Optical and Surface-Enhanced Raman Scattering Properties of Black and Metallic Silver Micro/Nano Structures Fabricated on Cicada Wings by Silver Mirror Reaction

Silver was deposited on cicada (Cryptotympana facialis) wings to fabricate black and metallic silver micro/nano structures on the wings (black-Ag wings and metallic-Ag wings) by the silver mirror reaction. The transparent cicada wings with close-packed nanopillar array structures were used as the substrates based on natural materials. As the silver mirror reaction proceeded, the color of the wing gradually changed from transparent to brown, then to black, and finally to metallic silver. A thin Ag film coated nanopillar array structure is seen in the black-Ag wing. The transmittance and reflectance of the black-Ag wing were nearly 0% and an average of about 4% in the wavelength range of 200-800 nm, respectively. Densely stacked colloidal Ag particles with an average diameter of 155 nm were observed on the surface of the metallic-Ag wing. The surface enhanced Raman scattering (SERS) signal intensities of Rhodamine 6G (R6G) dripped and dried on the black-Ag wing, thin Ag film sputtered on glass slides, and metallic-Ag wing increased in that order. In particular, the SERS signal intensities of R6G on metallic-Ag wing were greater than two orders of magnitude than those on the black-Ag wing and thin Ag film.