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ELECTRON TRANSFER FROM CHLOROPHYLL a TO QUINONE IN MONO‐ AND MULTILAYER ARRAYS
Author(s) -
Dodelet J.P.,
Lawrence M. F.,
Ringuet M.,
Leblanc R. M.
Publication year - 1981
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1981.tb05479.x
Subject(s) - fluorescence , quenching (fluorescence) , chemistry , analytical chemistry (journal) , excited state , photochemistry , electron transfer , chromophore , chlorophyll a , chlorophyll , flash photolysis , kinetics , reaction rate constant , chromatography , optics , atomic physics , physics , organic chemistry , biochemistry , quantum mechanics
— Mono‐ and multilayers of chlorophyll a (Chl a )– lecithin have been prepared on quartz slides, by means of the Blodgett‐Langmuir technique, for fluorescence studies. Self‐quenching of the Chl a fluorescence has been observed in Chl a ‐lecithin single layer excited with a laser light at 632.8 nm. The fluorescence yield is reduced by 50% at a concentration of 7 ± 10 12 Chl a molecules cm −2 . Chl a fluorescence quenching, by adding N,N ‐distearoyl‐1,4‐diaminoanthraquinone (SAQ), has been studied. in a single layer, in pure Chl a and also at various dilutions of Chl a in lecithin. The results are explained in terms of a dynamic quenching rather than in terms of a permanent complex formation, at the ground state, between Chl a and SAQ. The fluorescence quenching has been interpreted as the result of an electron transfer from excited Chl a to SAQ, and rate constants of 8.3 ± 10 −5 cm 2 molecule −1 S −1 and 2.4 ± 10 −4 cm 2 molecule −1 s −1 have been found for pure diluted Chl a , respectively. Ten per cent of the diluted Chl a fluorescence always remains unquenchable and independent of the quinone concentration. In multilayers, where SAQ and Chl a are in different layers, there is no fluorescence quenching for pure or diluted Chl a even when the chromophores are in two adjacent layers. This happens only if SAQ is not able to diffuse from one layer to another. A minimum value of 22.4 nm has been found for the singlet exciton diffusion length in pure Chl a multilayers.