Abstract
As a powerful spectroscopy technique, surface-enhanced Raman scattering (SERS) can provide non-destructive and sensitive characterization down to a single molecular level. Aiming to the main challenges of high-performance SERS-active substrates for their real-world applications involving the ultra-sensitive and reproducible signals detection and signal uniformity with large-area, herein, a facile and reliable strategy based on combination of thermal imprinting polycarbonate (PC) film with porous anodic aluminum oxide (AAO) mold and E-beam evaporation of gold is provided to fabricate a high-quality SERS-active substrate consisting of ultra-dense hot-spots with large-area uniformity. Two kinds of sub-10 nm gaps were obtained, including the nanogaps between the neighboring gold coated PC-nanopillars and those between gold on the top of the nanopillars and that on the base, which actually build up a three-dimensional (3D) hot-spot network for high-performance SERS detection. The effect of structural parameters on SERS enhancement was investigated numerically and experimentally, and by optimizing the structural parameters, a remarkable average SERS enhancement factor up to of 1.4×108 is achieved and it shows an excellent reproducibility with a relative standard deviation of 18%, which allows for enhanced practicability in the application of quantitative biochemical detection.
Highlights
Noble metallic nanostructures have attracted considerable interest in recent years due to their unique optical properties and great potentials for highly effective nanoscale optoelectronic devices in the fields of nanophotonics,[1] photothermics[2,3] or photovoltaics,[4] photocatalysis[5,6] and biosensing.[7]
To obtain a dense and uniform hot-spots array for large-area and high-performance surface-enhanced Raman scattering (SERS) substrate, a novel three-dimensional (3D) plasmonic nanoantenna array is fabricated through a typical Nanoimprint lithography (NIL) approach, which exhibited a remarkable field enhancement by coupling a 3D microcavity mode with the localized surface plasmon resonances (LSPRs) modes excited by individual nanodots.[33]
Before the thermal imprinting process, it is crucial to modify the surface of anodic aluminum oxide (AAO) templates with an anti-stick agent trichloro(1H,1H,2H,2H-perfluorooctyl)silane to reduce the surface energy for mold separation
Summary
The gold coated flexible polymer nanofingers array prepared via UV-curing NIL could be driven together by capillary force, which created reliable hotspots at the tiny gaps among the fingertips for SERS to detect the trapped molecule.[32] And recently, to obtain a dense and uniform hot-spots array for large-area and high-performance SERS substrate, a novel three-dimensional (3D) plasmonic nanoantenna array is fabricated through a typical NIL approach, which exhibited a remarkable field enhancement by coupling a 3D microcavity mode with the LSPR modes excited by individual nanodots.[33] as we know, the desired stamping mold is one of the critical bottlenecks to NIL process by virtue of EBL and FIB method, which is very tedious and time-consuming. The 3D plasmonic hot-spots network shows an excellent SERS uniformity with a relative standard deviation (RSD) of 15%, which might be very potential for quantitative biochemical detection
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