Facile Fabrication of Micro/Nano Hierarchical SERS Sensor via Anisotropic Etching and Electrochemical Treatment for Malachite Green Detection

Chu-Yu Huang,Chih-Hung Chien

doi:10.3390/app9235237

Abstract

We propose a facile method to produce micro/nano hierarchical surface-enhanced Raman scattering (SERS) active substrates using simple steps and inexpensive costs. The proposed SERS substrate is a silicon pyramid array covered by a nanostructured gold film (AuNS @ SiPA). Through finite element method (FEM) simulation, we showed that many strong local electric field enhancements (hot spots) were formed between the nano-gap of gold nanostructures. In addition, the micron-scale pyramid structure not only increases the sensing surface area of the sensor, but also helps trap light. By combining these micro and nano structures, the proposed micro/nano hierarchical SERS sensor exhibited high sensitivity. Experimental results confirmed that the AuNS @ SiPA substrate has high sensitivity. The SERS signal enhancement factor obtained from the Rhodamine 6G (R6G) probe molecules was as high as 1 × 107 and the SERS substrates were found to be able to detect a very low concentration of 0.01 nM malachite green (MG) solution. Therefore, this study provides a novel and practical method for fabricating SERS substrates that can facilitate the use of SERS in medicine, food safety, and biotechnology.

Highlights

Malachite green is often illegally used in aquaculture to prevent aquatic animals from being infected by parasites, fungi, and protozoa [1]
The results show that the substrate has high sensitivity and can measure very low concentrations of Rhodamine 6G (R6G) and malachite green
It can be seen that the longer the duration, the larger the diameter of these nanoparticles

Summary

Introduction

Malachite green is often illegally used in aquaculture to prevent aquatic animals from being infected by parasites, fungi, and protozoa [1]. Surface-enhanced Raman spectroscopy (SERS) technology has the potential to provide a very fast and sensitive method of detecting chemicals and biomolecules. It can be a solution for this unmet need. Substrates with only 3D microstructures are not sufficient to generate strong SERS signals, and studies have shown that strong local surface plasmons (SERS hot spots) occur at the nano-gaps between noble metal nanostructures [9,10]. By combining the micro-pyramid array and gold nanostructure on the pyramid surface, this micro/nano hierarchical structured SERS substrate can greatly enhance the Raman signal. The results show that the substrate has high sensitivity and can measure very low concentrations of R6G and malachite green

Fabrication of the Silicon Micro-Pyramid Structures

Experiments

As can be seen fromcurrent

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Simulations

Conclusions