Single-crystalline calcite nanorods elongated in the c direction formed through 1D oriented attachment of nanoblocks.

Sapphirinid copepods, which are marine zooplankton, exhibit tunable structural colors originating from a layered structure of guanine crystal plates. in the present study, the coloring portion of adult male of a sapphirinid copepod, Sapphirina nigromaculata, under the dorsal body surface was characterized to clarify the regulation and actuation mechanism of the layered guanine crystals for spectral control. The coloring portions are separated into small domains 70-100 µm wide consisting of an ordered array of stacked hexagonal plates ~1.5 µm wide and ~80 nm thick. We found the presence of chitin-based honeycomb frameworks that are composed of flat compartments regulating the guanine crystal plates. the structural color is deduced to be tuned from blue to achromatic via yellow and purple by changing the interplate distance according to vital observation and optical simulation using a photonic array model. the framework structures are essential for the organization and actuation of the particular photonic arrays for the exhibition of the tunable structural color.Structural color is generated by a combined effect of diffraction, refraction, reflection, and interference of light due to submicron-scale periodic structures 1-6 . Several organisms have characteristic parts that exhibit specific structural colors. For example, we can observe specific colors on feathers of peacock, necks of pigeon, and wings of morpho butterfly 7-9 . Adult males Sapphirina nigromaculata, which are marine zooplanktons, show tunable structural colors originating from a layered structure of guanine hexagonal plates ~1.5 µm wide and cytoplasm under the dorsal body surface 10,11 . A feature of the biological structural color on the Sapphirinid copepod is tunability from achromatic to yellow, red, and blue 12-14 . The iridescence of male sapphirinids has been reported to be optimized to communicate with non-iridescent females having relatively larger twin lens-eyes in the water column 13,14 . The disappearance of the structural color in the males is probably utilized as a defense system against visual predators, such as pelagic fishes 10,11,13,14 . The tunability of the structural colors of planktons is very interesting not only for clarification of the biological function but also for the development of biomimetic display technologies. The variation in the structural color with change in the interplate distance was reported by detailed observation using a cryo-technique for electron microscopy and an optical simulation 5,6,10,11 .An ordered array of guanine hexagonal plates ~1.5 µm wide and ~80 nm thick in each domain are regulated by flat compartments in a chitin-based honeycomb framework. Understanding the essence of the organization and regulation of tunable structural colors of S. nigroaculata would shed light on biomimetic engineering for novel coloring and display devices. experimental Structural analysis of sapphirinid copepods. Plankton samplings were conducted at 35°08.9′N 139°10.5′E in the western part of the Sagami Bay in the south ...

The micrometric morphology of anhydrous β-guanine crystals is adequately designed by various organisms for their specific optical properties. We successfully controlled the morphology of an anhydrous β-guanine crystal through the transformation of an amorphous intermediate consisting of guanine sodium salt under aqueous conditions. Biomimetic platy and columnar guanine crystals were selectively produced from the amorphous intermediate by changing the crystallization conditions.

The combination of heterogeneous inorganic nanocrystals provides novel nanometer-scale architectures for exploration of novel functions. In the present study, heterogeneous bilayers, such as BaTiO-FeO and MnO-CeO, are fabricated via layer-by-layer stacking of several rectangular nanoblocks 5-23 nm in size by evaporation-driven self-assembly. Specific heterojunctions between inorganic crystals are constructed by nanoscale simple brick work through spontaneous adjustment of the crystallographic orientations of the nanoblocks in the lower and upper layers.

The coercivity of magnetic nanoparticles is enhanced by the exchange coupling effect at the interface of ferrimagnetic and antiferromagnetic self-assembled monolayers.