We compared plasmonic transducers with different spatial confinement: a planar layer and spheres of different sizes.

We analyzed the responses of these systems and experimentally measured them by the subsequent adsorption of molecular layers.

We showed that smallest spheres yield the strongest non-linear dependence of the signal on deposited layers thickness.

We showed that the refractive index and the thickness layer can be obtained by analyzing the non-linear signal response.

We experimentally demonstrated that adsorption of the layers can be detected on a single nanoparticle.