Plasmonic-Fluorescent Janus Ag/AgS Nanoparticles for HO-Activated NIR-II Fluorescence Imaging.

Silver sulfide (AgS) has gained widespread attention in second near-infrared (950-1700 nm, NIR-II) window imaging because of its high fluorescence quantum yield and low toxicity. However, its "always on" fluorescence shows inapplicability for targeted molecule-activated biomedical applications. Herein, we first developed a novel silver/silver sulfide Janus nanoparticle (Ag/AgS JNP) for specific activatable fluorescence imaging in the NIR-II window. Inner-particle electron compensation from Ag to AgS upon laser irradiation endowed JNPs an "off" state of fluorescence, whereas the oxidization of Ag incubated with HO, decreasing the electron-transfer effect and illuminating the NIR-II fluorescence of the AgS part. In contrast, the absorption of Ag/AgS JNPs slightly decreased in an HO-dependent manner, showing an activated photoacoustic imaging mechanism. The Ag/AgS JNPs were used for noninvasive location and diagnosis of diseases , such as for liver injury and cancer, with high sensitivity and accuracy.