Mie Minagawa

Nanomaterial-enhanced all-solid flexible zinc--carbon batteries.

Solid-state and flexible zinc carbon (or Leclanche) batteries are fabricated using a combination of functional nanostructured materials for optimum performance. Flexible carbon nanofiber mats obtained by electrospinning are used as a current collector and cathode support for the batteries. The cathode layer consists of manganese oxide particles combined with single-walled carbon nanotubes for improved conductivity. A polyethylene oxide layer containing titanium oxide nanoparticles forms the electrolyte layer, and a thin zinc foil is used as the anode. The battery is shown to retain its performance under mechanically stressed conditions. The results show that the above configuration can achieve solid-state mechanical flexibility and increased shelf life with little sacrifice in performance.

Photoelectrochemical cell using dye sensitized zinc oxide nanowires grown on carbon fibers

Zinc oxide (ZnO) nanowires (NWs) grown on carbon fibers using a vapor transport and condensation approach are used as the cathode of a photoelectrochemical cell. The carbon fibers were obtained by electrospray deposition and take the form of a flexible carbon fabric. The ZnO NW on carbon fiber anode is combined with a “black dye” photoabsorber, an electrolyte, and a platinum (Pt) counterelectrode to complete the cell. The results show that ZnO NW and carbon fibers can be used for photoinduced charge separation/charge transport and current collection, respectively, in a photoelectrochemical cell.

Electrospun composite nanofiber yarns containing oriented graphene nanoribbons.

The graphene nanoribbon (GNR)/carbon composite nanofiber yarns were prepared by electrospinning from poly(acrylonitrile) (PAN) containing graphene oxide nanoribbons (GONRs), and successive twisting and carbonization. The electrospinning process can exert directional shear force coupling with the external electric field to the flow of the spinning solution. During electrospinning, the well-dispersed GONRs were highly oriented along the fiber axis in an electrified thin liquid jet. The addition of GONRs at a low weight fraction significantly improved the mechanical properties of the composite nanofiber yarns. In addition, the carbonization of the matrix polymer enhanced not only the mechanical but also the electrical properties of the composites. The electrical conductivity of the carbonized composite yarns containing 0.5 wt % GONR showed the maximum value of 165 S cm(-1). It is larger than the maximum value of the reported electrospun carbon composite yarns. Interestingly, it is higher than the conductivities of both the PAN-based pristine CNF yarns (77 S cm(-1)) and the monolayer GNRs (54 S cm(-1)). These results and Raman spectroscopy supported the hypothesis that the oriented GONRs contained in the PAN nanofibers effectively functioned as not only the 1-D nanofiller but also the nanoplatelet promoter of stabilization and template agent for the carbonization.

Top-Down Process Based on Electrospinning, Twisting, and Heating for Producing One-Dimensional Carbon Nanotube Assembly

Multiwalled carbon nanotube (MWNT)/poly(vinyl butyral) (PVB) composite nanofibers were prepared by electrospinning, successive twisting and heat treatment. The MWNTs were highly oriented in an electrified thin jet during electrospinning. The heat treatment of the twisted electrospun nanofiber yarns produced the characteristics of the CNT in the composite nanofiber yarns and enhanced their electrical properties, mechanical properties, and thermal properties. The electrical conductivity of the heated yarn was significantly enhanced and showed the maximum value of 154 S cm(-1) for the yarn heated at 400 °C. It is an order of magnitude higher than other electrospun CNT composite materials. These results demonstrated that the novel top-down process based on electrospinning, twisting, and heat treatment provide a promising option for simple and large-scale manufacture of CNT assemblies.

ZnO Nanowire and

In this paper, we report on the synthesis and applications of semiconducting nanostructures. Nanostructures of interest were zinc oxide (ZnO) nanowires and tungsten disulfide (WS2) nanotubes where transistors/phototransistors and photovoltaic (PV) energy conversion cells have been fabricated. ZnO nanowires were grown with both high- and low-temperature approaches, depending on the application. Individual ZnO nanowire side-gated transistors revealed excellent performance with a field-effect mobility of 928 cm2/V middots. ZnO networks were proposed for large-area macroelectronic devices as a less lithographically intense alternative to individual nanowire transistors where mobility values in excess of 20 cm2/V middots have been achieved. Flexible PV devices utilizing ZnO nanowires as electron acceptors and for photoinduced charge separation and transport have been presented. Phototransistors were fabricated using individual WS2 nanotubes, where clear sensitivity to visible light has been observed. The results presented here simply reveal the potential use of inorganic nanowires/tubes for various optoelectronic devices.

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Flexible carbon fabrics (CFs) prepared by electrospray deposition were used for the substrate of carbon nanotube (CNT) field emitter arrays. CNTs were grown on the CFs by chemical vapor deposition. The CNT field emitter arrays on CFs produced a higher current density at a lower turn-on voltage compared to ones on a Si substrate.

Nanotube Electronics

Abstract The current–voltage characteristics of bipolar membrane/LiCl+alcohol systems were measured and compared with those of the LiCl+water system. In this study, methanol, ethanol, 1-propanol, ethylene glycol and propylene glycol were examined and lithium chloride was employed as an electrolyte. The current–voltage curves suggested that the dissociation into the cation and the anion had occurred also in the methanol system in the interface between the anion exchange and cation exchange layers. The product in the anion exchange layer side was analyzed in the LiCl+methanol system to prove the generation of lithium methoxide. In addition, the difference in the current–voltage characteristics in the other LiCl+alcohol systems, compared with the LiCl+methanol system, and the effect of water as an impurity were discussed.

Carbon nanotubes on carbon fabrics for flexible field emitter arrays

An unzipped graphene oxide nanoribbon is patterned by surface selective deposition or inkjet printing, and its successive reduction to a graphene nanoribbon by vacuum annealing leads to highly conducting transparent graphene nanoribbon films. Such graphene nanoribbon films are used as source and drain electrodes in bottom-contact organic transistors based on pentacene and sexithiophene as well as C60.

Alcohol splitting in a bipolar membrane and analysis of the product

Abstract A new model of a sandwich-type bipolar membrane potential was constructed by assuming the potential behavior of a bipolar membrane as a combination of each layer potential between two different states, i.e. the different concentrations of the bulk solution. Hence, we introduced the coion exclusion parameter that is derived from the Donnan equilibrium as a combinatorial function, which combined all the potential equations involved in our system. We assumed that the existence of the intermediate phase due to its volume would allow the Donnan equilibrium to play an important role, i.e. the vanishing of the coion exclusion effect of the membrane layer facing the bulk solution phase in high concentration. Sandwich-type bipolar membranes, which consist of a cation- (K-501) and an anion-exchange layer (A-501) were used in this study. A series of concentration perturbations of the intermediate phase was performed to examine the membrane potential behavior of the bipolar membrane experimentally. The experimental results showed a good agreement with the theoretical results, which led to the conclusion that explained the contribution of the intermediate phase to the membrane potential behavior through its volume and electrochemical properties.

Inkjet Printing of Graphene Nanoribbons for Organic Field-Effect Transistors

This letter reports the polarized optical response of nanofiber-coated gold surfaces that originated from surface plasmon resonance (SPR). The reflection spectra of the poly(vinylpyrrolidone) nanofiber-coated gold surfaces prepared by electrospinning showed a clear polarization dependence. This indicates that the SPR at the air/gold interface was assisted by light scattering of the nanofibers. In addition, the optical response of the gold surface depends on the density of the coated nanofibers. This can be explained by the scattering and the interference of the surface plasmons in the pores between the nanofibers.