Gold elliptical nanoring-groove plasmonic sensor for enhanced label-free solution concentration analysis
摘要
Nano-plasmonic refractive index (RI) sensors have shown considerable potential in label-free solution concentration sensing applications. In order to achieve high sensitivity and a high figure of merit using surface plasmon effects, a nanoscale plasmonic sensor array was designed and numerically investigated using the finite-element method (FEM). The proposed structure consists of interconnected gold elliptical nanorings integrated on a silicon dioxide substrate. The coupling region between the nanorings generates enhanced localized electromagnetic fields and distinct plasmonic resonance characteristics. We investigated the nanoring structure without grooves as a reference configuration, which exhibited a figure of merit (FOM) of 4.42 RIU− 1, a sensitivity of 357.14 nm/RIU, and a full width at half maximum (FWHM) of 80.78 nm. By introducing a square groove beneath the nanoring structure, the interaction between the localized electromagnetic field and the surrounding analyte region was further enhanced. The groove-assisted configuration strengthens the plasmonic coupling effect and improves the overlap between the hotspot region and the analyte medium, increasing the FOM to 9.16 RIU− 1 and the sensitivity to 714.28 nm/RIU, with a FWHM of 77.99 nm. Compared with the reference structure without grooves, the sensitivity is approximately doubled, and the FOM is improved by about 107.24%. These results indicate that the proposed elliptical nanoring-groove sensor may provide potential for label-free detection of concentration-induced refractive-index variations in solution-based analytes.