Fluorescence imaging in the near-infrared II (NIR-II, 1000–1700 nm) region opens up new avenues for biological systems due to suppressed scattering and low autofluorescence at longer-wavelength photons. Nonetheless, the development of organic NIR-II fluorophores is still limited mainly due to the shortage of efficient molecular design strategy. Herein, we propose an approach of designing Janus NIR-II fluorophores by introducing electronic donors with distinct properties into one molecule. As a proof-of-concept, fluorescent dye 2 TT-m, oC6B with both twisted and planar electronic donors displayed balanced absorption and emission which were absent in its parent compound. The key design strategy for Janus molecule is that it combines the merits of intense absorption from planar architecture and high fluorescence quantum yield from twisted motif. The resulting 2 TT-m, oC6B nanoparticles exhibit a high molar absorptivity of 1.12 ⨯10⁴ M⁻¹ cm⁻¹ at 808 nm and a NIR-II quantum yield of 3.7%, displaying a typical aggregation-induced emission (AIE) attribute. The highly bright and stable 2 TT-m, oC6B nanoparticles assured NIR-II image-guided cancer surgery to resect submillimeter tumor nodules. The present study may inspire further development of molecular design philosophy for highly bright NIR-II fluorophores for biomedical applications.

由于在较长波长光子处的散射被抑制和低自发荧光，近红外II（NIR-II，1000-1700 nm）区域的荧光成像为生物系统开辟了新途径。尽管如此，有机NIR-II荧光团的开发仍然受到限制，这主要是由于缺乏有效的分子设计策略所致。本文中，我们提出了一种通过将具有不同特性的电子供体引入一个分子来设计Janus NIR-II荧光团的方法。作为概念验证，荧光染料2 TT- m，o具有扭曲的电子供体和平面电子供体的C6B表现出平衡的吸收和发射，这是其母体化合物所没有的。Janus分子的关键设计策略是它结合了平面结构的强吸收和扭曲基序的高荧光量子产率的优点。将得到的2 TT- M，O C6B纳米颗粒表现出1.12⨯10高摩尔吸光系数⁴ 中号^-1 厘米^-1和在808纳米的3.7％NIR-II量子产率，显示一个典型的聚合诱导的发射（AIE）属性。高亮度和稳定的2 TT- m，oC6B纳米颗粒确保了在NIR-II图像引导下的癌症手术中切除亚毫米级肿瘤结节。本研究可能会激发用于生物医学应用的高亮度NIR-II荧光团的分子设计理念的进一步发展。