Highly ordered 3D-silver nanoring arrays (3D-AgNRAs) for refractometric sensing

Abstract

The optical performance of two dimensional (2D) metallic nanoring arrays is inevitably affected by their substrate. This problem can be solved by using three dimensional (3D) nanorings, whose height is larger. However, most reported 3D-metallic nanoring arrays were prepared through focused ion beam lithography, which is high cost and low efficiency. Herein, we provided a new approach to fabricate highly ordered 3D-silver nanoring arrays (3D-AgNRAs) over a large area through multistep colloidal lithography combined with metal deposition. The specific structure of the 3D-AgNRAs could be facilely tuned by modulating the etching conditions. After gradual optimization of the 3D-AgNRAs’ structural parameters with respect to 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 per RIU and relative sensitivity of 50.2% per RIU. Ultimately, the optimized 3D-AgNRAs were employed as an immunoassay substrate to prove their label-free biosensing potential in the future.