Determination of the Quantum Yield of Intersystem Crossing of Rose Bengal

Abstract

The quantum yield of intersystem crossing (@is3 of a sensitizer is related to the quantum yield of singlet-oxygen production (@(lo2)) by the efficiency of the energy transfer (pet) and is an important parameter in the evaluation of potential applications of sensitized photo-oxidations. Using two different laser photolysis techniques, the energy-transfer method and the partial saturation method, @,% of rose bengal has been determined in MeOH and in aqueous solutions. The results confirm that with bi,(H20) = 1.05( * 0.06) and Qi,(MeOH) = 0.9q f 0.08), the generally assumed relation eiSc.pet = @(lo2), with pet = 1, cannot be maintained any longer (@('O,, H20) = 0.75 and @(lo2, MeOH) = 0.76). During these experiments, a second intermediate has been observed which is produced from the triplet state of rose bengal and, stabilized in a anionic micellar solution, has been shown to be the radical cation of the sensitizer. The efficiency of the electron transfer has heen evaluated from transient absorption and bleaching recordings, and it seems conclusive to attribute the results to the difference between @i% and @('02).Introduction. -In the domains of photophysics and photochemistry, dye-sensitized photo-oxidations [ 1-61 are increasingly investigated because of their many potential applications in photobiochemistry, photobiology, and photomedicine [7-101. Most often, singlet oxygen is claimed to be the reactive species; it is produced by energy transfer from the triplet state of the sensitizer (dye) to ground-state molecular oxygen (Reaction 1, type-I1 photo-oxidation).

Singlet‐Oxygen Quenching by Carotenoids: Steady‐state luminescence experiments

“…-'0, is produced by photosensitization (Reactions 1-3), using rose bengal or IH-phenalen-1-one as sensitizers. Rose bengal is known to be a very efficient '0, sensitizer [18] [19], and we have shown that this is also the case for phenalenone [20] which presents the additional advantage of being soluble in polar as well as in non-polar solvents.…”

Triplet-triplet absorption of eosin Y in methanol determined by nanosecond excimer laser excitation and picosecond light continuum probing

“…Phosphorescence [5] and delayed fluorescence [3,[6][7][8] have been observed even at room temperature. Triplet excited eosin Y has a high efficiency of singlet oxygen generation [9-11] (T+ 3 0 2 -S+ l 0 2 ; T is eosin Y in triplet state and S is eosin Y in singlet state) and it acts as photosensitizer of chemical reactions [12,13] (photosensitized oxidation [14][15][16][17][18] and photosensitized reduction [ 19,20]). …”

Rose Bengal‐Grafted Biodegradable Microcapsules: Singlet‐Oxygen Generation and Cancer‐Cell Incapacitation

“…In contract, a control experiment showed that pure ABDA was bleached to a small extent in the absence of photosensitive microcapsules (Figure 7 b, curve B), that is, photobleaching of ABDA is caused by oxidation of 1 O 2 generated from photosensitive microcapsules instead of its photoreaction in the excited state. [25] By using RB as reference (F RB = 0.75 [26] ), the 1 O 2 quantum yield of RB-CHI-coated capsules was calculated to be as high as 0.38 according to the method reported in the literature, [16b, 27] and this value seems reasonable because it lies in the broad range of quantum yields from 0.05 to 0.75 for RB-grafted polymers.…”