Rational Development of Near-Infrared Fluorophores with Large Stokes Shifts, Bright One-Photon, and Two-Photon Emissions for Bioimaging and Biosensing Applications

Fluorophores with near-infrared emissions play a crucial role in numerous bioimaging and biosensing applications, owing to their deep penetration depths, low auto-fluorescence,and minimal tissue damages. Herein,the rational development of anew class of near-infrared fluorophores with bright one-photon and two-photon emissions at ≈ 740 nm, large Stokes shifts ( ≈ 80 nm), significant two-photon action absorption cross-section (≈ 185 GM at 820 nm), excellent water solubility,outstanding photostability, and low toxicity is reported. Their biological applications n mitochondrial labelling, deep tissue imaging, and H₂S detection in live cells and mice are also demonstrated. In addition, a rational design strategy for enlarging the Stokes shifts and enhancing two-photon emissions of these fluorophores is presented. These fluorophores will serve as a useful platform for developing novel imaging and sensing agents, and the design methodologies will inspire the molecular engineering of abundant high-performance near-in-frared fluorophores.