FDTD Analysis of Hotspot-Enabling Hybrid Nanohole-Nanoparticle Structures for SERS Detection

Metallic nanoparticles (MNPs) and metallic nanostructures are both commonly used, independently, as SERS substrates due to their enhanced plasmonic activity. In this work, we introduce and investigate a hybrid nanostructure with strong SERS activity that benefits from the collective plasmonic response of the combination of MNPs and flow-through nanohole arrays (NHAs). The electric field distribution and electromagnetic enhancement factor of hybrid structures composed of silver NPs on both silver and gold NHAs are investigated via finite-difference time-domain (FDTD) analyses. This computational approach is used to find optimal spatial configurations of the nanoparticle positions relative to the nanoapertures and investigate the difference between Ag-NP-on-Ag-NHAs and Ag-NP-on-Au-NHAs hybrid structures. A maximum G(SERS) value of 6.8 x 10(9) is achieved with the all-silver structure when the NP is located 0.5 nm away from the rim of the NHA, while the maximum of 4.7 x 10(10) is obtained when the nanoparticle is in full contact with the NHA for the gold-silver hybrid structure. These results demonstrate that the hybrid nanostructures enable hotspot formation with strong SERS activity and plasmonic enhancement compatible with SERS-based sensing applications.

Automated summary

In this study, a hybrid nanostructure with strong surface-enhanced Raman scattering (SERS) activity is introduced and investigated. The nanostructure combines metallic nanoparticles (MNPs) and flow-through nanohole arrays (NHAs) to achieve collective plasmonic resonance. Computational analysis is used to determine the optimal spatial configuration of the nanoparticles and nanoapertures, and to compare the performance of silver nanoparticles on silver and gold NHAs. The results show that the hybrid nanostructures enable the formation of strong SERS-active hotspots and plasmonic enhancement, making them compatible for SERS-based sensing applications.