Lanthanide-doped nanocrystals

Lanthanide-doped nanocrystals embedded in amorphous matrices... 

Chatteriee, D.K., Rufalhah, A.J., and Zhang, Y. (2008) Upconversion fluorescence imaging of cells and small animals using lanthanide doped nanocrystals. Biomaterials, 29, 937—943. 

Lanthanide-doped nanocrystals embedded in amorphous matrices 129 5.6.4. Miscellaneous 6. Spectroscopy of lantiianides doped in core- 150... 

Both the lanthanide chelate-incorporated nanoparticles [27] and the inorganic lanthanide-doped nanocrystals [28] share some common characteristics of lanthanide... 

Liu Y., K. Ai, L. Lu. Designing lanthanide-doped nanocrystals with both up- and down-conversion luminescence for anti-counterfeiting. Nanoscale, 3, 4804—4810 (2011). 

Wang G. F., Q. Peng and Y. D. Li, Lanthanide-Doped Nanocrystals Synthesis, Optical-Magnetic Properties, and Applications, Acc. Chem. Res., 44, 322-332 (2011). 

In the past decade, lanthanide ions doped in nanocrystalline semiconductors have been the subject of numerous investigations. Although quantum size effects are not expected on lanthanide energy level structures, influence of quantum confinement in semiconductor on the luminescence properties of the lanthanides is expected. One of the advantages of lanthanide-doped semiconductor nanocrystals is that the lanthanide luminescence can be efficiently sen-... 

Although optical spectra of lanthanide-doped insulating nanociystals embedded in amorphous matrices are very similar to the free-standing nanocrystal counterparts, their excited state dynamics behaves very differently from that in simple nanocrystals. Some distinct dynamic properties have recently been found for nanocrystals embedded in polymers or glasses. Simple models for the interaction between lanthanide ions and the matrices were also proposed. However, further studies are needed in order to quantitatively understand the observed size-dependence and dynamic mechanisms. 

Generally, quantum size effects are not expected in lanthanide-doped nanoinsulators such as oxides since the Bohr radius of the exciton in insulating oxides, like Y2O3 and Gd2C>3, is very small. By contrast, the exciton Bohr radius of semiconductors is larger (e.g., 2.5 nm for CdS) resulting in pronounced quantum confinement effects for nanoparticles of about 2.5 nm or smaller (Bol et al., 2002). Therefore, a possible influence of quantum size effects on the luminescence properties of lanthanide ions is expected in semiconductor nanocrystals. 

Recently, many researchers have paid attention to the optical properties of lanthanide-doped III-V and II-VI semiconductor nanocrystals prepared by ion implantation, molecular-beam-epitaxy (MBE) or wet chemical syntheses. Although some controversies still exist, many important results have been achieved, which may be beneficial to the understanding of the basic physical or chemical properties of lanthanide-doped semiconductor nanocrystals. 

Although Bhargava s mistakes on the shortening of TM lifetime or lanthanide-doped ZnS have been pointed out by other researchers, many scientists still expect that lanthanide-doped II-VI semiconductor nanocrystals may form a new class of luminescent materials. Numerous papers on the luminescence of II-VI semiconductor nanocrystals doped with TM or lanthanide ions have appeared in an effort to achieve high efficient luminescence via ET from II-VI host to lanthanide ions. 

Quantum dots represent three-dimensional confinement in semiconductor materials. The optical spectroscopy of lanthanides-doped III-V semiconductor QDs has been observed to be very different from the bulk or thick film. For example, carrier confinement in QDs can strongly enhance the radiative quantum efficiency of the lanthanide emission, which thus makes lanthanide-doped III-V semiconductor QDs very promising candidates for full-color LEDs. It is notoriously difficult to dope lanthanide into III-V semiconductor nanocrystals by wet chemical synthesis methods. To date, most of these samples were prepared either by MBE, ion implantation or magnetron co-sputtering. 

Compared to III-V and II-VI semiconductor nanocrystals, much less work has been performed on lanthanide-doped III-VI (such as I Ss) or IV-VI (such as Ti02, SnC>2) semiconductor nanocrystals. One of the advantages of these hosts over III-V semiconductors is that they can be synthesized by wet chemical methods instead of the sophisticated techniques (eg., MBE) needed for GaN. 

BettineUi, M., A. Speghini, D. Falcomer, M. Daldosso, V. Dallacasa and L. Romano (2006). Photo-catalytic, spectroscopic and transport properties of lanthanide-doped Ti02 nanocrystals. Journal of Physics-Condensed Matter, 18(33), S2149-S2160. 

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

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. 

Wang, L.Y. and Li, Y.D. (2007) Controlled synthesis andluminescence of lanthanide doped NaYp4 nanocrystals. 

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