Surface-Enhanced Raman Scattering with Spheroidal Gold Nanoparticles in a Nanorods-on-Mirror Configuration

 

 

 

Raman spectroscopy is a label-free technique with the capability of identifying different molecules via fingerprint-like spectra and has become an increasingly useful tool in biological sensing. To improve the low sensitivity of this technique due to the weak process of Raman scattering, surface-enhanced Raman scattering (SERS) has been developed and attracted great attention in the early diagnosis of diseases [1,2]. However, many obstacles still exist in achieving consistent detection of targeted molecules with high sensitivity and specificity. Previous studies have shown that SERS enhancement can be as high as 10⁸ in nanorods-on-mirror substrates a result of the excitation of gap plasmons between the gold nanorods and the gold substrate beneath the rods.  In this study, we use numerical simulations to analyze the SERS enhancement produced by spheroidal gold nanoparticles placed on a gold substrate with a dielectric gap. By varying parameters including the dimensions of the gold spheroids, the thickness of the dielectric layer, and the direction of the exciting light, we show that the SERS enhancement can be optimized to reach 10⁵ at an incident wavelength of 532 nm and more than 10⁸ at 785 nm. SERS enhancement on these optimized structures is characterized by decorating the gold spheroids with a common Raman reporter, 4-mercaptobenzoic acid (4-MBA), and the results will be compared with theoretical predictions.

 

 

[1] T. J. Moore et al. Biosensors (Basel) 8, 46 (2018).

[2] J. Langer et al., ACS Nano 14, 28-117 (2020).

[3] E. Oksenberg et al., Adv. Funct. Mater. 33, 2211154 (2023).