Spectroscopic investigation of polyimide-based long-range surface plasmon resonance for mineral oil hydrocarbon detection in edible oils.

This study presents a polyimide (PI)-integrated long-range surface plasmon resonance (LRSPR) sensor specifically designed for the detection of mineral oil hydrocarbon in edible oil matrices. The integration of the PI dielectric layer introduces a novel sensing strategy that combines enhanced plasmon propagation with excellent compatibility for viscous oil media, overcoming limitations commonly faced by conventional plasmonic systems. The PI layer effectively improves light confinement and refractive index sensitivity, resulting in a pronounced red shift and broader FWHM compared to the bare Au configuration. The Au-PI LRSPR exhibited a low detection limit (0.683 ppm) and high linearity (R2 = 0.9581), demonstrating superior analytical performance suitable for oil-based sensing applications. Beyond its high sensitivity, the LRSPR system provides real-time, label-free, and non-destructive detection without complex sample preparation. The novelty of this work lies in the application of LRSPR within viscous oil matrix using PI as a dielectric layer, highlighting its potential as a robust, practical, and high-performance platform for in-situ oil quality monitoring and contaminant detection.