Luminescence luminescent sensitizers

THE DETERMINATION OF COPPER MICROAMOUNTS ON THE TERBIUM LUMINESCENCE SENSITIZED BY IT IN HETEROBINUCLEAR COMPLEX... 

The complex [Os(tpy)(tact-tpy)]2+ was examined in detail for potential application as a luminescence sensor. The complex emission was demonstrated to be sensitive to Cu2+ and Ni2+ in mixed aqueous acetonitrile solutions. The Ni2+ complex serves as a sensor for the anions ATP, AMP, and Cl . Finally, the authors demonstrated that sol-gel silica films containing the complex exhibited luminescence sensitive to oxygen [109]. 

As it is well known, sensitization of Ln-centered luminescence can be achieved via an intramolecular energy transfer upon excitation of organic ligands, instead of using direct excitation of the weak Lnm absorption bands. This phenomenon now called antenna effect or luminescence sensitization has first been observed in 1942 by Weissman for europium(III) complexes formed with salicylaldehyde and with /3-diketonates, more particularly benzoyl-acetonate (ba, 48a), dibenzoylmethanate (dbm, 48b) and wieta-nitrobenzoylacctonatc (47a, fig. 41) (Weissman, 1942). 

The first example of Ndm and Ybm luminescence sensitized by Ru11 and ferrocene appeared in 2000. The authors noticed that [Ru(bpy)3]2+ has an intersystem crossing yield near unity and that it enables excitation with visible light up to 500 run. On the other hand, ferrocene has weaker absorption bands in the visible spectrum, but its low-lying triplet state (wl3 300 cm-1) matches fairly well the Ndm (4F3/2, 11300 cm-1) and Ybm (2Fs/2,... 

To assess the effect of distance between the antenna chromophore and the Eu(III) center on luminescence sensitization, a series of four additional Eu(III) complexes, of ligands 57-60, each having the pendant phenanthridyl group at a different distance from the Eu(III) center, have been synthesized for comparison with [Eu(46)] + (76). 

Since the dipole strength of/-/ transitions are formally forbidden, typically, these extinction coefficients are of the order of 1 M cm an alternative path has to be used which is called luminescence sensitization or antenna effect, that is when the luminescent ion is coordinated with an organic ligand or imbedded into a matrix, then the energy absorbed will be transferred from the surrounding onto the luminescent ion and subsequently the ion emits characteristic light. 

Energy transfer from the ligand, evidenced for the first time in 1942 by Weissman (1942), is often referred to as the antenna effect (Sabbatini et al., 1996) or luminescence sensitization (Biinzli and Piguet, 2005). The overall quantum yield of the metal luminescence upon ligand excitation can be separated into three components characterizing successively (1) the rate constant =kf Q hiplet states) for the... 

We now report time-resolved and steady-state measurements of phthalocyanine luminescence sensitized by singlet oxygen dimols, produced both by photosensitization and by thermal processes the detailed kinetics strongly support Scheme 2. 

Law G-L, Wong K-L, Kwok W-M, Wong W-T (2007) Tanner P A (2007) Terbium luminescence sensitized through three-photon excitation in a self-assembled unlinked antenna. J Phys Chem B 111 10858-10861... 

Figure 2.14 Spectral characteristics of luminescence observed for Nonox Cl. (1) Excitation and emission spectra at room temperature, sensitivity scale 0.01, (2) excitation and emission spectra at -196 °C for total luminescence, sensitivity scale 0.01, (3) excitation and emission spectra at -196 °C for phosphorescence, sensitivity scale 0.01 Reproduced from Kirkbright and co-workers, Elsevier [86]...

Most of the basic principles needed to approach the luminescence of the lanthanide ions have been described. Luminescence is a fascinating phenomenon, but as it was shown, very intricate because many processes are involved. Therefore, the design of highly luminescent lanthanide compoimds and especially of highly luminescent-sensitized lanthanide complexes is quite unpredictable. From a theoretical point of view, the efficiency of the luminescence can always be associated with one particular feature of the environment of the lanthanide ion. It may be solvent molecules... 

The use of strongly absorbing d-block chromophores as sensitizers for the NIR emissions from lanthanide ions has attracted increasing attention since the first report by van Veggel and coworkers on the Nd + and Yb + luminescence sensitized by Ru(bpy)j+ and ferrocene in 2000. Subsequently, many d-block chromophores, based on related transition metals, such as R +, Ru +, Re+, Os +, Pd, Zn +, Cr +, and Co +, have been extensively studied in sensitizing the NIR emissions of lanthanide ions (i.e., Nd +,... 

Eliseeva S. V., D. N. Pleshkov, K. A. Lyssenko, L. S. Lepnev, J.-C. G. BtinzU, N. P. Kuzmina. Deciphering three beneficial effects of 2,2 -bipyridine,V,V -dioxide on the luminescence sensitization of lanthanide(III) hexafluoroacetylacetonate ternary complexes, Inorg. Chem., 50, 5137-5144 (2011). 

The sensitivity of the luminescence IP s in the systems employed here decreases with increasing x-ray energy more strongly than in the case of x-ray film. Therefore, this phenomenon must be compensated by using thicker lead front and back screens. The specific contrast c,p [1,3] is an appropriate parameter for a comparison between IP s and film, since it may be measured independently of the spatial resolution. Since the absorption coefficient p remains roughly constant for constant tube voltage and the same material, it suffices to measure and compare the scatter ratio k. Fig. 2 shows k as a function of the front and back screen thickness for the IP s for 400 keV and different wall thicknesses. The corresponding measured scatter ratios for x-ray films with 0,1 mm front and back screens of lead are likewise shown. The equivalent value for the front and back screen thicknesses is found from the intersection of the curves for the IP s and the film value. 

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