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Multilayered films prepared from graphene oxide (GO) subjected to a single oxidation process (1GO) can actuate in response to moisture, whereas those prepared from GO subjected to two oxidation processes (2GO) lose this ability. To elucidate the origin of this difference, the structures and properties of various multilayered films and their contents were analyzed. According to atomic force microscopy images, the lateral size of the GO monolayer in 2GO (2.0 ± 0.4 μm) was smaller than that in 1GO (3.2 ± 0.4 μm), although this size difference did not affect actuation. Scanning electron microscopy images of the cross sections of both films showed fine multilayered structures and X-ray diffraction measurements showed the moisture sensitive reversible change in the interlayer distances for both films. Both films adsorbed 30 wt% moisture in 60 s with different water contents at the bottom moist sides and top air sides of the films. Nanoindentation experiments showed hardness values (1GO: 156 ± 67 MPa; 2GO: 189 ± 97 MPa) and elastic modulus values (1GO: 4.7 ± 1.7 GPa; 2GO: 5.8 ± 3.2 GPa) typical of GO, with no substantial difference between the films. On the contrary, the 1GO film bent when subjected to a weight equal to its own weight, whereas the 2GO film did not. Such differences in the macroscopic hardness of GO films can affect their moisture-induced actuation ability.

A complex permittivity profile reconstruction for multilayered objects was presented in this study by incorporating compressed sensing (CS)-based thickness estimation with contrast source inversion (CSI) non-linear inverse scattering (IS) method using a terahertz (THz) frequency band. Several studies investigated permittivity estimation for multiple layers. However, they require a prior knowledge of the thickness of each layer. Moreover, a critical problem in this field is the simultaneous estimation of both the dielectric constant and the thickness of each layer. To address this, a super-resolution thickness estimator using a CS filter and the CSI-based dielectric profile reconstruction scheme was used. This problem was effectively solved by introducing the cost function estimated using the CSI scheme, where the number of layers is given. The finite-difference time-domain (FDTD) numerical test indicated that the proposed method provides an accurate estimation of the thickness and dielectric profile in double-layered objects.

In this Article, we report the results of studies on the aggregation of a diphosphine-ligated [Au6]2+ cluster in aqueous organic solvents, and we highlight the formation of ordered cluster assembli...

Biological materials, such as bones, teeth and mollusc shells, are well known for their excellent strength, modulus and toughness1–3. Such properties are attributed to the elaborate layered microstructure of inorganic reinforcing nanofillers, especially two-dimensional nanosheets or nanoplatelets, within a ductile organic matrix4–6. Inspired by these biological structures, several assembly strategies—including layer-by-layer4,7,8, casting9,10, vacuum filtration11–13 and use of magnetic fields14,15—have been used to develop layered nanocomposites. However, how to produce ultrastrong layered nanocomposites in a universal, viable and scalable manner remains an open issue. Here we present a strategy to produce nanocomposites with highly ordered layered structures using shear-flow-induced alignment of two-dimensional nanosheets at an immiscible hydrogel/oil interface. For example, nanocomposites based on nanosheets of graphene oxide and clay exhibit a tensile strength of up to 1,215 ± 80 megapascals and a Young’s modulus of 198.8 ± 6.5 gigapascals, which are 9.0 and 2.8 times higher, respectively, than those of natural nacre (mother of pearl). When nanosheets of clay are used, the toughness of the resulting nanocomposite can reach 36.7 ± 3.0 megajoules per cubic metre, which is 20.4 times higher than that of natural nacre; meanwhile, the tensile strength is 1,195 ± 60 megapascals. Quantitative analysis indicates that the well aligned nanosheets form a critical interphase, and this results in the observed mechanical properties. We consider that our strategy, which could be readily extended to align a variety of two-dimensional nanofillers, could be applied to a wide range of structural composites and lead to the development of high-performance composites. Layered nanocomposites fabricated using a continuous and scalable process achieve properties exceeding those of natural nacre, the result of stiffened matrix polymer chains confined between highly aligned nanosheets.

A water-dispersible bottlebrush polymer with well-regulated length (300 nm) and width (20 nm) was developed for uptake of hydrophobic guest in aqueous media. This bottlebrush polymer was designed t...

Superhydrophobic materials with micro/nanotextured surface have attracted tremendous attention owing to their potential applications such as self-cleaning, antifouling, anti-icing, and corrosion prevention. Such a micro/nanotextured surface is a key for high water repellency. However, such a texture is fragile and readily damaged when the material is deformed, scratched, or sliced off. Thus, it is challenging to develop superhydrophobic materials that can sustain high water repellency after experiencing such a mechanical deformation and damage. Here we report abrasion/scratching/slicing/droplet impacting/bending/twisting-tolerant superhydrophobic flexible materials with porcupinefish-like structure by using a composite of micrometer-scale tetrapod-shaped ZnO and poly(dimethylsiloxane). Owing to the geometry of the tetrapod and elasticity of poly(dimethylsiloxane), the composite material exhibits stable water repellency after 1000 abrasion and 1000 bending cycles, or even after their surfaces were sliced off many times. The material maintains superhydrophobicity even under a mechanically deformed state such as bending and twisting. The materials can be painted on a variety of substrates and molded into desired shapes and used in a myriad of applications that require superhydrophobicity.

Bottlebrush polymers (BPs) are highly tunable with regard to their glass transition temperature, refractive index, and shape. Herein, well-defined BPs were implemented as soft fillers to toughen multiphase plastics without loss of transparency and thermal stability, providing superior fracture toughness than a conventional linear polymer (LP). This study discloses a novel application of BPs and paves the way toward their further development.

The longest bottlebrush polymers reported so far (up to 7 μm in length) were synthesized in two steps from a norbornene derivative bearing two 2-bromoisobutylate moieties (NB). The key to this achievement is the excellent reactivity of NB in ring opening metathesis polymerization, which proceeded in a well-controlled manner with quantitative conversion of NB for monomer-initiator ratios ranging up to 10,000. The resultant polymer derived from NB was readily converted to various bottlebrush polymers in a divergent synthetic route by grafting vinyl monomers from the 2-bromoisobutylate units in NB via atom transfer radical polymerization. The structure of the ultra-long bottlebrush polymer was directly observed using atomic force microscopy.

The self-assembly of amphiphilic building blocks represents an elegant strategy to produce (nano)structures with unique functionalities and is often investigated for a wide range of applications in biology and materials science. Herein, we report micro- to nanoscale vesicular assembly made of naturally abundant dendritic polyphenols, tannic acid (TA). Rich content in several plant parts, nontoxicity, and the inherent ability of diverse molecular interactions including H-bonding, π–π interactions, and metal coordination make such polyphenols a promising class of natural building blocks for supramolecular assembly and precursors for natural surfactants. The facile modification of hydrophilic TA by introducing n-alkyl chains produced TA-based multiarm surfactants, which facilitates molecular assembly in water. Systematic manipulations of processing parameters including amphiphile concentration, cosolvent ratio, and mixing rate enabled us to achieve well-defined and size-tunable spherical vesicles in the rang...

Resettable thermosetting adhesive systems have been explored with the help of a thermo-reversible Diels–Alder (DA) reaction between a furan-bearing random copolymer and bismaleimide as a dynamic bond cross-linkage. The obtained adhesive materials exhibited good lap shear strength in the cross-linked state of up to ∼8 MPa. In addition, the bonding/debonding state of the adhesives could be reset by an appropriate choice of thermal treatment.

A novel ABA-triblock bottlebrush polymer ( PS - PD - PS ), whose terminal PS block and central PD block were densely grafted with polystyrene and poly[2-(dimethylamino)ethyl methacrylate], respectively, on polynorbornene backbones was synthesized by three mutually orthogonal types of controlled polymerization. Dynamic light-scattering analysis revealed that in polar solvents such as tetrahydrofuran/water (99:1, v/v), PS - PD - PS self-assembled into oligomeric-to-polymeric aggregates through solvophobic interaction of the PS block. The size of these aggregates depended on the concentration of PS - PD - PS and on the polarity of the solvent. Atomic-force microscopy (AFM), showed that single molecules of PS - PD - PS adopted a dumbbell shape in which the three blocks in PS - PD - PS could be clearly distinguished. In AFM samples prepared under appropriate conditions, PS - PD - PS self-assembled into discrete oligomeric aggregates with well-defined structure, including linear and cyclic dimers, a tadpole-like trimer, and higher oligomers. The arrangement and junctions of the monomeric units could be clearly visualized at a single-molecular level.

This paper proposes an indexing method of plasma waveforms for accelerating search and retrieval of their subsequences. The proposed method divides a waveform into fine-grained segments. The similar segments are grouped into a segment group. A multi-dimensional index is used for quick retrieval. Grouping segments could save the amount of the index. In the retrieval, a sequence of segments, which is called a section, is used as a unit in matching subsequences. Overlapping sections could overcome the shift errors of subsequences, and results in good retrieval correctness.

Ligand-controlled regioselective palladium-catalyzed decarboxylative hydrogenolysis of propargylic formates is described. A wide range of allenes and alkynes were obtained by using either 1,2-diphenylphosphinoethane (DPPE) or 1,6-bisdiphenylphosphinohexane (DPPH) as a catalyst ligand.

Ruthenium-catalyzed efficient preparation of the conjugated enynes can be carried out in the reactions of 1-cyclopropyl-2-propyn-1-ols with nitrogen- and oxygen-centered nucleophiles such as anilines and water in the presence of a catalytic amount of sulfur-bridged diruthenium complexes. The use of such complexes as catalysts realizes the completely stereoselective preparation of tri- and tetrasubstituted conjugated enynes, where ruthenium-allenylidene complexes work as key intermediates. The direct attack of nucleophiles on a cyclopropane ring connected to an allenylidene ligand is a key step to obtain the enynes stereoselectively.

Optically pure α-trifluoromethylated aziridinyl anions react with various electrophiles to give the corresponding optically pure 2-trifluoromethyl-2-substituted aziridines, which are general synthetic precursors for optically pure α-amino-α-trifluoromethylated compounds, such as trifluoromethylated α/β-amino acids, in good yields.

Mesoporous silica (MPS) thin film biosensor platforms were established. MPS thin films were prepared from tetraethoxysilane (TEOS) via using sol-gel and spin-coating methods using a poly-(ethylene oxide)-block-poly-(propylene oxide)-block-poly-(ethylene oxide) triblock polymer, such as P123 ((EO)20(PO)70(EO)20) or F127 ((EO)106(PO)70(EO)106), as the structure-directing agent. The MPS thin film prepared using P123 as the mesoporous template and treated via vacuum ultraviolet (VUV) irradiation to remove the triblock copolymer had a more uniform pore array than that of the corresponding film prepared via thermal treatment. Protein adsorption and enzyme-linked immunosorbent assay (ELISA) on the synthesized MPS thin films were also investigated. VUV-irradiated MPS thin films adsorbed a smaller quantity of protein A than the thermally treated films; however, the human immunoglobulin G (IgG) binding efficiency was higher on the former. In addition, protein A-IgG specific binding on MPS thin films was achieved without using a blocking reagent; i.e., nonspecific adsorption was inhibited by the uniform pore arrays of the films. Furthermore, VUV-irradiated MPS thin films exhibited high sensitivity for ELISA testing, and cytochrome c adsorbed on the MPS thin films exhibited high catalytic activity and recyclability. These results suggest that MPS thin films are attractive platforms for the development of novel biosensors.

[reaction: see text] Generation and reactions of oxiranyl anion 2 stabilized by a trifluoromethyl group are described. Treatment of (S)-2,3-epoxy-1,1,1-trifluoropropane (75% ee) with n-BuLi followed by electrophiles gave corresponding 2-alkylated epoxide 3 with retention of stereochemistry in moderate to good yields. The reaction is applicable for a general synthesis of optically active trifluoromethylated tertiary alcohols.

Three-dimensional m × n arrays of metal ion clusters can be assembled as aromatic stacks of planar polynuclear metal complexes within columnar coordination cages. The polynuclear complexes and cage height program the final array structures of the metal ion clusters. Cyclic trinuclear Au(I) complexes (m = 3) assembled into trigonal prismatic arrays (n = 1-3) within the cages and the array structures were clearly shown by X-ray crystallographic analysis. A silver-sandwiched hetero-Au(3)-Ag-Au(3) cluster was also prepared by treating a hexanuclear Au(3)-Au(3) cluster with Ag(I) ion.

Refractory metal ultrafine particles were synthesized by the irradiation of two synchronized-pulse Nd: YAG lasers on a refractory metal substrate in a low pressure inert gas atmosphere. A size distribution of the refractory metal ultrafine particles was measured by a low pressure differential mobility analyzer (LP-DMA) developed by ourselves for each pressure condition. The experimental results showed the peak of the size distribution was shifted from the several nm to the tens of nm level with increasing the pressure. The ultrafine particles of a 10 nm-size (σg=1.12) were precisely classified by the LP-DMA. We could control the shape of the particles from agglomeration condition to spherical one by using an electric furnace. In conclusion, the size classification of narrow distribution and the shape of the generated ultrafine particles could be well controlled.

The ruthenium-catalyzed oxypropargylation of alkenes with propargylic alcohols and simple alcohols has been found via ruthenium−allenylidene complexes as key intermediates. As a synthetic application, an intramolecular cyclization using this method has been developed to give the corresponding anti-1-alkoxy-3-ethynylindanes in high to excellent yields with a high diastereoselectivity.

A flow system for cyanide detection using Saccharomyces cerevisiae is described. This sensor system consists of two oxygen electrodes and immobilized S. cerevisiae whose respiration activity is measured by the oxygen electrodes. Since cyanide inhibits S. cerevisiae's respiration, it can be detected by measuring this inhibition. Two types of systems were constructed, characterized and compared. One is a membrane-type flow system in which S. cerevisiae was immobilized onto a cellulose membrane. The other is a reactor-type flow system in which S. cerevisiae was immobilized onto the glass beads. The sensor response was examined in the range from 0 to 15μM. The reactor-type sensor system displayed lower detection limit (0.15 μM) and better stability (16 days).

A microbial cyanide sensor using Saccharomyces cerevisiae for monitoring a river water is described. This sensor is based on the inhibition of S. cerevisiae's respiration by cyanide. This sensor is a reactor type flow system and composed of two oxygen electrodes and a reactor which contains S. cerevisiae immobilized beads. The S. cerevisiae's respiration activity is measured using the oxygen electrodes. The sensor showed a linear response in the range from 0 to 15 microM and maintained stable response for 9 days at ambient temperature. The sensor was optimized for the monitoring of river water and was applied to river water analysis.

The characteristics of yeast carbohydrate metabolism in a multistage bioreactor system for rapid beer fermentation were investigated. The yield of biomass in a continuous stirred-tank reactor (CSTR) was approx 10%, whereas the yield in an immobilized yeast packed-bed reactor (PBR) was below 1.0%. The overall ethanol productivity per extract consumed was slightly higher than for conventional beer fermentation owing to the restricted growth of immobilized yeast. The organic acid composition was different from a conventional fermentation broth, i.e., higher amount of succinate and lower amount of acetate. Virtually no acetate was produced in the CSTR. Succinate was produced in both the CSTR and PBR, but the amount produced per extract consumed was approximately two times larger in the CSTR. A large amount of α-acetolactate was produced in an early stage of a continuous operation of the PBR. However, once the immobilized yeast growth had stabilized, the productivity was lowered to approx 0.07 mg/(10 mg extract). Control of the amino acid composition of the wort fed to the PBR was not effective in repressing the production of α-acetolactate in the PBR. A strategy for controlling minor byproducts of carbohydrate metabolism in a multistage beer fermentation system was discussed.

A multistage bioreactor system for rapid beer fermentation was developed. The main fermentation process, which conventionally requires 7 d, could be shortened to 2 d by this system. The concentration of esters and higher alcohols are major factors in brewery fermentation, their production being closely related to the yeast growth phase. Yeast metabolism was successfully subdivided into a growth and a restricted phase through a combination of a continuous stirredtank reactor (CSTR) and an immobilized yeast packed-bed reactor (PBR). Production of higher alcohols was high in the CSTR because of its association with the level of biosynthetic activityde novo. A small amount was also produced in the PBR, however, possibly a result of an overflow in carbohydrate metabolism. Ester formation mainly occurred in the PBR, a linear increase in the level of ester being observed with flow through the PBR. The reactor system control strategy was to maximize the level of both higher alcohol and ester formation. The CSTR/PBR control range, based on extract consumption, was varied between 1:1 and 1:2. A ratio of 1:1 tended to create a flat beer, whereas a ratio 1:2 gave a beer of richer quality. Amino acid uptake by the yeast directly contributed to a reduction in the wort pH, whereas no relation could be observed between the level of organic acid production and pH.

The characteristics of yeast sulfite metabolism in a multistage bioreactor system for beer fermentation were investigated. No sulfite was produced in the continuous stirred-tank reactor (CSTR). However, large amounts were produced in the packed-bed reactor (PBR). Production of sulfite in the PBR seems to be inevitable when it is operated continuously. In order to control the sulfite level in the young beer, the yeast needs to be reactivated into the growth phase. One possible strategy to achieve this is to aerate and periodically remove yeast clogged in the reactor once every 6-7 months before the sulfite level exceeds a given concentration (e.g., 20 mg/L). It was confirmed that sulfite production is closely related to the growth condition of the yeast and is therefore important to consider in the control strategy for sulfite when using the immobilized yeast reactor for beer production.

Operational conditions for the maturation of beer using an immobilized yeast reactor were investigated. α-Acetolactate generated during alcohol formation could be reduced to 0.06 mg l −1 , below the threshold level, by a combination of heat treatment and bioreactor treatment. Operating temperatures above 4°C resulted in regeneration of α-acetolactate (precursor of diacetyl) and it was preferable to run the reactor between −1.0 to 1.0°C. For an initial diacetyl concentration below 1.0 mg l −1 , a residence time of 3 to 20 h was required to control regeneration of α-acetolactate below threshold. A pressure of 0.6 to 1.0 kg cm −2 was sufficient to prevent gas holdup if the extract consumption in the reactor was less than 0.5%. It was not necessary to maintain tight control over dissolved oxygen. Under the above conditions, almost no amino acids were consumed and the diacetyl (or total diacetyl) level was reduced to below threshold, where approx. 0.03% of extract was consumed per h of residence time. Because of the low operational temperature, diacetyl reducing performance could be maintained for more than 6 months.

Methods of heat treating young beer in order to accelerate the beer maturation process were investigated. In conventional beer brewing, the two-step conversion of α-acetolactate to diacetyl and of diacetyl to acetoin occurs concurrently and is a time-consuming process, the first step being rate limiting. The optimum conditions for achieving the first step by heat treatment and determination of the heat conversion rate constant are described. Under aerobic conditions, α-acetolactate was converted to diacetyl but under anaerobic conditions, it was converted to acetoin. The decay constant of α-acetolactate, however, was identical in both conditions. Operating pressure and the effect of heat treatment on beer quality were examined. The heat treatment of young beer under anaerobic conditions is a novel maturation method in that α-acetolactate can be converted directly to a flavorless substance (acetoin).

A three-stage bioreactor system for rapid beer brewing was developed and the characteristics and design factors of an immobilized yeast bioreactor using porous glass beads as carriers were investigated. The porous glass bead was advantageous for long-term operation of a packed bed reactor because of its physical strength and ease of handling. Immobilization capacity of the porous heads could be controlled by varying the mean pore size, leading to an immobilization performance comparable to that of calcium-alginate heads. In situ immobilization was made possible by circulating yeast suspended in the wort through the packed bed reactor. The reactor had good plug flow reaction properties which were verified by analyzing residence time distribution using a lactose impulse method. It was found that cooling equipment must be installed to avoid heat accumulation during scaling up of the reactor.