Plasmonic-Fluorescent Janus Ag/Ag2S Nanoparticles for In Situ H2O2-Activated NIR-II Fluorescence Imaging

Silver sulfide (Ag 2 S) 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/Ag 2 S JNP) for specific activatable fluorescence imaging in the NIR-II window. Inner-particle electron compensation from Ag to Ag 2 S upon laser irradiation endowed JNPs an “off” state of fluorescence, whereas the oxidization of Ag incubated with H 2 O 2, decreasing the electron-transfer effect and illuminating the NIR-II fluorescence of the Ag 2 S part. In contrast, the absorption of Ag/Ag 2 S JNPs slightly decreased in an H 2 O 2 -dependent manner, showing an activated photoacoustic imaging mechanism. The Ag/Ag 2 S JNPs were used for noninvasive location and diagnosis of diseases in vivo, such as for liver injury and cancer, with high sensitivity and accuracy.