Effects of Temperature and Concentration on the Rate of Photobleaching of Erythrosine in Water

Abstract

Erythrosine, a popular food dye, undergoes fast O-sensitive bleaching in water when subjected to visible light illumination. In dilute solution, erythrosine undergoes photobleaching via first-order kinetics, where the rate of bleaching depends critically on the rate of photon absorption and on the concentration of dissolved oxygen. Kinetic studies indicate that this inherent bleaching is augmented by self-catalysis at higher concentrations of erythrosine and on long exposure times. Under the conditions used, bleaching occurs by way of geminate attack of singlet molecular oxygen on the chromophore. Despite the complexity of the overall photobleaching process, the rate constants associated with both inherent and self-catalytic bleaching reactions follow Arrhenius-type behavior, allowing the activation parameters to be resolved. Bleaching remains reasonably efficient in the solid state, especially if the sample is damp, and provides a convenient means by which to construct a simple chemical actinometer.

Photo‐isomerization of the Cyanine Dye Alexa‐Fluor 647 (AF‐647) in the Context of dSTORM Super‐Resolution Microscopy

“…Indirect access to the triplet state was achieved by way of triplet‐triplet electronic energy transfer using Erythrosine as the donor (Figure S25). The latter forms a long‐lived ( τ T =1.2 ms) triplet in almost quantitative yield in deoxygenated water, having strong absorbance centred at 580 nm ( ϵ T =11 000 m −1 cm −1 ) . In the presence of increasing concentrations of AF‐647, the lifetime of triplet erythrosine decreased steadily (Figure S26), corresponding to a bimolecular quenching rate constant of 1.6±0.2×10 9 m −1 s −1 .…”

“…The latter forms al ong-lived (t T = 1.2 ms) triplet in almost quantitative yield in deoxygenated water,h aving stronga bsorbance centred at 580 nm (e T = 11 000 m À1 cm À1 ). [72] In the presenceo fi ncreasing concentrations of AF-647, the lifetime of triplet erythrosine decreased steadily ( Figure S26), corresponding to ab imolecular quenching rate constant of 1.6 AE 0.2 10 9 m À1 s À1 .T he acceptor triplet absorbsa t7 20 nm, where the corresponding differential molar absorption coefficient is found to be 82 000 m À1 cm À1 by comparisonw ith that of the donor( Figures S27 and S28). Returning to direct excitation of AF-647 at 610 nm, it can now be establishedt hat the quantum yield for inherent population of the triplet state is much less than 1% in the absence of as pinorbit promotor.T his finding is in agreement with earlyw ork by Chibisov [37a, 38b, 73] with relatedc yaninedyes.…”

“…Samples of 2-aminoethanethiol.HCl (RSH) were obtained from ThermoFisher Scientific and analysed by 1 Ha nd 13 CNMR spectroscopy.S amples of Erythrosine were available from an earlier study. [72] The imaging buffer used throughout this work was prepared from three separate solutions:…”

“…Photobleaching studies were made as described earlier. [72] Initial studies used aw hite light illuminator but more controlled experiments were made with ah igh-power LED emitting at 610 nm. Output from the LED was collimated and focused onto the sample cell.…”

“…It has also been reported that bleaching of as hort cyanine analoguei nvolves an activated process [100] and we have seen as imilar effect for the photobleaching of Erythrosine. [72] In general, there is no obvious correlationb etween light-induced blinking and permanent photobleaching of the fluorophore but it has been reported [74] that the presence of manganese(II) ions promotes both photobleaching and triplet blinking.…”