Abstract

Accurate detection of neutrophil activity is critical for assessing the severity of bacterial inflammation. Herein, we report an activatable dye-sensitized lanthanide nanoprobe (LnNP@ZW800-SC@PEG) with enhanced second near-infrared fluorescence for the real-time imaging of neutrophil-secreted hypochlorite in vivo. By screening of four cyanine derivatives, LnNP@ZW800-SC is identified with the brightest fluorescence at 1523 nm and the high absolute quantum yield (0.85%) compared to other derivatives. Mechanistic studies reveal that the high conjugation efficiency and enhanced absorption of the ZW800-SC dyes facilitate efficient energy transfer to Yb 3+ and Er 3+ , leading to boosted NIR-IIb emission. Leveraging the bright emission, LnNP@ZW800-SC enables high-resolution, sensitive, and specific imaging of hypochlorite, both in vitro and in a murine model of LPS-induced lymphatic inflammation. This work provides a rational design strategy for coordinating dye moieties to enhance dye sensitization, thereby boosting the second near-infrared fluorescence of lanthanides and optimizing their imaging performance for biological applications. Graphical Sulfur-bridged sensitization enables efficient energy transfer to LnNP, yielding bright NIR-IIb emission of the LnNP@ZW800 probe. The probe's ClO – responsivity achieves activatable imaging of neutrophil activity in bacterial inflammation.