Morphology evolution and NIR-II luminescence enhancement in LaF₃:Er³⁺ nanoparticles

Luminescence imaging in the second near-infrared (NIR-II) window (1000-1700 nm) has attracted extensive attention in recent years owing to its superior tissue penetration ability and weak spontaneous fluorescence effects in biological tissues. However, an important bottleneck restricting the development of NIR-II luminescence imaging technology is the lack of nanoprobes with suitable morphology, particle size and high luminescence intensity. In this work, NIR-II emitted LaF₃:Er³⁺ nanoparticles (NPs) were synthesized by a simple chemical precipitation method, where the size and morphology of LaF₃:Er³⁺ NPs were precisely controlled through the regulation of reaction conditions. The NIR-II luminescence of Er³⁺ was effectively enhanced for 8.4 times by Zr⁴⁺ doping. The results provides useful reference for the research of NIR-II luminescent imaging nanoprobes.