Optimal self-referenced sensing using long- and short- range surface plasmons.

Dual-mode surface-plasmon resonance (SPR) sensors use both long- and short- range surface plasmon waves to differentiate surface binding interactions from interfering bulk effects. We have optimized the design of these sensors for minimum surface limit of detection (LOD) using a Cramer-Rao lower bound for spectral shift estimation. Despite trade-offs between resonance width, minimum reflectivity, and sensitivity for the two modes, a range of reasonable design parameters provides nearly optimal performance. Experimental verification using biotin-streptavidin binding as a model system reveals that sensitivity and LOD for dual-mode sensors remains competitive with single-mode sensors while compensating for bulk effects.