Refractometric sensing using propagating versus localized surface plasmons: a direct comparison.

We present a direct experimental comparison between the refractive index sensing capabilities of localized surface plasmon resonances (LSPRs) in gold nanodisks and propagating surface plasmon resonances (SPRs) on 50 nm gold films. The comparison is made using identical experimental conditions, and for the same resonance wavelength, lambda(SP) congruent with 700 nm. Biosensing experiments with biotin-avidin coupling reveal that the two sensing platforms have very similar performance, despite a superior bulk refractive index sensing figure of merit for the SPR sensor. The results demonstrate that LSPR sensing based on simple transmission or reflection measurements is a highly competitive technique compared to the traditional SPR sensor.