Oxygen indicator films of acrylate photopolymers and TiO2 nanoparticles with tunable response times

An easy and fast fabrication strategy to obtain Photochromic Films (PFs) for naked-eye detection of oxygen is presented. These PFs are based on the photoreductive activity of TiO2 nanoparticles combined with the redox-driven color switching property of methylene blue, embedded in a photocurable and tunable air-permeable polyethylene glycol diacrylate (PEGDA) matrix. The PF is fabricated by a single-step process: the UVA light exposure initiates the polymerization and simultaneously reduces the blue-color dye in its colorless form. The resulting PF exhibits fast discoloration and modulable recoloration time in the air. The tunability of PFs color-switching can be used for engineering colorimetric sensors with preset oxygen responsive ranges to fulfill specific application requirements.