An Efficient 1064 nm NIR‐II Excitation Fluorescent Molecular Dye for Deep‐Tissue High‐Resolution Dynamic Bioimaging

Abstract A small‐molecule fluorophore FD‐1080 with both excitation and emission in the NIR‐II region has been successfully synthesized for in vivo imaging. A heptamethine structure is designed to shift the absorption and emission into NIR‐II region. Sulphonic and cyclohexene groups are introduced to enhance its water solubility and stability. The quantum yield of FD‐1080 is 0.31 %, and can be increased to 5.94 % after combining with fetal bovine serum (FBS). Significantly, 1064 nm NIR‐II excitation was demonstrated with the high tissue penetration depth and superior imaging resolution compared to previously reported NIR excitation from 650 nm to 980 nm. FD‐1080 is not only capable of realizing non‐invasive high‐resolution deep‐tissue hindlimb vasculature and brain vessel bioimaging, but also quantifying the respiratory rate based on the dynamic imaging of respiratory craniocaudal motion of the liver for the awake and anaesthetized mouse.