Substituent-Driven Electronic Modulation of Azo Bond: Enabling the Design of Ultrafast and Exceptionally Sensitive Fluorescent Probe for Hypoxia

group, exhibits superior performance in hypoxia detection, achieving the fastest response time (50 s) and the highest fluorescence enhancement (690-fold). Furthermore, cellular imaging in hypoxic HeLa cells and in vivo studies using mouse models of ischemia-induced hypoxia confirm that the sensitivity and response speed of the DCM-Azo-Rs probes are enhanced in biological systems as the electron-withdrawing strength of the substituent increases.