Helical Plasmonic Nanocrevices Formed by Metallic Double Helices for Ultrasensitive Chiral Detection and High-Performance Chiral Photoluminescence

Plasmonic double helices made of Ag present large electric field enhancement and optical chirality, which can serve as a versatile platform for ultrasensitive chiral detection and high performance of chiral photoluminescence. However, the fabrication challenge of the desired helical configuration hinders their further exploration for these practical applications. Here we employ a superelastic nanomolding technique to directly compress the metal piece into a spiral porous Si template for massive generation of Ag double helices of high quality. These Ag double helix enantiomers present strong chiroptic response with g-factor up to ±0.8, which can serve as a chiral sensing device with the detection limit of 10^–19 mole and circularly polarized light emission and waveguide device with luminescence dissymmetry (g_lum) up to ∼0.5. This work highlights the important role of strong optical chirality for the superior performance of chiral sensing and chiral luminescence, which serves as a general guideline for the design and optimization of chiroptic devices.