Modeling and Theoretical Analysis of the SERS Enhancement Factor Considering the Electronic Structural Energy

Xu Yang,Kangkang Guo,Shoubo Zhao,Jia Qi,Siqi Zhang,Zhen Zhou

doi:10.1109/access.2021.3107507

Abstract

The enhancement factor is one of the key parameters characterizing the phenomenon of surface-enhanced Raman scattering. At present, this parameter is described by an empirical formula or a certain single physical mechanism instead of a unified model of the chemical and electromagnetic enhancement mechanisms. It is necessary to integrate the dual enhancement mechanisms of SERS to more accurately obtain the SERS enhancement factor with molecular selectivity. Therefore, we propose a quantitative model for the prediction of the enhancement factor that includes the two main contributions, metal plasmon resonance and electronic structure. Theoretical analysis and verification by experimental results prove that the new predictive enhancement factor (EF) model of electronic structural energy improves the enhancement factor by approximately 10 times and can be used to calculate the enhancement factors of different molecules on the same substrate material, which can provide molecular selectivity and more accurate EF predictions. This paper presents a theoretical model of the SERS enhancement factor that includes the adsorption of the adsorbed molecules and the surface of the substrate, combines the electromagnetic and chemical enhancement mechanisms for surface-enhanced Raman scattering, and provides a deep comprehension of the phenomenon of surface-enhanced Raman scattering.

Highlights

Surface-enhanced Raman scattering (SERS), based on theRaman effect of adsorbed molecules, is a new spectral detection technique with high efficiency, sensitivity, real time data acquisition and good specificity [1, 2], and it is widely used for molecular identification and characterization, surface treatment of engineering materials, and applications in life science, food safety and other fields [3,4,5,6]
Pyridine (Py) is one of the most important SERS probe molecules [40], so we studied the Raman enhancement effect after it interacts with metal nanoparticles
This paper introduces electronic structural energy to revise the theoretical model of the SERS enhancement factor by

Summary

INTRODUCTION

Raman effect of adsorbed molecules, is a new spectral detection technique with high efficiency, sensitivity, real time data acquisition and good specificity [1, 2], and it is widely used for molecular identification and characterization, surface treatment of engineering materials, and applications in life science, food safety and other fields [3,4,5,6]. Based on the above discussion, this paper establishes a theoretical model for the calculation of SERS enhancement factors of metal nanoparticles based on the local surface plasma effect and electronic structure theory, analyzes the effects of the properties, size and shape of metal nanoparticles on SERS enhancement, and considers the influence of the adsorption between the molecule to be tested and the substrate material on the SERS enhancement. Pyridine (Py) is one of the most important SERS probe molecules [40], so we studied the Raman enhancement effect after it interacts with metal nanoparticles. We analyzed the electronic structural energy and Raman enhancement effect when the molecule of interest interacts with the metal cluster. The coupling of the benzene ring carbon-carbon, hydrocarbon and carbon-sulfur bond bending vibrations is caused by clusters

TABLE II ENHANCEMENT FACTOR COMPARISON

CONCLUSIONS