Design of AIEgens for near-infrared IIb imaging through structural modulation at molecular and morphological levels

TLDR

Near‑infrared IIb (1500–1700 nm) fluorescence imaging offers great promise for tissue imaging, yet organic probes are scarce because efficient long‑wavelength materials are lacking. The study proposes a molecular design philosophy to create pure organic NIR‑IIb fluorophores. This approach manipulates twisted intramolecular charge transfer and aggregation‑induced emission at both molecular and morphological levels. The authors synthesized an organic dye emitting up to 1600 nm with an 11.5 % quantum yield, enabling high‑clarity NIR‑IIb imaging of blood vessels and the intestinal tract in live mice and encouraging further development of pure organic NIR‑IIb dyes.

Abstract

Abstract Fluorescence imaging in near-infrared IIb (NIR-IIb, 1500–1700 nm) spectrum holds a great promise for tissue imaging. While few inorganic NIR-IIb fluorescent probes have been reported, their organic counterparts are still rarely developed, possibly due to the shortage of efficient materials with long emission wavelength. Herein, we propose a molecular design philosophy to explore pure organic NIR-IIb fluorophores by manipulation of the effects of twisted intramolecular charge transfer and aggregation-induced emission at the molecular and morphological levels. An organic fluorescent dye emitting up to 1600 nm with a quantum yield of 11.5% in the NIR-II region is developed. NIR-IIb fluorescence imaging of blood vessels and deeply-located intestinal tract of live mice based on organic dyes is achieved with high clarity and enhanced signal-to-background ratio. We hope this study will inspire further development on the evolution of pure organic NIR-IIb dyes for bio-imaging.