Spontaneous hybrids of graphene and carbon nanotube arrays at the liquid-gas interface for Li-ion battery anodes.

We demonstrate that hybrid structures of graphene and single-walled carbon nanotubes (SWNTs) are precisely controlled at the liquid-gas interface. The functionalized SWNT Langmuir monolayers anchor single-layer graphene nanosheets (GNSs) suspended in water via Coulomb interaction at the interface. This GNS/SWNT hybrid multilayer electrode can be a promising anode material for Li-ion batteries, offering high specific capacity, outstanding power capability, and excellent cyclability.

Roll-to-roll sputtered and patterned Cu2-x O/Cu/Cu2-x O multilayer grid electrode for flexible smart windows.

We fabricated cost-effective Cu2-x O/Cu/Cu2-x O multilayer grid electrodes using roll-to-roll (RTR) sputtering and patterning processes for use as transparent and flexible electrodes in flexible smart windows. To optimize the patterned Cu2-x O/Cu/Cu2-x O multilayer grid, the electrical and optical properties of the Cu2-x O/Cu/Cu2-x O multilayer grid electrodes were investigated as a function of grid width and pitch, which directly influence the filling factor of the grid. At the optimized grid width of 16 and pitch of 600 µm, the Cu2-x O/Cu/Cu2-x O multilayer grid had a sheet resistance of 7.17 Ohm per square and an optical transmittance of 87.6%. In addition, the mechanical properties of the optimized Cu2-x O/Cu/Cu2-x O multilayer grid electrode was compared to those of brittle ITO electrodes to demonstrate its outstanding flexibility. To show the potential of the Cu2-x O/Cu/Cu2-x O multilayer grid for smart windows, we fabricated a flexible and transparent thin film heater (TFH) and a flexible electrochromic (EC) device, which are key components of smart windows. The low saturation voltage of the Cu2-x O/Cu/Cu2-x O grid-based TFH and the fast on-off performance of the Cu2-x O/Cu/Cu2-x O grid-based EC device indicates that the RTR-processed Cu2-x O/Cu/Cu2-x O multilayer grid is promising as a low-cost and large-area flexible transparent electrode for high-performance smart windows.

Pseudocapacitive Desalination of Brackish Water and Seawater with Vanadium-Pentoxide-Decorated Multiwalled Carbon Nanotubes.

A hybrid membrane pseudocapacitive deionization (MPDI) system consisting of a hydrated vanadium pentoxide (hV2 O5 )-decorated multi-walled carbon nanotube (MWCNT) electrode and one activated carbon electrode enables sodium ions to be removed by pseudocapacitive intercalation with the MWCNT-hV2 O5 electrode and chloride ion to be removed by non-faradaic electrosorption of the porous carbon electrode. The MWCNT-hV2 O5 electrode was synthesized by electrochemical deposition of hydrated vanadium pentoxide on the MWCNT paper. The stable electrochemical operating window for the MWCNT-hV2 O5 electrode was between -0.5 V and +0.4 V versus Ag/AgCl, which provided a specific capacity of 44 mAh g-1 (corresponding with 244 F g-1 ) in aqueous 1 m NaCl. The desalination performance of the MPDI system was investigated in aqueous 200 mm NaCl (brackish water) and 600 mm NaCl (seawater) solutions. With the aid of an anion and a cation exchange membrane, the MPDI hybrid cell was operated from -0.4 to +0.8 V cell voltage without crossing the reduction and oxidation potential limit of both electrodes. For the 600 mm NaCl solution, the NaCl salt adsorption capacity of the cell was 23.6±2.2 mg g-1 , which is equivalent to 35.7±3.3 mg g-1 normalized to the mass of the MWCNT-hV2 O5 electrode. Additionally, we propose a normalization method for the electrode material with faradaic reactions based on sodium uptake capacities.

Long-Term Cyclability of Electrochromic Poly(3-hexyl thiophene) Films Modified by Surfactant-Assisted Graphene Oxide Layers.

Organic electrochromic (EC) materials are generally known to be electrochemically unstable during the ion intercalation/deintercalation process. One effective method to stabilize them is incorporating graphene derivatives in the polymer matrix, thereby creating strong interaction between graphene derivatives and polymer. However, previous studies are limited to specific polymers and bulk-blended systems, such as mixing the polymer with graphene derivatives. In this study, we developed a polymer-graphene derivative complex with the chemical assistance of a surfactant (octadecylamine, ODA). Graphene oxide (GO) was introduced as a protective layer on the electrochromic poly(3-hexyl thiophene) (P3HT) films by the Langmuir-Schaefer method. The deposition of the GO-ODA protective layer with high coverage was confirmed by atomic force microscopy and high-resolution X-ray reflectivity. The strong interactions between GO-ODA and P3HT were examined with UV-vis spectrophotometry and X-ray photoelectron spectroscopy. Electrochemical and electrochromic investigations revealed that the GO-ODA layer greatly improved the long-term cyclability of the P3HT film. These findings imply that the GO-ODA complex can significantly stabilize the EC cycling, due to its strong interaction with the P3HT film.

Roll-to-Roll sputtered ITO/Cu/ITO multilayer electrode for flexible, transparent thin film heaters and electrochromic applications.

We fabricate high-performance, flexible, transparent electrochromic (EC) films and thin film heaters (TFHs) on an ITO/Cu/ITO (ICI) multilayer electrode prepared by continuous roll-to-roll (RTR) sputtering of ITO and Cu targets. The RTR-sputtered ICI multilayer on a 700 mm wide PET substrate at room temperature exhibits a sheet resistance of 11.8 Ω/square and optical transmittance of 73.9%, which are acceptable for the fabrication of flexible and transparent EC films and TFHs. The effect of the Cu interlayer thickness on the electrical and optical properties of the ICI multilayer was investigated in detail. The bending and cycling fatigue tests demonstrate that the RTR-sputtered ICI multilayer was more flexible than a single ITO film because of high strain failure of the Cu interlayer. The flexible and transparent EC films and TFHs fabricated on the ICI electrode show better performances than reference EC films and TFHs with a single ITO electrode. Therefore, the RTR-sputtered ICI multilayer is the best substitute for the conventional ITO film electrode in order to realize flexible, transparent, cost-effective and large-area EC devices and TFHs that can be used as flexible and smart windows.

Synthesis of poly(p-phenylene-vinylene) derivatives containing an oxadiazole pendant group and their applications to organic electronic devices.

Poly(p-phenylene vinylene) (PPV) derivatives with 2,5-diphenyl-1,3,4-oxadiazole-diyl (OXD) as the side chain, poly[2-{4-[5-(4-(heptyloxy)phenyl)-1,3,4-oxadiazole-2-yI]phenyl-oxy}-1,4-phenylene-vinylene] (OXH-PPV), poly[2-{4-[5-(4-(heptyloxy)phenyl)-1,3,4-oxadia-zole-2-yl]phenyl-oxy}-1,4-phenylenevinylene-co-2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (OXH-PPV-co-MEH-PPV), and poly[2-methoxy-5-(2'-ethylhexyl-oxy)-p-phenylene vinylene] (MEH-PPV), were synthesized via a modified Gilch route. The electron-deficient oxadiazole moiety was introduced on the side chain of the polymer backbone to increase the electron-affinity of the polymers. The electroluminescent (EL) properties of the resulting polymers as an active layer, were investigated by the fabrication of single-layer LEDs and the devices using OXH-PPV-co-MEH-PPV showed better EL properties than those using pure MEH-PPV. Also, to investigate the switching properties of the resulting polymers as an active layer, OFET devices were fabricated in a top-contact/bottom-gate configuration. The resulting FETs exhibited typical p-channel characteristics, field-effect mobility of 6.5 x 10(-4) - 7.0 x 10(-5) cm2 V(-1) s(-1), and on-off ratio of about 10(4)-10(5).

Enhanced electrochromic coloration of poly(3-hexylthiophene) films by electrodeposited Au nanoparticles.

Au nanoparticles and poly(3-hexylthiophene) (P3HT) composite films were prepared by electrodeposition of Au nanoparticles using pulse-current electrodeposition followed by the spin coating of P3HT and their enhanced electrochromic coloration was investigated. A relatively uniformed Au nanoparticle was obtained by the controlled electrodeposition on indium tin oxide (ITO) substrate and plasmon absorption band of Au nanoparticles were observed. Optical and electrochemical properties of Au/P3HT composite films were compared with the pure P3HT films. The enhanced electrochromic absorption of the composite films was observed due to the surface plasmon resonance of the Au nanoparticles.

Polythiophene infiltrated TiO2 nanotubes as high-performance supercapacitor electrodes.

We report exceptional electrochemical specific capacitance (640 F g(-1)) for polythiophene (PTh) infiltrated into TiO(2) nanotubes (TNTs) by a controlled electropolymerization route. The resulting PTh-TNTs also exhibit excellent electrochemical behavior with long-term stability. This reproducible and superior performance of PTh-TNT electrodes makes them attractive candidates for energy storage.

In situ polymerization of acetylene polymer on single-walled carbon nanotube and its application to photoinduced charge transfer system.

An acetylene polymer is formed on single-walled carbon nanotubes (SWNTs) using in situ polymerization. The acetylene polymers/SWNTs composite is hydrophilic even water-soluble, and has a structure of donor/acceptor dyad. In measurements of photocurrents-voltage curves, the composite film exhibits a power conversion efficiency of 1.50 x 10(-2%) under illumination (I = 80 mW/cm2, air mass 1.5 condition).

Sequential chemical bath deposition of Cu(2-x)Se/CdS film by suppressing ion-exchange reaction.

Chemical bath deposition is an attractive technique to form single- and multilayered metal oxide/chalcogenide films on electrode surfaces. However, the occurrence of desorption and/or ion-exchange reaction during subsequent chemical bath deposition has so far limited preparation of multilayered metal oxide/chalcogenide films. In this paper, we report a method to prevent desorption and ion-exchange reaction of metal oxide/chalcogenide on electrode surfaces using a polyelectrolyte multilayer during sequential chemical bath deposition. By controlling the ion permeability of the polyelectrolyte multilayer, Cu(2-x)Se film was successfully deposited on the CdS film. The Cu(2-x)Se/CdS film is confirmed by UV-vis absorption spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray powder diffractometer. Furthermore, the Cu(2-x)Se/CdS films were investigated as photoinduced charge transfer devices which showed photocurrents of 0.22 mA/cm(2) under illumination (I = 100 mW/cm(2)).

Interfacially treated dye-sensitized solar cell with in situ photopolymerized iodine doped polythiophene.

A thin film of iodine doped polythiophene was grown photoelectrochemically around the dye-sensitized TiO(2) nanoparticles in a Grätzel cell, and the effect of iodine doping level on the cell performance was investigated using X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and photovoltage decay. At an optimum doping level, the cell demonstrated the enhanced energy conversion efficiency by 27.52% compared to the cell without polythiophene.

Doped TiO2 and TiO2 nanotubes: synthesis and applications.

TiO(2) is one of the most investigated compounds in contemporary materials science. Due to a set of virtually unique electronic properties, it finds intense use in photoelectrochemical applications such as photocatalysis or solar cells. The main drawback in view of direct exploitation of solar-light-based effects is its large band gap of >3 eV. Visible-light-activated TiO(2) can be prepared by doping (band-gap engineering) through incorporation or decoration with other metal ions, nonmetal ions, and semiconductors. Most recently, efforts in TiO(2) research have been even more intensified by the finding of self-organized nanotubular oxide architectures that can be prepared by a simple but optimized anodization of Ti metal surfaces. These nanotubular geometries provide large potential for enhanced and novel functional features. This Review examines doped TiO(2) and in particular TiO(2) nanotubes. Various types of dopants, doping methods, and applications of modified TiO(2) nanotubes are discussed.

Nitrogen doping of nanoporous WO3 layers by NH3 treatment for increased visible light photoresponse.

Nanoporous WO(3) layers were grown by electrochemical anodization of W in a fluoride containing electrolyte. These layers were exposed to a thermal treatment in NH(3) to achieve nitrogen doping of the material. The morphology, crystal structure, composition and photoresponse of pure and nitrogen doped WO(3) were compared using scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and photoelectrochemical measurements. The results clearly show that successful nitrogen doping into WO(3) layers can be achieved by controlling the temperature and time during the NH(3) treatment. Most importantly, it is demonstrated that for the nitrogen doped WO(3) layers the photocurrent is significantly enhanced in the visible light region.

Self-organized nano-tubes of TiO2-MoO3 with enhanced electrochromic properties.

Self-organized TiO(2)-MoO(3) composite oxide nano-tubes with tunable dimensions are successfully fabricated by anodization of a Ti-Mo alloy and these nano-tube layers exhibit a significantly enhanced electrochromic color contrast compared with plain TiO(2) nano-tubes.

TiO2-WO3 composite nanotubes by alloy anodization: growth and enhanced electrochromic properties.

The present work demonstrates that uniform and highly ordered arrays of TiO(2)-WO(3) nanotubes can be grown by anodization of Ti alloys in an ethylene glycol/fluoride based electrolyte under selected electrochemical conditions. These aligned mixed oxide nanotube structures are highly suitable for enhanced electrochromic reactions; in particular we show that already small amounts of WO(3) (such as 0.2 at%) present in the tube oxide drastically improve the electrochromic properties (contrast, onset potential, cycling stability) of nanotube layer based devices.