Luminescent lanthanide ions

Figure 3 Energy level diagram for selected luminescent lanthanide ions.

Assays based on luminescent lanthanide ions were developed initially in the 1970s, when instrumentation became available which could distinguish long-lived luminescence from a shortlived background. Leif and co-workers reported the first attempts to use lanthanide complexes (in this case europium complexes with 1,10-phenanthroline and 7-diketonates, i.e., [Eu(phen)(diketo-nate)3]) as tags for antibodies.107 These proved kinetically unstable in the pH regime required... 

For some recent reviews, see (a) Leonard JP, Nolan CB, Stomeo F et al (2007) Photochemistry and photophysics of coordination compounds lanthanides. Top Curr Chem 281 1-43 (b) Biinzli J-CG, Piguet C (2005) Taking advantage of luminescent lanthanide ions. Chem Soc Rev 34 1048-1077 (c) Parker D (2000) Luminescent lanthanide sensors for pH, p02 and selected anions. Coord Chem Rev 205 109-130... 

Biinzli, J.C.G and Piguet, C. (2005) Taking advantage of luminescent lanthanide ions. Chemical Society Reviews, 34, 1048-1077. 

Steemers, F.J., Verboom, W, Reinhoudt, D.N., et al (1995) New sensitizer-modified calix[4]arenes enabling near-UV excitation of complexed luminescent lanthanide ions. Journal of the American Chemical Society, 117, 9408-9414. 

VicinelU, V, Ceroni, R, Maestri, M., etal. (2002) Luminescent lanthanide ions hosted in a fluorescent polylysin dendrimer. Antenna-Uke sensitization of visible and near-infrared emission. Journal of the American Chemical Society, 124, 6461. 

Figure 13.2 Principles of (a) time-resolved spectroscopy, (h) heterogeneous immunoassays, and (c) homogeneous immunoassays [1]. (Reproduced from J.C.G Bunzli and C. Piguet, Taking advantage of luminescent lanthanide ions, Chemical Society Reviews, 34, 1048—1077, 2005, by permission of The Royal Society of Chemistry.)...

For coordinating and sensing luminescent lanthanide ions, a luminescent ruthenium bipyridyl complex has been covalently linked to one, two or six lower rim acid-amide modified caUx[4]arene moieties in receptors 155-157. All these complexes coordinated with lanthanide ions, Nd , Eu and Tb, with the formation of adducts of variable stoichiometries. The adduct formation affected the Ru luminescence, which was strongly quenched by Nd ion, increased by the Tb ion and moderately quenched or increased by Eu ion (2004IC3965). 

Near-Infrared Luminescent Lanthanide Ions in Inorganic Nanoparticles. 150... 

Excitation of Near-hifrared Luminescent Lanthanide Ions and Complexes. 152... 

The lifetime data contains a range of different ligand systems, in different solvents, and is only intended as an indication of usually observed values. As will be explained below, the surrounding ligand and solvent have profound effects on the non-radiative deactivation of NIR luminescent lanthanide ions. 

Concerning the luminescence of the second group of NIR luminescent lanthanide ions, the ions Tm and Ho " display even weaker luminescence in solution than Nd and Er, and the luminescence of their complexes has only... 

One recent example of the sensitisers proposed specifically for NIR luminescent lanthanide ions is azulene, which is a chromophore that has long fascinated photochemists [36]. Its use may have been inspired by scientific curiosity as azulene has only a modest absorption in the red, and more powerful sensitisers do exist. Another recent example is the curcuminoids [51], which are molecules of natural origin (constituents of curcuma or turmeric). The use of naturally occurring chromophores with the NIR luminescent ions is reminiscent of the application of naturally occurring dipicolinic acid and salicylic acid with Eu and Tb, which were among the very first chromophores to be used for the photosensitisation of lanthanide ions. 

Luminescent lanthanide ions have numerous practical applications in chemistry and technical devices, some of them involving electrical excitation of the lanthanide ions. Photophysical properties of lanthanide ions as well as perhaps the most important application field, photoluminescence of lanthanide chelates, and lanthanide-containing nanoparticles are treated elsewhere in this volume. 

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