Tailoring SWIR emission in tri-lanthanide-doped CaF2 nanoparticles

Abstract

Erbium (Er) doped CaF₂ nanophosphors with enhanced short-wavelength infrared light (SWIR) emission synthesized in this work have promising potential for biomedical applications in diagnostics and deep tissue imaging due to their low vibrational energy, large optical transparency and superior biocompatibility. For deep tissue imaging application, it is critical to achieve highly emissive SWIR emitting CaF₂ nanophosphors to enhance detection resolution and depth using the “tissue-transparent window”. In this work, we demonstrate substantial enhancement in the IR emission of CaF₂ nanocrystals using a tri-doping scheme of ytterbium (Yb), erbium (Er) and cerium (Ce). The effects of Er, Ce and Yb dopant concentration on the IR emission intensity was systematically studied and the optimum Er, Ce and Yb dopant concentration was estimated to be ∼2, ∼10 and ∼20 mol%, respectively. At Yb 20 mol%, the IR emission intensity was increased ∼12 fold by optimizing the Ce dopant concentration.