Oil-in-water microemulsion: an effective medium for triplet–triplet annihilated upconversion with efficient triplet acceptors

Abstract

The oil-in-water (o/w) microemulsion containing bimolecular system of acceptor (9,10-dinaphthylanthracene) and sensitizer (Pd(II)tetratolylporphyrin), i.e., upconverted o/w microemulsion, was firstly reported for the triplet–triplet annihilated upconversion (TTA-UC) by temperature effects. The correlation between structure/up-conversion performance of three 9,10-dinaphthylanthracenes doped with Pd(II)tetratolylporphyrin were investigated. Under excitation at an ultralow power density at 60 mW cm⁻², the up-converted o/w microemulsion emits green-to-blue upconversion and an efficiency (Φ_UC) increase is accompanied by an increase in temperature. The maximum Φ_UC value for the upconverted o/w microemulsion obtained was as high as 33.12%, which is comparable to its counterpart in a pure organic solvent. Very importantly, there is no need for the upconverted o/w microemulsion to deaerate, which is of critical importance for applications such as upconversion-powered photoelectrochemistry. To the best of our knowledge, the current study represents a simple approach to obtain high TTA-UC without degassing.