High-Throughput Fabrication of Triangular Nanogap Arrays for Surface-Enhanced Raman Spectroscopy

Abstract

Squeezing light into nanometer-sized metallic nanogaps can generate extremely high near-field intensities, resulting in dramatically enhanced absorption, emission, and Raman scattering of target molecules embedded within the gaps. However, the scarcity of low-cost, high-throughput, and reproducible nanogap fabrication methods offering precise control over the gap size is a continuing obstacle to practical applications. Using a combination of molecular self-assembly, colloidal nanosphere lithography, and physical peeling, we report here a high-throughput method for fabricating large-area arrays of triangular nanogaps that allow the gap width to be tuned from ∼10 to ∼3 nm. The nanogap arrays function as high-performance substrates for surface-enhanced Raman spectroscopy (SERS), with measured enhancement factors as high as 10 8 relative to a thin gold film. Using the nanogap arrays, methylene blue dye molecules can be detected at concentrations as low as 1 pM, while adenine biomolecules can be detected down to 100 pM. We further show that it is possible to achieve sensitive SERS detection on binary-metal nanogap arrays containing gold and platinum, potentially extending SERS detection to the investigation of reactive species at platinum-based catalytic and electrochemical surfaces.

Identification of Poly(ethylene terephthalate) Nanoplastics in Commercially Bottled Drinking Water Using Surface-Enhanced Raman Spectroscopy

“…As shown in Figure e, well-defined nanotriangluar cavities (side length of 160 nm) were formed along the prenanosphere-templated nanotriangular edges of Ag over a large area. Such nanoscale sharp apex and edges of cavities can generate tremendous electromagnetic field enhancements and localization of incident light and thus are suitable for SERS analysis. ,− To elucidate the mechanism and further optimization of a TCA substrate for SERS application, electric field distribution simulations were performed under illumination wavelengths of 532, 633, and 785 nm, as shown in Figure S2. The enhanced field is mostly concentrated in the apex and edges of the triangular cavities and is the strongest under the illumination of 532 nm.…”

The Influence of Geometry on Plasmonic Resonances in Surface- and Tip-Enhanced Raman Spectroscopy

“…Another way to boost the hotspots is to bring two or more particles in close vicinity. Therefore, many agglomerated structures are practically used to increase the SERS enhancement employing the interaction among the single monomers to fulfill the "dimer" condition, such as clusters [123], trimers [67,[124][125][126][127][128], tetramers [125,129,130], chains [131,132], and arrays [133][134][135][136][137]. Detailed studies to understand such agglomerates were performed by several groups.…”

Hybrid metal-dielectric gratings (HMDGs) as an alternative UV-SERS substrate

“…9 Therefore, noble metals, such as Au and Ag, have been well-designed to act as active SERS substrates due to their excellent SPR characteristics in the visible and infrared regions. 10 However, because the electronic absorption bands of many important biomolecules are mostly in the ultraviolet (UV) or deep-ultraviolet (DUV) region, relevant studies of ultraviolet-SERS (UV-SERS) have attracted researcher's interest in recent years. [11][12][13][14][15] Aluminium (Al), as the most abundant metal on the earth, can support SPR in the DUV and UV regions.…”