High-Throughput Tailorable Fabrication of Long-Range Ordered Plasmonic Coaxial Multi-Circular Nano-Slit Arrays Down to 2 nm for SERS Detection

摘要

Plasmonic patterns with gaps of less than 10 nm have wide applications forvarious optoelectronic devices, for example, the surface-enhanced Ramanspectroscopy (SERS) detection of toxic pesticide contaminants that pose aserious threat to human health. Here, a cost-effective and highly controllableapproach for such ultrafine patterns by combining the characteristic strengthsof two techniques, the tunable and ordered porous structure of the anodicaluminum oxide template technique and the conformal atomic layer-by-layergrowth feature of the atomic layer deposition technique, is reported. Thisnovel nanofabrication approach can tailor the geometry and dimension of theinner-pillar/outer-ring or inner-ring/outer-ring nano-arrays at the nanometerscale with high reproducibility. As a result, multiple large-area (cm2 scale)ordered and high-density coaxial circular nano-slit arrays with adjustable slitwidth down to 2 nm are produced. Such narrow metallic nano-slits cangenerate strong “hot spots” where huge signal enhancement happens,leading to a SERS enhancement factor of up to 4 × 10~8. This enables thedetection of rhodamine 6G at an ultra-low concentration of 10 fm, as well astoxic pesticide contaminants such as chlorpyrifos and thiram in lake water,with limits of detection of 0.25 ppm and 1.8 ppb, respectively.