Upconversion nanocrystals

Wang, R and Liu, X.G. (2009) Recent advances in the chemistry of lanthanide-doped upconversion nanocrystals. 

Cao, T.Y., Yang, Y., Gao, Y., Zhou, J., Li, Z.Q., Li, F.Y., 2011. High-quality water-soluble and surface-functionalized upconversion nanocrystals as luminescent probes for bioimaging. Biomaterials 32, 2959—2968. 

Dou, Q.Q., Zhang, Y., 2011. Tuning of the structure and emission spectra of upconversion nanocrystals by alkali ion doping. Langmuir 27, 13236—13241. 

Figure 5 TEM images of upconversion nanocrystals. (a), (b) Ultrasmall LaF3 Yb/Er nanoparticles prepared by Yi and Chow via coprecipitation method, (c), (d) 8-NaYF4 Yb/Er nanoparticles and nanoplates prepared by Yan et al via thermal decomposition method, (e), (f) a-NaYF4 Yb, Er nanoparticles prepared by Capobianco et al via thermal decomposition method, (g), (h) NaYF4 Yb r nanoparticles and nanorods prepared by Wang and LP via hydrothermal method. (Reproduced from Ref. 3 with permission of The Royal Society of Chemistry.)...

He M, Huang P, Zhang C, Hu H, Bao C, He R, Cui D (2011) Dual phase-controlled synthesis of uniform lanthanide-doped NaGdp4 upconversion nanocrystals via an OA/ionic liquid two-phase system for in vivo dual-modality imaging. Adv Funct Mater 21 4470-4477... 

Zhang F., R. Che, X. LI C. Yao, J. Yang, D. Shen, P. Hu, W. Li and D. Zhao, Direct Imaging the Upconversion Nanocrystal Core/SheU Structure at the Suhnanometer Level Shell Thickness Dependence in Upconverting Optical Properties, Nano Lett., 12, 2852-2858... 

Underwood, D. E., Kippeny, T. and Rosenthal, S. J. (2001) Ultrafast carrier dynamics in CdSe nanocrystals determined by femtosecond fluorescence upconversion spectroscopy. /. Phys. Chem. B, 105,436-443. 

Lanthanide (Ln) - or rare-earth-doped upconverting nanocrystals usually have similar optical properties as their bulk counterparts [45]. Upconversion is characterized by the successive absorption of two or more photons via intermediate... 

Fig. 12. Comparison of the upconversion spectra of Y2(>3 Er3+ (1 at%), Yb3+ (1 at%) at room temperature (a) bulk crystals and (b) nanocrystals, where the emission bands correspond to (i) 2Hu/2, 4S3/2 —> 4I 5/2 and (ii) 4F9/2 —> 4Ii5/2- The excitation wavelength is 978 nm (reprinted with permission from Vetrone et al. (2004)).

Fig. 18. Upconversion luminescence from ZnS Eu3+ nanocrystals. The emission following excitation at 929 nm is significantly stronger than the emission following excitation only a few nanometers away. For comparison, a PL spectrum is shown as well (reprinted with permission from Chen et al. (2004a, 2004b, 2004c)).

Heer, S., Kompe, K., Gudel, H.U., and Haase, M. (2004) Highly efficient multicolour upconversion emission in transparent colloids of lanthanide-doped NaYp4 nanocrystals. Advanced Materials, 16, 2102-2105. 

Qian, H.S. and Zhang, Y. (2008) Synthesis of hexagonal-phase core-shell NaYR4 nanocrystals with tunable upconversion fluorescence. Langmuir, 24, 12123-12125. 

Li, Z. and Zhang, Y. (2006) Monodisperse siUca-coated polyvinylpyrrolidone/NaYF4 nanocrystals with multicolor upconversion fluorescence Qvtnssion. Angewandte Chemie International Edition, 45, 7732—7735. 

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