More Is Better: Acceptor Engineering for Constructing NIR-II AIEgens to Boost Multimodal Phototheranostics

The manipulation of electron donor/acceptor (D/A) shows endless impetus for innovating optoelectronic materials. Because of the diversity of electron-donating species, the study on donor engineering has explored systematically, whereas the research on electron acceptor engineering received a snub by contrast. Inspired by the philosophical idea of “more is different”, two systems with D−D−A−D−D (1A system) and D−D−A−A−D−D (2A system) structures based on the acceptor engineering were ingeniously designed and studied. It was demonstrated that the 1A system presented a weak aggregation-induced emission (AIE) to aggregation-caused quenching (ACQ) phenomenon along with the increased acceptor electrophilicity. Interestingly, the 2A system exhibited an opposite ACQ-to-AIE transformation, manifesting the dual-acceptor tactic could facilitate AIE activity. Owing to the highest molar absorptivity, second near-infrared emission, superior AIE property, favorable production ability of reactive oxygen species and excellent photothermal conversion efficiency, a representative member of 2A system handily performed in multimodal imaging-guided photodynamic-photothermal synergetic therapy for efficient tumor elimination.