808 nm NIR light excited single-band red upconversion emission in lanthanide-doped KMnF3 nanocrystals

A new type of upconversion nanoparticles (UCNPs) whose excitation and emission peaks are both located in the biological window has been developed based on the combination of Nd3+ sensitization and efficient energy transfer between Mn2+ and Er3+ ions. In our design, Nd3+ ions act as sensitizers for efficient absorption of 808 nm NIR photons, while the usage of Yb3+ ions as energy migrators facilitates the efficient energy transfer from Nd3+ to Er-3 ions. More importantly, the introduction of Mn2+ ions plays a key role in the realization of single-band red UC emission of Er3+ ions via the efficient energy transfer process between Mn2+ and Er-3. Consequently, upon 808 nm laser excitation, single-band red UC emission can be obtained in the as-synthesized Nd3+/Yb3+ /Er3+ tri-doped KMnF3 nanocrystals, which could be considered as attractive alternative to conventionally used UCNPs for deep-tissue imaging with mitigation of the attenuation effect associated with the emission peaks outside biological window and the overheating constraints imposed by the conventional 980 nm laser excitation. (C) 2017 Elsevier B.V. All rights reserved.