Hydrothermal synthesis and application of Ho3+-activated NaYbF4 bifunctional upconverting nanoparticles for in vitro cell imaging and latent fingerprint detection

The Ho3+-activated NaYbF4 upconverting nanoparticles (UCNPs) were synthesized via a facile hydrothermal method and characterized by X-ray diffraction pattern, transmission electron microscope image and upconversion (UC) emission spectrum. Upon the excitation of 980 nm light, the as-prepared UCNPs exhibited bright green and red UC emissions corresponding to the (5F4,5S2) → 5I8 and 5F5 → 5I8 transitions of Ho3+ ions, respectively. The cell toxicity test result revealed that the synthesized UCNPs possessed remarkable low cytotoxicity. With the introduction of the resultant UCNPs into the HeLa cells, intense green and red UC emissions were observed, indicating that the HeLa cells can be labeled by the obtained UCNPs and they had potential application in live cell imaging. Additionally, the practicality of the resultant UCNPs for latent fingerprint was also systematically investigated. These results suggest that the Ho3+-activated NaYbF4 UCNPs are very promising as a bifunctional nanoparticle for in vitro cell imaging and latent fingerprint detection.