Invertible Nanocup Array Supporting Hybrid Plasmonic Resonances

Continuous inverse nanocup array films are fabricated utilizing a simple and efficient colloidal lithography method. The structured films further can be easily transferred to arbitrary substrates and laid upside down during transfer. The topologically continuous film consisted of a frustum-like void core surrounded by a concentric metal shell. The unique structure with a cavity element provides hybrid plasmonic resonances coupling between frustum-like mode and void-like surface plasmon (SP) mode, leading to a greatly enhanced SP energy, which largely improves plasmonic sensing and surface enhanced Raman scattering performance. Moreover, the existence of hybrid modes induces distinct electric field distributions inside and outside the nanocup, allowing the structured film to act as a spatial selective sensor.