Alkyl-π Liquids as Condensed-State Singlet Oxygen Photosensitizers

Functional materials capable of generating singlet oxygen (¹O₂), a highly reactive but short-lived species used to destroy organic materials, including chemical pollutants and biological entities, typically incorporate a chromophore that acts as a photosensitizer into a tertiary scaffold. Current functional materials that produce ¹O₂ include metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), polymeric nanoparticles, modified glasses, and supramolecular assemblies. Whilst multi-component functional materials have been widely reported, producing functional materials using a single small molecule in a condensed state has hardly been reported. Herein, we report the first use of functional molecular liquids (alkyl-π liquids), non-volatile single-component condensed-state fluidic materials, as photosensitizers for the generation of ¹O₂ at an alkyl-π liquid-water interface. We investigate the incorporation of various chromophores into alkyl-π liquids that are suitable for ¹O₂ production and analyze the molecular structure required to produce efficient alkyl-π liquid photosensitizers. The alkyl-π liquids were studied, impregnated into porous membranes, and as thin films on quartz and Si wafers, the limitations of ¹O₂ production were investigated. A system was successfully fabricated that can generate ¹O₂ within an alkyl-π liquid impregnated membrane and migrate across a membrane-water interface to destroy small organic molecules, demonstrating the potential of these systems for water decontamination.