Sci. adv. 4, eaas9552 (2018)

Under intense illumination, most organic dyes tend to degrade. This photobleaching is the result of a reaction between the dye in a long-lived photoexcited state, such as a triplet state, and molecules in the environment, such as molecular oxygen. In functional devices, photobleaching is therefore considered detrimental for long-term operations. Now, Munkhbat et al. have reported a system in which the rate of photobleaching can be substantially reduced.

Credit: AAAS; reproduced under a Creative Commons Licence (http://creativecommons.org/licenses/by-nc/4.0/)

The researchers study the photochemistry of a J-aggregate in the vicinity of a plasmonic nanoantenna. The plasmonic mode and the molecular exciton form a hybrid light–matter state (polariton) that modifies the photochemistry of the dye molecules. In particular, the polariton is characterized by two new energy levels that split the excited singlet state of the dye. The lower polariton state has lower energy than the triplet state of the dye. Therefore, on irradiation of this coupled system, the probability of populating the reactive triplet state is greatly reduced. The researchers show in particular that by selectively irradiating the lower polaritonic band, the photo-oxidation rate of their dye can be decreased by 100-fold.