Uniform Periodic Bowtie SERS Substrate with Narrow Nanogaps Obtained by Monitored Pulsed Electrodeposition

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive technique with molecular specificity, making it an ideal analytical tool in various fields. However, the breadth of practical applications of SERS has been severely limited because it is still a great challenge to achieve simultaneously a high sensitivity and a high reproducibility. Herein, we report a highly controllable method to fabricate periodic bowtie SERS substrates with a narrow nanogap, high SERS enhancement, and good uniformity over a large area. The periodic bowtie template is first fabricated over a gold film by holographic lithography (HL), followed by Au deposition to obtain a conductive plasmonic bowtie array. The gap size is then narrowed down by pulsed electrodeposition of Ag simultaneously monitored in situ by electrochemical dark field spectroscopy. Thus, we are able to observe the most sensitive change in the scattering spectra when the gap is just about to merge and obtain uniform SERS substrates with a gap size down to around 5 nm. The average enhancement factor of 5 × 10 7 to 1 × 10 8 is obtained, which is 50 times larger than that from Au nanoparticle-assembled substrates and 140 times larger than that from commercial Klarite chips. This substrate offers a promising opportunity for SERS practical applications.

Versatile Graphene‐Isolated AuAg‐Nanocrystal for Multiphase Analysis and Multimodal Cellular Raman Imaging†

“…SERS‐based bioanalytical applications involve the interactions of SERS substrate with complex biological systems. [ 14‐16 ] Undoubtedly, the SERS substrate is a pivotal factor for governing sensitivity and reproducibility of SERS bioanalysis. [ 17‐19 ] Au nanocrystals (Au NCs) with strong surface plasmonic resonance (SPR) properties and superior chemical stability have been extensively used as SERS substrates.…”

Recent Progress in the Nanoskiving Approach: A Review of Methodology, Devices, and Applications

“…[ 63 ] Raman enhancement factors as high as 10 9 for metal nanogaps have been observed experimentally and this is sufficient for use in the detection of single molecules. [ 64,65 ] Several approaches to the manufacture of nanogaps with controllable spacing have been proposed, including electron‐beam lithography, [ 66 ] the mechanical break junction method, [ 67 ] electromigration, [ 68 ] electrochemical deposition, [ 69 ] and atomic layer deposition. [ 70 ] However, the characteristics of these serial methods are unsuitable for high‐throughput and low‐cost manufacturing applications.…”

Biosensors for Studies on Adhesion-Mediated Cellular Responses to Their Microenvironment

“…Cells can be seeded on SERS substrates, and once they adhered and spread, their chemical composition near the surface can be studied by irradiating the substrate and measuring the Raman spectra. Over the years, a wide diversity of metal nanostructured surfaces have been created for SERS, such as nanoparticles attached to a surface (Freeman et al, 1995;Zhai et al, 2009;Lussier et al, 2016), nanopillars (Kang et al, 2015;Li et al, 2016), nanoholes (Abdelsalam et al, 2005;Luo et al, 2019), and others (Yüksel et al, 2017;Yao et al, 2020). A detailed review on the fabrication of SERS substrates can be found in Fan et al (2011).…”