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OperandoNanocavity-Confined Raman Spectroscopy Uncoversa Drilling-Shearing Mechanism in Nanoplastic Photodegradation
Summary
Scientists used a powerful new microscope technique to watch, in real time, exactly how sunlight-triggered chemical reactions break down individual nanoplastic particles — the tiny plastic fragments increasingly found in our water, food, and even our bodies. They discovered two different molecular "attackers" work together like a drill and a pair of shears: one chews away at the surface while the other cracks the plastic apart from within, speeding up its breakdown. Understanding this mechanism could help researchers design better ways to break down plastic pollution before it becomes the kind of nanoplastic particles that may pose health risks to 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 (•O2–) 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.