Refractive Index Response of Metal Nanoparticles

Theoretically, the sensitivity of the optical properties of metal nanoparticles to the refractive index of the surrotmding medium is described by simplified Mie theory. Plasmons resonate in a nanoparticle when the denominator in Eq. (1) is at a minimum, as shown below 

Experimentally, the sensor optical response (R), defined as the change in extinction or shift in peak resonance wavelength as a function of the refractive index of the surroimding medium can be represented by Eq. (S), as follows  

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