Theoretical investigation and numerical optimization of multi-cone Au nanostructures for plasmonic resonance and SERS sensitivity

In this paper, innovative multi-cone gold nanostructures are proposed and simulated to explore their potential for localized surface plasmon resonance (LSPR)-based applications, including highly enhanced surface-enhanced Raman scattering (SERS). By systematically analyzing two-, four-, and six-cone geometries with a fixed diameter and varying heights, it is demonstrated that the designed nanostructures support intensely localized hot spots and strong near-field enhancements. The optical responses of nanostructures are investigated, and the results show that cone number and geometry tune the LSPR and the magnitude of near-field amplification. Notably, all designed configurations exhibit significant field enhancements and red-shifted LSPR compared with simpler geometries like spherical gold nanoparticles. Increasing the cone number from two to six leads to a red shift in LSPR wavelength and lower maximum electric field enhancement, indicating that a biconical or two-cone gold nanoparticle has the best efficiency for the mentioned applications. Also, studying the coupling effects in the two-cone nanoparticle reveals pronounced interparticle plasmonic interactions, a pronounced red shift of LSPR, and ultra-high electric-field magnitudes in the gap region, yielding substantial Raman enhancements beyond conventional Raman spectroscopy. The results indicate that carefully engineered multi-cone nanostructures offer a versatile platform for highly sensitive and selective sensing, with potential applications in biomedical diagnostics and environmental monitoring. Our findings provide a systematic framework for designing nanostructures with tailored plasmonic responses and provide the way for future advances in nanoscale sensing, photonics, and plasmonic technologies.