Abstract— 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 ± 1012 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 cm2 molecule−1 S−1 and 2.4 ± 10−4 cm2 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.
|Original language||English (US)|
|Number of pages||8|
|Journal||Photochemistry and Photobiology|
|State||Published - 1981|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry