The quenching of anthracene fluorescence

Abstract

The quenching of the fluorescence of anthracene excited by light of wave-length 3650 Å by oxygen, sulphur dioxide, and by carbon tetrabromide, has been investigated both in the gaseous state and in paraffin solutions of viscosities from 0·003 to 1·9 poises. In the gaseous state quenching occurs on nearly every collision. The quenching in dilute solution is shown to be controlled ( a ) by static quenching whereby light is absorbed by anthracene molecules contiguous to quencher molecules, and ( b ) by the diffusion together of excited molecules and quencher molecules. The former process is of greater importance in solutions of high viscosity. The latter predominates at more usual viscosities, and is found to be more nearly proportional to the diffusion coefficient of anthracene than to the fluidity of the solvent. Measured diffusional quenching constants are in good agreement with calculated values. The magnitudes of static constants indicate that in solutions containing anthracene and a quenching substance the two solutes are not randomly distributed but tend to associate with one another.

Photophysical and Photochemical Studies of Polycyclic Aromatic Hydrocarbons in Solutions Containing Tetrachloromethane. III. Photochemical Interaction of Excited Polycyclic Aromatic Hydrocarbons with Tetrachloromethane in Two-Component Mixtures

“…For instance, the rate constant of the fluorescence quenching is higher in methanol than in hexane. This confirms the participation of the exciplex in fluorescence quenching [10,[13][14][15]29]. In many solvents, whose electric permeabilities differ from that of CC14.…”

“…The re action course via the exciplex for reactions of perylene and benzopyrene with CC14 was detected by Encinas et al [13]. Such a reaction mechanism had been ad vanced earlier by Bowen and Metcalf [14] as well as by Lewis and Ware [15] on the basis of the results of fluorimetric measurements.…”

“…Fhe correlation between the quantum yield of fluorescence and that of the photochemical reaction supports a mechanism, postulated by different au thors, involving participation of the hydrocarbon in its first singlet excited state in the photochemical reaction [6,10,[13][14][15], Bromobenzene quenches the fluorescence of anthracene, thus raising the efficiency of intersystem transition [26], Fhe similarity of the slopes of the fluorescence quenching and of the reac tion of anthracene by bromobenzene in all the mix tures confirms the suggestion that the photoaddition of CC14 to anthracene starts from the excited singlet state of the hydrocarbon [20. 29], The start of the reaction from the state of the hydrocarbons enables the explanation of the relation ship between the quantum yield of hydrocarbon de crease and CC14 concentration on the basis of the fluorescence quenching curves.…”

Vertical fluctuations of phospholipid acyl chains in bilayers

“…For the 'active sphere' model of static quenching [15], instantaneous quenching is assumed to occur if the quencher molecule approaches to within a given radius of the fluorophore. The radius of this sphere is characteristic for a given fluorophore/ quencher pair.…”

“…For the active sphere model of static quenching, V is related to the radius (R) of the sphere by the approximation, R = (400I/) 1/3 [15]. Combining eqns 1 and 2 provides:…”