NIR-I-Responsive Single-Band Upconversion Emission through Energy Migration in Core-Shell-Shell Nanostructures

Here we report a new strategy to tune both excitation and emission peaks of upconversion nanoparticles (UCNPs) into the first infrared biowindow (NIR-I, 650-900 nm) with high NIR-I-to-NIR-I upconversion efficiency. By introducing the sensitizer Nd3+, activator Er3+, energy migrator Yb3+ and energy manipulator Mn2+ into specific region to construct proposed energy migration processes in the designed core-shell-shell nanoarchitecture, back energy transfer (BET) from activator to sensitizer or migrator can be greatly blocked and the NIR-to-red upconversion emission can be efficiently promoted. Consequently, BET-induced photon quenching and the undesired green-emitting radiative transition are entirely eliminated, leading to high-efficiency single-band red upconversion emission upon 808 nm NIR-I laser excitation. Our findings provide insights into fundamental lanthanide interactions and advance the development of UCNPs for bioapplications with techniques that overturn traditional limitations.

Automated summary

Here, we present a new strategy to tune the excitation and emission peaks of upconversion nanoparticles, enabling efficient upconversion emission in the first infrared biowindow. By constructing energy migration processes in a specific core-shell-shell nanoarchitecture, the efficiency of the emission is greatly enhanced.