Plasmonic Gold Nanohole Arrays for Surface-Enhanced Sum Frequency Generation Detection.

Wei Guo,Bowen Liu,Yongyan Zhang,Enming You,Shengchao Huang,Yuhan He,Zhaohui Wang,Jingjing Wang

doi:10.3390/nano10122557

Wei Guo, Bowen Liu + Show 6 more

Open Access

https://doi.org/10.3390/nano10122557

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Journal: Nanomaterials	Publication Date: Dec 19, 2020
Citations: 7	License type: CC BY 4.0

Affiliation: Xiamen University, Lanzhou University

Abstract

Nobel metal nanohole arrays have been used extensively in chemical and biological systems because of their fascinating optical properties. Gold nanohole arrays (Au NHAs) were prepared as surface plasmon polariton (SPP) generators for the surface-enhanced sum-frequency generation (SFG) detection of 4-Mercaptobenzonitrile (4-MBN). The angle-resolved reflectance spectra revealed that the Au NHAs have three angle-dependent SPP modes and two non-dispersive localized surface plasmon resonance (LSPR) modes under different structural orientation angles (sample surface orientation). An enhancement factor of ~30 was achieved when the SPP and LSPR modes of the Au NHAs were tuned to match the incident visible (VIS) and output SFG, respectively. This multi-mode matching strategy provided flexible controls and selective spectral windows for surface-enhanced measurements, and was especially useful in nonlinear spectroscopy where more than one light beam was involved. The structural orientation- and power-dependent performance demonstrated the potential of plasmonic NHAs in SFG and other nonlinear sensing applications, and provided a promising surface molecular analysis development platform.

Highlights

Sum-frequency generation (SFG) has spurred increasing interest because of its high surface specificity, sub-monolayer sensitivity, and capability of controllable new frequency generation
As a second order nonlinear optical process, SFG is forbidden in any medium with centrosymmetry under electric-dipole approximation, but is active at the surface/interface where the centrosymmetry is broken
SFG is often frustrated by its high incident power and low signal flux, especially for in situ characterization and dynamic analysis of trace concentration species

Summary

Introduction

Sum-frequency generation (SFG) has spurred increasing interest because of its high surface specificity, sub-monolayer sensitivity, and capability of controllable new frequency generation. As a second order nonlinear optical process, SFG is forbidden in any medium with centrosymmetry under electric-dipole approximation, but is active at the surface/interface where the centrosymmetry is broken This makes SFG an intrinsically surface-sensitive technique, which can exclude the contributions from the bulk, and be a surgical tool to study the adsorbed species at interfaces, such as water/air interfaces [1,2,3,4], solid/air interfaces [5], protein surfaces [6,7], and electrochemical surfaces [8,9]. Compared with LSPR systems, most surface plasmon polariton (SPP) nanostructures are more specific in structure, with a relatively larger uniform area [17,18]. 2D metal grating [28] and its combination with NPs [29] have a greater electromagnetic field area and EF in surface-enhanced Raman scattering (SERS) through the coupling of LSPR and SPP. The SFG enhancement of 4-Mercaptobenzonitrile (4-MBN) on Au NHAs was observed, and the influence of the structural orientation of the Au NHAs was investigated

Chemicals and Materials

Fabrication of Au NHAs

Characterization of the Au NHAs