Adsorption of Rose Bengal on a self-assembled fibrillar network affords a thermally switchable oxygenation photocatalyst and a thermochromic soft material

Abstract

Rose Bengal (RB) can be homogeneously dispersed in dichloromethane by its adsorption on the fibrillar network of a molecular gel formed in this solvent. The RB loaded gel was visualized by confocal scanning laser microscopy, revealing homogenous distribution all over the self-assembled fibers. Thermal gel disassembly provokes discoloration of the system because of protonation of RB by the acidic molecular gelator. Thermochromism was evaluated by UV–vis spectroscopy, showing that color change is fully reversible and associated with gel assembly/disassembly, as corroborated by 1H NMR determination of the amount of free gelator. Singlet oxygen photogeneration from the RB-loaded gel was assayed using 9,10-dimethylanthracene as a 1O2 trap. It was found that the photosensitizing activity of the system is on /off thermally switched, controlled by reversibly gel formation, resulting in a smart thermoresponsive photocatalytic material.