SERS Amplification in Au/Si Asymmetric Dimer Array Coupled to Efficient Adsorption of Thiophenol Molecules.

Grégory Barbillon,Andrey K Sarychev,Andrey Ivanov

doi:10.3390/nano11061521

Abstract

Maximizing the surface-enhanced Raman scattering (SERS) is a significant effort focused on the substrate design. In this paper, we are reporting on an important enhancement in the SERS signal that has been reached with a hybrid asymmetric dimer array on gold film coupled to the efficient adsorption of thiophenol molecules on this array. Indeed, the key factor for the SERS effect is the adsorption efficiency of chemical molecules on the surface of plasmonic nanostructures, which is measured by the value of the adsorption constant usually named K. In addition, this approach can be applied to several SERS substrates allowing a prescriptive estimate of their relative performance as sensor and to probe the affinity of substrates for a target analyte. Moreover, this prescriptive estimate leads to higher predictability of SERS activity of molecules, which is also a key point for the development of sensors for a broad spectrum of analytes. We experimentally investigated the sensitivity of the Au/Si asymmetric dimer array on the gold film for SERS sensing of thiophenol molecules, which are well-known for their excellent adsorption on noble metals and serving as a proof-of-concept in our study. For this sensing, a detection limit of 10 pM was achieved as well as an adsorption constant K of 6 × 10 M. The enhancement factor of 5.2 × 10 was found at the detection limit of 10 pM for thiophenol molecules.

Highlights

IntroductionSeveral designs have already been explored, such as nanorods, nanodisks, and nanodimers, allowing high enhancement factors (EF) values (EF = 106 –109 ) [18,19]
The aim of this paper is to present a very sensitive detection of chemical molecules with a design based on Au/Si asymmetric dimer array deposited on gold film
From the Surface-Enhanced Raman Scattering (SERS) spectrum obtained for the concentration of 1 mM depicted in Figure 4a, four Raman peaks of thiophenol molecules [46,47,48] are well-observed like those at 999 cm−1 attributed to the C–H out-ofplane bending and ring out-of-plane deformation (called: γ(CH) and r-o-d), 1023 cm−1 corresponding to the ring in-plane deformation and C–C symmetric stretching (called: r-i-d and ν(CC)), 1075 cm−1 corresponding to the C–C symmetric stretching and C–S

Summary

Introduction

Several designs have already been explored, such as nanorods, nanodisks, and nanodimers, allowing high EF values (EF = 106 –109 ) [18,19] Among these latter, the nanodimers as disk dimers separated by a nanogap enable a high field enhancement within the nanogap and to obtain a sensitive detection of various molecules up to the single molecule level [20]. The nanodimers as disk dimers separated by a nanogap enable a high field enhancement within the nanogap and to obtain a sensitive detection of various molecules up to the single molecule level [20] Another way for enhancing the Raman signal of molecules is to realize the plasmonic nanostructures on a metallic film, which increases the enhancement factor by 1 or 2 magnitude orders due to a coupling between the nanosystems via surface plasmon polaritons or hybridization of localized plasmonic modes with the image modes in a plasmonic film [21,22,23,24]

Objectives

Results

Conclusion