Fluorescence of lanthanides

The aim of this work was to study the influence of a second ligand, the concentration and nature of surfactants on flumequine-sensitized fluorescence of lanthanides and the usage of such a mixed-ligand complex for fluorimetric determination of flumequine in hen meat tissues. 

Soini, E., and Lovgren, T. (1987) Time-resolved fluorescence of lanthanide probes and applications in biotechnology. CRC Crit. Rev. Anal. Chem. 18, 104-154. 

Eu(III) complexes of quinolinecarboxylic acids, including 5, were studied (00MI31). Those of complexes of 5 with Eu(III) and Tb(III) ion were studied, and they were applied for analysis of 5 in medicinal preparations (00UKZ115). Stability of lanthanide complexes with 5 was studied (00MI67). The fluorescence spectra of 5 complexed with Co(II) and ATP was measured (01SA(A)1317). 

Homogeneous Time Resolved Fluorescence (HTRF) (Cisbio International) is an assay based on the proximity of a lanthanide cryptate donor and a fluorescent acceptor molecule whose excitation wavelength overlaps that of the cryptate s emission. The utility of this technique is based on the time resolved fluorescence properties of lanthanides. Lanthanides are unique in the increased lifetime of their fluorescence decay relative to other atoms, so a delay in collection of the emission intensity removes the background from other fluorescent molecules. An example of the HTRF assay is a generic protein-protein interaction assay shown in Fig. 2. 

Lanthanide chelates also can be used in FRET applications with other fluorescent probes and labels (Figure 9.51). In this application, the time-resolved (TR) nature of lanthanide luminescent measurements can be combined with the ability to tune the emission characteristics through energy transfer to an organic fluor (Comley, 2006). TR-FRET, as it is called, is a powerful method to develop rapid assays with low background fluorescence and high sensitivity, which can equal the detection capability of enzyme assays (Selvin, 2000). 

Addition of lanthanide ions to dendrimer solutions showed that (a) the absorption spectrum of the dendrimer is almost unaffected, (b) the fluorescence of the dansyl units is quenched (c) the quenching effect is very large for Nd3+ (Fig. 7) and Eu3+, moderate for Er3+ and Yb3+, small for Tb3+, and very small for Gd3+ (d) in the case of Nd3+ (Fig. 7), Er3+, and Yb3+ quenching of the dansyl fluorescence is accompanied by the sensitized near-infrared emission of the lanthanide ion [42]. 

Although in this text they are not described as such, many of the applications described in section 3.5.6 fall into the category of luminescent signalling. For instance, the detection of in section 3.S.6.3, the measurement of pH in section 3.5.6.4, and the use of lanthanide chelates in DNA studies outlined in section 3.5.6.9 all use the change in fluorescence for both the signalling and quantification of the target. 

A novel approach for determining metal-metal distances in proteins in solution was applied to thermolysin by Horrocks et al. (16), As mentioned earlier, thermolysin has four Ca2+ binding sites. Three of the four can be replaced by trivalent lanthanide ions. Tb3 + fluorescence is enhanced when Tb3+ is bound to the so-called 1 Ca2+ site of thermolysin. When Co2+ is added to the Zn2 + active site, the fluorescence of bound Tb3+ is quenched by... 

The ternary complex formed by the reaction of lanthanide ions (La(III) and Y(III)) with 7-(l-naphthylamineazo)-8-hydroxyquinoline-5-sulfonic acid has been exploited for the fluorimetric determination of EDTA over the range of 2-20 pM. The fluorescence is measured at 525/350 nm [37], A similar method based on the reaction of Ca(II) with Fluo-3 and EDTA... 

Many applications of lanthanide materials make use of the 4f 15d excited configuration. These applications include scintillator materials, VUV lasers, and phosphors for fluorescent lighting and plasma displays (Blasse and Grabmaier, 1994 Feldmann et al., 2003). An understanding of these states is crucial to the development of advanced materials. 

Apart from Eu3+ and Tb3+, few studies have been reported on optical properties of lanthanide ions doped in ZnS nanociystals. Bol et al. (2002) attempted to incorporate Er3"1" in ZnS nanociystal by ion implantation. They annealed the sample at a temperature up to 800 °C to restore the crystal structure around Er3"1", but no Er3"1" luminescence was observed. Schmidt et al. (1998) employed a new synthesis strategy to incorporate up to 20 at% Er3"1" into ZnS (1.5-2 nm) cluster solutions which were stabilized by (aminopropyl)triethoxysilane (AMEO). Ethanolic AMEO-stabilized Er ZnS clusters in solutions fluoresce 200 times stronger at 1540 nm than that of ethanolic AMEO-Er complexes. This is explained by the very low phonon energies in ZnS QDs, and indicates that Er3+ ions are trapped inside chalcogenide clusters. However the exact position of Er3+ in ZnS clusters remains unknown. Further spectroscopic and structural analyses are required in order to obtain more detailed information. 

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