  Electronic excitations in metallic nanoparticles in the optical regime that
have been of great importance in surface enhanced spectroscopy and emerging
applications of molecular plasmonics, due to control and confinement of
electromagnetic energy, may also be of potential to control the motion of
nanoparticles and molecules. Here, we propose a concept for trapping
polarizable particles and molecules using toroidal metallic nanoparticles.
Specifically, gold nanorings are investigated for their scattering properties
and field distribution to computationally show that the response of these
optically resonant particles to incident photons permit the formation of a
nanoscale trap when proper aspect ratio, photon wavelength and polarization are
considered. However, interestingly the resonant plasmonic response of the
nanoring is shown to be detrimental to the trap formation. The results are in
good agreement with analytic calculations in the quasi-static limit within the
first-order perturbation of the scalar electric potential. The possibility of
extending the single nanoring trapping properties to two-dimensional arrays of
nanorings is suggested by obtaining the field distribution of nanoring dimers
and trimers.
