Tunable Plasmon Resonances and Enhanced Local Fields of Spherical Nanocrescents

The tunable plasmon resonances of nanostructures with sharp features play an important role in the surface-enhanced spectroscopy. The maximum enhancement factor can be achieved by tuning the resonance wavelengths. In this study, the discrete-dipole approximation was used to investigate the resonance modes of the spherical nanocrescents that possess the hot spots located at the ring-tip. We applied the plasmon hybridization theory to interpret the excitation and shift of resonance modes of the nanostructure with reduced symmetry. The resonance wavelengths can be tuned from the visible to the near-infrared regime by varying the geometrical parameters. The intraparticle coupling at the ring-tip explained the significant influence of the incident light polarization on the enhancement of local fields. The spherical nanocrescents can be developed as a powerful substrate in surface-enhanced spectroscopy for the tunable plasmon resonances and enhanced local fields.