Self‐Illuminating NIR‐II Chemiluminescence Nanosensor for In Vivo Tracking H(2)O(2) Fluctuation

Chemiluminescence (CL) imaging, as an excitation‐free technique, exhibits a markedly improved signal‐to‐noise ratio (SNR) owing to the absence of an excitation light source and autofluorescence interference. However, conventional chemiluminescence imaging generally focuses on the visible and first near‐infrared (NIR‐I) regions, which hinders high‐performance biological imaging due to strong tissue scattering and absorption. To address the issue, self‐luminescent NIR‐II CL nanoprobes with a second near‐infrared (NIR‐II) luminescence in the presence of hydrogen peroxide are rationally designed. A cascade energy transfer, including chemiluminescence resonance energy transfer (CRET) from the chemiluminescent substrate to NIR‐I organic molecules and Förster resonance energy transfer (FRET) from NIR‐I organic molecules to NIR‐II organic molecules, occurs in the nanoprobes, contributing to NIR‐II light with great efficiency and good tissue penetration depth. Based on excellent selectivity, high sensitivity to hydrogen peroxide, and long‐lasting luminescence performance, the NIR‐II CL nanoprobes are applied to detect inflammation in mice, showing a 7.4‐fold enhancement in SNR compared with that of fluorescence.