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Optical Characterization of the Photonic Ball as a Structurally Colored Pigment
摘要： A photonic ball is a spherical colloidal crystal. Because it can exhibit vivid structural colors, many attempts have been made to apply it as a structurally colored pigment. However, the optical properties of the photonic ball are complicated because di?erent crystal planes can be involved in the coloration mechanism, depending on the size of the constituent colloidal particles. In this paper, we report a comparative study of photonic balls consisting of silica particles with sizes ranging from 220 to 500 nm. We ?rst analyze the re?ectance spectra acquired in a nearly backscattering geometry and con?rm that Bragg di?raction from di?erent crystal planes causes several spectral peaks. Second, the angular dependence of re?ection is experimentally characterized and theoretically analyzed with appropriate models. These analyses and a comparison with a planar colloidal crystal reveal that the spherical shape plays an essential role in the minor iridescence of photonic balls. We ?nally discuss a method to enhance color saturation by incorporating small light-absorbing particles. We also discuss the iridescence of the photonic ball under directional and ambient illumination conditions.
关键词： structural coloration,photonic ball,iridescence,colloidal crystal,Bragg diffraction
更新于2025-09-23 15:21:01
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Signal or cue: the role of structural colors in flower pollination
摘要： Angle dependent colors, such as iridescence, are produced by structures present on flower petals changing their visual appearance. These colors have been proposed to act as signals for plant–insect communication. However, there is a paucity of behavioral data to allow for interpretations of how to classify these colors either as a signal or a cue when considering the natural conditions under which pollination occurs. We sampled flowers from 6 plant species across various viewpoints looking for changes in the visual appearance of the petals. Spectral characteristics were measured with different instruments to simulate both the spectral and spatial characteristics of honeybee’s vision. We show the presence of color patches produced by angle dependent effects on the petals and the calyx of various species; however, the appearance of the angle dependent color patches significantly varies with viewpoint and would only be resolved by the insect eye at close distances. Behavior experiments with honeybees revealed that pollinators did not use angle dependent colors to drive behavior when presented with novel flower presentations. Results show that angle dependent colors do not comply with the requirements of a signal for plant–pollinator communication since the information transmitted by these colors would be unreliable for potential, free-flying pollination vectors. We thus classify angle dependent colors produced by micro- and ultra-structures as being a cue (a feature which has not evolved for communication), and observe no evidence supporting claims of these angle dependent colors having evolved as visual signal.
关键词： pollination,vision,color,photography,iridescence,flower,approach angle
更新于2025-09-19 17:15:36
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Iridescence and thermal properties of <i>Urosaurus ornatus</i> lizard skin described by a model of coupled photonic structures
摘要： This research shows that the morphological characteristics of the external microstructure of the beautiful skin of the Urosaurus ornatus lizard contribute to the explanation of the origin of their iridescent and thermal properties. High-resolution scanning electron microscopy studies revealed that the skin surface of the U. ornatus lizard is constituted by a semi-ordered array of hexagonal photonic crystals with sub-micrometric structural parameters. The iridescence properties of the ventral patch and dorsal surface of the U. ornatus lizard were numerically simulated modeling both surfaces by a set of coupled photonic crystals with structural parameters proposed from statistical measurements of the lattice parameter and holes diameter of its skin surface. The dorsal surface showed the ability to re?ect visible light and at least in a signi?cant range the ultraviolet and near infrared radiation. A complete photonic band gap for the transverse magnetic polarization mode of the incident light in both dorsal and ventral surfaces was predicted by calculations. The spectral re?ectance and the structure of photonic bands obtained explain the re?ection of the infrared radiation by the dorsal surface which might help to the thermoregulation of the lizard body. The results obtained suggest that the selective re?ection of incident light performed by the photonic structural array de?ned on the skin surface of the U. ornatus has a signi?cant contribution to its apparent color.
关键词： thermoregulation,iridescence properties,Urosaurus ornatus,organic photonic structures,skin surface model
更新于2025-09-16 10:30:52
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Recent advances in the manipulation of circularly polarised light with cellulose nanocrystal films
摘要： Significant advances have been made to control the iridescence and the selective reflection of left circularly polarised (LCP) light, and transmission of right circularly polarised (RCP) light of solid films prepared from cellulose nanocrystals (CNCs). However the manipulation of the photonic properties of the CNCs films, which reflect both RCP and LCP light is less investigated. Solid films prepare from natural sources as CNCs have advantageous characteristics that are absent in other synthetic structures, such as wide availability and renewability. Here we review and compare recent research activity involving the production and characterization of photonic band gap structures resulting from an anisotropic layer inserted between two cholesteric layers with different helical pitches but the same handedness. We make connections between systems existing in Nature and synthetic ones with the hope of advancing in the production and manipulation of CNCs-based photonic structures.
关键词： Cellulose nanocrystals,Photonics,Circularly polarised light,Bio-inspired materials,Iridescence,Liquid crystals
更新于2025-09-10 09:29:36
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Optical Properties of <i>Greta oto</i> Butterfly Wings: Relation of Iridescence with Photonic Properties
摘要： This work presents an experimental and theoretical study about the optical properties of the wings of butter?y 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 re?ectance 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 butter?y Greta oto. In particular, photonic behavior could be associated with the iridescent phenomenon on the butter?y wings.
关键词： Greta oto Butter?y,Iridescence,Re?ectance,Structural Color
更新于2025-09-09 09:28:46