Methylene blue encapsulated in silica-based mesophases: characterisation and electrochemical activity

A hybrid CTABr-silica mesophase of the MCM-41 structure type has been synthesized which hosts molecules of methylene blue (MB). XRD and UV-Vis evidence show that MB molecules act as co-surfactant and are located in the proximity of the internal silica surface. Their electrochemical activity has been studied by means of cyclic voltammetry (CV) and compared to that of MB adsorbed on surfactant-free MCM-41, and in aqueous solutions. MB molecules are not released to the solution during CV measurements and are accessible to H3O+ species. The presence of micelles affects the kinetics of the redox process through H3O+ diffusion. With the hybrid system, a second MB species is observed, probably in prevailing interaction with the micelle.