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

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.