Virus-templated iridium oxide-gold hybrid nanowires for electrochromic application

A highly porous electrode comprised of biologically templated iridium oxide-gold (IrO(2)-Au) hybrid nanowires is introduced for electrochromic applications. A filamentous M13 virus is genetically engineered to display IrO(2)-binding peptides on the viral surface and used as a template for the self-assembly of IrO(2) nanoclusters into a nanowire. The open porous morphology of the prepared nanowire film facilitates ion transport. Subsequently, the redox kinetics of the IrO(2) nanowires seems to be limited by the electric resistance of the nanowire film. To increase the electron mobility in the nanowires, gold nanoparticles are chemically linked to the virus prior to the IrO(2) mineralization, forming a gold nanostring structure along the long axis of the virus. The resulting IrO(2)-Au hybrid nanowires exhibit a switching time of 35 ms for coloration and 25 ms for bleaching with a transmission change of about 30.5% at 425 nm. These values represent almost an order of magnitude faster switching responses than those of an IrO(2) nanowire film having the similar optical contrast. This work shows that genetically engineered viruses can serve as versatile templates to co-assemble multiple functional molecules, enabling control of the electrochemical properties of nanomaterials.     

High performance of a solid-state flexible asymmetric supercapacitor based on graphene films

Solid-state flexible energy storage devices hold the key to realizing portable and flexible electronic devices. Achieving fully flexible energy storage devices requires that all of the essential components (i.e., electrodes, separator, and electrolyte) with specific electrochemical and interfacial properties are integrated into a single solid-state and mechanically flexible unit. In this study, we describe the fabrication of solid-state flexible asymmetric supercapacitors based on an ionic liquid functionalized-chemically modified graphene (IL-CMG) film (as the negative electrode) and a hydrous RuO(2)-IL-CMG composite film (as the positive electrode), separated with polyvinyl alcohol-H(2)SO(4) electrolyte. The highly ordered macroscopic layer structures of these films arising through direct flow self-assembly make them simultaneously excellent electrical conductors and mechanical supports, allowing them to serve as flexible electrodes and current collectors in supercapacitor devices. Our asymmetric supercapacitors have been optimized with a maximum cell voltage up to 1.8 V and deliver a high energy density (19.7 W h kg(-1)) and power density (6.8 kW g(-1)), higher than those of symmetric supercapacitors based on IL-CMG films. They can operate even under an extremely high rate of 10 A g(-1) with 79.4% retention of specific capacitance. Their superior flexibility and cycling stability are evident in their good performance stability over 2000 cycles under harsh mechanical conditions including twisted and bent states. These solid-state flexible asymmetric supercapacitors with their simple cell configuration could offer new design and fabrication opportunities for flexible energy storage devices that can combine high energy and power densities, high rate capability, and long-term cycling stability.     

Opuntia humifusa Supplementation Increased Bone Density by Regulating Parathyroid Hormone and Osteocalcin in Male Growing Rats

We investigated the effect of Opuntia humifusa (O. humifusa) supplementation on bone density and related hormone secretion in growing male rats. Sixteen six-week-old male Sprague-Dawley rats were randomly divided into two groups; control diet group (CG, n = 8), and experimental diet group (EG, n = 8). The rats in the CG were given a control diet and those in the EG were given 5% O. humifusa added to the control diet for eight weeks. The serum OC level of the EG was significantly higher than that of the CG, and the serum parathyroid hormone (PTH) level of EG was significantly lower than that of the CG. In addition, the femoral and tibial BMD of the EG were significantly higher values than those of the CG, and the tibial BMC of the EG was significantly higher than that of the CG. These results suggest that O. humifusa supplementation has a positive effect on bone density by suppressing PTH and increasing the OC level in growing male rats.     

Enhanced mechanical properties and pre-tension effects of polyurethane (PU) nanofiber filaments prepared by electrospinning and dry twisting

We studied the mechanical properties of polyurethane (PU) nanofiber filaments prepared by electrospinning and dry twisting, and compared them with those of the corresponding nonwoven PU nanofiber webs. The morphologies and mechanical properties of the nonwoven PU nanofiber webs and the corresponding PU nanofiber filaments were investigated by scanning electron microscopy (SEM) and through the use of a universal testing machine (UTM), respectively. The tensile strength and the Young’s modulus of the nanofiber filaments improved dramatically as the number of twists or the width of the nanofiber webs was increased compared with the nonwoven PU nanofibers. Moreover, it was found that applying pre-tension was an effective method of increasing the mechanical properties of PU nanofiber filaments.     

Low-temperature synthesis of LiFePO<Subscript>4</Subscript> nanocrystals by solvothermal route

LiFePO₄ nanocrystals were synthesized at a very low temperature of 170°C using carbon nanoparticles by a solvothermal process in a polyol medium, namely diethylene glycol without any heat treatment as a post procedure. The powder X-ray diffraction pattern of the LiFePO₄ was indexed well to a pure orthorhombic system of olivine structure (space group: Pnma) with no undesirable impurities. The LiFePO₄ nanocrystals synthesized at low temperature exhibited mono-dispersed and carbon-mixed plate-type LiFePO₄ nanoparticles with average length, width, and thickness of approximately 100 to 300 nm, 100 to 200 nm, and 50 nm, respectively. It also appeared to reveal considerably enhanced electrochemical properties when compared to those of pristine LiFePO₄. These observed results clearly indicate the effect of carbon in improving the reactivity and synthesis of LiFePO₄ nanoparticles at a significantly lower temperature.     

Synthesis and characterization of integrated layered nanocomposites for lithium ion batteries

The series of Li[Ni _x M _x Li_1/3-x Mn_2/3-x ]O₂ cathodes, where M is cobalt or chromium with a wide compositional range x from 0 to 0.33, were prepared by hydroxide coprecipitation method with subsequent quenching. The sample structures were investigated using X-ray diffraction results which were indexed completely on the basis of a trigonal structure of space group with monoclinic C2/m phase as expected. The morphologies and electrochemical properties of the samples obtained were compared as the value of x and substituted transition metal. The particle sizes of cobalt-substituted Li[Ni _x Co _x Li_1/3-x Mn_2/3-x ]O₂ samples are much smaller than those of the Li[Ni _x Cr _x Li_1/3-x Mn_2/3-x ]O₂ system. The electrode containing Li[Ni _x Co _x Li_1/3-x Mn_2/3-x ]O₂ with x = 0.10 delivered a discharge capacity of above 200 mAh/g after 10 cycles due to the activation of Li₂MnO₃.     

LiNi<Subscript>0.4</Subscript>Co<Subscript>0.3</Subscript>Mn<Subscript>0.3</Subscript>O<Subscript>2</Subscript> thin film electrode by aerosol deposition

LiNi_0.4Co_0.3Mn_0.3O₂ thin film electrodes are fabricated from LiNi_0.4Co_0.3Mn_0.3O₂ raw powder at room temperature without pretreatments using aerosol deposition that is much faster and easier than conventional methods such as vaporization, pulsed laser deposition, and sputtering. The LiNi_0.4Co_0.3Mn_0.3O₂ thin film is composed of fine grains maintaining the crystal structure of the LiNi_0.4Co_0.3Mn_0.3O₂ raw powder. In the cyclic voltammogram, the LiNi_0.4Co_0.3Mn_0.3O₂ thin film electrode shows a 3.9-V anodic peak and a 3.6-V cathodic peak. The initial discharge capacity is 44.6 μAh/cm², and reversible behavior is observed in charge-discharge profiles. Based on the results, the aerosol deposition method is believed to be a potential candidate for the fabrication of thin film electrodes.     

Physicochemical properties and bioactivity of brown seaweed fucoidan prepared by ultra high pressure-assisted enzyme treatment

The effects of ultra-high pressure (UHP, 100 MPa, 40, 24 h) processing and enzyme treatment on the physicochemical properties and anticoagulant activity of fucoidan obtained from Undaria pinnatifida sporophyll (UPS) were investigated. Crude UPS fucoidan (F _UPS ) with an average MW of 877 kDa was slightly depolymerized by UHPassisted Tunicase treatment, yielding fucoidan with a lower MW (600–800 kDa). UHP-enzyme treatment decreased the sulfate, fucose and galactose contents of F _UPS but increased its glucose content. From FT-IR spectrum, UHP-enzyme treatment was found not to cause a structural change on S=O and C-O-S. After UHP-enzyme treatment, the sulfate content and average MW of F _UPS decreased with the increase of Tunicase concentration. It was found that among the UHP-enzyme-treated fucoidans, F _UPS -T0.3-U (Tunicase 0.3% treatment+UHP treatment) possessed the highest anticoagulant activity. F _UPS -T0.3-U appeared to inhibit blood coagulation via intrinsic pathway. With the increase of sulfate content in F _UPS , activated partial thromboplastin time (APTT) and thrombin time (TT) showed a tendency of increase. APTT and TT had the highest values in F _UPS -T0.3-U in which the sulfate concentration was 24%, but on the contrary decreased at a sulfate concentration of above 24%. This result indicates that there is an optimum sulfate concentration for the anticoagulant activity of fucoidan. Consequently, UHP-assisted enzymatic treatment was found to be helpful for the improvement of anticoagulant activities of fucoidan.     

Effects of Amino Acids and Peptide on Lipid Oxidation in Emulsion Systems

We investigated the effects of amino acids and peptide on lipid oxidation in emulsion systems. For comparative purposes, we also tested the antioxidant activity of ferulic acid, a typical phenolic antioxidant. Histidine and cysteine retarded lipid oxidation (the amount of thiobarbituric acid [TBA]-reactive substances reached approximately 13 and 18 μM after 7 days, respectively), whereas arginine, methionine, and tryptophan did not inhibit the progression of oxidation. Soy peptide also inhibited lipid oxidation. Ferulic acid was found to be the most effective suppressor of lipid oxidation (TBA-reactive substances were suppressed to <3 μM over 7 days). The antioxidant activities of soy peptide and ferulic acid were related to the purity of the emulsifier used. The radical scavenging activities of soy peptide and ferulic acid were closely related to their inhibitory effects on lipid oxidation. However, this was not the case for amino acids. Decreases in the turbidity of emulsions were closely related to increases in TBA values.     

In situ neutron radiography analysis of graphite/NCA lithium-ion battery during overcharge

Overcharge of lithium-ion batteries can lead to the deposition of lithium ions on the surface of graphite electrodes. The phenomenon of lithium deposition causes reduced electrochemical performance and presents safety concerns for lithium-ion batteries in high-power applications. This study presents a technique using neutron radiography (NR) for in situ visualization of the effects of overcharge in a graphite/NCA (LiNi_0.8Co_0.15Al_0.05O₂) lithium-ion cell. Patterns of deposition of solid material on the surface of the graphite electrode observed in the radiographs were confirmed by direct observation of the electrode. Inductively coupled plasma mass spectrometry was used to verify the elemental contents of the deposited material. NR is shown to be a promising tool for the study of lithium-ion batteries in high-power applications.