Effect of Plasmonic Au and Ag/Au Nanoparticles and Sodium Citrate on the Optical Properties of Chitin-Based Photonic Nanoarchitectures in Butterfly Wing Scales

Abstract

Porous butterfly wings with hierarchically organized structures from nanometer to centimeter scales were tested as substrates for carrying plasmonic Au and Ag/Au nanoparticles with potential application in photocatalysis. Wings exhibiting structural color generated by chitin-air nanocomposites were used. Hundreds of butterfly species possess these types of color-generating photonic nanoarchitectures, producing color by a similar mechanism to manmade photonic crystals. Artificial photonic crystals are known to enhance photocatalytic processes through the slow light effect. The impact of pure water, water-based sodium citrate solution, and Au and Ag/Au alloy nanoparticles on the optical properties of the natural photonic structures were separated. While water and aqueous sodium citrate solutions change the wing reflectance by the alteration of the wing scale position with respect to the wing plane, Au and Ag/Au alloy nanoparticles form a new, hybrid nanostructure with the chitin nanoarchitecture modifying the structural color of the butterfly wings. The optical properties of the new types of hybrid photonic nanoarchitectures (consisting of butterfly wings and plasmonic nanoparticles) are different from those of the components.

Breeding Polyommatus icarus Serves as a Large-Scale and Environmentally Friendly Source of Precisely Tuned Photonic Nanoarchitectures

“…In our work focusing on Morpho butterflies, we were able to increase the catalytic efficiency of the butterfly wings covered by a conformal 20 nm thin layer of ZnO by about ten times as compared to a flat glass substrate [ 50 ]. Previous work on plasmonic Au nanoparticles and the photonic nanoarchitectures of male Polyommatus icarus wings showed that the Au nanoparticles incorporated into the photonic nanoarchitecture of the butterfly wings exhibited hybridization between the photonic nanoarchitecture and the metallic nanoparticles with plasmonic properties [ 57 ]. These findings strongly support our belief that combining photonic nanoarchitectures of biologic origin with various well established materials science methods may bring important advantages in a cheaper and more environmentally friendly way in several fields.…”