Fluorophores lanthanide complexes

These systems are promising as potential labels due to high emission quantum yields and excited-state lifetimes that can be as long as several tenths of a millisecond (108). A cyclen (12-ane-N4) unit connected to a phenanthridine moiety in fluorophore-spacer-receptor conhguration (Fig. 26) exhibit strong Tb(III) based luminescence (109) in the absence of protons and oxygen. Few other luminescent lanthanide complexes are available in the literature (110,... 

Another important parameter is the photostabUity of the luminophores as this determines the total number of photons that will be emitted by the complex before it is destroyed by a photoinduced process. Data on the photostability of lanthanide complexes is very scarce. The photostabUity of lanthanide complexes is expected to be superior to that of organic fluorophores since the excitation energy only remains on the organic ligand a very short time before it is transferred to the lanthanide ion, which usually does not undergo any photochemical transformations. 

In theory, the photostability of luminescent lanthanide complexes should be superior to the photostabihty of purely organic chromophores since excited lanthanide ions do not undergo photochemistry, and the energy transfer from the antenna chromophore to the lanthanide ion deactivates any organic excited states that would give rise to destructive photochemistry. Direct comparison of the photostability of NIR luminescent lanthanide complexes and organic fluorophores has not yet been carried out. 

Keywords Amplification Fluorescent reporter Fluorophore FRET In vitro In vivo Labeling Lanthanide chelate Multiplexing Nanoparticle Quantum dot Transition metal complex... 

The use of europium chelates, with their unusually long fluorescence decay times, as labels for proteins and antibodies has provided techniques that are referred to as time-resolved fluoroimmunoassays (TRFIA). Fluorophores as labels for biomolecules will be the topic of Sect. 3. Nevertheless, TRFIAs always have to compete with ELISA (enzyme-linked immunosorbent assays) techniques, which are characterized by their great versatility and sensitivity through an enzyme-driven signal amplification. Numerous studies have been published over the past two decades which compare both analytical methods, e.g., with respect to the detection of influenza viruses or HIV-1 specific IgA antibodies [117,118]. Lanthanide luminescence detection is another new development, and Tb(III) complexes have been applied, for instance, as indicators for peroxidase-catalyzed dimerization products in ELISAs [119]. 

The rate constants contain contributions from the radiative and nonradiative transitions. The stimulated emission is neglected. One example of systems 1 and 11 is a donor-acceptor complex where the donor is a lanthanide ion and the acceptor an organic fluorophore. An experimental example of this energy transfer system will be given at the end of this chapter. 

The water-soluble assemblies, which were encapsulated in lanthanide nanoparticles by an amphiphilic polymer shell containing photochromic dithienylethenes, were prepared. Fluorescence emission in the visible region was observed, when the assemblies were excited with NIR at 980 nm. The emission could be controlled by the photoswitch of the dithienylethenes. Photoswitchable nanoparticles constructed with the Ir complex (110) as a fluorophore and the dithienylethene (111) were developed. The fluorescence photoswitching of the... 

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