Mechanochemical transformation of fluorescent hydrogel based on dynamic lanthanide-terpyridine coordination

As a burgeoning research field, ultrasound-responsive materials have attracted intense interest in healthcare research. However, the basic mechanism of sonochemical effect in the quasi-solid state is far from being well understood than those in the solution. Herein, we showcase mechanochemical transformations of europium(III) complexes in a supramolecular hydrogel matrix. With the combination of labile terpyridine-europium complexes (TPY-Eu 3+ ) as mechanochromic moieties and an ultrasound-responsive fluorogen (URF) as a molecular tweezer, the hydrogel produces a notable fluorescence change in response to ultrasound. The mechanochemical transformation was elucidated by molecular dynamics (MD) simulations, and fully probed and evidenced by electrochemical experiments, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. By combining labile terpyridine-europium complexes as mechanochromic moieties and an ultrasonic-responsive fluorogen (URF) as a molecular tweezer, the hydrogel displays a visible fluorescence change in response to ultrasound.