Spectroscopic investigations, characterization and chemical sensor application of composite Langmuir-Schäfer films of anthocyanins and oligophenylenevinylene derivatives

Anthocyanins, extracted from grape skin (Vitis vinifera), were dissolved in ultrapure aqueous subphase and an oligophenylenevinylene derivative was spread on the subphase surface. Such oligomer was chosen as anionic counterpart of hydrosoluble anthocyanins in order to perform a LangmuireSchäfer film of the dyad. Interface interactions between oligophenylenevinylene derivative and anthocyanins were studied by Brewster angle microscopy and reflection spectroscopy. Additionally, the oligomer exhibits a chemical structure able to ensure an enhancement of the stability under UVevisible irradiations of the film of the dyad without any variation of the natural pigment absorption in the visible range. The visible spectra of cast anthocyanins film and LangmuireSchäfer oligomer/anthocyanins film after exposure to 254 nm irradiation showed a remarkable increase of the film stability, probably due to the screening effect of the oligomer. Preliminary test of a LangmuireSchäfer film of oligophenylenevinylene derivative/anthocyanins as a herbicide sensor showed that sensing is completely reversible, stable and repeatable.