Donor/π-Bridge Manipulation for Constructing a Stable NIR-II Aggregation-Induced Emission Luminogen with Balanced Phototheranostic Performance

Taking advantages of the versatile functionality and tunable energy dissipation, aggregation-induced emission lumino-gens (AIEgens) emerge as a rising star to afford multimodal theranostics platform. Nevertheless, the construction of AIE-active phototheranostic agent in the second near-infrared window (NIR-II, 1000−1700 nm) which allows superior resolu-tion and minimized photodamage is still a formidably challenging suffering from the limited candidate of building blocks. Herein, benzo[c]thiophene is innovatively utilized as electron-rich and bulky donor (D)/π-bridge neighboring to the elec-tron acceptor (A), which can enlarge the conjugation length and distort the backbone. By precise D/π-bridge engineering, highly stable NIR-II AIEgen DPBTA-DPTQ NPs with acceptable NIR-II fluorescence quantum yield and excellent photo-thermal conversion efficiency of 40.6% under 808 nm laser irradiation are successfully obtained. Compared with the re-ported NIR-II AIEgens, the exactly spatial conformation of DPBTA-DPTQ is determined for the first time by associating X-ray single crystal diffraction and theoretical simulations, elaborately revealing the relationship between structure and AIE effect/photothermal performance. Extensive in vitro tests demonstrate that DPBTA-DPTQ NPs with good biocom-patibility show efficient photothermal therapeutic effects. Furthermore, their prominent performance on fluorescence-photoacoustic-photothermal trimodal imaging-guided photothermal eradication of tumor is verified in HepG2 and B16-F10 tumor-xenografted mice, demonstrating distinguished cancer theranostic capability.