Tiwari, Z. Duan, M. Liao, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Size-dependent upconversion luminescence and quenching mechanism of LiYF4: Er3+/Yb3+ nanocrystals with oleate ligand adsorbed,” Opt. Mater. Express 3(7), 989–999 (2013).
[Crossref]

X. Xue, M. Liao, R. Tiwari, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Intense ultraviolet and blue upconverison emissions in Tb3+/Yb3+ codoped KY3F10 nanocrystals,” Appl. Phys. Express 5(9), 092601 (2012).
[Crossref]

Lin, J.

G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
[Crossref]

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

Ling, Y.

D. Gao, X. Zhang, H. Zheng, P. Shi, L. Li, and Y. Ling, “Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+ nanorods,” Dalton Trans. 42(5), 1834–1841 (2013).
[Crossref] [PubMed]

Liu, H.

L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
[Crossref]

H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
[Crossref] [PubMed]

Liu, J.

S. Song, Y. Kuang, J. Liu, Q. Yang, L. Luo, and X. Sun, “Separation and phase transition investigation of Yb3+/Er3+ co-doped NaYF4 nanoparticles,” Dalton Trans. 42(37), 13315–13318 (2013).
[Crossref] [PubMed]

Liu, K.

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

Liu, M.

M. Liu, Y. Ye, C. Yao, W. Zhao, and X. Huang, “Mn2+-doped NaYF4:Yb/Er upconversion nanoparticles with amplified electrogenerated chemiluminescence for tumor biomarker detection,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6626–6633 (2014).
[Crossref]

Liu, S.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

Liu, X.

X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
[Crossref] [PubMed]

X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
[Crossref] [PubMed]

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

Z. Li, L. Wang, Z. Wang, X. Liu, and Y. Xiong, “Modification of NaYF4:Yb,Er@SiO2 nanoparticles with gold nanocrystals for tunable green-to-red upconversion emissions,” J. Phys. Chem. C 115(8), 3291–3296 (2011).
[Crossref]

Liu, Y.

Y. Liu, D. Tu, H. Zhu, and X. Chen, “Lanthanide-doped luminescent nanoprobes: controlled synthesis, optical spectroscopy, and bioapplications,” Chem. Soc. Rev. 42(16), 6924–6958 (2013).
[Crossref] [PubMed]

Lu, C.

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

Lu, S.

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Lu, W.

L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
[Crossref]

H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
[Crossref] [PubMed]

Luo, L.

S. Song, Y. Kuang, J. Liu, Q. Yang, L. Luo, and X. Sun, “Separation and phase transition investigation of Yb3+/Er3+ co-doped NaYF4 nanoparticles,” Dalton Trans. 42(37), 13315–13318 (2013).
[Crossref] [PubMed]

Ma, P.

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

Misiak, M.

K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
[Crossref] [PubMed]

Ni, Y.

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

Niu, N.

H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
[Crossref] [PubMed]

Ohishi, Y.

X. Xue, S. Uechi, R. N. Tiwari, Z. Duan, M. Liao, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Size-dependent upconversion luminescence and quenching mechanism of LiYF4: Er3+/Yb3+ nanocrystals with oleate ligand adsorbed,” Opt. Mater. Express 3(7), 989–999 (2013).
[Crossref]

X. Xue, Z. Duan, T. Suzuki, R. N. Tiwari, M. Yoshimura, and Y. Ohishi, “Luminescence properties of α-NaYF4:Nd3+ nanocrystals dispersed in liquid: local field effect investigation,” J. Phys. Chem. C 116(42), 22545–22551 (2012).
[Crossref]

X. Xue, M. Liao, R. Tiwari, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Intense ultraviolet and blue upconverison emissions in Tb3+/Yb3+ codoped KY3F10 nanocrystals,” Appl. Phys. Express 5(9), 092601 (2012).
[Crossref]

Ohulchanskyy, T. Y.

G. Chen, H. Ågren, T. Y. Ohulchanskyy, and P. N. Prasad, “Light upconverting core-shell nanostructures: nanophotonic control for emerging applications,” Chem. Soc. Rev. 44(6), 1680–1713 (2015).
[Crossref] [PubMed]

Pan, G.

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Pan, K.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

Pang, M.

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

Peng, C.

G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
[Crossref]

Prasad, P. N.

G. Chen, H. Ågren, T. Y. Ohulchanskyy, and P. N. Prasad, “Light upconverting core-shell nanostructures: nanophotonic control for emerging applications,” Chem. Soc. Rev. 44(6), 1680–1713 (2015).
[Crossref] [PubMed]

Prorok, K.

K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
[Crossref] [PubMed]

Qin, G.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Qin, W.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Qu, Y.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

Rao, L.

H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
[Crossref] [PubMed]

L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
[Crossref]

Ren, W.

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

Ren, X.

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Sedlmeier, A.

A. Sedlmeier and H. H. Gorris, “Surface modification and characterization of photon-upconverting nanoparticles for bioanalytical applications,” Chem. Soc. Rev. 44(6), 1526–1560 (2015).
[Crossref] [PubMed]

Shang, M.

G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
[Crossref]

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

Shi, P.

D. Gao, X. Zhang, H. Zheng, P. Shi, L. Li, and Y. Ling, “Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+ nanorods,” Dalton Trans. 42(5), 1834–1841 (2013).
[Crossref] [PubMed]

Sobczyk, M.

K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
[Crossref] [PubMed]

Song, H.

W. Yu, W. Xu, H. Song, and S. Zhang, “Temperature-dependent upconversion luminescence and dynamics of NaYF4:Yb3+/Er3+ nanocrystals: influence of particle size and crystalline phase,” Dalton Trans. 43(16), 6139–6147 (2014).
[Crossref] [PubMed]

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Song, S.

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

S. Song, Y. Kuang, J. Liu, Q. Yang, L. Luo, and X. Sun, “Separation and phase transition investigation of Yb3+/Er3+ co-doped NaYF4 nanoparticles,” Dalton Trans. 42(37), 13315–13318 (2013).
[Crossref] [PubMed]

Strek, W.

K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
[Crossref] [PubMed]

Sun, C. Q.

J. Li, L. Yang, Y. Zhang, J. Zhong, C. Q. Sun, and P. K. Chu, “Pump-power tunable white upconversion emission in lanthanide-doped hexagonal NaYF4 nanorods,” Opt. Mater. 33(6), 882–887 (2011).
[Crossref]

Sun, X.

S. Song, Y. Kuang, J. Liu, Q. Yang, L. Luo, and X. Sun, “Separation and phase transition investigation of Yb3+/Er3+ co-doped NaYF4 nanoparticles,” Dalton Trans. 42(37), 13315–13318 (2013).
[Crossref] [PubMed]

Suzuki, T.

X. Xue, S. Uechi, R. N. Tiwari, Z. Duan, M. Liao, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Size-dependent upconversion luminescence and quenching mechanism of LiYF4: Er3+/Yb3+ nanocrystals with oleate ligand adsorbed,” Opt. Mater. Express 3(7), 989–999 (2013).
[Crossref]

X. Xue, M. Liao, R. Tiwari, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Intense ultraviolet and blue upconverison emissions in Tb3+/Yb3+ codoped KY3F10 nanocrystals,” Appl. Phys. Express 5(9), 092601 (2012).
[Crossref]

X. Xue, Z. Duan, T. Suzuki, R. N. Tiwari, M. Yoshimura, and Y. Ohishi, “Luminescence properties of α-NaYF4:Nd3+ nanocrystals dispersed in liquid: local field effect investigation,” J. Phys. Chem. C 116(42), 22545–22551 (2012).
[Crossref]

Tian, C.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

Tian, G.

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

Tiwari, R.

X. Xue, M. Liao, R. Tiwari, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Intense ultraviolet and blue upconverison emissions in Tb3+/Yb3+ codoped KY3F10 nanocrystals,” Appl. Phys. Express 5(9), 092601 (2012).
[Crossref]

Tiwari, R. N.

X. Xue, S. Uechi, R. N. Tiwari, Z. Duan, M. Liao, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Size-dependent upconversion luminescence and quenching mechanism of LiYF4: Er3+/Yb3+ nanocrystals with oleate ligand adsorbed,” Opt. Mater. Express 3(7), 989–999 (2013).
[Crossref]

X. Xue, Z. Duan, T. Suzuki, R. N. Tiwari, M. Yoshimura, and Y. Ohishi, “Luminescence properties of α-NaYF4:Nd3+ nanocrystals dispersed in liquid: local field effect investigation,” J. Phys. Chem. C 116(42), 22545–22551 (2012).
[Crossref]

Tu, D.

Y. Liu, D. Tu, H. Zhu, and X. Chen, “Lanthanide-doped luminescent nanoprobes: controlled synthesis, optical spectroscopy, and bioapplications,” Chem. Soc. Rev. 42(16), 6924–6958 (2013).
[Crossref] [PubMed]

Tu, L.

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

Uechi, S.

van Veggel, F. C. J. M.

N. J. J. Johnson and F. C. J. M. van Veggel, “Sodium lanthanide fluoride core-shell nanocrystals: a general perspective on epitaxial shell growth,” Nano Res. 6(8), 547–561 (2013).
[Crossref]

Wang, G.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

Wang, H.

H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
[Crossref] [PubMed]

L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
[Crossref]

Wang, L.

Z. Li, L. Wang, Z. Wang, X. Liu, and Y. Xiong, “Modification of NaYF4:Yb,Er@SiO2 nanoparticles with gold nanocrystals for tunable green-to-red upconversion emissions,” J. Phys. Chem. C 115(8), 3291–3296 (2011).
[Crossref]

Wang, T.

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

Wang, Y.

X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
[Crossref] [PubMed]

L. Lei, D. Chen, J. Xu, R. Zhang, and Y. Wang, “Highly intensified upconversion luminescence of Ca2+ -doped Yb/Er:NaGdF4 nanocrystals prepared by a solvothermal route,” Chem. Asian J. 9(3), 728–733 (2014).
[Crossref] [PubMed]

L. Lei, D. Chen, P. Huang, J. Xu, R. Zhang, and Y. Wang, “Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping,” Nanoscale 5(22), 11298–11305 (2013).
[Crossref] [PubMed]

D. Chen, Y. Wang, K. Zheng, T. Guo, and Y. Yu, “Bright upconversion white light emission in transparent glass ceramic embedding Tm3+/Er3+/Yb3+: beta-YF3 nanocrystals,” Appl. Phys. Lett. 92, 1903 (2007).

Wang, Z.

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

Z. Li, L. Wang, Z. Wang, X. Liu, and Y. Xiong, “Modification of NaYF4:Yb,Er@SiO2 nanoparticles with gold nanocrystals for tunable green-to-red upconversion emissions,” J. Phys. Chem. C 115(8), 3291–3296 (2011).
[Crossref]

Wu, C.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Wu, F.

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

Xing, G.

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

Xiong, Y.

Z. Li, L. Wang, Z. Wang, X. Liu, and Y. Xiong, “Modification of NaYF4:Yb,Er@SiO2 nanoparticles with gold nanocrystals for tunable green-to-red upconversion emissions,” J. Phys. Chem. C 115(8), 3291–3296 (2011).
[Crossref]

Xu, J.

L. Lei, D. Chen, J. Xu, R. Zhang, and Y. Wang, “Highly intensified upconversion luminescence of Ca2+ -doped Yb/Er:NaGdF4 nanocrystals prepared by a solvothermal route,” Chem. Asian J. 9(3), 728–733 (2014).
[Crossref] [PubMed]

L. Lei, D. Chen, P. Huang, J. Xu, R. Zhang, and Y. Wang, “Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping,” Nanoscale 5(22), 11298–11305 (2013).
[Crossref] [PubMed]

H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
[Crossref] [PubMed]

Xu, W.

W. Yu, W. Xu, H. Song, and S. Zhang, “Temperature-dependent upconversion luminescence and dynamics of NaYF4:Yb3+/Er3+ nanocrystals: influence of particle size and crystalline phase,” Dalton Trans. 43(16), 6139–6147 (2014).
[Crossref] [PubMed]

Xu, Z.

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

Xue, X.

X. Xue, S. Uechi, R. N. Tiwari, Z. Duan, M. Liao, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Size-dependent upconversion luminescence and quenching mechanism of LiYF4: Er3+/Yb3+ nanocrystals with oleate ligand adsorbed,” Opt. Mater. Express 3(7), 989–999 (2013).
[Crossref]

X. Xue, M. Liao, R. Tiwari, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Intense ultraviolet and blue upconverison emissions in Tb3+/Yb3+ codoped KY3F10 nanocrystals,” Appl. Phys. Express 5(9), 092601 (2012).
[Crossref]

X. Xue, Z. Duan, T. Suzuki, R. N. Tiwari, M. Yoshimura, and Y. Ohishi, “Luminescence properties of α-NaYF4:Nd3+ nanocrystals dispersed in liquid: local field effect investigation,” J. Phys. Chem. C 116(42), 22545–22551 (2012).
[Crossref]

Yan, L.

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

Yang, D.

G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
[Crossref]

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

Yang, G.

H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
[Crossref] [PubMed]

Yang, L.

J. Li, L. Yang, Y. Zhang, J. Zhong, C. Q. Sun, and P. K. Chu, “Pump-power tunable white upconversion emission in lanthanide-doped hexagonal NaYF4 nanorods,” Opt. Mater. 33(6), 882–887 (2011).
[Crossref]

Yang, P.

H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
[Crossref] [PubMed]

Yang, Q.

S. Song, Y. Kuang, J. Liu, Q. Yang, L. Luo, and X. Sun, “Separation and phase transition investigation of Yb3+/Er3+ co-doped NaYF4 nanoparticles,” Dalton Trans. 42(37), 13315–13318 (2013).
[Crossref] [PubMed]

Yao, C.

M. Liu, Y. Ye, C. Yao, W. Zhao, and X. Huang, “Mn2+-doped NaYF4:Yb/Er upconversion nanoparticles with amplified electrogenerated chemiluminescence for tumor biomarker detection,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6626–6633 (2014).
[Crossref]

Yao, S.

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

Ye, Y.

M. Liu, Y. Ye, C. Yao, W. Zhao, and X. Huang, “Mn2+-doped NaYF4:Yb/Er upconversion nanoparticles with amplified electrogenerated chemiluminescence for tumor biomarker detection,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6626–6633 (2014).
[Crossref]

Yi, Z.

L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
[Crossref]

H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
[Crossref] [PubMed]

Yin, S.

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

Yin, W.

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

Yoshimura, M.

X. Xue, S. Uechi, R. N. Tiwari, Z. Duan, M. Liao, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Size-dependent upconversion luminescence and quenching mechanism of LiYF4: Er3+/Yb3+ nanocrystals with oleate ligand adsorbed,” Opt. Mater. Express 3(7), 989–999 (2013).
[Crossref]

X. Xue, Z. Duan, T. Suzuki, R. N. Tiwari, M. Yoshimura, and Y. Ohishi, “Luminescence properties of α-NaYF4:Nd3+ nanocrystals dispersed in liquid: local field effect investigation,” J. Phys. Chem. C 116(42), 22545–22551 (2012).
[Crossref]

X. Xue, M. Liao, R. Tiwari, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Intense ultraviolet and blue upconverison emissions in Tb3+/Yb3+ codoped KY3F10 nanocrystals,” Appl. Phys. Express 5(9), 092601 (2012).
[Crossref]

Yu, F.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Yu, W.

W. Yu, W. Xu, H. Song, and S. Zhang, “Temperature-dependent upconversion luminescence and dynamics of NaYF4:Yb3+/Er3+ nanocrystals: influence of particle size and crystalline phase,” Dalton Trans. 43(16), 6139–6147 (2014).
[Crossref] [PubMed]

Yu, Y.

D. Chen, Y. Wang, K. Zheng, T. Guo, and Y. Yu, “Bright upconversion white light emission in transparent glass ceramic embedding Tm3+/Er3+/Yb3+: beta-YF3 nanocrystals,” Appl. Phys. Lett. 92, 1903 (2007).

Zeng, Q.

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

Zeng, S.

H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
[Crossref] [PubMed]

L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
[Crossref]

Zeng, T.

L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
[Crossref]

H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
[Crossref] [PubMed]

Zhai, X.

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

Zhang, C.

C. Zhang and J. Y. Lee, “Prevalence of anisotropic shell growth in rare earth core-shell upconversion nanocrystals,” ACS Nano 7(5), 4393–4402 (2013).
[Crossref] [PubMed]

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

Zhang, H.

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

Zhang, J.

D. Gao, X. Zhang, and J. Zhang, “The effects of structural characterization on the luminescence of Eu3+-doped fluoride nano/microcrystals,” CrystEngComm 16(48), 11115–11121 (2014).
[Crossref]

Zhang, R.

L. Lei, D. Chen, J. Xu, R. Zhang, and Y. Wang, “Highly intensified upconversion luminescence of Ca2+ -doped Yb/Er:NaGdF4 nanocrystals prepared by a solvothermal route,” Chem. Asian J. 9(3), 728–733 (2014).
[Crossref] [PubMed]

L. Lei, D. Chen, P. Huang, J. Xu, R. Zhang, and Y. Wang, “Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping,” Nanoscale 5(22), 11298–11305 (2013).
[Crossref] [PubMed]

Zhang, S.

W. Yu, W. Xu, H. Song, and S. Zhang, “Temperature-dependent upconversion luminescence and dynamics of NaYF4:Yb3+/Er3+ nanocrystals: influence of particle size and crystalline phase,” Dalton Trans. 43(16), 6139–6147 (2014).
[Crossref] [PubMed]

Zhang, X.

D. Gao, X. Zhang, and J. Zhang, “The effects of structural characterization on the luminescence of Eu3+-doped fluoride nano/microcrystals,” CrystEngComm 16(48), 11115–11121 (2014).
[Crossref]

D. Gao, X. Zhang, H. Zheng, P. Shi, L. Li, and Y. Ling, “Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+ nanorods,” Dalton Trans. 42(5), 1834–1841 (2013).
[Crossref] [PubMed]

Zhang, Y.

X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
[Crossref] [PubMed]

Q. Dou, N. M. Idris, and Y. Zhang, “Sandwich-structured upconversion nanoparticles with tunable color for multiplexed cell labeling,” Biomaterials 34(6), 1722–1731 (2013).
[Crossref] [PubMed]

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

J. Li, L. Yang, Y. Zhang, J. Zhong, C. Q. Sun, and P. K. Chu, “Pump-power tunable white upconversion emission in lanthanide-doped hexagonal NaYF4 nanorods,” Opt. Mater. 33(6), 882–887 (2011).
[Crossref]

Zhao, C.

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

Zhao, D.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Zhao, L.

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

Zhao, W.

M. Liu, Y. Ye, C. Yao, W. Zhao, and X. Huang, “Mn2+-doped NaYF4:Yb/Er upconversion nanoparticles with amplified electrogenerated chemiluminescence for tumor biomarker detection,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6626–6633 (2014).
[Crossref]

Zhao, Y.

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

Zheng, H.

D. Gao, X. Zhang, H. Zheng, P. Shi, L. Li, and Y. Ling, “Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+ nanorods,” Dalton Trans. 42(5), 1834–1841 (2013).
[Crossref] [PubMed]

Zheng, K.

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

D. Chen, Y. Wang, K. Zheng, T. Guo, and Y. Yu, “Bright upconversion white light emission in transparent glass ceramic embedding Tm3+/Er3+/Yb3+: beta-YF3 nanocrystals,” Appl. Phys. Lett. 92, 1903 (2007).

Zhong, J.

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

J. Li, L. Yang, Y. Zhang, J. Zhong, C. Q. Sun, and P. K. Chu, “Pump-power tunable white upconversion emission in lanthanide-doped hexagonal NaYF4 nanorods,” Opt. Mater. 33(6), 882–887 (2011).
[Crossref]

Zhou, L.

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

Zhou, W.

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

Zhu, H.

Y. Liu, D. Tu, H. Zhu, and X. Chen, “Lanthanide-doped luminescent nanoprobes: controlled synthesis, optical spectroscopy, and bioapplications,” Chem. Soc. Rev. 42(16), 6924–6958 (2013).
[Crossref] [PubMed]

ACS Nano (1)

C. Zhang and J. Y. Lee, “Prevalence of anisotropic shell growth in rare earth core-shell upconversion nanocrystals,” ACS Nano 7(5), 4393–4402 (2013).
[Crossref] [PubMed]

Adv. Mater. (1)

G. Tian, Z. Gu, L. Zhou, W. Yin, X. Liu, L. Yan, S. Jin, W. Ren, G. Xing, S. Li, and Y. Zhao, “Mn2+ dopant-controlled synthesis of NaYF4:Yb/Er upconversion nanoparticles for in vivo imaging and drug delivery,” Adv. Mater. 24(9), 1226–1231 (2012).
[Crossref] [PubMed]

Appl. Phys. Express (1)

X. Xue, M. Liao, R. Tiwari, M. Yoshimura, T. Suzuki, and Y. Ohishi, “Intense ultraviolet and blue upconverison emissions in Tb3+/Yb3+ codoped KY3F10 nanocrystals,” Appl. Phys. Express 5(9), 092601 (2012).
[Crossref]

Appl. Phys. Lett. (1)

D. Chen, Y. Wang, K. Zheng, T. Guo, and Y. Yu, “Bright upconversion white light emission in transparent glass ceramic embedding Tm3+/Er3+/Yb3+: beta-YF3 nanocrystals,” Appl. Phys. Lett. 92, 1903 (2007).

Biomaterials (1)

Q. Dou, N. M. Idris, and Y. Zhang, “Sandwich-structured upconversion nanoparticles with tunable color for multiplexed cell labeling,” Biomaterials 34(6), 1722–1731 (2013).
[Crossref] [PubMed]

Chem. Asian J. (1)

L. Lei, D. Chen, J. Xu, R. Zhang, and Y. Wang, “Highly intensified upconversion luminescence of Ca2+ -doped Yb/Er:NaGdF4 nanocrystals prepared by a solvothermal route,” Chem. Asian J. 9(3), 728–733 (2014).
[Crossref] [PubMed]

Chem. Soc. Rev. (4)

A. Sedlmeier and H. H. Gorris, “Surface modification and characterization of photon-upconverting nanoparticles for bioanalytical applications,” Chem. Soc. Rev. 44(6), 1526–1560 (2015).
[Crossref] [PubMed]

X. Liu, R. Deng, Y. Zhang, Y. Wang, H. Chang, L. Huang, and X. Liu, “Probing the nature of upconversion nanocrystals: instrumentation matters,” Chem. Soc. Rev. 44(6), 1479–1508 (2015).
[Crossref] [PubMed]

Y. Liu, D. Tu, H. Zhu, and X. Chen, “Lanthanide-doped luminescent nanoprobes: controlled synthesis, optical spectroscopy, and bioapplications,” Chem. Soc. Rev. 42(16), 6924–6958 (2013).
[Crossref] [PubMed]

G. Chen, H. Ågren, T. Y. Ohulchanskyy, and P. N. Prasad, “Light upconverting core-shell nanostructures: nanophotonic control for emerging applications,” Chem. Soc. Rev. 44(6), 1680–1713 (2015).
[Crossref] [PubMed]

Chemistry (1)

W. Yin, L. Zhao, L. Zhou, Z. Gu, X. Liu, G. Tian, S. Jin, L. Yan, W. Ren, G. Xing, and Y. Zhao, “Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging,” Chemistry 18(30), 9239–9245 (2012).
[Crossref] [PubMed]

CrystEngComm (2)

G. Li, M. Shang, D. Geng, D. Yang, C. Peng, Z. Cheng, and J. Lin, “Multiform La2O3:Yb3+/Er3+/Tm3+ submicro-/microcrystals derived by hydrothermal process: morphology control and tunable upconversion luminescence properties,” CrystEngComm 14(6), 2100–2111 (2012).
[Crossref]

D. Gao, X. Zhang, and J. Zhang, “The effects of structural characterization on the luminescence of Eu3+-doped fluoride nano/microcrystals,” CrystEngComm 16(48), 11115–11121 (2014).
[Crossref]

Dalton Trans. (7)

W. Yu, W. Xu, H. Song, and S. Zhang, “Temperature-dependent upconversion luminescence and dynamics of NaYF4:Yb3+/Er3+ nanocrystals: influence of particle size and crystalline phase,” Dalton Trans. 43(16), 6139–6147 (2014).
[Crossref] [PubMed]

S. Song, Y. Kuang, J. Liu, Q. Yang, L. Luo, and X. Sun, “Separation and phase transition investigation of Yb3+/Er3+ co-doped NaYF4 nanoparticles,” Dalton Trans. 42(37), 13315–13318 (2013).
[Crossref] [PubMed]

D. Gao, X. Zhang, H. Zheng, P. Shi, L. Li, and Y. Ling, “Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+ nanorods,” Dalton Trans. 42(5), 1834–1841 (2013).
[Crossref] [PubMed]

D. Chen and P. Huang, “Highly intense upconversion luminescence in Yb/Er:NaGdF4@NaYF4 core-shell nanocrystals with complete shell enclosure of the core,” Dalton Trans. 43(29), 11299–11304 (2014).
[Crossref] [PubMed]

M. Pang, X. Zhai, J. Feng, S. Song, R. Deng, Z. Wang, S. Yao, X. Ge, and H. Zhang, “One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission,” Dalton Trans. 43(26), 10202–10207 (2014).
[Crossref] [PubMed]

Y. Li, K. Pan, G. Wang, B. Jiang, C. Tian, W. Zhou, Y. Qu, S. Liu, L. Feng, and H. Fu, “Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of dual-mode luminescent NaYF4:Yb3+/Er3+.,” Dalton Trans. 42(22), 7971–7979 (2013).
[Crossref] [PubMed]

H. Fu, G. Yang, S. Gai, N. Niu, F. He, J. Xu, and P. Yang, “Color-tunable and enhanced luminescence of well-defined sodium scandium fluoride nanocrystals,” Dalton Trans. 42(22), 7863–7870 (2013).
[Crossref] [PubMed]

J. Mater. Chem. (1)

C. Zhang, P. Ma, C. Li, G. Li, S. Huang, D. Yang, M. Shang, X. Kang, and J. Lin, “Controllable and white upconversion luminescence in BaYF5: Ln3+(Ln= Yb, Er, Tm) nanocrystals,” J. Mater. Chem. 21(3), 717–723 (2011).
[Crossref]

J. Mater. Chem. B Mater. Biol. Med. (2)

M. Liu, Y. Ye, C. Yao, W. Zhao, and X. Huang, “Mn2+-doped NaYF4:Yb/Er upconversion nanoparticles with amplified electrogenerated chemiluminescence for tumor biomarker detection,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6626–6633 (2014).
[Crossref]

L. Rao, W. Lu, T. Zeng, Z. Yi, H. Wang, H. Liu, and S. Zeng, “Sub-10 nm BaLaF5: Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging,” J. Mater. Chem. B Mater. Biol. Med. 2(38), 6527–6533 (2014).
[Crossref]

J. Phys. Chem. C (3)

Z. Li, L. Wang, Z. Wang, X. Liu, and Y. Xiong, “Modification of NaYF4:Yb,Er@SiO2 nanoparticles with gold nanocrystals for tunable green-to-red upconversion emissions,” J. Phys. Chem. C 115(8), 3291–3296 (2011).
[Crossref]

X. Bai, H. Song, G. Pan, Y. Lei, T. Wang, X. Ren, S. Lu, B. Dong, Q. Dai, and L. Fan, “Size-dependent upconversion luminescence in Er3+/Yb3+-codoped nanocrystalline Yttria: saturation and thermal effects,” J. Phys. Chem. C 111(36), 13611–13617 (2007).
[Crossref]

X. Xue, Z. Duan, T. Suzuki, R. N. Tiwari, M. Yoshimura, and Y. Ohishi, “Luminescence properties of α-NaYF4:Nd3+ nanocrystals dispersed in liquid: local field effect investigation,” J. Phys. Chem. C 116(42), 22545–22551 (2012).
[Crossref]

Microporous Mesoporous Mater. (1)

Z. Bai, M. Fujii, K. Imakita, and S. Hayashi, “Green to red tunable upconversion fluorescence from Bi–Er–Yb codoped zeolites,” Microporous Mesoporous Mater. 173, 43–46 (2013).
[Crossref]

Nano Res. (1)

N. J. J. Johnson and F. C. J. M. van Veggel, “Sodium lanthanide fluoride core-shell nanocrystals: a general perspective on epitaxial shell growth,” Nano Res. 6(8), 547–561 (2013).
[Crossref]

Nanoscale (4)

K. Prorok, A. Bednarkiewicz, B. Cichy, A. Gnach, M. Misiak, M. Sobczyk, and W. Strek, “The impact of shell host (NaYF₄/CaF₂) and shell deposition methods on the up-conversion enhancement in Tb³⁺, Yb³⁺ codoped colloidal α-NaYF₄ core-shell nanoparticles,” Nanoscale 6(3), 1855–1864 (2014).
[Crossref] [PubMed]

L. Lei, D. Chen, P. Huang, J. Xu, R. Zhang, and Y. Wang, “Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping,” Nanoscale 5(22), 11298–11305 (2013).
[Crossref] [PubMed]

C. Zhao, X. Kong, X. Liu, L. Tu, F. Wu, Y. Zhang, K. Liu, Q. Zeng, and H. Zhang, “Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles,” Nanoscale 5(17), 8084–8089 (2013).
[Crossref] [PubMed]

H. Wang, W. Lu, T. Zeng, Z. Yi, L. Rao, H. Liu, and S. Zeng, “Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging,” Nanoscale 6(5), 2855–2860 (2014).
[Crossref] [PubMed]

Opt. Mater. (1)

J. Li, L. Yang, Y. Zhang, J. Zhong, C. Q. Sun, and P. K. Chu, “Pump-power tunable white upconversion emission in lanthanide-doped hexagonal NaYF4 nanorods,” Opt. Mater. 33(6), 882–887 (2011).
[Crossref]

Opt. Mater. Express (1)

RSC Advances (1)

D. Zhao, H. Chen, K. Zheng, X. Chuai, F. Yu, H. Li, C. Wu, G. Qin, W. Di, and W. Qin, “Growth of hexagonal phase sodium rare earth tetrafluorides induced by heterogeneous cubic phase core,” RSC Advances 4(26), 13490–13494 (2014).
[Crossref]

Sci. Rep. (1)

M. Ding, D. Chen, S. Yin, Z. Ji, J. Zhong, Y. Ni, C. Lu, and Z. Xu, “Simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb3+/Er3+ microcrystals by simply tuning the KF dosage,” Sci. Rep. 5, 12745 (2015).
[Crossref] [PubMed]

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Figures (6)

Fig. 1
Fig. 1 XRD patterns (a) CaF2 core; (b) CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs; (c) CaF2 (JCPDS NO. 35-816); (d) β-NaYF4 (JCPDS NO. 16-334)

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Fig. 2
Fig. 2 (a) TEM images of CaF2 core NCs; (b) TEM image of CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs; (c) Size distribution of CaF2 core NCs; (d) Size distribution of CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs; (e) EDX analysis of elemental composition of CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs.

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Fig. 3
Fig. 3 XRD patterns (left), UCL spectra excited by a 80 mW 980 nm laser (right-top) and corresponding UC photographic (right-bottom) of HNCs samples prepared with different reaction material or different reaction sequence: (a) NaCl as Sodium source, KF as Fluorine source; (b) NaNO3 as Sodium source, KF as Fluorine source; (c) NaF as Sodium source and KF as Fluorine source; (d) KF as Fluorine source in the core growth, NaF as Sodium source and Fluorine source in the shell growth; (e) All the reaction materials of sample (a) was mixed directly (non-core induce).

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Fig. 4
Fig. 4 XRD patterns of CaF2@NaYF4:20 mol%Yb, 2 mol%Er HNCs. with shell growth time of (a) 6h; (b) 12h; (c) 24h.

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Fig. 5
Fig. 5 (a) The UCL spectra of CaF2@NaYF4:20 mol%Yb, 2 mol%Er, x mol%Tm (x = 0, 0.5, 1, 1.5, 2, 2.5, 3, 4) nanocrystals excited by a 80 mW 980 nm laser; (b) Corresponding UC emission red/green intensity ratio and total luminescence integrated intensity; (c) Photostability of CaF2@NaYF4:20 mol%Yb, 2 mol%Er, 2 mol%Tm NCs. Emission was collected by a 652 nm channel. Time interval of imaging data collection = 0.5 s; (d) UC photographic of nanocrystals water solution excited by a 80 mW 980 nm laser.

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Fig. 6
Fig. 6 Energy level diagrams of Er3+ and Tm3+ ions and possible energy transfer mechanism under 980 nm excitation.

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Tables (1)

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Table 1 The detail of reaction process and the Crystallographic phase of product.

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