Nanohoop anchored plasmonic surfaces for polarity-dependent ultrasensitive sensing

The widespread presence of plasticizers in edible oils poses serious food safety concerns, necessitating the development of rapid, sensitive, and reliable analytical techniques for detecting trace-level contamination. Indeed, surface-enhanced Raman spectroscopy (SERS) offers high sensitivity, speed, and reproducibility without complex sample pretreatment for qualitative and quantitative analysis. Herein, we develop a superhydrophobic cyclic conjugated aromatic thiophene-triazole nanohoop (TTN) [4 + 4] as a high-performance substrate for SERS. The resulting TTN serves as a platform for anchoring plasmonic silver nanoparticles (denoted as TTN@AgNPs) and demonstrates exceptional detection and quantification of di-butyl phthalate (DBP) with a significant sensitivity reaching 20 ppb in edible vegetable oil. The superior performance of TTN@AgNP hybrids stems from their heterogeneous porous surface enriched with nitrogen and sulfur, which enhances the electron density, AgNP binding, and "hot spot" formation, while crucial interactions such as hydrogen bonding, van der Waals forces, and π-π stacking further facilitate DBP adsorption, enabling highly sensitive detection. Furthermore, density functional theory calculations elucidated the interaction mechanism between TTN@AgNPs and DBP, highlighting its selective detection. This work advances understanding of plasticizer contamination in edible oils and establishes a foundation for future research on identifying key contaminants and assessing variations across oils and packaging using SERS.