Micellar carrier for triplet-triplet annihilation-assisted photon energy upconversion in a water environment

In this paper, we demonstrate energetically conjoined triplet-triplet annihilation-assisted photon energy upconversion (UC) operating in an aqueous environment. Obtained micellar structures show very efficient UC emission in a water environment under extremely low excitation light intensity, down to 10 mW cm-2. The demonstrated sub-linear intensity dependence of the UC emission is of crucial importance for life science applications, allowing upconverted photons to be generated even at low intensity that then serve as a local, in situ, optical excitation source for subsequent light-triggered processes.