Single-Particle Nanoplastic Identification by Liquid–Liquid Interfacial Assembly for Correlative SERS-SEM/EDX

Understanding the environmental fate and risks of nanoplastics requires correlating their chemical composition with their particle morphology, a task that remains highly challenging for most analytical techniques. In this study, we propose a liquid-liquid interface separation strategy that enables the in situ enrichment of nanoplastics and the simultaneous construction of surface-enhanced Raman scattering (SERS) substrates. By driving nanoplastics and silver nanoparticles (Ag NPs) toward the two-phase interface, this method achieves an enrichment efficiency of over 95% for particles ranging from 100 to 800 nm in suspensions diluted to 1 μg mL^-1. It preserves the original nanoplastic morphology and facilitates effective coating of the surface of nanoplastics with Ag NPs, which promotes the formation of localized surface plasmon resonance (LSPR) hotspots. By integrating SERS with colocalized scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), we achieved comprehensive characterization of individual nanoplastics, including both chemical composition and morphology. The platform was further applied to environmental water samples from the Lhasa River, identifying the morphological characteristics of various types of nanoplastics, such as polyethylene (PE) and polystyrene (PS), through their characteristic Raman spectra. The ability to simultaneously determine the chemical composition, size, and morphology of nanoplastics provides critical insight into their environmental transformation and risk, establishing a versatile tool for trace detection and comprehensive characterization in complex matrices.