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

Abstract

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 via photostimulation. To that aim, we synthesized graft copolymers, made of poly(3-hexylthiophene) (P3HT) and poly(ε-caprolactone) (PCL), P3HT-g-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 (E′) 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 (λ = 467 nm), leading to the spatiotemporal production of H₂O₂ at non-cytotoxic levels for future non-invasive redox medicine applications.