Intensity of phosphorescence

Quencher Q lowers the intensity of phosphorescence. The dependence of the light intensity of phosphorescence /ph on the quencher concentration obeys the Stern-Volmer equation... 

Photoinduced electron transfer from eosin and ethyl eosin to Fe(CN)g in AOT/heptane-RMs was studied and the Hfe time of the redox products in reverse micellar system was found to increase by about 300-fold compared to conventional photosystem [335]. The authors have presented a kinetic model for overall photochemical process. Kang et al. [336] reported photoinduced electron transfer from (alkoxyphenyl) triphenylporphyrines to water pool in RMs. Sarkar et al. [337] demonstrated the intramolecular excited state proton transfer and dual luminescence behavior of 3-hydroxyflavone in RMs. In combination with chemiluminescence, RMs were employed to determine gold in aqueous solutions of industrial samples containing silver alloy [338, 339]. Xie et al. [340] studied the a-naphthyl acetic acid sensitized room temperature phosphorescence of biacetyl in AOT-RMs. The intensity of phosphorescence was observed to be about 13 times higher than that seen in aqueous SDS micelles. 

The kinetics of the emission process has been developed in terms of excitation, emission, and collisional deactivation steps. If intramolecular energy-loss processes (IC or ISC) occur, then additional first-order terms must be added to the denominator of Eq. 24. A similar, but more complex and extended, steady-state treatment can be developed to predict the intensity of phosphorescent emission. 

The fluorescence efficiencies of aromatic molecules are reduced by heavy atom substituents such as bromine and iodine and by certain other groups such as aldehyde and keto as well as nitro groups. However, in many cases the substituents that decrease the intensity of fluorescence enhance the intensity of phosphorescence. Consequently, aromatic nitro compounds, bromo- and iodo-derivatives, aldehydes, ketones, and some A-heterocyclics tend to fluoresce very weakly or not at all. However, most of them phosphoresce quite intensely. On the other hand, many substituents that are electron donors such as amino, hydroxy, and methoxy often tend to increase the quantum yields of fluorescence of molecules to which they are attached. 

Figure 9. The decrease (curve 1) of the intensity of phosphorescence of 2,4,6-tribromophenylazide along with the irradiation of 84 00 cm light following me first order reaction rate (curve 2). Co means initial conceniration att—0.

Plots of ln(I -I ), where 1 is approximated in this study as the intensity of phosphorescence at 77K, provide apparent... 

FIGURE 2, Perrin plot of an Iq/I against concentration of cyclooctadiene (COD) for thermally oxidized poly(butadiene) in 1-1 tetrahydrofuran diethyl ether solution at 77K. Iq is intensity of phosphorescence from an ap-unsaturated carbonyl in absence of COD ... 

The relation between the intensity of phosphorescence emission and concentration is similar to that in Equation 9.6, but the full expression is more complicated [5, 6]. 

It is worth mentioning that while many metal ions form rigid complexes with 8-quinolinol-5-sulfonic acid, relatively few exhibit analytically useful fluorescence. This is due to the internal heavy atom effect and/or paramagnetism causing intersystem crossing, which is manifested (in some instances) by increased intensity of phosphorescence. 

This explains the linear portions of the Arrhenius plots shown in Figure 4. This equation is, however, inadequate in cases where Ip and Ip are of comparable magnitude. In these instances, use of eq. (8) will give activation energies which are too low. In some instances it is possible to approximate Ip by the intensity of phosphorescence at 77 K, Ip(77), which then can be substituted in eq. (7). 

The ternary complex often exhibits room temperature phosphorescence or exciplex emission. As the phosphorescence and exciplex emissions occur at longer wavelength than the normal fluorescence, one can follow the complexation from the intensity of phosphorescence or exciplex emission. In these case, 7° in Eq. (20) becomes zero and 7p or /exciplex is used instead of A/ in the equations equivalent to Eqs. (9) and (10) [26]. 

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