Manipulation of up-conversion emission in NaYF4core@shell nanoparticles doped by Er3+, Tm3+, or Yb3+ions by excitation wavelength—three ions—plenty of possibilities

Core@shell nanoparticles showing up-conversion under 808, 975, 1208 or 1532 nm excitation were synthesised. Nanoparticles revealed their multifunctionality and emission bands covering the visible to near-infrared range (475 to 1625 nm).