Atomic Engineering and Aggregation Effect to Regulate Synergistically Type I Reactive Oxygen Species of AIE‐Active Deep Red/Near Infrared Red Photosensitizer

"Molecular science" has long been regarded as the golden rule to guide the design of organic materials' performances in the past many years, but some interesting phenomena of conventional aggregation-caused fluorescence quenching and new aggregation-induced emission reflect that materials' properties would be changed from "molecule" to "aggregate". Therefore, "molecular science" theory faces certain limitations to guide regulating the performance of materials at aggregation. In this work, it is discovered that the photosensitizer's performances contain fluorescence and reactive oxygen species, which could be affected by changing molecular atoms and aggregation form. The introduction of oxygen and selenium atoms could redshift fluorescence and improve reactive oxygen species (ROS) efficiency. In addition to the atomic effect, the ROS efficiency of photosensitizers could be affected after coating a polymeric shell, that is, the production of type II ROS singlet oxygen (¹O₂) is suppressed, while the type I ROS of superoxide anion (O₂ ^-•) is improved. This work discovers that the fluorescence and ROS efficiency of photosensitizers are relevant to the atomic effect and polymeric aggregation effect, and discussing deeply the influence mechanism, which has important research significance for modulating precisely the performances of photosensitizers and promoting the development of type I photodynamic therapy.