Fluorescent Polymers for Environmental Monitoring: Targeting Pathogens and Metal Contaminants with Naphthalimide Derivatives

The continuous monitoring of Hg2+ levels in aqueous environments is crucial to assess a potential indication of methylmercury contamination via bacterial conversion, yet existing methods often require extensive sample treatment, expensive equipment, and transportation to a specialized facility. To mitigate this issue, this study introduces the synthesis and application of three naphthalimide-based compounds with significant fluorescent and solvatochromic behaviour (C1, C2 and C3) for the detection of mercury ions, with an inherent associated antibacterial activity, creating a dual-functionality material. The incorporation of these compounds into polymers, such as polyvinyl chloride (PVC), poly (methyl methacrylate-co-methacrylic acid) (PUMA), and starch, allowed for the development of solid-support sensors/surfaces with a strong antibacterial profile, highlighting the inherent dual-functionality of the compounds. Most interestingly, the C2-doped starch biopolymer allowed for the detection of Hg2+ ions at concentrations as low as 2 ppm in an aqueous environment through a rapid, on-site evaluation without the need for sample treatment. This biopolymer was constructed following a sustainable, green-chemistry-oriented, temperature-dependent water/starch synthetic route, without the addition of plasticizers, and without any associated ecotoxicity. The study promotes the use of sustainable methods for environmental monitoring and antibacterial applications, advancing material science to offer effective, accessible, and eco-friendly solutions for detecting and mitigating mercury pollution and bacterial contaminations, enhancing environmental and health safety.