Cationic metal detection using an Al–Al2O3 nanoengineered SPR sensor

This study reports a surface plasmon resonance (SPR) sensor concept for detecting heavy metal ions in water using a cost-effective multilayer stack based on aluminum (Al), aluminum oxide (Al 2 O 3 ), and 2D nanomaterials. The architecture is numerically analyzed using the transfer matrix method (TMM) under TM-polarized illumination at 633 nm. Key design parameters, including prism material, Al and Al 2 O 3 thicknesses, and 2D nanomaterial coatings (GO, rGO, sSWCNT, and graphene), are optimized to improve sensitivity and resonance definition. CaF 2 is identified as the optimal prism, and an Al thickness of 40–45 nm combined with a 6 nm Al 2 O 3 layer provides a favorable trade-off between resonance sharpness and field confinement. Among the evaluated coatings, rGO yields the best overall performance. For Pb 2+ sensing, the optimized configuration achieves an angular sensitivity of 195.67°/RIU, a detection accuracy (DA) of 0.334, and a figure of merit (FoM) of 481.62 RIU −1 . Electric-field analysis indicates strong confinement at the sensing interface. Overall, the proposed Al–Al 2 O 3 /2D SPR platform supports real-time, label-free detection of toxic metal ions and highlights aluminum-based stacks as a scalable alternative to noble-metal configurations for environmental sensing.