Plasmonic nanostar@metal organic frameworks as strong adsorber, enricher, and sensor for trace nanoplastics via surface-enhanced Raman spectroscopy

Nanoplastics (NPs) have become a new risk to ecosystems and human health due to their widespread presence, difficulty in degradation, and synergistic toxicity with various pollutants. It is an urgent need to develop efficient NPs detection technology. Surface-enhanced Raman spectroscopy (SERS) is considered to be a powerful tool for rapid trace analysis of NPs with rich molecular fingerprints, but the hydrophobicity of NPs results in poor surface affinity with noble metal nanoparticles and huge difficulty in enriching in plasmonic hotspots. Here we develop a metal–organic framework (MOF) shell-encapsulated plasmonic Au nanostars (GNSs) as forceful adsorber, enricher, and sensor for NPs analysis, termed as GNS@ZIF-8. This hybrid material has the "pore-like-filling" effect, electrostatic interaction, and π-π interaction and breaks through the bottleneck of efficient capture of NPs in complex media with an enrichment capacity of 13.03 mg/g. Strong electromagnetic fields were induced by the lightning-rod effect from sharp spikes of GNSs and the expansion effect of MOF-induced surface electromagnetic field enhancement solved the problem of SERS sensitivity of NPs analysis, which generates a limit of detection (LOD) of ppm levels. In addition, GNS@ZIF-8 realized simultaneous SERS analysis on NPs with synergistic chemical pollutants, e.g. methylene blue (MB) and biological toxin pyocyanin (PYO), and the LOD of MB and PYO was 5.6 and 1.69 ppb, respectively. This study provides a new solution for developing integrated technology with broad development prospects for NPs adsorption, enrichment, and detection in the future.