Fluorescence (FL) imaging in the second near-infrared window (NIR-II, 1000–1700 nm) has emerged as a promising bioimaging modality that enables noninvasive visualization of deep tissue with an unprecedented resolution. However, there is a paucity of studies on high-quality responsive NIR-II FL molecules. Herein we report a novel activated NIR-II FL molecule, 4,7-bis­(5-(4-(diphenylamine)­phenyl)-2-thiophene) [1,2,5]­selenadiazolo­[3,4-f]­benzo­[c]­[1,2,5]­thiadiazole (SeTT), which exhibits fast and specific responsive capability to hypochlorous acid (HClO). To obtain the NIR-II ratiometric nanoprobe, SeTT was encapsulated on the surface of Er3+-doped down-conversion nanoparticles (DCNP), achieving the DCNP@SeTT nanoprobe. With a single 980 nm laser excitation, the ratiometric FL signal of SeTT at 1150 nm and DCNP at 1550 nm (I 1150 nm/I 1550 nm) was linearly correlated with the concentration of HClO with a detection limit of 0.4 μM. The ratiometric nanoprobe was successfully investigated for variations in HClO concentration in the tumor progression, visualization of anatomical structures of the peritoneal cavity in the mice model with inflammation, and quantitative detection of the HClO concentration in a rabbit model of osteoarthritis, achieving a fast response and high selectivity for the detection of HClO. The NIR-II-responsive nanoprobe can serve as a promising and effective tool for highly sensitive monitoring and imaging of HClO in living systems.

A water-stable and pH-independent sensor for qualitative and quantitative detection of nicotine in urine solution and living cell was successfully developed. This material, named MB@UiO-66-NH 2 , can be synthesized by encapsulating methylene blue (MB) with a well-known metal−organic framework (MOF) UiO-66-NH 2 through a simple impregnation method. The fluorescence intensity of the system was significantly enhanced when a certain amount of nicotine was added. In the meanwhile, MB is reduced by reductive nicotine to form leucomethylene blue (LB). The proposed sensor displayed excellent selectivity and sensitivity toward nicotine with limit of detection (LOD) of 0.98 μM, which is comparable or even better than that of the electrochemistry detecting methods for nicotine. The obvious enhancement and blue shift of the emission arise from the photoinduced electron transfer (PET) from LB to the UiO-66-NH 2 . The photophysical properties and the sensing applications of MB@ UiO-66-NH 2 suggest that this composite can be acted as a sensitive, selective, recyclable, and fluorogenic sensor for nicotine determination in urine solution and living cell.

Photothermal therapy, an excellent therapeutic approach, has received much attention in recent years. Herein, a novel diketopyrrolopyrrole polymer (DPP‐BDP) is prepared, which shows intense near‐infrared (NIR) optical absorption and admirable photothermal conversion efficacy. Impressively, after assembly into nanoparticles (DB‐FA), the as‐prepared conjugated polymer demonstrates a uniformly distributed size around 200 nm with remarkable NIR absorption at 808 nm. Additionally, it displays high biocompatibility and photostability. More interestingly, the obtained DB‐FA NPs are uptaken by cancer cells and present excellent anticancer in vitro and in vivo under 0.8 W cm−2 or 1 W cm−2 NIR laser irradiation, respectively. Hence, this work is expected to pave the way for using conjugated‐polymer nanoparticles as a powerful photothermal agents for anticancer applications.

Pure organic materials with room-temperature phosphorescence (RTP) have promising applications in bioimaging, information storage, and encryption. However, these materials are still very scarce due to a lack of design guidelines. Herein, a series of commercial/lab-synthesized carbazole-based derivatives is prepared by manipulating the positions of the chlorine substituents on the phenyl ring. The results show that 4CDCzB-Cm and 5CDCzB-Cm have ultralong phosphorescence lifetimes of 699.13 and 710.96 ms with good conjugation, longer than lab-synthesized ones due to the existence of isomers in the commercial samples. Remarkably, 2CDCzB-Cm shows photoactivated ultralong RTP with increased lifetimes from 51.24 to 631.83 ms by manipulating intermolecular interactions upon UV irradiation. The phosphor can also be deactivated back to its original state after standing in the dark for 5 h. The extraordinary photoresponsive and highly reversible properties of 2CDCzB-Cm provide a significant step forward in expanding the scope of organic phosphorescence applications.

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