Light Trapping in Plasmonic Nanovessels

Inverse hollow nanocone arrays are fabricated by an efficient colloidal lithography technique and a facile transfer process. These structures have the peculiar features of nanobeakers, which may be promising reaction vessels. Local field distribution near this beaker and the influence on optical properties are investigated. A majority of light at the resonance wavelength can be trapped in the cavity due to multiple internal reflections in the cone and coupling with the surface plasmon of the nanostructures. Due to the strongly enhanced electric field distributed in air, the resonant reflection dip shows sensitive response to changes of the surrounding environment, with excellent linearity and relative sensitivity up to 62% per refractive index unit (RIU). Moreover, the Raman signal becomes much weaker when excited at the resonance wavelength, demonstrating the strong ability of trapping light. This nanostructure and the investigation of the plasmonic performances may contribute to the generation of nanovessels for optical tweezers and plasmon-assisted chemistry.