Ferroelectric-assisted gold nanoparticles array for centimeter-scale highly reproducible SERS substrates

Xiaoyan Liu,Donghui Si,Takahiro Nagata,Minoru Osada,Kenji Kitamura

doi:10.1038/s41598-017-03301-y

Abstract

Assemble metal nanoparticles into various ordered structures with scale up to centimeter area is required to meet diverse needs of lab-on-a-chips and analytic components. Here, we present the uniform and high-yield fabrication of centimeter-scale gold nanoparticles (AuNPs) array for SERS substrates. Ferroelectric-assisted assembly of AuNPs line array is successfully fabricated by using a periodically poled LiNbO3 (PPLN) single crystal as a template. SNOM-Raman shows that the uniform assembly of AuNPs exhibits a high density of “hot spots” arising from strong electromagnetic (EM) field coupling induced by adjacent AuNPs. Quantitative analysis based on SERS detection describes an excellent reproducibility with an intensity variation less than 7% at 1649 cm−1 of Rhodamine 6G. SERS spectra combined with 3D-FDTD modelling indicate that the EM enhancement occurs at all three excitation wavelength of 515, 561 and 633 nm and the 561-nm-laser displays the strongest Raman enhancement with an enhancement factor in an order of 109. The corresponding experimental and theoretical results present a new strategy to fabricate large-area, highly reproducible and sensitive SERS substrates for practical applications.

Highlights

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive vibrational spectroscopy that allows for the detection of analytes at extremely low concentrations[1, 2]
The periodically proton exchanged LiNbO3 (PPELN) substrates made by periodically proton exchanged method exhibit surface morphology with steps between the +Z and −Z domains at a height of 6–8 nm[27], which could be a demerit as used for SERS substrates
Photochemically-induced assembly of AuNPs array on the periodically poled LiNbO3 (PPLN) was performed with optimized parameters of illumination and HAuCl4 aqueous solution

Summary

Introduction

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive vibrational spectroscopy that allows for the detection of analytes at extremely low concentrations[1, 2]. We report an easy-to-control technique based on ferroelectric-assisted assembly of AuNPs line array as high-performance SERS substrates with excellent reproducibility at a centimeter-scale area. This technique can be applied to assemble metal nanoparticles into various ordered structures, such as spot array with scale up to centimeter area (Fig. S1) to meet the diverse needs of lab-on-a-chips and analytic components. This ferroelectric-assisted assembly presents a new strategy to fabricate large-area and high reproducible SERS substrates

Methods

Results

Conclusion