Plasma Functionalization Enables Diffusion Control of Reactive Oxygen Species.

Reactive oxygen species (ROS) are promising green candidates for tackling challenges ranging from antimicrobial resistance to water decontamination. Metal oxide nanomaterials structured as thin films, deposited at room temperature (RT) using plasma technology, can deliver ROS to the environment by catalyzing oxygen and water following a chemodynamics approach. This study proposes thin film plasma polymerization as a strategy to precisely control ROS delivery, unravel ROS formation mechanism at the catalytic interface, and ensure ROS-driven chemistry. A proper combination of semiconductors, specifically silver oxide and titanium oxide, is used as a model system for ROS production. This specific coupling of semiconductors produces ROS in the dark due to charge separation without ion leaching. Plasma surface functionalization with nanoporous SiOx-like films in the 1-100 nm range allows selective control of the delivery of radicals with different characteristic lifetimes such as superoxide anion and singlet oxygen based on the thickness of the functional layer. As proof of promising applications, results regarding radicals' detection are correlated with the antimicrobial activity of the ROS-releasing system. Thin film plasma surface functionalization allows control of ROS delivery, ensuring that the material efficacy is due to ROS and not by other direct redox chemistry or leaching processes.