Photo-induced Raman amplification for detecting and monitoring degradation of micro- and nano-sized PVC plastics

Abstract

The increasing environmental and health concerns posed by micro- and nanoplastics (MNPs) in various environmental matrices continue to call for urgent solutions. Given the inherent toxicity, persistence, bioaccumulation, and ability to absorb other pollutants, the development of highly sensitive catalytic materials and advanced analytical techniques for the detection and degradation of MNPs, particularly polyvinyl chloride (PVC-MNPs), in water and those originating from medical devices (MDs), is now of critical importance. Surface-enhanced Raman spectroscopy (SERS) shows potential for such detection; however, fabricating SERS-active substrates with hot spots and high sensitivity for detecting PVC-MNPs remains a challenge, necessitating advanced sensing approaches. In this study, we used a previously developed ultra-sensitive flower-like Ag nanoflake (Ag NF)-decorated TiO₂ platform with a high contact area alongside the photo-induced enhanced Raman spectroscopy (PIERS) technique under continuous UV irradiation for PVC-MNPs detection and degradation monitoring. The fabricated Ag NF-TiO₂ platform and PIERS approach facilitated the rapid detection of PVC particles down to 20 nm in water with a sensitivity increase of ∼2.6 × 10²-fold over conventional SERS. The synergistic interplay between plasmonic effects and photo-induced charge transfer processes within the PIERS substrates significantly amplified the Raman signals of PVC-MNPs under UV irradiation. Furthermore, the PVC-MNPs loaded onto the Ag NF-decorated TiO₂ were photocatalytically degraded within 10 minutes of UV exposure. We proposed that photocatalytic-assisted dehydrochlorination and chain scission of PVC particles are the primary degradation mechanisms during the PIERS monitoring. The ultra-sensitive Ag NF-decorated TiO₂ platform and our innovative PIERS approach demonstrate significant potential for detecting and monitoring PVC-MNPs and can significantly advance the detection of MNPs in various environmental contexts.