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

Abstract

AbstractPlasmonic patterns with gaps of less than 10 nm have wide applications for various optoelectronic devices, for example, the surface‐enhanced Raman spectroscopy (SERS) detection of toxic pesticide contaminants that pose a serious threat to human health. Here, a cost‐effective and highly controllable approach for such ultrafine patterns by combining the characteristic strengths of two techniques, the tunable and ordered porous structure of the anodic aluminum oxide template technique and the conformal atomic layer‐by‐layer growth feature of the atomic layer deposition technique, is reported. This novel nanofabrication approach can tailor the geometry and dimension of the inner‐pillar/outer‐ring or inner‐ring/outer‐ring nano‐arrays at the nanometer scale with high reproducibility. As a result, multiple large‐area (cm2 scale) ordered and high‐density coaxial circular nano‐slit arrays with adjustable slit width down to 2 nm are produced. Such narrow metallic nano‐slits can generate strong “hot spots” where huge signal enhancement happens, leading to a SERS enhancement factor of up to 4 × 108. This enables the detection of rhodamine 6G at an ultra‐low concentration of 10 fm, as well as toxic pesticide contaminants such as chlorpyrifos and thiram in lake water, with limits of detection of 0.25 ppm and 1.8 ppb, respectively.