RESUMO
Photonic crystals are some of the more spectacular realizations that periodic arrays can change the behavior of electromagnetic waves. In nature, so-called structural colors appear in insects and even plants. Some species create beautiful color patterns as part of biological behavior such as reproduction or defense mechanisms as a form of biomimetics. The interaction between light and matter occurs at the surface, producing diffraction, interference and reflectance, and light transmission is possible under suitable conditions. In particular, there are two Colombian butterflies, Morpho cypris and Greta oto, that exhibit iridescence phenomena on their wings, and in this work, we relate these phenomena to the photonic effect. The experimental and theoretical approaches of the optical response visible region were studied to understand the underlying mechanism behind the light-matter interaction on the wings of these Colombian butterflies. Our results can guide the design of novel devices that use iridescence as angular filters or even for cosmetic purposes.
Assuntos
Borboletas/anatomia & histologia , Asas de Animais/anatomia & histologia , Animais , Borboletas/química , Borboletas/fisiologia , Borboletas/ultraestrutura , Cristalização , Iridescência , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Fótons , Pigmentação , Asas de Animais/química , Asas de Animais/fisiologia , Asas de Animais/ultraestruturaRESUMO
This work presents an experimental and theoretical study about the optical properties of the wings of butterfly Greta oto. UV-Vis spectroscopy was used to obtain the optical response of the sample as function of the incident light angle. It was possible to observe a shift in the maximum of the reflectance spectra towards lower values of lambda when the angle of incident light increases. The theoretical modeling allows us to relate photonic behavior with the optical properties of the wings of butterfly Greta oto. In particular, photonic behavior could be associated with the iridescent phenomenon on the butterfly wings.
Assuntos
Borboletas , Animais , Iridescência , Óptica e Fotônica , Análise Espectral , Asas de AnimaisRESUMO
Using a tight-binding model, we study the transport of charge carriers through DNA molecular wires. In double-stranded DNA chains, according to Chargaff's rules, only Adenine-Thymine (AT) and Cytosine-Guanine (CG) pairs are allowed. In our model, a decimation procedure allows us to represent each pair of bases by a single site with one localized electronic state. We consider chains of different lengths with only AT (CG) sites, and ordered and disordered chains with both types of sites. Disordered chains may include short range correlation. Additionally, hydration is considered in the form of a change of the site energy. We find a conductor-to-semiconductor-to-insulator transition as a function of the three effects taken into account: chain size, intrinsic disorder of CG and AT pairs, and hydration. This model predicts that an appropriate choice of chain size and concentration of AT pairs can be used to tailor the electrical behavior of DNA strands.