LAUSR

Lanthanide-based photoluminescent emitters have gained strong attention over the past years because they provide certain advantages over organic fluorophores. Especially their excellent photostability has given rise to efforts in applying lanthanides for stimulated emission depletion (STED) nanoscopy. While STED has been demonstrated for dual lanthanide-based upconversion nanoparticles and single lanthanide ions embedded in yttrium aluminum garnet, a proof of the general lanthanide applicability for STED nanoscopy is still missing. Here we show that doping sodium yttrium fluoride (NaYF4) nanocrystals with either dysprosium or europium ions leads to working Stokes-side STED labels. The vast number of states inherent to most of the lanthanide ions should also allow the discovery of other lanthanides as potential Stokes-side STED labels in similar or alternative hosts.