Fluorescence quenching, time-resolved

The probe molecule pyrene (-10"6 M) was used in time-resolved fluorescence quenching experiments using a single photon counting apparatus, cetylpiridinium chloride (CpyC, 10"3 M) being introduced as a quencher of the pyrene fluorescence[ll-13]. All the experiments were performed at 303K. From these fluorescence studies the micelle aggregation number (N) and the pyrene fluorescence lifetime (x) were obtained [14]. 

Karvinen, J. et al. 2002. Homogeneous time-resolved fluorescence quenching assay (LANCE) for caspase 3. J. Biomol. Screen. 1, 223-231. 

The ratio of the slope above to the slope below the cmc provided an estimate of P [7]. The binding constant was also used to estimate the concentration of alcohol in the bulk phase. Time resolved fluorescence quenching of dimethylnaphthalene by cetylpyridinium bromide solubilized in the micelles was used to obtain estimates of the mean aggregation number of the surfactant in the mixed micelles. 

Fluorescence techniques were used to study micelles in clear solutions. Time-resolved fluorescence quenching (recording of the fluorescence decay curves on a single photon counting apparatus) was used to determine the pyrene (used as the probe molecule) fluorescence lifetime (t). Micelle aggregation numbers (N), which correspond to the number... 

Molecular assemblies in anionic environments influence the efficiency of fluorescence quenching by electron transfer . Viseu and Costa use a combination of steady state and time resolved fluorescence quenching data to evaluate partition coefficients of fluorescent molecules into micelles. The breakdown of rod-like micelles and light induced viscosity changes in micelles are effects that can both be induced by isomerization of azo-compounds in a variety of surfactants. ... 

In both the procedures, by varying to, the dimensions of the synthesised particles can be altered. The pictorial representations of the above protocols are illustrated in Fig. 6.2. As can be seen, the internal phenomenon of droplet fusion followed by fission takes place. The materials formed during fusion by reaction get distributed among the droplets upon fission. By probability, some droplets may remain empty which is more in dilute solution of the reactants. The occurrence of the process of fusion and fission has been established by the TRFQ (time-resolved fluorescence quenching method [ 18-20]). The internal dynamics of the disperse particles essentially guide the formation characteristics of nanoparticles. 

Hansson P, Almgren M. Polyelectrolyte-induced micelle formation of ionic surfactants and binary surfactant mixtures studied by time-resolved fluorescence quenching. J Phys Chem 1995 99 16684—16693. 

Type B PCET systems of Fig. 17.3 may also be assembled using the three-point hydrogen bond of Watson-Crick base pairs such as guanine (G) and cytosine (C). Sessler and coworkers provided the first example of this assembly with 5, for which only energy transfer is observed [101,102]. A Type B PCET is realized when the cytosine of the GC base pair is appended with an Ae functional group. In 6, a Zn porphyrin serves as De and p-benzoquinone as Ae [103]. Time resolved fluorescence quenching experiments reveal that the rate of ET across the GC interface... 

Time-resolved fluorescence quenching has been applied to measurement of degrees of aggregation of SDS and 1-pentanol in... 

M. Gehlan and F. C. DeSchryver, Time-resolved fluorescence quenching in micellar assemblies. Chem. Rev., 93 (1993), 199-221. 

This name is preferred to time-resolved fluorescence quenching, because phosphorescence is sometimes involved. 

Static fluorescence quenching has been used to measure the mean aggregation number of surfactant-related systems [27-29]. This method was originally developed by Turro and Yekta for anionic surfactant micelles [30]. This method works well without significant errors when kjk1 and no quencher redistribution has taken place. On the other hand, fluorescence-decay experiment, namely, time-resolved fluorescence quenching (TRFQ), has been extensively used to determine the micelle aggregation number in a surfactant system. The reader is referred to the review [24] on this subject. 

Electron-transfer theories (11) predict that the highly exothermic production of the ground states proceeds in the inverted region. This allows the formation of the excited state to be kineticaUy competitive with other non-radiative pathways which are predicted to occur near the diffusion-controlled limit. Time-resolved fluorescence quenching has commonly... 

Zana, R., W. Binana-Limbel, N. Kamenka, and B. Lindman (1992). Ethyl (hydroxyethyl) cellulose-cationic surfactant interactions Electrical conductivity, self-diffusion and time-resolved fluorescence quenching investigations. The Journal of Physical Chemistry 96(13) 5461-5465. 

We have seen earlier that the microemulsion formation is a spontaneous process which is controlled by the nature of amphiphile, oil, and temperature. The mechanical agitation, heating, or even the order of component addition may affect microemulsification. The complex structured fluid may contain various aggregation patterns and morphologies known as microstmctures. Methods like NMR, DLS, dielectric relaxation, SANS, TEM, time-resolved fluorescence quenching (TRFQ), viscosity, ultrasound, conductance, etc. have been used to elucidate the microstructure of microemulsions [25,26]. 

By using the information obtained when the emission of the probe molecule is quenched, i.e. either by eximer formation of the probe itself or by addition of a molecule that quenches the exited state of the probe, it is possible to further characterize the system in terms of micellar shape. This is a technique frequently used in a wide variety of systems, including binary water-surfactant or polymer-surfactant systems, or microemulsions. Two methods are worth extra attention, namely the steady-state fluorescence quenching (SSFQ) and the time-resolved fluorescence quenching (TRFQ) methods. For more comprehensive texts describing these techniques, the reader is referred to refs (21) and (22). 

Alargova, R. G., Kochijashky, I. I., Sierra, M. L. and Zana, R., Micelle aggregation numbers of surfactants in aqueous solutions A comparison between the results from steady-state and time-resolved fluorescence quenching, Langmuir, 14, 5412-5418 (1998). 

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