Lanthanide ions sensors

Keywords Luminescence Energy transfer Electron transfer Lanthanide ions Sensors. 

The aim of this chapter is limited to reviewing some recent developments concerning luminescent dendrimers that can play the role of ligands and sensors for luminescent and nonluminescent metal ions, mainly investigated in our laboratories, with particular references to transition metal or lanthanide ions. We will not discuss dendrimers constituted by polypyridine metal complexes [21] and porphyrins [22] since it is outside the scope of the present paper. 

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... 

Cation recognition by luminescence sensing has also been reported. As referred to above, release and recapture of alkali and alkaline earth metal ions for [(bpy)Re(CO)3L ]+, where Lj contains an azacrown ether [63] was controlled by light. A sensor for lanthanide ions is shown in Fig. 27. The photoactive center was RcI( bpy ) and its emission was quenched by the lanthanide ion [119]. 

Although the conductivity of the trivalent-ion / ""-aluminas is too low for solid electrolyte applications (e g. batteries, sensors), they have potential use in optics, phosphors, and lasers because they can serve as single crystal or powder hosts for the optically active lanthanide ions. For example, Eu +-/3""-alumina emits red luminescence when excited by UV rays. A Nd +-/3""-alumina single crystal shows luminescent... 

Ancillary ligands can dramatically improve detection strategies based on sensitized Ln luminescence by stabilizing the lanthanide to pH variations. Such enhancements in stability and reproducibility allow the use of lanthanide sensors in situ and also potentially in vivo, where free lanthanide ions might precipitate and/or have toxic effects. 

Figure 13.4 Typical design principle of lanthanide complex-based chemosensors based on binding of an analyte (an) (a) directly influencing the Ln(III) luminescence, (b) influencing photophysical properties of the ligand, and (c) addition of a sensitizing analyte onto a poorly luminescent lanthanide-containing sensor [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.)...

The luminescence of lanthanide ions in solids has been the subject of several books or chapters [1-12] and has an immense scope. Since 1 was asked to write this review within a short time, I have failed to give a comprehensive survey but have given a qualitative overview of several areas with some references to more quantitative treatments. Topics such as lanthanide luminescence of laser materials [4,8,13,14], sensors [15], hybrid materials [16], organolanthanide, and coordination compounds [17] are missing. So what is here in October 2009 - basically, a description of the luminescence spectra of lanthanide ions in the solid state and some applications of phosphor materials. 

The hypersensitivity of certain emission bands turns LLCs into promising candidates as probes for analytes such as anions, pH, oxygen, nucleic acids, DNA, proteins, cofactors and coenzymes. The number of probes that have been reported in literature is rather large. Therefore, this chapter is confined to complexes with the capability to be applied in sensor devices. Foremost, they have to be respraisive in aqueous solution at a pH range from 6 to 9. Furthermore, this overview does not cover lanthanide systems in which the analyte itself actuates as sensitizer for the lanthanide ion. This principle can be used for the determinatirHi of antibiotics in aqueous solution [15-17]. 

LLCs are promising candidates as probes for humidity sensors due to the distinct quenching effect of water molecules which can reversibly coordinate to lanthanide ions. The decrease in lifetime of the Dq transititMi of europiumflll) perchlorate was used for the determination of small amounts of water in DMF and DMSO [106]. Wang and Li have presented luminescent nanospheres for die determination of small amounts of water (0.05-3.0 vol%) in ethanol [107]. They coated silica nanoparticles with a thin layer of a salicylic acid-La /Tb " coordination compound. The green fluorescence peaking at 549 nm corresponds to the D4 transition of Tb and is strongly quenched by trace amounts of water. The nanoparticles can be excited at wavelengths around 350 nm. 

The responses of LLCs to organic (bio)molecules capable of coordinating to the lanthanide as additional ligand have been outlined in Chap. 2.2. Examples have been shown for ATP or NADP. The plurality of these interactions indicates the problems of sensors including lanthanide complexes as receptors for the specific recognition of a certain analyte. The same is the case for free lanthanide ions that have been presented for the luminescent determination of pharmaceutically active compotmds such as antibiotics [15-17]. Nevertheless, Molina-Diaz et al. have... 

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