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

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 x 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. We develop a new nano-peeling technique to realize high-density Ag nanoneedle forest arrays for sensitively detecting target molecules in the NIR region. The excellent SERS performance is ascribed to abundant hotspots from both gaps and tips formed in the unique Ag nanoneedle forest structure.