Long-Range Anisotropic Structural Films and Fibers Formed from Lyotropic Liquid Crystal Gels Containing Hetero-Double-Helices with C16 Terminal Groups.

Long-range anisotropic structural materials exhibit notable optical and mechanical properties, and an efficient method for synthesizing such materials involving self-assembly of well-defined monodispersed organic molecules is described here. Hetero-double-helices are formed in toluene using a pseudoenantiomeric mixture of an ethynylhelicene ( M)-tetramer with C16 terminal groups and a ( P)-pentamer. When the concentration of the mixture was increased, the hetero-double-helices self-assembled to form lyotropic liquid crystal gels. On evaporating the solvent by drop casting, a long-range anisotropic structural film with a single domain and a size of up to centimeter order was spontaneously formed. Kinetics analysis of the film formation indicated the generation of perpendicularly aligned liquid crystal domains at the interface of the liquid and solid phases. When the lyotropic liquid crystal gel was extruded into methanol, a long-range anisotropic structural fiber with a single domain was formed. Different shapes of long-range anisotropic structural materials were obtained by different mechanical treatments of lyotropic liquid crystal gels.

Mechanochemically assisted hydrothermal synthesis of Sn-substituted MFI-type silicates.

Substitution of Al atoms in a zeolite framework by catalytic metal atoms has attracted considerable attention because the catalytic behavior can be tuned by the substituted atoms. In the present study, Sn-substituted MFI-type silicates were synthesized using a hydrothermal reaction of an amorphous Si-O-Sn precursor prepared by mechanochemical grinding of SiO2 and Sn(OH)4. The mechanochemical treatment was found to be a key technique for obtaining the amorphous Si-O-Sn precursor, where tetrahedral Sn4+ species were incorporated into the amorphous matrix. The Sn content in the framework of the MFI-type silicates was successfully controlled by the initial HCl/Si molar ratio of the hydrothermal procedures. Optical reflectance measurements revealed that the Sn4+ ions were dispersedly incorporated into the silicate framework while preserving the initial tetrahedrally coordinated species. Infrared results imply that the resulting Sn-substituted MFI-type silicate has Brønsted acid character. Precise control of the Brønsted and Lewis acid properties by Sn doping is a promising approach to the development of novel types of zeolite-based catalytic materials.

Dynamic and Reversible Polymorphism of Self-Assembled Lyotropic Liquid Crystalline Systems Derived from Cyclic Bis(ethynylhelicene) Oligomers.

A self-assembled lyotropic liquid crystal (LLC) system exhibiting dynamic and reversible polymorphism was developed using the synthetic cyclic ethynylhelicene oligomers cyclobis[(M)-D-n] (n = 4 and 6), in which two oligomer moieties are connected by two flexible linkers. The cyclic molecular structure was designed to control aggregation properties ranging from the molecular level to the macroscopic level. The cyclic oligomer changed its structure between random coils and an intramolecular homo-double helix induced by temperature and solvents. In the presence of pseudoenantiomeric acyclic oligomers, cyclobis[(M)-D-4] formed trimolecular complexes with a total molecular weight of over 10 000 Da containing two intermolecular hetero-double helices. The trimolecular complex formation predominated over bimolecular complex formation. The trimolecular complex self-assembled at high concentrations and formed LLCs composed of anisotropically aligned fibers. The result is in contrast to acyclic systems, which form gels composed of randomly oriented fibers. The LLCs changed into turbid gels composed of randomly oriented bundles upon cooling, and the LLCs were regenerated by heating. This is a notable example of a self-assembled LLC system exhibiting dynamic and reversible polymorphism between two ordered structures in a closed system consisting of fully synthetic molecules.

Ultrasensitive Surface-Enhanced Raman Scattering Platform for Protein Detection via Active Delivery to Nanogaps as a Hotspot.

Surface-enhanced Raman scattering (SERS) is an attractive technique in molecular detection with high sensitivity and label-free characteristics. However, its use in protein detection is limited by the large volume of proteins, hindering its approach to the narrow spaces of hotspots. In this study, we fabricated a Au nanoTriangle plate Array on Gel (AuTAG) as an SERS substrate by attaching a Au nanoTriangle plate (AuNT) arrangement on a thermoresponsive hydrogel surface. The AuTAG acts as an actively tunable plasmonic device, on which the interparticle distance is altered by controlling temperature via changes in hydrogel volume. Further, we designed a Gel Filter Trapping (GFT) method as an active protein delivery strategy based on the characteristics of hydrogels, which can absorb water and separate biopolymers through their three-dimensional (3D) polymer networks. On the AuTAGs, fabricated with AuNTs modified with charged surface ligands to prevent the nonspecific adsorption of analytes to particles, the GFT method helped the delivery of proteins to hotspot areas on the AuNT arrangement. This combination of a AuTAG substrate and the GFT method enables ultrahigh sensitivity for protein detection by SERS up to a single-molecule level as well as a wide quantification concentration range of 6 orders due to their geometric advantages.

Forming a Homeotropic SmA Structure of Liquid Crystalline Epoxy Resin on an Amine-Modified Surface.

The molecular orientation of a liquid crystalline (LC) epoxy resin (LCER) on silane coupling surfaces of amorphous soda-lime-silica glass substrates was investigated. The LC epoxy monomer on the silane coupling surfaces of the substrates was revealed to form a smectic A (SmA) phase with planar alignments because of the relatively low surface free energy. An LCER with a curing agent, however, formed a homeotropically aligned SmA structure by curing on a substrate surface modified using a silane coupling agent with amino groups. This formation of homeotropic alignment was considered due to the attribution of the reaction between the amino group on the surface of the substrate and the epoxy group of the LCER. The homeotropic alignment had a relatively high orientation parameter of 0.95. Therefore, it is expected to possess high thermal conductivity and be applied as high-thermal-conductivity adhesives or packaging materials for electrical and electronic devices.

Simple cubic packing of gold nanoparticles through rational design of their dendrimeric corona.

The first simple-cubic liquid crystal was obtained by coating monodisperse Au nanoparticles (NPs) with a thick corona of amino-substituted organic dendrons. This unusual structure was determined by grazing-incidence diffraction and electron density reconstruction and explained by analyzing the radial density profile of the corona. Another novel structure is proposed for the phase preceding the cubic one: a hexagonal superlattice composed of alternating dense and sparse strings of Au NPs.

Fluoride-free synthesis of high-silica CHA-type aluminosilicates by seed-assisted aging treatment for starting gel.

High-silica CHA-type aluminosilicates (Si/Al molar ratio >100) were synthesized hydrothermally in the absence of fluoride media, where the seed-assisted aging treatment played an important role on the crystallization. These aluminosilicates showed a long catalytic lifetime with high selectivity toward lower olefins in the methanol-to-olefins reaction.

A mild aqueous synthesis of ligand-free copper nanoparticles for low temperature sintering nanopastes with nickel salt assistance.

An organic ligand-free aqueous-phase synthesis of copper (Cu) nanoparticles (NPs) under an air atmosphere was successfully achieved by reducing copper(II) oxide particles with a leaf-like shape in the presence of Ni salts at room temperature. The resulting Cu NPs with a mean particle diameter of ca. 150 nm exhibited low-temperature sintering properties due to their polycrystalline internal structure and ligand-free surface. These Cu NPs were applied to obtain Cu NP-based nanopastes with low-temperature sintering properties, and the resistivities of the obtained Cu electrodes after annealing at 150 °C and 200 °C for 30 min were 64 µΩ∙cm and 27 µΩ∙cm, respectively. The bonding strength between oxygen-free Cu plates prepared using the Cu NP-based nanopastes reached 32 MPa after pressure-less sintering at 260 °C for 30 min under a nitrogen atmosphere. The developed manufacturing processes using the developed Cu nanopastes could provide sustainable and low-CO2-emission approaches to obtain Cu electrodes on flexible films and high-strength bonding between metal plates as die-attach materials for power devices under energy- and resource-saving conditions.

A nanoparticle-mist deposition method: fabrication of high-performance ITO flexible thin films under atmospheric conditions.

Indium tin oxide (ITO) thin films with low resistivity and high transparency in the visible light region have been prepared on flexible plastic films by a deposition method using water mist containing ITO nanoparticles (NPs) under atmospheric conditions. The ITO NP-mist was generated by ultrasonic irradiation of a water dispersion. Our developed protrusion-rich ITO NPs were applied as the ITO NPs. The ITO NPs show high dispersion stability in water without the use of any dispersant. Comparison investigations revealed that utilization of the ITO NPs played a critical role in fabricating high-performance ITO thin films on flexible films, and the resistivity reached 9.0 × 10-3 Ω cm. The system could be expected to provide promising advances in the development of a mild and sustainable fabrication procedure for ITO thin films under mild atmospheric conditions without the use of expensive vacuum production systems or harmful and environmentally undesirable chemicals.

Magnetorheological Fluids with Surface-Modified Iron Oxide Magnetic Particles with Controlled Size and Shape.

This study is focused on surface-modified Fe3O4@SiO2 particles with precisely controlled sizes and shapes applied in magnetorheological (MR) fluids. After the preparation of the monodisperse spindle-shaped and cubic Fe3O4@SiO2 particles, surface modification with dodecyltrimethoxysilane (DTM) was carried out via a silane coupling reaction to increase the dispersion stability of the particles. Afterward, MR fluids were prepared by mixing the DTM-modified Fe3O4@SiO2 particles with silicon oil. Transmission electron microscopy observations demonstrated that spindle-shaped Fe3O4@SiO2 particles could form a more stable chain-like structure than cubic Fe3O4@SiO2 particles upon application of an external magnetic field. The rheological measurements of MR fluids also indicated that the surface modification with DTM, the introduction of anisotropic shapes, and the increase in the particle size all played positive roles in the improvement in MR properties.

Deep convolutional neural network image processing method providing improved signal-to-noise ratios in electron holography.

An image identification method was developed with the aid of a deep convolutional neural network (CNN) and applied to the analysis of inorganic particles using electron holography. Despite significant variation in the shapes of α-Fe2O3 particles that were observed by transmission electron microscopy, this CNN-based method could be used to identify isolated, spindle-shaped particles that were distinct from other particles that had undergone pairing and/or agglomeration. The averaging of images of these isolated particles provided a significant improvement in the phase analysis precision of the electron holography observations. This method is expected to be helpful in the analysis of weak electromagnetic fields generated by nanoparticles showing only small phase shifts.

Organic Structure-Directing Agent-Free Synthesis of Mordenite-Type Zeolites Driven by Al-Rich Amorphous Aluminosilicates.

Mordenite (MOR)-type zeolites with a Si/Al molar ratio of up to 13 with crystallite sizes of ca. 60 nm were successfully synthesized from Al-rich aluminosilicates with a Si/Al ratio of 2 and additional SiO2 under seed-assisted hydrothermal conditions for 6 h or longer without any organic structure-directing agents (OSDAs). In stark contrast, under the same hydrothermal conditions for 6 h, control experiments using starting reagent(s), such as Al-poor aluminosilicate, pure SiO2, tetraethyl orthosilicate, and Al(NO3)3, all of which are typically employed for zeolite synthesis, failed to yield MOR-type zeolites. The penta-coordinated Al species, which are present in Al-rich aluminosilicates and are more reactive than the tetra- and hexa-coordinated Al species typically found in alumina and Al-poor aluminosilicates, played a decisive role in the OSDA-free synthesis of MOR-type zeolites.

Transcription-induced formation of paired Al sites in high-silica CHA-type zeolite framework using Al-rich amorphous aluminosilicate.

The paired Al species pre-formed in Al-rich amorphous aluminosilicates were transcribed into high-silica CHA-type zeolite frameworks under hydrothermal conditions, which offers a new approach to creating paired Al sites in zeolite frameworks. This Al-pair-rich CHA exhibited a higher Sr2+ uptake than the control CHA zeolite synthesized by the conventional procedure.

Homeotropically Aligned Monodomain-like Smectic-A Structure in Liquid Crystalline Epoxy Films: Analysis of the Local Ordering Structure by Microbeam Small-Angle X-ray Scattering.

For the development of functional thin films with high thermal conductivity, the local ordering structure of a cured liquid crystalline epoxy resin (LCER) droplet was investigated by using synchrotron radiation microbeam small-angle X-ray scattering. The cured LCER in the vicinity of a substrate with low surface free energy was revealed to form a polydomain smectic-A (SmA) structure in which the normal direction of the layers was random in each domain, although the alignment was planar near the air interface. On the other hand, the cured LCER on a substrate with high surface free energy formed a homeotropically aligned SmA structure in the region within 21 µm from the surface of the substrate. Therefore, a 20 µm thick LCER film was fabricated and found to form a homeotropically aligned monodomain-like SmA structure throughout the whole film with a high thermal conductivity (0.81-5.8 W m-1 K-1). This film with a high thermal conductivity is expected to be applicable for adhesion and precoating materials for electrical and electronic devices.

Self-assembly of photoresponsive azo-containing phospholipids with a polar group as the tail.

Vesicles or micelles prepared from amphiphiles with azobenzene (Az) moieties and long alkyl chains have attracted much attention in drug delivery systems. To induce release behavior from smart carriers via trans-cis photoisomerization of the Az groups, UV light exposure is typically used, but it can damage DNA and hardly penetrates cells. In this paper, Az-containing phospholipids without long alkyl tails were designed and synthesized; in these compounds, the end group of the Az moiety was substituted with a -NO2 and -OCH3 group (abbreviated N6 and M6, respectively). N6 self-assembled into H-aggregates with an interdigitated bilayered structure in water through the antiparallel orientation due to π-π interactions of the Az group, the attractive van der Waals forces, and the interactions and bending behavior of the phosphocholine groups. Vesicles showing visible light stimuli-responsive behavior were obtained by mixing N6 and M6, and the release of encapsulated calcein was triggered by visible light.

Magnetic field induced uniaxial alignment of the lyotropic liquid-crystalline PMMA-grafted Fe3O4 nanoplates with controllable interparticle interaction.

Magnetite (Fe3O4) nanoplates with a hexagonal platelet shape were synthesized by two steps: hydrothermal synthesis of iron(iii) oxide (α-Fe2O3) nanoplates followed by wet chemical reduction of the α-Fe2O3 nanoplates. Then, poly(methyl methacrylate) (PMMA) chains were grafted onto the surface of the hexagonal Fe3O4 nanoplates (F) via surface-initiated atom transfer radical polymerization (SI-ATRP), which ensures dispersion stability in organic solvents and ionic liquids. After mixing with 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Emim+][NTf2 -]), a representative ionic liquid, the resulting PMMA-modified F were found to show good lyotropic liquid-crystalline (LC) behaviour in [Emim+][NTf2 -] and to exhibit a fast response to the application of an external magnetic field. Ultrasmall-angle synchrotron X-ray scattering (USAXS) measurements verified that the PMMA chain length, the weight ratio of the ionic liquid and the external magnetic field could significantly influence the interparticle distance (I D) of the PMMA-modified F in [Emim+][NTf2 -]. In particular, the lyotropic LC phase could be assigned as a nematic phase with a columnar alignment. In addition, the PMMA-modified F maintained a uniaxially aligned nematic columnar structure along the magnetic field direction. Our study also determined the mechanism for the special alignment of the PMMA-modified F under an external magnetic field by analysing the growth axis, the easy magnetic axes, and the interparticle distance of F. The results suggested that the special alignment of the PMMA-modified F was affected by the interparticle interaction caused by the PMMA long chains on F under the magnetic field. Furthermore, the present study revealed that PMMA-modified F exhibited a new magnetic field responsive behaviour that led not only to the formation of a uniaxial alignment structure but also to control of I D with the help of the PMMA soft corona under the application of a magnetic field. These features could prove to be a promising advance towards novel applications of magnetic nanoparticles (NPs), such as functional magnetic fluids, rewritable magnetic switching devices, and smart magneto-electrochemical nanosensors.

Ambient Aqueous-Phase Synthesis of Copper Nanoparticles and Nanopastes with Low-Temperature Sintering and Ultra-High Bonding Abilities.

Copper nanoparticles (NPs) with an average particle diameter of 50-60 nm were successfully obtained by reducing an aqueous solution of a copper(II)-nitrilotriacetic acid complex with an aqueous hydrazine solution at room temperature under an air atmosphere. Copper NP-based nanopastes were printed onto a glass substrate using a metal screen mask and pressureless sintered under a nitrogen atmosphere at 200 °C for 30 min. The electrical resistivity of the resulting copper electrode was 16 µΩ · cm. For a metal-to-metal bonding test, copper nanopaste was printed on an oxygen-free copper plate, another oxygen-free copper plate was placed on top, and the bonding strength between the copper plates when pressureless sintered under a nitrogen atmosphere at 200 °C for 30 min was 39 MPa. TEM observations confirmed that highly crystalline metal bonding occurred between the copper NPs and the copper plate to introduce the ultrahigh strength. The developed copper NPs could provide promising advances as nanopastes for sustainable fabrication of copper electrodes and die attachment materials for the production of next-generation power semiconductors.

Self-assembled structure of dendronized CdS nanoparticles.

Self-assembled dendronized CdS nanoparticles have been attracting considerable attention because of their photoluminescence properties depending on annealing treatments. In this study, their annealing-induced self-assembled structure was investigated via scanning transmission electron microscopy; thin foil specimens of self-assembled dendronized CdS nanoparticles were prepared by ultramicrotomy and the STEM images revealed their ordered structure and the effect of the annealing treatment. In addition, a structural order belonging to the P213 space group was identified via an autocorrelation analysis. The results indicated that this structural order could be achieved only over a few tens of nanometers.

Preferential adsorption of selenium oxyanions onto {1 1 0} and {0 1 2} nano-hematite facets.

As the commercial use of nano metal oxides, including iron oxides, becomes more prevalent, there is a need to understand functionality as it relates to the inherent properties of the nanomaterial. Many applications of nanomaterials rely on adsorption, ranging from catalysis to aqueous remediation. In this paper, adsorption of selenium (Se), an aqueous contaminant, is used as a model sorbate to elucidate the relationships of structure, property, and (adsorptive) function of nano-hematite (nα-Fe2O3). As such, six nα-Fe2O3 particles were synthesized controlling for size, shape and surface area without capping agents. Sorbent characteristics of the six particles were then assessed for their impact on selenite (HSeO3-) and selenate (SeO42-) adsorption capacity and mechanism. Mechanism was assessed using in-situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and extended X-ray absorption fine edge spectroscopy (EXAFS). Regression analyses were then performed to determine which characteristics best describe adsorption capacity and binding mechanisms of Se on nα-Fe2O3. The results demonstrate that crystal surface structure, specifically presence of the {0 1 2} facet promotes adsorption of Se and the presence of {0 1 2} facets promotes SeO42- sorption to a greater extent than HSeO3-. The data further indicates that {1 1 0} facets bind HSeO3- with binuclear complexes while {0 1 2} facets bind HSeO3- via mononuclear inner-sphere complexes. Specific nα-Fe2O3 facets also likely direct the ratio of inner to outer-sphere complexes in SeO42- adsorption.

Triethylsilane as a mild and efficient reducing agent for the preparation of alkanethiol-capped gold nanoparticles.

The reaction of HAuCl(4).4H(2)O and n-C(12)H(25)SH with 1 equiv. of Et(3)SiH in an organic solvent affords spherical gold nanoparticles (AuNPs) with narrow dispersity.