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

Abstract

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 GSERS value of 6.8 × 109 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 × 1010 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.

Nanoparticles/Parabolic Nanobowl Hybrid Structure as a Surface-Enhanced Raman Scattering Substrate: Insights Using the FDTD Method

“…The simplified enhancement factor equation for the SERS-active substrate was used to calculate the electromagnetic field enhancement of the PNB structure where ω L is the excitation light frequency, ω R is the Raman frequency, and E Loc (ω L ) and E 0 are the amplitudes of the local electric field and the incident electric field, respectively. , …”

“…where ω L is the excitation light frequency, ω R is the Raman frequency, and E Loc (ω L ) and E 0 are the amplitudes of the local electric field and the incident electric field, respectively. 29,30 NPs@PNB Structure Configurations. FDTD simulations were carried out to investigate the curvature of PNB, the size of NPs, and the materials of the NPs@PNB structure.…”

Direct Synthesis of Gold Nanoparticles in Polymer Matrix

“…Here, we performed numerical simulations using a commercial three-dimensional finite-difference time-domain (FDTD) solver (Ansys Lumerical software) to study the optical properties of Au NPs in a polymeric medium. The FDTD method is recognized as a powerful numerical method to simulate the optical effect of metal NPs or nanostructures [ 47 , 48 , 49 , 50 , 51 ].…”

A Nonstandard Path Integral Model for Curved Surface Analysis

“…To evade these difficulties, an assortment of proficient techniques has been proposed (and summarized in [8]), ranging from curvilinear or nonorthogonal FDTD variations to modified Cartesian and conformal algorithms. Nonetheless, the research on this significant topic is constantly escalating, thus leading to various schemes which offer treatment to many contemporary applications from the microwave and optical regime [19][20][21][22][23][24][25][26][27][28][29][30][31] and paving the way to the trustworthy analysis of many future state-of-the-art scientific fields [32][33][34][35][36][37][38][39][40][41][42][43]. Therefore, the manipulation of arbitrarily-curved surfaces or material interfaces via a staircase model deteriorates the reliability of any FDTD-based approach and, particularly, of the NS-FDTD scheme, whose stencils must be very carefully selected.…”