We report a new strategy to construct fluorescence switches by taking advantage of the E–Zisomerization of the hydrazone group. The switch, synthesized by linking pyridyl-2-aldehydehydrazone to a BODIPY fluorophore, was able to exist in three forms: E-BODIPY, Z-BODIPY and protonated BODIPY with different photophysical properties. Reversible ON/OFF fluorescence switching among them was realized by multiple stimuli such as irradiation and addition of acid/base. 

RSC Adv., 2016,6, 41002-41006