NIR II-responsive photon upconversion through energy migration in an ytterbium sublattice

An ytterbium sublattice in an erbium-sensitized multilayer core-shell structure enables photon upconversion from lanthanide ions under 1,530 nm irradiation. Smart control of photon upconversion is a key strategy for lanthanide-based materials used in biological and photonic applications. However, this has remained a challenge for the upconversion luminescence of lanthanides under excitation in the second near-infrared (NIR II) biowindow instead of at the conventional 980 and 808 nm wavelengths. Here, we report a conceptual design for an energy-migratory ytterbium sublattice in an erbium-sensitized multilayer core-shell nanostructure that is able to achieve photon upconversion from a broad range of lanthanide ions (Yb3+, Tm3+, Ho3+, Gd3+, Eu3+ and Tb3+) under 1,530 nm irradiation. The quasi-single-band upconversion in the first near-infrared (NIR I) biowindow is also realized through fine manipulation of the introduced cross-relaxations. By establishing an interfacial energy-transfer-mediated nanostructure, we also gain a deep insight into the mechanistic features of the energy migration. These results open new opportunities in a variety of frontier applications, such as information security.