Self-organized Materials Research Articles

Optically Transparent Conductive Network Formation Induced by Solvent Evaporation from Tin-Oxide-Nanoparticle Suspensions

This investigation describes an optically transparent antistatic film composed of antimony-doped tin oxide (ATO) nanoparticles dispersed in a polymer matrix, with remarkably improved electrical and optical properties. The film is fabricated on the basis of a synergistic interaction between self-assembling nanoparticles and self-organizing matrix materials. The antistatic property of the film is obtained at ATO concentrations above a threshold value. A scaling analysis of the data yields an extremely low critical concentration (0.0020 volume fraction), which is considerably lower than the value predicted by percolation theory. Microscopic observations of the film have revealed a characteristic microstructure: "single-stranded" chainlike (linear form or fibrous) aggregates consisting of ATO nanoparticles and large ATO-depleted areas. The experiment results suggest that the high optical transparency and the low critical concentration are derived from the characteristic microstructures of the film.

Development of a Functional Chromosome Nano-Dissection System Using Porous Anodic Alumina Pattern Chip and Cantilever

The dissection of chromosomes followed by extraction of specific DNA fragments constitutes a topic of high interest, especially for cytogenetic studies in the post genome era. The dissected chromosomes can be used in various conventional applications, including establishing probes for fluorescence in situ hybridization (FISH), the generation of chromosome band-specific libraries and physical mapping for cytogenetic analysis. In the present study, we developed a functional chromosome nano-dissection system that can dissect various chromosomes in one-chip by using the pattern chip with porous anodic alumina. The porous anodic alumina, that makes use of self-organized nanoarray materials as a template for the pattern chip, has a highly oriented porous structure with uniform and nearly parallel pores that can be organized in an almost precise close-packed hexagonal structure. The most characteristic feature of this material has been emphasized with the extremely high aspect ratio of their channels that is difficult to achieve with conventional lithographic techniques. This chromosome nano-dissection system can dissect directly a specific chromosome into nano-pores on the porous anodic alumina (PAA) pattern chip without an atomic force microscope (AFM) dissection process. Thus, we expect that our PAA pattern chip is very suitable for arraying chromosome fragments without the recovery process and the possibility of direct immobilization of chromosome fragments into the nano-pores of this chip.

Synthesis of self-organizing mesogenic materials containing a sulfur-based five-membered heterocyclic core

The majority of low molar mass calamitic mesogenic systems in the literature contain linear cores based on the 1,4-disubstituted phenyl ring. Heterocyclic cores such as thiophene impart unique physical properties as their slightly bent structure leads to features including a reduced packing ability (generally giving rise to lower melting points than their phenyl counterparts), a medium to strong lateral dipole, high anisotropy of the polarizability, low viscosity etc. This critical review describes the most recent synthetic methodology that has been used to prepare thiophene, 1,3-thiazole, and 1,3,4-thiadiazole-based mesogenic materials.

1,3,4-Thiadiazole-2-carboxylate esters: new synthetic methodology for the preparation of an elusive family of self-organizing materials

A series of alkyl 5-(4-octyloxyphenyl)-1,3,4-thiadiazole-2-carboxylates has been prepared via a novel chemoselective ring-closure of appropriate tricarbonyl precursors. This paper represents the first report of a general and reproducible synthetic methodology for the preparation of 1,3,4-thiadiazole-2-carboxylate esters. The 1,3,4-thiadiazole esters synthesized were designed to evaluate the feasibility of this new core unit for potential ferroelectric applications. The core unit was found to promote strongly the formation of tilted smectic phases (the smectic C phase in particular). The 1,3,4-thiadiazole ester was found to be a stronger promoter of the smectic C phase than its phenyl-based counterpart.

Heating, movement and visualization challenges in the use of iron oxide nanoparticles for biomedical applications

One of the most important classes of synthetic systems for creating self-assembled nanostructures is amphiphilic block copolymers. By controlling the architecture of individual molecules, it is possible to generate nanostructures either in an undiluted melt or in solution. These ordered nanostructures are tunable over a broad variety of morphologies, ranging from discrete micelles and vesicles to continuous network structures. Their synthetic nature allows the design of interfaces with different chemical functional groups and geometrical properties. This, in combination with molecular architecture, determines the levels of ordering in self-organizing polymeric materials. For these and other reasons, block copolymer micelles, vesicles, and mesophases are finding applications in several areas, ranging from nanocomposites to biomedical devices.

Porphyrin nanoparticles as supramolecular systems

Certain applications of supramolecular porphyrinic systems, such as molecular sieves and photonics, rely on precise nanoarchitectural control of the molecules and/or atoms; therefore they require self-assembled systems of discrete arrays and highly ordered crystals. Other applications, such as oxidation catalysts for simple substrates, may be affected by the use of self-organized materials with less supramolecular order. Colloidal porphyrin nanoparticles can be considered self-organized systems that are governed by the principles of supramolecular chemistry. The formation and potential applications of nanoparticles of these chromophores are discussed in this report with special emphasis on the parameters in the methods used to make these materials, and in terms of the supramolecular chemistry. These principles, concepts, and methodologies are applicable to a wide variety of organic dyes. “Mais Dieu a choisi celuy qui est le plus parfait, c’est a dire celuy qui en meme temps le plus simple en hypotheses, et le plus rich en phenomenes.” Gottfried Leibniz.

Functional Liquid‐Crystalline Assemblies: Self‐Organized Soft Materials

In the 21st century, soft materials will become more important as functional materials because of their dynamic nature. Although soft materials are not as highly durable as hard materials, such as metals, ceramics, and engineering plastics, they can respond well to stimuli and the environment. The introduction of order into soft materials induces new dynamic functions. Liquid crystals are ordered soft materials consisting of self-organized molecules and can potentially be used as new functional materials for electron, ion, or molecular transporting, sensory, catalytic, optical, and bio-active materials. For this functionalization, unconventional materials design is required. Herein, we describe new approaches to the functionalization of liquid crystals and show how the design of liquid crystals formed by supramolecular assembly and nano-segregation leads to the formation of a variety of new self-organized functional materials.

Development of a novel chromosome dissection chip for chromosomal analysis with nanometer size

Abstract The dissection of chromosomes followed by extraction of specific DNA fragments constitutes a topic of high interest, especially for cytogenetic studies in the post genome era. The dissected chromosomes can be used in various conventional applications, including establishing probes for fluorescence in situ hybridization (FISH), the generation of chromosome band-specific libraries and physical mapping for cytogenetic analysis. For this purpose, several reports using micro- and nano-dissection methods by micromanipulators have been published. In the present study, we developed a functional chromosome dissection chip that can dissect various chromosomes in one-chip by using the pattern chip with nanometer-scale porous anodic alumina. The porous anodic alumina that is to make use of self-organized nano-array materials as a template for the pattern chip has a highly oriented porous structure with very uniform and nearly parallel pores that can be organized in an almost precise close-packed hexagonal structure. The most characteristic feature of this material has been emphasized with the extremely high aspect ratio of their channels that is difficult to achieve with conventional lithographic techniques. We have proceeded as follows for this study; the pattern chip with nanometer-scale porous anodic alumina was fabricated. Then, metaphase chromosomes were prepared by dropping the cell suspension onto pattern chip and air-drying until use. Finally, the chromosomes that were penetrated into the nano-pores on the pattern chip by pressing with a tender silicon plate were dissected with nanometer size. This technique will form the basis for the development of new system such as “Nano-scale chromosome dissection chip” that arrays chromosomal fragments with nanometer scale on a chip for DNA and protein nano-analysis.

Self-organized materials and graft copolymers of polymethylmethacrylate and polyamide-6 obtained by reactive blending

Nanostructured blends of poly(methylmethacrylate) and polyamide-6 (PMMA/PA6) were prepared by reactive blending. The grafting reaction occurs between the amino end-group of PA6 and glutaric anhydride units randomly distributed along the backbone of PMMA. Short PA6 grafts were used to facilitate reaction at the interface. Very fine morphologies were obtained after blending. Annealing the blends above the melting point of polyamide reveals that the amount of anhydride present on PMMA chains controls self assembly of the blends and stability of the copolymer at the interface. In some cases, stable swollen lamellar assemblies were achieved. These materials exhibit interesting properties such as transparency, creep resistance and solvent resistance.

Self-organized amorphous material in silicon (0 0 1) by focused ion beam (FIB) system

A method using a focused ion beam (FIB) to prepare a silicon amorphous material is presented. The method involves the redeposition of sputtered material generated during the interaction of the Ga + ion beam with a silicon substrate material. The shape and dimensions of this amorphous material are self-organized and reproducible. The stability of this amorphous material under electron irradiation was investigated in the transmission electron microscopy (TEM). Electron irradiation can induce recrystallization of the amorphous material, resulting in the lateral and vertical growth, starting at an amorphous–crystalline interface, of polysilicon containing defects.

Self-organization of nanostructured functional dendrimers

In this article, we review some of our recent work on the development and study of the properties of self-organizing supermolecular liquid crystalline dendritic materials. Prior to this purpose, the state of the art in the field of molecular design, structure and properties of liquid-crystalline dendrimers (LCDs) will be briefly reviewed, and illustrated by a selection of pioneering examples. The first type of LC dendrimer takes into account the location of their functional elements (mesogens) in the periphery of the macromolecules and its topology of attachment, and the nature of the mesogen. We will show how functionality can be in-built into such materials so that self-organising functional systems can be created. Side-chain liquid-crystalline dendrimers exhibiting lamellar, columnar and nematic phases are shown. The mechanism of mesophase formation (mesogen interaction versus microphase separation) is also discussed in relation to the molecular structure (the nature of the mesogen and of the dendritic matrix, dendritic generation number). The second type of LC dendrimer introduced presents a different topology in that the mesogens are now inserted within the dendritic matrix and in the periphery. Owing to their particular constitution, it will be shown that the mesophases of the lamellar and columnar types possess unusual morphologies.

A New Hybrid Organic–Inorganic Membrane Based on Self-Organized Urea Macrocyclic Siloxane Material as Useful Facilitated Transport Device for Biological Solutes

A new organic-inorganic hybrid membrane was synthesized in which organic moieties presented a self-assembly of anionic and cationic complexing sites covalently bonded to a siloxane network. The effects of sol–gel parameters (hydrolysis ratio, catalyst and temperature) on the self-organization of the organic functions were studied. Transport experiments underlined the results of such ordering on the improvement of the solute permeability.

Self-Organization of Self-Assembled Tetrameric Porphyrin Arrays on Surfaces

The incorporation of designed self-assembled supramolecular structures into devices requires deposition onto surfaces with retention of both structure and function. This remains a challenge and can present a significant barrier to developing devices using self-organizing materials. To examine the role of peripheral groups in the self-organization of self-assembled multiporphyrinic arrays on surfaces, Pd(II)-linked square and Pt(II)-linked trapezoidal tetrameric porphyrin arrays with peripheral tert-butylphenyl or dodecyloxyphenyl functionalities were investigated using various spectroscopies and atomic force microscopy. The Pd(II) assembled squares disassemble upon deposition on glass surfaces, while the Pt(II) assembled trapezoids are more robust and can be routinely cast on these surfaces. The orientation and length of the peripheral alkyl substituents influence the resultant structures on surfaces. The tert-butylphenyl-substituted porphyrin array forms discrete columnar stacks, which assemble in a vertical direction via pi-stacking interactions among the macrocycles. The tetrameric porphyrin array with dodecyloxyphenyl groups forms a continuous film via van der Waals interactions among the peripheral hydrocarbon chains. The super-molecules with liquid crystal-forming moieties also form three-dimensional crystalline structures at higher deposition concentrations. These observations clearly demonstrate that the number, position, and nature of the peripheral groups and the supramolecular structure and dynamics, as well as the energetics of interactions with the surface, are of key importance to the two-dimensional and three-dimensional self-organization of assemblies such as porphyrin arrays on surfaces.

Ion-driven ATP pump by self-organized hybrid membrane materials.

We report new hybrid organic-inorganic materials, based on macrocyclic receptors 1-3 self-organized in tubular superstructures prepared by sol-gel process. Fourier transform infrared (FTIR) and NMR spectroscopic analyses demonstrate that the self-organization by hydrogen bonding of organogel superstructures of 2 and 3 were preserved in the hybrid materials throughout the sol-gel process. The molecular arrangement of heteroditopic receptors defines a particularly attractive functional transport device for both cation (tubular macrocycles) and anion (sandwich-urea) directional-diffusion transport mechanism in the hybrid membrane material. This system has been employed successfully to design a solid dense membrane, functioning as an ion-powered adenosine triphosphate (ATP(2)(-)) pump, and illustrates how a self-organized hybrid material performs interesting and potentially useful functions.

ミニ特集「自己組織化材料研究の現状と課題」企画にあたって

ミニ特集「自己組織化材料研究の現状と課題」企画にあたって

Micro/Nanoengineering of the self-organized three-dimensional fibrous structure of functional materials.

A crystallographic mismatch branching mechanism, rather than molecular self-assembly, controls the architecture of the crystalline structure. Self-organized functional materials with a 3D fibrous network structure (see scanning electron micrographs; right) have been constructed from needlelike crystals of lanosterol:dihydrolanosterol and diisooctylphthalate (left) by using an ethylene/vinyl acetate copolymer as a branching creator.

Layered Ionic Liquids: Anisotropic Ion Conduction in New Self-Organized Liquid-Crystalline Materials

Layered Ionic Liquids: Anisotropic Ion Conduction in New Self-Organized Liquid-Crystalline Materials

Self-organized quantum-well materials for ultrafast optical processing

Self-organized quantum-well materials for ultrafast optical processing

All-optical serial-to-parallel conversion of T-bits/s signals using a four-wave-mixing process

We report a simple method of a serial-to-parallel conversion that does not use a Fourier-transform system. The method is based on directly picking up a narrow temporal range of the skewed input signal by using a nonlinear wave mixing with the reference pulse. We show theoretically that the pick-up method is less influenced by the relaxation times of the nonlinear material. We demonstrate our method experimentally using a self-organized quantum-well material, and confirm that T-bits/s pulses are clearly converted into spatial patterns with conversion rates of 140 GHz.

Time-to-space conversion of Tbits/s optical pulses using a self-organized quantum-well material

We report a time-to-space conversion technique using a material which has a large χ(3)(≃10−6 esu) and a fast response time (<7 ps) at room temperature. The material is a self-organized quantum-well system consisting of inorganic well layers and organic barrier layers. We achieve a high conversion sensitivity even for nJ-order optical pulses. We demonstrate serial-to-parallel conversion of nJ-order Tbits/s signals at room temperature with conversion rates of 140 GHz.