Colloidal Cu2O nanoparticles can exhibit both photocatalytic activity under visible
light illumination and resonant Mie scattering, but, for their practical application,
they have to be immobilized on a substrate. Butterfly wings, with complex hierarchical
photonic nanoarchitectures, constitute a promising substrate for the immobilization
of nanoparticles and for the tuning of their optical properties. The native wax layer
covering the wing scales of Polyommatus icarus butterflies was removed by simple ethanol
pretreatment prior to the deposition of Cu2O nanoparticles, which allowed reproducible
deposition on the dorsal blue wing scale nanoarchitectures via drop casting. The samples
were investigated by optical and electron microscopy, attenuated total reflectance
infrared spectroscopy, UV–visible spectrophotometry, microspectrophotometry, and hyperspectral
spectrophotometry. It was found that the Cu2O nanoparticles integrated well into the
photonic nanoarchitecture of the P. icarus wing scales, they exhibited Mie resonance
on the glass slides, and the spectral signature of this resonance was absent on Si(100).
A novel bio-nanohybrid photonic nanoarchitecture was produced in which the spectral
properties of the butterfly wings were tuned by the Cu2O nanoparticles and their backscattering
due to the Mie resonance was suppressed despite the low refractive index of the chitinous
substrate.
