Highly ordered 3D-silver nanoring arrays (3D-AgNRAs) for refractometric sensing
Two dimensional (2D) metallic nanoring arrays’ optical performance are always affected by their substrate, which can be solved by three dimensional (3D) nanorings, whose height is larger. However, most reported 3D-metallic nanoring arrays were prepared through focus ion beam lithography, which is high cost and low efficient. Herein, we provided a new approach to fabricate highly ordered 3D-silver nanoring arrays (3D-AgNRAs) over large area through multistep colloidal lithography combining metal deposition. The specific structure of 3D-AgNRAs could be facilely tuned by modulating the etching conditions. After gradual optimization of the 3D-AgNRAs’ structural parameters considering their optical and sensing performance, the optimized 3D-AgNRAs’ structural features were finally settled to be 1 μm period, 200 nm nanoring height, 300 nm silver layer thickness, 830 nm outer diameter, and 428 nm inner diameter. The optimized 3D-AgNRAs achieved high refractometric sensitivity of 1105.8 nm/RIU and relative sensitivity of 50.2%/RIU. Ultimately, the optimized 3D-AgNRAs were employed as an immunoassay substrate to prove their label-free biosensing potential in the future.