Tuning Electrochemiluminescence in Multistimuli Responsive Hydrogel Films

Luminescent and redox properties of stimuli-responsive hydrogel materials have been modulated by different external stimuli which trigger swelling or collapse of the polymer matrix. There is very rapid development in the field of such "smart" materials particularly combined with other sensing functionalities. Here, a poly(N-isopropylacrylamide) matrix incorporating covalently bound phenylboronic acids as a saccharide-sensing unit and redox-active [Ru(bpy)₃]²⁺ luminophores was designed and exhibited multistimuli responsive electrochemical and luminescent switching behaviors. Redox activity of the films is reversibly changed by sequential stimuli (fructose and temperature) which control the swelling and the collapse of the films. Finally, electrogenerated chemiluminescence (ECL) is enhanced by a ∼16-fold factor during the film collapse induced by the temperature, whereas the swelling due to fructose provokes the decrease of the light emission. We demonstrate for the first time that ECL response correlates intrinsically with the swelling ratio and is finely modulated by both stimuli. The multistimuli responsive characteristics of such ECL-active hydrogels should find promising applications in biosensing, new luminescent materials, and logic gates in bioelectronic devices.