Solvent- and Light-Sensitive AIEE-Active Azo Dye: From Spherical to 1D and 2D Assemblies

Fluorescent molecular assembly systems provide an exciting platform for creating stimuli-responsive nano- and microstructured materials with optical, electronic, and sensing functions. To understand the relationship between (i) the plausible molecular structures preferentially adopted depending on the solvent polarity (such as N,N-dimethylformamide [DMF], tetrahydrofuran [THF], and toluene), (ii) the resulting spectroscopic features, and (iii) self-assembled nano-, micro-, and macrostructures, we chose a sterically crowded triangular azo dye (3Bu) composed of a polar molecular core and three peripheral biphenyl wings. The chromophore changed the solution color from yellow to pink-red depending on the solvent polarity. In a yellow DMF solution, a considerable amount of the twisted azo form could be kept stable with the help of favorable intermolecular interactions with the solvent molecules. By varying the concentration of the DMF solution, the morphology of self-assembled structures was transformed from nanoparticles to micrometer-sized one-dimensional (1D) structures such as sticks and fibers. In a pink-red toluene solution, the periphery of the central ring became more planar. The resulting significant amount of the keto-hydrazone tautomer grew into micro- and millimeter-sized 1D structures. Interestingly, when THF-H₂O (1:1) mixtures were stored at a low temperature, elongated fibers were stacked sideways and eventually developed into anisotropic two-dimensional (2D) sheets. Notably, subsequent exposure of visible-light-irradiated sphere samples to solvent vapor resulted in reversible fluorescence off↔on switching accompanied by morphological restoration. These findings suggest that rational selection of organic dyes, solvents, and light is important for developing reusable fluorescent materials.     

Fine-tuned,molecular-composite,organosilica membranes for highly efficient propylene/propane separation via suitable pore size

Fine-tuned, molecular-composite, organosilica membranes were fabricated via the co-condensation of organosilica precursors bis(triethoxysilyl)acetylene (BTESA) and bis(triethoxysilyl)benzene (BTESB). Fourier transform infrared and UV–vis spectra confirmed the co-condensation behaviors of BTESA and BTESB. The evolution of the network structure indicated that the incorporated BTESB decreased the membrane pore size, which was determined by a modified gas translation model according to the steric effect of the phenyl groups. The incorporation of BTESB to BTESA finely tuned the membrane structure and endowed the resultant composite membrane with improved separation properties. The BTESAB 9:1 membrane (molar ratio of BTESA/BTESB was 9:1) exhibited high C₃H₆ permeance at 4.5 × 10⁻⁸ mol m⁻² s⁻¹ Pa⁻¹ and a C₃H₆/C₃H₈ permeance ratio of 33 at 50°C. One of the most important developments of this study involved clearly defining the relationship between membrane pore size and C₃H₆/C₃H₈ separation performance for organosilica membranes in single and binary separation systems.     

Nondestructive determination of fatty acid composition of husked sunflower (Helianthus annua L.) seeds by near-infrared spectroscopy

Determination of the fatty acid composition of sunflower (Helianthus annua L.) seeds by near-infrared (NIR) spectroscopy was examined. Sunflower seeds were husked (removed from their hulls by a husking machine or manually with a knife). NIR spectra of these seeds were scanned from 1100 to 2500 nm at 2-nm intervals in a whole-grain cell with a wideangle moving drawer for machine-husked seeds or in a single-grain cup for a manually husked single-grain seed. The extracted oils from machine-husked seeds also were scanned by sandwiching them between a pair of slide glasses to create a thin layer and by placing them on a syrup cup. For extracted oil, the absorption band around 1720 nm filled out to the shorter wavelength region in the NIR second-derivative spectra as the percentage of the linoleic acid moiety increased, because linoleic acid absorbs in this region. On the other hand, for husked seeds and for a single-grain seed, as the percentage of linoleic acid increased, the trough at 1724 nm where oleic and saturated acids absorb decreased in the second-derivative NIR spectra. Determination of the fatty acid composition of sunflower seeds could be carried out successfully according to the NIR spectral pattern for both extracted oil (r=−0.989) and kernel seed (r=−0.993). This is important, especially for a manually husked single-grain seed (r=−0.971), because it can still be germinated after such nondestructive analysis.     

Morphology‐dependent electrocatalytic activity of nanostructured Pt/C particles from hybrid aerosol–colloid process

An optimum nanostructure and pore size of catalyst supports is very important in achieving high catalytic performances. In this instance, we evaluated the effects of various carbon nanostructures on the catalytic performances of carbon‐supported platinum (Pt/C) electrocatalysts experimentally and numerically. The Pt/C catalysts were prepared using a hybrid method involving the preparation of dense, hollow, and porous nanostructured carbon particle via aerosol spray pyrolysis followed by microwave‐assisted Pt deposition. Electrochemical characterization of the catalysts showed that the porous Pt/C catalyst gave the best performance; its electrochemical surface area was much higher, more than twice than those of hollow or dense Pt/C. The effects of pore size on electrocatalysis were also studied. The results showed the importance of a balance between mesopores and macropores for effective catalysis with a high charge transfer rate. A fluid flow model showed that good oxygen transport contributed to the catalytic activity. © 2015 American Institute of Chemical Engineers AIChE J, 62: 440–450, 2016     

Preparation of poly(ethylene glycol)-modified poly(amidoamine) dendrimers with a shell of hydrophobic amino acid residues and their function as a nanocontainer

We studied the use of poly(ethylene glycol) (PEG)-modified dendrimers as a nanocapsule with a biocompatible surface. We designed PEG-modified dendrimers having a shell of hydrophobic amino acid residues in the peripheral moiety of the dendrimer to increase their encapsulation ability. Subsequently, l-phenylalanine or γ-benzyl-l-glutamate residues were introduced to all chain ends of the poly(amidoamine) G4 dendrimers. Furthermore, PEG (MW 2000) chains were attached to the amino acid residues. These hydrophobic amino acid residues rendered the PEG-modified dendrimers as more compact. After binding of Rose Bengal (RB) guest molecules to dendrimers, an assay using the Klotz plot showed that the hydrophobic amino acid layer slightly affected the guest site number, but significantly increased intrinsic binding of the dendrimers to guest molecules. The PEG-modified dendrimers with the hydrophobic amino acid layer were better able to retain guest molecules than the dendrimer without the layer: they are therefore useful for drug delivery.     

Si-C-O glass-like compound/exfoliated graphite composites for negative electrode of lithium ion battery

Two low molecular weight silicone compounds, a cyclic type having vinyl groups and a chain-type having Si-H bonds, a catalyst for curing, and a catalyst regulator were mixed. The mixture was impregnated into exfoliated graphite (EG) by sorption, and cured in air at 200 °C. By this process cross-linked silicone coatings were formed on graphite flakes. The composites of Si-C-O glass-like compounds and EG were synthesized by heat treatment of this precursor at 1000-1400 °C for 1 h in argon. The composites formed at 1000-1300 °C were amorphous by XRD and had practically the same chemical composition: Si 44-45, C 27-29, O 25-26, H < 0.5, all in mass%. The ²⁹Si MAS-NMR spectra indicated that the compound formed at 1000 °C was mainly composed of siloxane bonds and amorphous silica, whereas in the compound formed at 1300°C, Si-C bonds and amorphous silica were predominant. The insertion/extraction characteristics of lithium ions for the electrode prepared with composite:poly(vinylidene fluoride) = 90:10 mass% were examined in 1 mol L⁻¹ LiClO₄ solution of ethylene carbonate:diethyl carbonate = 50:50 vol%. High, 650-700 mA h g⁻¹, capacities and steady cycle performance at 50 mA g⁻¹ were achieved with the composites formed at 1250-1300 °C. Capacities of the composites formed at 1200 °C and lower were initially higher but decreased with increasing number of cycles. The composites formed at 1350 °C showed good cycle performance but the capacity was about 500 mA h g⁻¹ due to the formation of β-SiC. Except for the first cycle, the capacity-potential characteristics were similar to those of hard carbons and the coulomb efficiency was 95-100%. For all the composites the capacity was larger than that of graphite (372 mA h g⁻¹) in the range of 50-200 mA g⁻¹. Due to the large insertion capacity of the first cycle, the efficiency was low (60-70%) at first. By short-circuiting the working electrode to the lithium foil counter electrode for a certain period, the irreversible capacity of the first cycle was almost eliminated. It indicates that direct doping of lithium ions into composites is a promising way to increase the efficiency of the first cycle.     

Anhydrous proton conductor consisting of pectin–inorganic composite material

An organic–inorganic proton conductive composite material consisting of a biopolymer was prepared by mixing the pectin, tetraethyl titanate, and imidazole. Although the pectin material without the composite dissolved in water, the pectin–inorganic composite material did not show water solubility. In addition, in the composite material, the pectin and imidazole formed an acid–base structure by an electrostatic interaction, and as a result, these composite materials showed a thermal stability at intermediate temperatures (100–200°C). Furthermore, these composite materials indicated the proton conductivity of 5.6 × 10^?4 S cm^?1 at 180°C under anhydrous conditions. The activation energy of the proton conduction under anhydrous conditions was 0.32–0.22 eV and these values were one order of magnitude higher than that of the typical humidified perfluorinated membrane, such as Nafion^®. The organic–inorganic composite material consisting of a biocomponent may have the potential to be utilized as a novel proton conductor under anhydrous conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42433.     

Applications of microstructures fabricated by proton beam writing to electric-micro filters

Fabrication of high-aspect-ratio microstructures was performed by proton beam writing (PBW) using a microbeam line at Takasaki Ion Accelerators for Advanced Radiation Application (TIARA), JAEA Takasaki, JAPAN. As one of the applications of the high-aspect-ratio structures micro-machined by PBW, we utilized the high-aspect pillars for electric-micro filters of microbes such as Escherichia coli and Yeast based on the dielectrophoretic force. The filter is equipped with high-aspect pillars with a height of ～20 μm and a diameter of ～1 μm on a glass plate. Evaluation of the dielectrophoresis (DEP) device for capturing E. coli and Yeast was made using either observation by optical microscope or photoluminescence (PL) measurements.     

Physicochemical properties of monosodium glutamate-compounded tapioca starch exceeds those of simple heat-moisture treated starch

Monosodium glutamate (GluNa)-compounded starch was prepared by heat-moisture treating a mixture of tapioca starch and GluNa. GluNa-compounded starch exhibited a higher gelatinization temperature and reduced swelling and solubility, essentially lower hardness of the granule center, and paste viscosity than those of the heat-moisture treated tapioca starch and the untreated starch. However, its appearance, unit chain length distribution, and α-amylase digestibility were similar to those of the heat-moisture treated tapioca. It is thus concluded that GluNa compounding is useful for providing a unique type of starch that possesses a less swollen and viscous texture than that produced with simple heat-moisture treatment.