The effect of mutual orientation on the spectra of metal nanoparticle rod-rod and rod-sphere pairs

A simple quasistatic treatment for the plasmon resonance spectra of nanoparticle rod-rod and rod-sphere pairs is presented. Spectra are calculated for gold particle pairs at different distances and mutual orientations. For rod-rod and rod-sphere pairs, the spectral changes that occur as a result of interparticle interaction are different for end-to-end (axial) and side-to-side (lateral) orientations. Axial interactions generally lead to a red shift of the most intense (longitudinal axis) plasmon resonance band. Lateral interactions usually lead to a blue shift of the main plasmon band. In general, lateral orientation yields more pronounced spectral changes than the axial case, especially as the aspect ratio of the rod member(s) increases.