Polarized fluorescence, First demonstrated

With respect to fiber-optic-based fluorescence sensing, most of the past approaches have employed either excitation or emission wavelength selectivity (10,11). The other selectivity parameters fluorescence lifetime, steady-state polarization, and rotational diffusion rates have received little if any attention. The acquisition of fluorescence lifetime information via optical fibers has been demonstrated previously (12) however, the time resolution and ability to resolve multiexponential decays of fluorescence were neither demonstrated nor possible with this earlier instrument. Recently, our own group (13,1 ) has developed and described the first fiber-optic-based fluorescence lifetime instrumentation capable of unequivocally determining single, double, and/or triple exponential decays of fluorescence in remotely-located samples. 

The first systems without anomalous fluorescence discussed in the context of TICT states were coumarine laser dyes. Jones and coworkers208210 demonstrated that dialkylaminocoumarines like 7C showed an increase of the nonradiative decay rate in strongly polar solvents. This effect is dramatically increased if the acceptor properties of the coumarine skeleton are stronger, for example, in F7C. On the other... 

Even if the described system demonstrated an unexpected selectivity for Cu " ions, it is obvious that the modification of the outer shell of silica with other functional groups could increase the affinity of the system toward the desired metal ion, as the same authors have demonstrated for another self-organized fluorescent nanosensor able to detect Pb " ions [108]. Mancin et al. prepared in this case three different batches of DDSNs always following the StoberA an Blaaderen procedure. The first ones (about 50 nm in diameter) presented dansyl units covalently bound inside and a surface coated with (mercaptopropyl)tiiethoxy-Isilane (MPS). These particles are soluble in polar solvents (including water) and their photophysical properties are typical of the dansyl dye. The presence of thiols... 

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