Upconversion: Tunable Near Infrared to Ultraviolet Upconversion Luminescence Enhancement in (α‐NaYF4:Yb,Tm)/CaF2 Core/Shell Nanoparticles for In situ Real‐time Recorded Biocompatible Photoactivation (Small 19/2013)

Upconversion nanoparticles (UCNPs) can convert tissue-penetrable nearinfrared light into UV emission, making them promising as transducers for photoactivation in biology. However, the choice of the UV emitting UCNPs is limited and their NIR-to-UV efficiency is low. G. Han and co-workers have addressed this issue by developing a family of CaF2-coated UCNPs with tunable UV enhancement. As reported on page 3213, such design outperforms known optimal UCNPs and in situ realtime live-cell photoactivation is recorded for the first time with such nanoparticles. This result is a potential game changer in photoactivation in living systems and a new tool for other biophotonic applications.