Silver nanoparticles deposited on TiO2-coated cicada and butterfly wings as naturally inspired SERS substrates

Ag nanoparticles were photocatalytically deposited on TiO 2 -coated cicada and butterfly wings (Ag/TiO 2 -coated wings). Wings of two species of cicadas ( Cryptotympana facialis and Graptopsaltria nigrofuscata ) and one species of butterfly ( Parnassius citrinarius ) were investigated as substrates based on natural materials. Uniform ordered nanopillar arrays and irregular sub-micron sized pillar structures were observed on the wing surfaces of Cryptotympana facialis and Graptopsaltria nigrofuscata , respectively. On the surface of wing scales of Parnassius citrinarius , a uniform ordered ridge structure was observed. A small number of Ag nanoparticles were also deposited on the intact bare cicada and butterfly wings without TiO 2 (Ag/wings) by photoreduction. The surface enhanced Raman scattering (SERS) signal intensities of rhodamine 6G (R6G) dripped and dried on the Ag thin film sputtered on glass slides, Ag/wings and Ag/TiO 2 -coated wings increased in that order. In particular, the SERS signal intensities of R6G on the Ag/TiO 2 -coated wing of Cryptotympana facialis were more than 25 times larger than those on the Ag thin film. Ag nanoparticles were photocatalytically deposited on TiO 2 -coated cicada and butterfly wings (Ag/TiO 2 -coated wings).