New plasmonic probes, based on silica microspheres decorated with metal
nanoparticles (Figure 1), are built and used to confine and enhance the electric field
in their interaction with the sample, giving ultra-high optical resolution in a wide
variety of samples [1]. The coverage and aggregation processes of nanoparticles on
plane and spherical substrates were systematically studied [2]. These probes present
red shifted resonances, dominated by the formation of small nanoparticle clusters [3].
Approach curves with the new probes show clearly field enhancement at very short
probe-sample distances, and depend strongly on the incoming wavelength and
polarization. Optical contrast was achieved in flat samples composed by materials of
different dielectric constants, and images were obtained using optical feedback.
