Annihilation Upconversion in Cells by Embedding the Dye System in Polymeric Nanocapsules

Abstract The first energetically conjoined TTA‐assisted photon energy upconversion operating in cell tissue is described. The synthesized nanocapsules with the encapsulated UC dye system consisting of an emitter and a sensitizer show very efficient UC emission in aqueous dispersion under extremely low excitation intensity down to 0.05 W · cm −2 so that tissue and cells are not affected by the excitation light. The demonstrated sub‐linear intensity dependence of the UC emission is of crucial importance for life‐science applications as the UC photon could serve as a local or in situ optical excitation source for subsequent light‐triggered processes. magnified image