Lanthanide-doped phosphors

Studies of lanthanide complexes under such multiphoton excitation are rare [24, 76-78], and further work is necessary to identify complexes that have a suitable response towards multiphoton excitation under biological conditions. We note that multiphoton-excited luminescence, which involves the simultaneous absorption of several photons, is different from the upconversion luminescence for lanthanide-doped phosphors described earlier in this chapter, which is based on the sequential absorption of photons. 

Lanthanide-doped inverse photonic crystals have been reported.282 The lattices were prepared by infilling self-assembled polystyrene sphere templates with a mixture of zirconium alkoxide and europium at 450 °C, the polystyrene spheres were burnt out leaving hollow spheres of air, and the infilled material was converted to Zr02 Eu3+. The PL properties of the resulting photonic lattice were reported.282 The possibility of including phosphors into photonic lattices could lead to many... 

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Guo H, Sim S (2012) Lanthanide-doped upconverting phosphors for bioassay and therapy. Nanoscale 4 6692-6706... 

In addition, the lanthanide ions are always embedded in a chemical environment. This environment might be either inorganic or organic. Both types of compounds may be stoichiometric compounds where a lanthanide ion represents at least 1 equiv. of the total composition, or doped compounds where the lanthanide ions are only present as impurities in a defined matrix (thus representing a small percentage of the total composition). A typical example of a lanthanide-doped material is an inorganic phosphor. On the other hand, a typical example of a stoichiometric lanthanide compounds is a lanthanide complex where ideally all the lanthanide ions are surrounded by the same coordination sphere. 

Suppose that you are going to develop an ultraviolet-emitting phosphor based on a trivalent lanthanide rare earth ion doped crystal. If you want this phosphor... 

A number of other -alumina related phases have been prepared. In some of these the spinel blocks have an increased thickness, the so-called P, P" and P " phases, while in others, the Na or A1 components have been replaced with similar species. Related structures, such as BaMgAlnOiy doped with Eu +, are widely used as phosphors. Crystal-structure studies on such materials show that the defects present depend sensitively upon both temperature and the constituents of the phase. Large replacement ions, lanthanide or alkali metals, tend to occupy the interlayer regions as interstitial defects, but surprisingly, some also enter the spinel blocks as substitutional defects, in association with oxide ion vacancies. Smaller ions occupy the spinel blocks as substitutional point defects. The delicate balance between oxygen interlayer interstitials and spinel block cation vacancies varies with composition. These defect interactions can often be successfully explored by using simulation techniques. Ordering occurs at lower temperatures see Ionic Conductors). 

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