Gold cone-film composite nanostructure: A new structure for efficient excitation of the "lightning rod effect" of the tip

Gold nanocones have attracted significant attention extensively for the "lightning rod effect" at the tip. In this study, we systematically investigated the plasmonic characteristics of the gold cone-film composite nanostructure and studied the “lighting rod effect” of the tip. It is discovered that by altering the distribution of the polarized charges, the nanofilm successfully affect the "lightning rod effect" of the tip in dipole resonance (l = 1) and multipole resonance (l = 3). The field enhancement factors of the two resonance modes of the gold nanocone are 23 (l = 1) and 27 (l = 3), respectively. By modifying the gold nanofilm's thickness (T) and the distance between the gold nanofilm and the gold nanocone (S), the field enhancement factors of the two resonance modes can be controlled between 23 and 130 (l = 1) and 16 - 137 (l = 3). This is strongly related to the change in the number of polarized charges. The result expands the application of gold nanocones in enhancement spectroscopy and proposes a new method for tuning the "lightning rod effect" in different resonance modes of the nanoparticles with tips. •The local filed enhancement factors of the gold nanocone in two resonance modes were both studied and demonstrated.•By adjusting T and S, the field enhancement factors of the two resonance modes can be well controlled.•The field enhancement factors of the two resonance modes can be increased by up to 5 times compared to the gold nanocone.