Synthesis and luminescent properties of ZnWO4: Cr3+ nanoparticles for NIR-II fluorescence imaging

Fluorescence imaging is of paramount importance in the health and medical aspect, especially for emission in second near-infrared window, where high-resolution deep-tissue imaging can be achieved. Herein, ZnWO4: Cr3+ nanoparticles (NPs) with broadband NIR-II emission were synthesized by a facile solvothermal+calcination method. It is found that Cr3+-doping have no obvious effect of ZnWO4 phase, and the particles of as-prepared NPs are of mono-dispersed cube-shape with average size of ∼100 nm. At optimal 520 nm excitation, the as-synthesized ZnWO4: Cr3+ NPs exhibit an efficient NIR emission peaking at 987 nm and EQE of 4.03% with FWHM of 212 nm. The ZnWO4: Cr3+ NPs possess excellent stability, good biocompatibility and high brightness. NIR-II imaging with high penetration depth and micron spatial resolution was achieved on a mice model. To sum up, our work indicates that ZnWO4: Cr3+ NPs has great application potential as fluorescent agent for NIR-II bio-imaging.