Generally, an important parameter to describe and compare the performance of optical refractive index (RI), sensors is sensitivity (S), which represents the shift of the resonance peak position per unit RI change, which is usually defined by the following formula;
S = Δλ/Δn
where Δn represents the change in RI, and Δλ represents the shift of the peak position of the resonance.
to calculate RIS you have to obtain (measure or simulate) absorption spectra for different refractive indices of the medium. RIS is then the shift of the spectral peak position divided by the difference in medium refractive index.
According to the Drude model, the surface plasmon peak position for a spherical particle depends on the refractive index of the surrounding medium(17,19).
l2 = lp2 (e¥ + 2em)
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The Refractive Index (RI) Sensitivity is defined as S =Δλ/Δn, where Δλ is the
shift of the LSPR wavelength and Δn is the change of the RI
of the surrounding medium Whereas, FOM is defined as FOM= S/
FWHM, where FWHM stands for full width at half maximum.
Hi Raj, the formula that you provided is correct. So it is based on the red-shift of the plasmon band or LSPR (or lattice resonance band) with changing refractive index. However, in many sensing applications like for instance gas sensing, the change refractive index is too small to induce a redshift that is detectable by the wavelength resolution of the device without statistical errors. An alternative strategy in that case is to just probe the optical intensity at the resonance or close to resonance. Or ellipsometry can also be even better than just optical intensity. This recent work may be useful for you in that regard:
Article Self-Assembled Ligand-Capped Plasmonic Au Nanoparticle Films...
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