Solar-Driven Plasmonic Nanoreactors for In-situ Monitoring of Microplastics in Aquatic Environments

In this study, a solar-powered Au-Ag plasmonic nanoreactor system was created that integrates the detection (via surface-enhanced Raman scattering, SERS) and degradation (via photocatalytic reactive oxygen species, ROS, generation) of microplastics within one eco-friendly platform.The rapid increase in microplastic contamination and persistent organic pollutants in aquatic environments poses a twofold challenge: detection accuracy and cleanup efficiency. Herein, we developed Au–Ag plasmonic nanoreactors as a multifunctional platform that integrates solar-light-promoted photocatalytic degradation with ultrasensitive sensing. Although Raman investigations showed considerable hotspot formation required for SERS activity, structural and morphological analysis confirmed the establishment of stable bimetallic nanostructures with characteristic localised surface plasmon resonance (LSPR) peaks. Even with the presence of naturally occurring natural organic matter, the nanoreactors facilitated the ppb-level detection of microplastics, e.g., polystyrene (PS) and polyethylene terephthalate (PET), with clear discrimination in the spectrum. Between 10 ppm and 100 ppb, a linear dependence between SERS intensity and concentration was observed with a detection limit of around 85 ppb and reproducibility with a relative standard deviation (RSD) below 7%. Parallel to this, kinetic analysis yielded a pseudo-first-order rate constant (k = 0.021 min⁻¹), nearly five times that of conventional photocatalysts, and photocatalytic examination revealed > 90% model pollutant degradation in 120–150 min. Radical scavenger studies confirmed the primary breakdown processes to be superoxide (•O₂⁻) and hydroxyl (•OH) radicals. Notably, the sensing–remediation integrated setup retained more than 80% efficacy after five cycles of operation, validating the stability and reusability of the nanoreactors. Due to its dual functionality, plasmonic nanoreactors represent a realistic and scalable method of continuous monitoring of water quality and degradation of contaminants, with immense potential to be applied in environmental remediation technology in the future. Schematic representation of solar-driven Au-Ag plasmonic nanoreactors showing dual actions. The graphical abstract presents a simple diagram illustrating the solar-powered Au–Ag plasmonic nanoreactors working in water. The sunlight hits the Au–Ag nanostructures and causes the creation of very strong plasmonic “hotspots.” There are two things that these hotspots can do simultaneously: The entire process resembles a mono platform that is solar powered where real time sensing and remediation of the pollutants can be done in aquatic habitats.