A high-density Ag nanoneedle forest array by using a nano-peeling technique for near-infrared SERS detection

Abstract

Surface-enhanced Raman scattering (SERS) substrates with tips have been proven to be extremely efficient for detecting biochemical molecules due to the “lightening-rod”-induced electromagnetic field enhancement. Even though fabrication methods for nanotips have been developed in the last few decades, a low-cost and high-yield synthesis remains a great challenge in practical applications. Herein, we present a new nano-peeling technique to realize the high-density Ag nanoneedle forest array for sensitively detecting target molecules in the near-infrared region (NIR). The proposed Ag nanoneedle forest array has abundant hotspots from both gaps and tips, thus achieving efficient detection of 4-aminothiophene, along with a minimum detection limit of 10⁻¹¹ M and enhancement factor of 1.48 × 10⁸. The minimum standard deviation of NIR-SERS signals for the Ag nanoneedle forest array was calculated to be 8.44%, indicating a superior reproducibility. Moreover, this NIR-SERS sensor can be extended to the multiple detection of molecules with high efficiency. This work paves an effective scale-up way to achieve an NIR-SERS sensor with high-density hotspots for pushing the practical applications in a new generation of near-infrared biochemical sensors.