Optical sensors based on spectroscopy of localized surface plasmons on metallic nanoparticles: sensitivity considerations.

Surface plasmon resonance (SPR) sensors use two types of surface plasmons: (i) propagating along a metal-dielectric interface and (ii) localized on metallic nano-objects. This article presents theoretical analysis of sensitivity of SPR sensors based on spectroscopy of localized surface plasmons on metallic nanoparticles. Analytical formulas inter-relating bulk and surface refractive index sensitivity with main design parameters are derived using the electrostatic approximation. The effect of particle diameter is accounted for by means of Mie theory. Figures of merit for SPR sensors using localized and propagating surface plasmons are calculated and compared. Although sensors based on spectroscopy of localized surface plasmons on gold spherical particles show promise for detection of processes occurring in the close proximity of the particle surface, their performance is still inferior to that of SPR sensors based on spectroscopy of propagating surface plasmons.