The Structure Of Color Couplers Mechanism And Preparation Methods

Structural color results from the interactions of natural light with microstructures with a featured size comparable to visible wavelengths via optical phenomena such as interference, diffraction or scattering. The investigation of structural colors in the biological world is of great significance since it can not only reveal the interesting way of color steering in nature but also inspire our design and fabrication of photonic structures. In this thesis, we study the color origin of pigeon and parrot feathers. We also discuss the origin of the blue color in the glaze of ancient chinaware. The fabrication of inverse structures using parrot feathers as template is discussed.The thesis consists of six chapters. In Chapters One and Two, structural coloration and its experimental and theoretical methods are briefly introduced.In Chapter Three, we study the origin of green and purple iridescence in the neck feathers of domestic pigeons. We found that both green and purple barbules are composed of an outer keratin cortex layer surrounding a medullary layer consisting of randomly dispersed melanin granula. Structural colors originate from the thin-film interference of the top keratin layer while the medullary layer plays a role of a poor mirror. Different iridescence resides in the different thickness of the keratin layer. Interestingly, we found that green barbules vary colors from green to purple with the observing angle changed from normal to oblique. Oppositely, purple barbules change their colors from purple to green. This opposite iridescence may contain biological significance.In Chapter Four, we systematically study the blue, green and yellow coloration in parrot feathers. We found that the blue color is purely from the spongy microstructures in the barbs, while green and yellow are produced by the color mixing of the blue color from the spongy microstructures and pigments. Interestingly, it is found that the spongy microstructures are indeed amorphous diamond structures which could produce a bright structural color. Their implications in photonic crystals are discussed.In Chapter Five, we present results on the fabrication of inverse sponge microstructure using parrot barbs as template. We obtained two amorphous diamond structures:one based on SiO2and the other one on TiO2. These synthesized structures show obvious structural colors. Structural characterizations revealed that SiO2-based structures possess better structural quality than TiO2-based ones. These artificial structures can be the basis for the further study of the optical properties of amorphous diamond structures.In Chapter Six, we study the coloration of the light blue glaze of the ancient chinawares:Jun and Ru Ware. Our results suggest that the blue color would originate from the microstructures in the glaze. The microstructures are formed during the firing process owing to the unstable decomposition, leading to randomly dispersed Si-rich and Ca-rich micro-domains. Since these micro-domains have different refractive index light will be scattered coherently, producing eventually a light blue color. From the theory of phase separation, we also discussed the ways to fabricate materials with strcutural colors in porcelains, polymers and metals.