ROOM TEMPERATURE TIME‐RESOLVED IN μs RANGE DELAYED LUMINESCENCE OF CHLOROPHYLL a AND CHLOROPHYLL‐LUTEIN MIXTURE SOLUTIONS

Planner, A.; Fra̧ckowiak, D.

doi:10.1111/j.1751-1097.1991.tb02039.x

Cited by 24 publications

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“…One cannot exclude some influence of PVA on the electron trapping in our experiments, but it is not the crucial effect for DL gen-eration, because of the similar features of Chl DL in PVA and other media. 2 On the basis of the absorption and emission spectra it seems that more than one type of emission center is responsible for the DL emission of both Chl and Rhod samples.…”

Section: Discussionmentioning

confidence: 99%

“…The molecular mechanism responsible for the generation of Chl a D L in solution is as yet unclear. 2 The observed bands o f D L are related t o various aggregated forms of Chl. In general the D L can be related to several molecular mechanisms such as the thermally activated triplet-singlet transition (type a-DL), the transition from triplet to singlet ground state (type @-DL), recombination of light-induced radical pairs or annihilation of singlet or triplet excitonsf8(type P-DL) ( Fig.…”

Section: Introductionmentioning

confidence: 94%

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DELAYED EMISSION OF CHLOROPHYLL a AGGREGATES AND RHODAMINE 6G EMBEDDED IN POLYMER MATRIX*

Fra̧ckowiak

Planner

Goc

1993

Photochem & Photobiology

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Delayed luminescence (in the microsecond time range) of the chlorophyll (Chl) a“dry” form as well as hydrated dimers located in a polyvinylalcohol film was measured from room temperature down to 8 K. In the same matrix the delayed luminescence of rhodamine 6G (Rhod) was investigated. The delayed emission both of Chl a and Rhod is probably due to the formation and delayed recombination of a radical pair. It seems that this process occurs without participation of triplet states, as it does not reflect their well‐known sensitivity to oxygen. The temperature dependence of the delayed luminescence of vanous Chl forms is different. In the region around 678 nm (dry monomer) delayed luminescence needs a thermal activation energy of about 0.03 eV, whereas at 740 nm (wet aggregates) delayed luminescence intensity increases linearly with decreasing temperature. Its assignment as a‐type delayed luminescence from the low‐lying triplet state can consistently be excluded from both the weak temperature dependence of the delayed fluorescence and its large intensity as compared to the prompt fluorescence. Delayed luminescence of Rhod is almost independent of temperature between 8 K and 300 K. The dependence of delayed luminescence intensity on exciting light intensity is linear at lower intensities and tends to saturation at higher. Therefore the delayed luminescence is not related to exciton annihilation. Positions and intensities of the Chl delayed luminescence bands show that it is not phosphorescence (β‐type delayed luminescence). The aggregation of both Chl and Rhod molecules strongly influences delayed luminescence since it differs in several properties if excited in the monomer or in the aggregate absorption range. Every aggregational form of dye emits its characteristic delayed luminescence band.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%