Improved Surface-Enhanced-Raman Scattering Sensitivity Using Si Nanowires/Silver Nanostructures by a Single Step Metal-Assisted Chemical Etching

Abstract

In this study, we developed highly sensitive substrates for Surface-Enhanced-Raman-Scattering (SERS) spectroscopy, consisting of silicon nanowires (SiNWs) decorated by silver nanostructures using single-step Metal Assisted Chemical Etching (MACE). One-step MACE was performed on p-type Si substrates by immersion in AgNO3/HF aqueous solutions resulting in the formation of SiNWs decorated by either silver aggregates or dendrites. Specifically, dendrites were formed during SiNWs’ growth in the etchant solution, whereas aggregates were grown after the removal of the dendrites from the SiNWs in HNO3 aqueous solution and subsequent re-immersion of the specimens in a AgNO3/HF aqueous solution by adjusting the growth time to achieve the desired density of silver nanostructures. The dendrites had much larger height than the aggregates. R6G was used as analyte to test the SERS activity of the substrates prepared by the two fabrication processes. The silver aggregates showed a considerably lower limit of detection (LOD) for SERS down to a R6G concentration of 10−13 M, and much better uniformity in terms of detection in comparison with the silver dendritic structures. Enhancement factors in the range 105–1010 were calculated, demonstrating very high SERS sensitivities for analytic applications.

Molecular Fingerprinting of the Omicron Variant Genome of SARS-CoV-2 by SERS Spectroscopy

“…This approach, indeed, allows for a dense forest of silicon nanowires (Si NWs) whose length can be tuned and whose large surface can be decorated with other materials [47,58], such as metal nanostructures. This occurrence permits realizing very sensitive 3D SERS substrates [59][60][61]. Furthermore, during the fabrication process of Si NWs by means of MACE, silver dendrites are obtained as a waste product of the chemical reaction, representing good candidates for highly sensitive SERS performances [33,59].…”

“…This occurrence permits realizing very sensitive 3D SERS substrates [59][60][61]. Furthermore, during the fabrication process of Si NWs by means of MACE, silver dendrites are obtained as a waste product of the chemical reaction, representing good candidates for highly sensitive SERS performances [33,59].…”

A flap endonuclease 1-assisted universal viral nucleic acid sensing system using surface-enhanced Raman scattering

“…37,38 Silver nanowires grown on a highly ordered porous aluminum oxide template have been widely employed as SERS substrates because their nanostructures and nanopatterns, along with an enhancement factor, can be easily tuned by varying the etching time. 39 Here, we present an optical biosensing platform based on FEN1-assisted cleavage activity and electrochemically deposited silver nanopillar structures for the highly sensitive and multiplexed detection of an avian influenza A (H9N2) virus. 40,41 We adopted a nanostructured solid platform with electrochemically grown silver nanopillars as a solid-state SERS substrate, displaying gaps of several nanometers between each adjacent pillar.…”

Surface-Enhanced Raman Sensing of Semi-Volatile Organic Compounds by Plasmonic Nanostructures

“…Functional plasmonic nanostructures have gained increasing interest in energy and environmental fields [1]. SERS has recently been introduced for effective sensing combined with noble metal systems by introducing hotspots to enhance electromagnetic enhancements [2,3]. Biosensing [4,5] can also be achieved using novel nanostructures [6].…”