In aqua structuralization of a three-dimensional configuration using biomolecules

Ferritin nanoparticles ornamented with a Ti-binding peptide are versatile nanoscaled building blocks. Their specific binding ability is strong enough to position them on nanopatterned Ti regions on a Pt substrate. Furthermore, the peptides mineralization activity enables the formation of titania on the outer side of the particle, and the particle's inner nanospaces can serve as a carrier for inorganic nanodots. Making use of all these properties, here we show controlled in aqua fabrication of three-dimensional nanoscale structures. The X-Y positioning obeyed the specific binding of the peptide, while fabrication in the Z-dimension entailed stepwise formation of titania and ferritin layers by alternately applying the binding and mineralization abilities of the Ti-binding peptide. This method paves the way for in aqua fabrication of nanodevices having complicated structures and functions.     

Hydrogel of biodegradable cellulose derivatives. I. Radiation‐induced crosslinking of CMC

Radiation crosslinking of carboxymethylcellulose (CMC) with a degree of substitution (DS) from 0.7 to 2.2 was the subject of the current investigation. CMC was irradiated in solid‐state and aqueous solutions at various irradiation doses. The DS and the concentration of the aqueous solution had a remarkable affect on the crosslinking of CMC. Irradiation of CMC, even with a high DS, 2.2 in solid state, and a low DS, 0.7 in 10% aqueous solution, resulted in degradation. However, it was found that irradiation of CMC with a relatively high DS, 1.32, led to crosslinking in a 5% aqueous solution, and 20% CMC gave the highest gel fraction. CMC with a DS of 2.2 induced higher crosslinking than that with a DS of 1.32 at lower doses with the same concentration. Hence, it was apparent that a high DS and a high concentration in an aqueous solution were favorable for high crosslinking of CMC. It is assumed that high radiation crosslinking of CMC was induced by the increased mobility of its molecules in water and by the formation of CMC radicals from the abstraction of H atoms from macromolecules in the intermediate products of water radiolysis. A preliminary biodegradation study confirmed that crosslinked CMC hydrogel can be digested by a cellulase enzyme. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 278–283, 2000     

Bisanthracene‐Based Donor–Acceptor‐type Light‐Emitting Dopants: Highly Efficient Deep‐Blue Emission in Organic Light‐Emitting Devices

Deep‐blue fluorescent compounds are particularly important in organic light‐emitting devices (OLEDs). A donor–accepotor (DA)‐type blue‐emitting compound, 1‐(10‐(4‐methoxyphenyl)anthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)benzene ( BD3 ), is synthesized, and for comparison, a nonDA‐type compound, 1,4‐bis(10‐phenylanthracene‐9‐yl)benzene ( BD1 ) and a weak DA‐type compound, 1‐(10‐phenylanthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)‐benzene ( BD2 ), are also synthesized. The twisted conformations of the two anthracene units in the compounds, confirmed by single crystal X‐ray analysis, effectively prevent π‐conjugation, and the compound shows deep‐blue photoluminescence (PL) with a high PL quantum efficiency, almost independent of the solvent polarity, resulting from the absence of an intramolecular charge transfer state. The DA‐type molecule BD3 in a non‐doped device exhibits a maximum external quantum efficiency (EQE) of 4.2% with a slight roll‐off, indicating good charge balance due to the DA‐type molecular design. In the doped device with 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (CBP) host, the BD3 exhibits higher EQE than 10% with Commission International de L'Eclairge (CIE) coordinates of (0.15, 0.06) and a narrow full‐width at half‐maximum of 45 nm, which is close to the CIE of the high definition television standard blue.     

Improvement of processability of poly(ε‐caprolactone) by radiation techniques

Improvement of processability of Poly(ε‐caprolactone) (PCL) was achieved by introduction of a branch structure using gamma‐irradiation from a ⁶⁰Co source. Irradiated PCL has higher molecular weight by producting a branch structure. Hence, the irradiation at a lower dose, such as 3 Mrad, leads to a higher melt viscosity. The branched structure gave improved properties for dynamic viscoelasticity and elongational viscosity. High elongational viscosity was observed by entanglement due to branch chain formed during irradiation, and the elongational viscosity for 3 Mrad is higher than 1.5 Mrad. Due to a higher elongational viscosity, PCL foam can be produced by a molding process. Foam produced from irradiated PCL pellets at 3 Mrad has honeycomb‐like structure, and the foam showed higher enzymatic degradation compared to film samples. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1815–1820, 1999     

Bidirectional growth of indium phosphide nanowires

We present a bidirectional growth mode of InP nanowires grown by selective-area metalorganic vapor-phase epitaxy (SA-MOVPE). We studied the effect of the supply ratio of DEZn ([DEZn]) on InP grown structure morphology and crystal structures during the SA-MOVPE. Two growth regimes were observed in the investigated range of the [DEZn] on an InP(111)B substrate. At low [DEZn], grown structures formed tripod structures featuring three nanowires branched toward the [111]A directions. At high [DEZn], we obtained hexagonal pillar-type structures vertically grown on the (111)B substrate. These results show that the growth direction changes from [111]A to [111]B as [DEZn] is increased. We propose a growth mechanism based on the correlation between the incident facet of rotational twins and the shapes of the grown structures. Our results bring us one step closer to controlling the direction of nanowires on a Si substrate that has a nonpolar nature. They can also be applied to the development of InP nanowire devices.     

Growth of ZnO crystal on sapphire and nitridated sapphire substrates at 1000 °C by halide vapor phase epitaxy

Using a halide vapor phase epitaxy (HVPE) technique in which the starting materials are ZnCl₂ generated by the reaction between high purity Zn metal (7 N grade) and Cl₂ gas, and H₂O, ZnO crystals have been grown at a high temperature of 1000 °C on sapphire substrates with and without surface nitridation treatment. It was found that the nitridation treatment resulted in a change of the (112?0) sapphire surface to a (0001) AlN structure, leading to two possible sets of orientations for (0001) ZnO crystals. In addition, the nitridation treatment leads to a smaller average ZnO grain size and a higher density of nuclei.     

Magnesia supported Au and Ag catalysts for the preparation of few-layer graphene–metal nanocomposites: relationship between catalyst structure and the properties of graphene composites

Magnesia supported Au, Ag, and Au–Ag nanostructured catalysts were prepared, characterized, and used to synthesize few-layer graphene–metal nanoparticle (Gr–MeNP) composites. The catalysts have a mezoporous structure and a mixture of MgO and MgO·H₂O as support. The gold nanoparticles (AuNPs) are uniformly dispersed on the surface of the Au/MgO catalysts, and have a uniform round shape with a medium size of ~8 nm. On the other hand, the silver nanoparticles (AgNPs) present on the Ag/MgO catalyst have an irregular shape, larger diameters, and less uniform dispersion. The Au–Ag/MgO catalyst contains large Au–Ag bimetallic particles of ~20–30 nm surrounded by small (5 nm) AuNPs. Following the RF-CCVD process and the dissolution of the magnesia support, relative large, few-layer, wrinkled graphene sheets decorated with metal nanoparticles (MeNPs) are observed. Graphene–gold (Gr–Au) and graphene–silver (Gr–Ag) composites had 4–7 graphitic layers with a relatively large area and similar crystallinity for samples prepared in similar experimental conditions. Graphene–gold–silver composites (Gr–Au–Ag) presented graphitic rectangles with round, bent edges, higher crystallinity, and a higher number of layers (8–14). The MeNPs are encased in the graphitic layers of all the different samples. Their size, shape, and distribution depend on the nature of the catalyst. The AuNPs were uniformly distributed, had a size of about 15 nm, and a round shape similar to those from Au/MgO catalyst. In Gr–Ag, the AgNPs have a round shape, very different from that of the Ag/MgO catalyst, large size distribution and are not uniformly distributed on the surface. Agglomerations of AgNPs together with large areas of pristine few-layer graphene were observed. In Gr–Au–Ag composites, almost exclusively large bimetallic particles of about 25–30 nm, situated at the edge of graphene rectangles have been found.     

Flow boiling of non-azeotropic mixture R32/R1234ze(E) in horizontal microfin tubes

Flow boiling of a potential refrigerant R32/R1234ze(E) in a horizontal microfin tube of 5.21 mm inner diameter is experimentally investigated. The heat transfer coefficient (HTC) and pressure drop are measured at a saturation temperature of 10 °C, heat fluxes of 10 and 15 kW m^?2, and mass velocities from 150 to 400 kg m^?2 s^?1. The HTC of R1234ze(E) is lower than that of R32. Degradation in the HTC of the R32/R1234ze(E) mixture is significant; the HTC is even lower than that of R1234ze(E). The HTC is minimized at the composition 0.2/0.8 by mass, where the temperature glide and the mass fraction distribution are maximized. A predicting correlation based on Momoki et al. (1995) associated with the correction methods of Thome (1981) to consider the mass transfer resistance and Stephan (1992) to consider the additionally required sensible heat is proposed and validated with the experimental results.     

High-oil-load encapsulation of medium-chain triglycerides and D-limonene mixture in modified starch by spray drying

Oil mixtures of medium-chain triglycerides (MCT) and D-limonene in mixing ratios from 10 to 100 wt% were encapsulated in modified starch (wall material) by spray drying to produce oil-rich powders. The oil load (mass ratio of oil mixture to wall material) of the infeed emulsion markedly influenced the properties of the infeed liquid and the characteristics of the resulting powder. The viscosity of the infeed liquid and the particle size of the powder exponentially decreased with increasing oil load, while the emulsion droplet size in the infeed liquid increased. In addition, retention of D-limonene during spray drying also decreased markedly with increasing oil load. Irrespective of the different oil loads and concentrations of the wall material, D-limonene retention was well correlated with the emulsion droplet diameter of the infeed liquid. The encapsulation efficiency of the oil mixture exhibited a maximum value (almost 100%) at an oil load between 0.5 and 1.0, before decreasing at higher oil loads. At an oil load of 2.0, the encapsulation efficiency of D-limonene was reduced to almost zero, while around 40% of the initial MCT was encapsulated in the powder. The increase in oil load also led to increased amounts of surface oil of MCT and D-limonene in the resulting powder due to the increasing emulsion droplet diameter of the infeed liquids. PRACTICAL APPLICATION: This study proposes the microencapsulation of medium-chain triglycerides under high-oil-load conditions by spray drying. The powders prepared by this process provide significant benefits in terms of rapid energy conversion after consumption without accumulation in the body. Important quality factors of the powder products such as the encapsulation efficiency and the amount of surface oil were examined to understand the optimum process conditions for spray drying.     

Development of function-graded proton exchange membrane for PEFC using heavy ion beam irradiation

The graded energy deposition of heavy ion beam irradiation to polymeric materials was utilized to synthesize a novel proton exchange membrane (PEM) with the graded density of sulfonic acid groups toward the thickness direction. Stacked Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films were irradiated by Xe⁵⁴⁺ ion beam with the energy of 6 MeV/u under a vacuum condition. The induced trapped radicals by the irradiation were measured by electron spin resonance (ESR) spectroscopy. Irradiated films were grafted with styrene monomer and then sulfonated. X-ray photo-electron spectroscopy (XPS) spectra showed that the densities of sulfonic acid groups were controlled for injection “Surface” and transmit “Back” sides of the fabricated PEM. The membrane electrode assembly (MEA) fabricated by the function-graded PEM showed improved fuel cell performance in terms of voltage stability. It was expected that the function-graded PEM could control the graded concentration of sulfonic acid groups in PEM.