The influence of gap spacing in localized surface plasmon resonance (LSPR) spectra of Ag nanorod-coupled with end-to-end assembly using boundary element method

We have systematically investigated the Localized Surface Plasmon Resonance (LSPR) of Ag nanorod-coupled with end-to-end assembly and influence distance between nanorod using metallic nanoparticle based on the boundary element method (MNPBEM). We focused on the extinction curve of LSPR spectra for investigating the effect of gap spacing for this work. It was found that the extinction curve showed two behaviours, for lower wavelength known as the transversal mode and higher wavelength as the longitudinal mode. For further understanding, we also analyzed the electric field related to LSPR spectra of Ag nanorod-coupled. In end-to-end assembly, the resonance peak of transversal mode shifted to lower wavelength (blue-shift) while for longitudinal mode shifted to higher wavelength (red-shift), both as the spacing gap decreased. Interestingly, for the case in parallel polarization, the peaks of wavelength decay as the gap spacing increased followed a plasmon ruler. We observed the dipole-dipole interaction was the influence in LSPR spectra of Ag nanorod-coupled. According to this result, it is essential to understand the distance dependence in LSPR spectra in coupled noble particle system.