Persistent luminescence is not affected by background autofluorescence, and thus holds the promise of high-contrast bioimaging. However, at present, persistent luminescent materials for in vivo imaging are mainly bulk crystals characterized by a non-uniform size and morphology, inaccessible core–shell structures and short emission wavelengths. Here we report a series of X-ray-activated, lanthanide-doped nanoparticles with an extended emission lifetime in the second near-infrared window (NIR-II, 1,000–1,700 nm). Core–shell engineering enables a tunable NIR-II persistent luminescence, which outperforms NIR-II fluorescence in signal-to-noise ratios and the accuracy of in vivo multiplexed encoding and multilevel encryption, as well as in resolving mouse abdominal vessels, tumours and ureters in deep tissue (~2–4 mm), with up to fourfold higher signal-to-noise ratios and a threefold greater sharpness. These rationally designed nanoparticles also allow the high-contrast multiplexed imaging of viscera and multimodal NIR-II persistent luminescence–magnetic resonance–positron emission tomography imaging of murine tumours.

持久发光不受背景自发荧光的影响，因此有望实现高对比度生物成像。然而，目前用于活体成像的持久发光材料主要是块状晶体，其特点是尺寸和形貌不均匀，核壳结构难以接近，发射波长短。在这里，我们报告了一系列在第二个近红外窗口（NIR-II，1,000–1,700 nm）中具有延长发射寿命的 X 射线激活、镧系元素掺杂的纳米粒子。核-壳工程实现了可调谐的 NIR-II 持久发光，在信噪比、体内多重编码和多级加密的准确性以及分辨小鼠腹部血管、肿瘤和输尿管方面优于 NIR-II 荧光在深层组织中（~2-4 毫米），具有高达四倍的信噪比和三倍的清晰度。这些合理设计的纳米粒子还可以实现内脏的高对比度多重成像和小鼠肿瘤的多模式 NIR-II 持久发光-磁共振-正电子发射断层扫描成像。