Triplet–triplet annihilation upconversion in LAPONITE®/PVP nanocomposites: absolute quantum yields of up to 23.8% in the solid state and application to anti-counterfeiting
Lingling Wei, Chunying Fan, Ming Rao, Fanrui Gao, Cheng He, Yujiao Sun, Sijia Zhu, Qiuhui He, Cheng Yang, Wanhua Wu
Abstract
-vinyl-2-pyrrolidone) (PVP), which serves as excellent matrix for solid-state TTA-UC even in air. In the hybrid hydrogel doped by TTA-UC components, the anionic acceptors are arranged in an ordered manner at the nano-disk edge through electrostatic attraction, which avoids haphazard accumulation of the acceptors and allows for highly efficient inter-acceptor triplet energy migration. Moreover, the entangled PVP could not only protect the triplet excitons from oxygen quenching but even proactively eliminate oxygen by photoirradiation. Significantly, the dried gel prepared by completely removing water from the hydrogel gave absolute UC quantum efficiencies of up to 23.8% (out of a 50% maximum), which is the highest TTA-UC efficiency obtained in the solid state. The dried gels are readily made into powder by grinding with maintained UC emissions, making them convenient for application to information encryption and anti-counterfeiting security by virtue of the high UC quantum efficiency and insensitivity to oxygen.