Active-core/active-shell nanostructured design: an effective strategy to enhance Nd3+/Yb3+ cascade sensitized upconversion luminescence in lanthanide-doped nanoparticles†
In recent years, intensive research efforts around the world have been devoted to lanthanide-doped upconversion nanoparticles because of their promising application in biological imaging. However, the overheating issue caused upon 980 nm laser irradiation in conventional Yb3+-based nanoparticles is needed to be addressed, and thus Nd3+/Yb3+-based upconversion nanoparticles with 808 nm excitation are investigated as promising alternatives because they can significantly decrease the optical absorption of water. Due to the cascade sensitization process, Nd3+/Yb3+-based upconversion nanoparticles, however, always suffer from the intrinsic low luminescence efficiency. To solve this problem, here we proposed the active-core/active-shell nanostructured design as an effective strategy for upconversion improvement of Nd3+/Yb3+-based upconversion nanoparticles. We found that after growing an optimized active-shell containing both Nd3+ and Yb3+ ions, a maximum 522-fold enhancement in upconversion luminescence was realized upon excitation at 808 nm. These findings would be of great importance to the community developing high-performance upconversion nanoparticles for bioimaging applications.