Erythrosin, fluorescence

Figure 5. Relative quenching rate of erythrosin fluorescence t(0)/i(X), as a function of molar fraction of water (X) (18).

Bailey R.T., Cruickshank F.R., Deans G., Gillanders R.N., Tedford M.C., Characterization of a fluorescent sol-gel encapsulated erythrosine B dissolved oxygen... 

The second family ofxanthene dyes is fluorescein and its derivatives. Fluorescein itself is only slightly fluorescent in alcohol solution. In contrast, the alkali salt obtained by addition of alkali exhibits the well-known yellow-green fluorescence characteristic of the fluorescein dianion (uranin). Fluorescein and its derivatives, e.g. eosin Yand erythrosin Y, are known to be very sensitive to pH and can thus be used as pH fluorescent probes (see Chapter 10). 

Singlet lifetimes, fluorescence quantum yields, and singlet oxygen quantum yields are compared for Rose Bengal, Erythrosin, Eosin, and fluorescein in a number of different solvents in Table 11. In virtually every case water differs from the other solvents studied. 

Figure 4. Fluorescence kinetics of erythrosin in water measured by the streak camera-OMA system. The decay is a single exponential with a decay time of 78...

Fig. 19. (a) Fluorescence kinetics of erythrosin in water measured by a streak camera, (b) Single exponential nature of the fluorescence decay of erythrosin in solution. o> Full trace of the decay curve in (a) solid line has a decay time of 78 ps. The curve is arbitrarily shifted from the zero of the abscissa. (After ref. 67.)... 

In the vast majority of cases reported where a streak camera has been used to measure fluorescence lifetimes, the measurements have been made from a single laser shot. Since a high fluorescence efficiency is necessary for single shot experiments, most of these studies have been concerned with measuring the lifetimes and quenching of organic dye molecules in solution. For example, Yu etal. [67] have made a study of the fluorescence lifetime of malachite green as a function of solvent viscosity and the lifetime and relative yield of erythrosin as a function of water concentration in a water—acetone mixture. The fluorescence lifetimes of these dyes are... 

The fluorescence kinetics of erythrosin in water measured with the system described above is shown in Fig. 19. The fluorescence decay showed single exponential behavior with a lifetime of 78 ps. In acetone, the fluorescence lifetime was 2.4 ns. The lifetime varied linearly between 2.4 ns and 75 5 ps with the mole fraction of water in the acetone—water mixture. The quenching of fluorescence from erythrosin in acetone—water mixtures was interpreted in terms of the kinetics of solvent quenching and was attributed to a change in the intersystem crossing rate. 

The triplet-photochrome labeling method has been used to study very rare encounters in a system containing the Erythrosin B sensitiser and SITC photochrome probe (Mekler and Likhtenshtein, 1986). Both types of the molecules were covalently bound to a-chymotrypsin. The photoisomerisation kinetics was monitored by fluorescence decay of the frans-SITS. The rate constants of the triplet-triplet energy transfer between Erythrosin B and SITS (at room temperature and pH 7) were found k,r = 2 xlO7 NT s-1 and ktT = 107 M V. It should be emphasized that the concentration of the triplet sensitiser attached to the protein did not exceed 10 7 M in those experiments, and the collision frequencies were close to 10 s 1 which are 8-9 orders of magnitude less than those measured with the regular luminescence or ESR techniques. 

The commercial products known as erythrosin are iodine derivatives of fluorescein corresponding to eosins. The alkali-salts, which are the commercial products, are soluble in water, and possess a much bluer tone than the corresponding eosins, and their solutions do not exhibit the fluorescence characteristic of the latter bodies. 

Only three other time-resolved measurements of the fluorescence of dyes adsorbed- on wide bandgap semiconductor surfaces seem to have been reported to date. In the earliest of these, Kamat and Fox (19) investigated erythrosin B solutions containing TiOj colloidal particles. The decays followed [9], with in the 0.20 - 0.36 ns range attributed to adsorbed dye, guite similar to our results for rhodamine B on SnOj and 10203. On the other hand, the results of Kamat and Fox are in sharp contrast to those of Itoh et al. (16), who found that sputtered TiOj thin film surfaces had almost no effect on the fluorescence of rhodamine B. This may mean that some physical or chemical characteristic of these poorly defined surfaces is more important than the identity of the semiconductor. 

The picosecond kinetics of tetracene dianions have been studied using a new extension of picosecond spectroscopy methods.100 The rise times of the Stokes-shifted fluorescence from rhodamine B, rhodamine 6G, and erythrosine dissolved in water have been investigated using picosecond techniques. Figure 4 schematically indicates the situation following excitation. The best fit to the data corresponds to a relaxation time within the vibronic manifold of S of <1 ps.101 Although these fast spectroscopic techniques provide direct means of examining the behaviour of short-lived species, indirect methods are more convenient and often quite successful. Such is the case for the determination of rf from calculated radiative rate constants and measured Of values for a series of cyanine dyes.102... 

---