Yuya Oaki

Abstract We demonstrate nanoscale architectures in real biominerals and their biomimetics. Mimicking biomineralization, that is, crystal design in association with organic molecules, has been demonstrated in recent years. Although the macroscopic morphologies in real biominerals and biomimetics have been extensively studied, the nanoscopic structures in terms of the crystal growth are still not fully understood. We show that both materials form oriented architectures of bridged nanocrystals with

Mother-of-pearl has a three-level nanoscopic-to-macroscopic hierarchical architecture, which provides storage for organic molecules at the nanoscale. A material that mimics the hierarchical architecture and nanostorage properties of nacre emerges from the simple crystallization of potassium sulfate and poly(acrylic acid) (see picture). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z500338_s.pdf or from the author. Please note:

The sponge skeleton of the spine of sea urchins is found to be generated from nanocrystals 20–50 nm in size (main image). The nanocrystals make up the oriented architectures of various living species (see insets) in association with biopolymers; together they are in the form of inorganic–organic nanocomposites. This nanoengineering strategy offers the promise of the construction of unique macroscopic morphologies.

Sheet materials: Manganese oxide nanosheets and their oriented thin films can be prepared by a bottom-up approach in aqueous solution under ambient conditions (left). Chelation between the manganese species and ethylenediaminetetraacetate (EDTA) ligands results in birnessite-type nanosheets (see micrographs and diffraction pattern). The biomimetic pathway allows simultaneous control of synthesis and morphogenesis by the EDTA chelating agent. Supporting information for this article is available o

Transparent and stable composites of calcium carbonate and an acidic macromolecule are obtained at mild conditions. The nanosegregated structure is formed in the amorphous composite materials in the bulk and thin-film states. The transparent, stable, and crack-free thin films might be beneficial for coating of materials. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2089/2008/adma200800773_s.pdf or from the author. Please note: The publ

We have found a novel type of morphological chiral tuning on inorganic helical crystals through stereochemical recognition of organic molecules. Helical forms consisting of twisted twins emerged from triclinic crystals under diffusion-limited conditions. The proportion of the right- and left-handed helices was precisely tuned with the addition of a specified amount of chiral molecules, such as d- and l-glutamic acids. The chiral molecules recognized the enantiomeric surface of the triclinic crys

Visualization and quantitative detection of external stimuli are significant challenges in materials science. Quantitative detection of friction force, a mechanical stress, is not easily achieved using conventional stimuli-responsive materials. Here, the quantitative detection of friction force is reported, such as the strength and accumulated ammount, from the visible color of organic layered composites consisting of polydiacetylene (PDA) and organic amines without an excitation light source. T

Measurement of mechanical stresses, such as compression, shear, and tensile stresses, contributes toward achieving a safer and healthier life. In particular, the detection of weak compression stresses is required for healthcare monitoring and biomedical applications. Compression stresses in the order of 10⁶ -10¹⁰ Pa have been visualized and/or quantified using mechano-responsive materials in previous works. However, in general, it is not easy to detect compression stresses

Calcite crystals grown with association of an organic gel matrix led to the generation of a hierarchical, self-similar architecture possessing rhombohedral habit under ambient conditions.

Enhanced green luminescence is seen in barium tungstate–poly(acrylic acid). This nanohybrid spontaneously forms into h-WO3 nanosheets through a bottom-up approach in aqueous solution around room temperature (see figure). The coordination of electrolytes to the inorganic species can lead to the morphological evolution of crystals and can control the modification of the chemical structure relevant to various optical and magnetic properties. Supporting information for this article is available on t

The morphology of potassium sulfate (K(2)SO(4)) crystals grown in a viscous polymer solution of poly(acrylic acid) (PAA) was remarkably changed from the tilted columnar assembly into zigzag and helical architectures with increasing PAA concentration. The habit modification of orthorhombic K(2)SO(4) with adsorption of PAA molecules on a specified crystal face fundamentally led to the formation of tilted unit crystals. Concurrently with the habit modification, a diffusion-limited condition control

Abstract Stimuli‐responsive properties of soft materials originate from dynamic structure changes. Layered polydiacetylene (PDA) shows color‐change properties with the application of external stimuli, such as thermal and mechanical stresses. Layered organic materials possessing intercalation capabilities and dynamic properties have potentials for tuning their structures and properties by the intercalated guests. A variety of sensing and imaging devices can be developed by control of the stimuli

Synthesis and morphogenesis of polypyrrole (PPy) with hierarchical structures from nanoscopic to macroscopic scales have been achieved by using hierarchically organized architectures of biominerals. We adopted biominerals, such as a sea urchin spine and nacreous layer, having hierarchical architectures based on mesocrystals as model materials used for synthesis of an organic polymer. A sea urchin spine led to the formation of PPy macroscopic sponge structures consisting of nanosheets less than 1

A hierarchically organized architecture in multiple scales was generated from potassium hydrogen phthalate crystals and poly(acrylic acid) based on our novel biomimetic approach with an exquisite association of polymers on crystallization.