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Operando Nanocavity-Confined Raman Spectroscopy Uncovers a Drilling-Shearing Mechanism in Nanoplastic Photodegradation
Summary
Scientists used a powerful new microscope technique to watch, in real time, exactly how sunlight-triggered reactive molecules break down individual nanoplastic particles — some molecules "drill" into the surface while others cause the plastic to crack and shatter from within. Understanding this two-step breakdown process matters because it could help researchers design better ways to speed up plastic degradation in the environment, potentially reducing the amount of nanoplastics that end up in our water, food, and bodies. That said, this study focused on the chemistry of plastic breakdown itself, not on direct health effects of nanoplastics in humans.
Deciphering how reactive oxygen species (ROS) govern nanoplastic photodegradation remains unresolved due to the lack of approaches capable of directly correlating chemical transformations with ROS activity at the single-particle level. Here, we report a nanocavity-confined Raman platform that enables operando molecular fingerprinting of individual nanoplastics with ultralow detection limits in both size and concentration. This approach allows real-time tracking of degradation intermediates within single photocatalytic nanoreactors. Time-resolved Raman analysis, combined with ROS-selective quenching experiments and electron paramagnetic resonance measurements, reveals distinct ROS-dependent pathways in which hydroxyl radicals ( • OH) induce progressive surface oxidation, whereas superoxide radicals ( • O 2 – ) promote bond cleavage and bulk fragmentation. These assignments are further supported by electron microscopy, which shows morphology-dependent structural evolution under different ROS environments. Collectively, these converging lines of evidence support a cooperative degradation mechanism in which surface activation and subsurface fragmentation proceed concurrently. This coupled process gives rise to a drilling-shearing mechanism that accelerates nanoplastic breakdown. This work establishes a direct correlation between ROS activity and nanoscale chemical transformations at the single-particle level, providing a mechanistic framework for understanding and controlling nanoplastic photodegradation.