Probes luminescence lifetime

The commercialization of inexpensive robust LED and laser diode sources down to the uv region (370 nm) and cheaper fast electronics has boosted the application of luminescence lifetime-based sensors, using both the pump-and-probe and phase-sensitive techniques. The latter has found wider application in marketed optosensors since cheaper and more simple acquisition and data processing electronics are required due to the limited bandwidth of the sinusoidal tone(s) used for the luminophore excitation. Advantages of luminescence lifetime sensing also include the linearity of the Stem-Volmer plot, regardless the static or dynamic nature of the quenching mechanism (equation 10) ... 

In the transition metal polypyridyl complex group, tris(4,7-diphenylphen-antroline) ruthenium(II) (Ru(dpp)2+) is widely used as a probe for a PSP. The luminescence lifetime of Ru(dpp)2+ is long compared with the other ruthe-nium(II) polypyridyl complexes [17]. The absorption and emission maxima of Ru(dpp)2+ are 457 and 610 nm, respectively. The luminescence lifetimes under nitrogen- and air-saturated conditions are ca. 4.0 and 2.0 ps, respec-... 

Luminescence decay curves are also often used to verify that samples do not contain impurities. The absence of impurities can be established if the luminescence decay curve is exponential and if the spectrum does not change with time after pulsed excitation. However, in some cases, the luminescence decay curve can be nonexponential even if all of the luminescing solutes are chemically identical. This occurs for molecules with luminescence lifetimes that depend upon the local environment. In an amorphous matrix, there is a variation in solute luminescence lifetimes. Therefore, the luminescence decay curve can be used as a measure of the interaction of the solute with the solvent and as a probe of the micro-environment. Nag-Chaudhuri and Augenstein (10) used this technique in their studies of the phosphorescence of amino acids and proteins, and we have used it to study the effects of polymer matrices on the phosphorescence of aromatic hydrocarbons (ll). 

Luminescence of metal complexes is widely applied (eg to sensors or luminescent probes [17,24,25,29,35,36]) the effects of components (chromophores) and ambient medium (solvents) on its lifetime have been intensively studied. To prolong luminescence lifetime, metal complexes have recently been built into supramolecu-lar systems [24, 37,38],... 

With this understanding, the spectra of Eu could probe the microstructure of nanomaterials, because the Dq to Fi transition was very sensitive to the site symmetry. Yan et al. used laser selective excitation technique to research the high-resolution spectra of f-YV04 Eu NPs (Yan et al., 2003a). When the Eu dopants approach the NPs surface, the D2d symmetry is broken. In emission spectra this is reflected by several points the increased number of emission lines the shortened luminescent lifetime, the enhanced splitting of energy levels, and the broadened emission peaks. 

There is an impressive battery of spectroscopic techniques available for probing interactions between metal complexes and DNA. The oldest of these, UV/vis spectroscopy, is still one of the most sensitive ways to analyze dye-DNA interactions. For chiral metal complexes, circular dichroism is an invaluable tool. Fluorescence spectroscopy has in particular made great strides in recent years with respect to these applications, and aside from the measurement of simple emission from an excited metal complex, one can utilize emission polarization, luminescence lifetimes, and differential fluorescence quenching to obtain still more information about the environment about a metal complex. The application of ruthenium complexes, in particular, to developing probes for DNA, has been initiated in our laboratory and we focus here on some of its applications. 

The luminescent lifetime of the anhydrous compound has also been studied but no definitive result was obtained. The authors concluded this paper saying that the anhydrous microporous phase presenting ID channels can be potentially considered as luminescent probe for detecting small molecules. That is the reason why two years later another group published another paper on this family. In this paper (Pan et al., 2001) the synthesis, via hydrothermal method, and the crystal stracture (see fig. 12) of a compound with chemical formula Er4(bdc)6-6H20 are described. 

Keywords Luminescence lifetime Luminescent probe Optical sensor... 

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