Theoretical studies on the near field properties of non-concentric core–shell nanoparticle dimers

The concentric core–shell nanoparticle dimers have “hot spots” with enhanced electric fields in their junctions, which can be used in the surface enhanced Raman spectra analysis. Here the non-concentric core–shell nanoparticle dimers are proposed by introducing a shift between the dielectric core and the metal shell. By using the three dimensional finite difference time domain method, the plasmon resonances and the near field properties of the core–shell nanoparticle dimers affected by the non-concentric shift, dimer separation, excitation wavelength and polarization are analyzed in detail. The results show that the local near fields of the non-concentric core–shell nanoparticle dimers can be much more enhanced than those of the concentric ones. Also the plasmon resonance wavelengths of the dimers can be effectively tuned by the non-concentric shifts between the core and shell. The proposed nanostructures can have great potential in various near field applications.