Ln3+-doped nanoparticles with enhanced NIR-II luminescence for lighting up blood vessels in mice

at 1530 nm increased 10 times, while the upconversion luminescence decreased to less than 1%. After being modified with polyacrylic acid and polyethylene glycol, the as-obtained water-soluble probe exhibits continuous high-resolution for distinguishing 0.25 mm blood vessels even 10 h after injection. Noteworthily, the imaging of tumors was achieved by injecting the probe, indicating that the designed NIR-II probe has sufficient brightness and the ability to passively target tumor tissue.