Nanostructured films from poly(3-hexylthiophene)-<i>graft</i>-poly(ε-caprolactone) as light-responsive generators of reactive oxygen species

The design of smart photoelectrodes is used to modulate and control the spatio-temporal production of reactive oxygen species (ROS). In this work, we develop photoactive films with tunable nanostructured morphologies to favor ROS production <i>via</i> photostimulation. To that aim, we synthesized graft copolymers, made of poly(3-hexylthiophene) (P3HT) and poly(ε-caprolactone) (PCL), P3HT-<i>g</i>-PCL, which were employed to fabricate compact films by drop casting. The films were further subjected to a thermo-oxidative treatment in the presence of H₂O₂ at 42 °C. This led to nanostructured films with a porosity (∼500 nm diameter and ∼70 nm height) controlled at specific copolymer compositions, as determined by atomic force microscopy (AFM). The nanostructured P3HT films possess higher storage moduli (<i>E</i>') than flat P3HT films, as determined by nanoindentation measurements. Finally, the performance of nanostructured P3HT films as photoelectrodes is assessed in a three-electrode electrochemical cell upon visible-light irradiation (<i>λ</i> = 467 nm), leading to the spatiotemporal production of H₂O₂ at non-cytotoxic levels for future non-invasive redox medicine applications.