Reusable Surface-Enhanced Raman Spectroscopy Substrates Made of Silicon Nanowire Array Coated with Silver Nanoparticles Fabricated by Metal-Assisted Chemical Etching and Photonic Reduction.

Shi Bai,Chunyan Wang,Jian Wu,Yongjun Du,Koji Sugioka

doi:10.3390/nano9111531

Abstract

Surface-enhanced Raman spectroscopy (SERS) has advanced over the last four decades and has become an attractive tool for highly sensitive analysis in fields such as medicine and environmental monitoring. Recently, there has been an urgent demand for reusable and long-lived SERS substrates as a means of reducing the costs associated with this technique To this end, we fabricated a SERS substrate comprising a silicon nanowire array coated with silver nanoparticles, using metal-assisted chemical etching followed by photonic reduction. The morphology and growth mechanism of the SERS substrate were carefully examined and the performance of the fabricated SERS substrate was tested using rhodamine 6G and dopamine hydrochloride. The data show that this new substrate provides an enhancement factor of nearly 1 × 108. This work demonstrates that a silicon nanowire array coated with silver nanoparticles is sensitive and sufficiently robust to allow repeated reuse. These results suggest that this newly developed technique could allow SERS to be used in many commercial applications.

Highlights

The three-dimensional (3D) surface-enhanced Raman spectroscopy (SERS) substrate is a powerful analytical method with applications in the fields of medicine, environmental monitoring, and spectral imaging [1,2,3,4]
The metallic nanoparticles act as sensing units to generate hot spots in association with localized surface plasmon resonance, which greatly enhances the extent of Raman scattering [9]
Oh et al reported a 3D SERS substrate comprising a glass nanopillar array with silver nanoislands [11]. This substrate was found to have a high enhancement factor (EF) and increased the SERS signals by more than one order of magnitude compared to a 2D SERS substrate

Summary

Introduction

The three-dimensional (3D) surface-enhanced Raman spectroscopy (SERS) substrate is a powerful analytical method with applications in the fields of medicine, environmental monitoring, and spectral imaging [1,2,3,4]. This substrate was found to have a high enhancement factor (EF) and increased the SERS signals by more than one order of magnitude compared to a 2D SERS substrate This improved performance was attributed to the ability of the silver nanoislands to generate a high density of hot spots on both the top and side of the glass nanopillar array [11]. We developed a simple means of fabricating the 3D SERS substrates, based on coating silicon nanowire arrays with silver nanoparticles (Ag-NP/Si-NW) The morphology of these SERS substrates, which is critical to their performance, could be controlled using metal-assisted chemical etching (MACE) followed by photonic reduction. These 3D SERS substrates were applied for the analysis of dopamine (DA) to verify that they provide both high sensitivity and reliability

Silicon Nanowire Array Fabrication by Metal-Assisted Chemical Etching

Silver Nanoparticles Synthesized by Photonic Reduction

SERS Analyses