A asa da borboleta e a nanotecnologia: cor estrutural

Abstract

Cores estruturais são aquelas geradas como resultado da interferência construtiva da difração em uma grade ou em estruturas com certa ordenação nanométrica. A cor estrutural difere da cor química (encontrada na maioria dos seres vivos) pela ausência de pigmentos, sendo resultado apenas de efeitosóticos superficiais. As asas das borboletas são os melhores exemplos de geradoras de cores estruturais e com o advento da microscopia, o detalhamento dessas estruturas permitiu elevar o conhecimento do fenômeno assim como com o recentemente avanço da nanotecnologia, as primeiras reproduções artificiais dessas estruturas foram obtidas com potenciais aplicações em diversos campos. Neste artigo apresentamos as principais diferenças entre uma cor química e uma estrutural, do ponto de vista físico, com um formalismo bastante simples mostrando que conceitosóticos básicos podem explicar, ainda que de forma simplificada, a geração de cor estrutural. Palavras-chave: cor estrutural, pigmentos, difração e refração de luz, estruturas nanométricas.Structural colors are those generated as a result of constructive interference from a diffraction grade or from nanometric ordered structures. The structural color differs from chemical color (found in the majority of living beings) by having no pigments or colorants, but as a result of optical surface effects. The butterfly wings are the best examples of structural color's generator and, with microscopic observations, details of these structures were described and the knowledge of this phenomenon increased. With the advances of the nanotechnology, the first ones artificial replications of these structures were attained with potential application in several technological fields. In this paper the main differences between chemical and structural color, from the physical point of view, are presented by using a quite simple formalism, though sufficient enough to explain the main optical concepts involved in the structural color generation.

Dyeing process optimization in natural fiber through the Photoacoustic Spectroscopy

“…As bigger the linear molecular geometry is, longer wavelengths will be absorbed. In other words, the energy required to excite electrons reduces with the increasing number of chemical bonds (Assis, 2013). Thus, the PAS results suggest that, the chemical composition of color and/or the molecule size is of great influence for process of fiber dyeing.…”

Analogies between optical physics and quantum mechanics

“…The light incident on a thin film undergoes multiple reflections on the faces of the film, resulting in multiple interferences between the reflected components. Known examples of this phenomenon are the color composition on the surface of soap bubbles and some butterflies wings [11]. We consider two semi-infinite media with refraction index n 1 = n 3 , separated by a dielectric of thickness d with refraction index n 2 < n 1 as shown in figure 6.…”