Facile and Large-Scale Route to the Fabrication of CuO Nanosheets from a Lamellar Mesophase and Their Reversible Self-Assembly

CuO and ZnO nanosheets were conveniently synthesized on a multigram scale under ambient conditions by using a surfactant lamellar mesophase as a soft template. The fabricated nanosheets were found to exhibit reversible self-assembling properties. By using the nanosheets as a basic building block and surfactants as structure-directing agents, highly ordered lamellar mesostructures were reassembled on the substrate

Facile Preparation of Highly Conductive Metal Oxides by Self-Combustion for Solution-Processed Thermoelectric Generators

Highly conductive indium zinc oxide (IZO) thin films were successfully fabricated via a self-combustion reaction for application in solution-processed thermoelectric devices. Self-combustion efficiently facilitates the conversion of soluble precursors into metal oxides by lowering the required annealing temperature of oxide films, which leads to considerable enhancement of the electrical conductivity of IZO thin films. Such enhanced electrical conductivity induced by exothermic heat from a combustion reaction consequently yields high performance IZO thermoelectric films. In addition, the effect of the composition ratio of In to Zn precursors on the electrical and thermoelectric properties of the IZO thin films was investigated. IZO thin films with a composition ratio of In:Zn = 6:2 at the low annealing temperature of 350 °C showed an enhanced electrical conductivity, Seebeck coefficient, and power factor of 327 S cm–1, 50.6 μV K–1, and 83.8 μW m–1 K–2, respectively. Moreover, the IZO thin film prepared at an even lower temperature of 300 °C retained a large power factor of 78.7 μW m–1 K–2 with an electrical conductivity of 168 S cm–1. Using the combustive IZO precursor, a thermoelectric generator consisting of 15 legs was fabricated by a printing process. The thermoelectric array generated a thermoelectric voltage of 4.95 mV at a low temperature difference (5 °C). We suggest that the highly conductive IZO thin films by self-combustion may be utilized for fabricating n-type flexible printed thermoelectric devices

Enhanced Diffraction Efficiency in a Photorefractive Liquid Crystal Cell with Poly(9-vinylcarbazole)-Infiltrated Mesoporous TiO₂ Layers

The photorefractive effect of a layer-structured liquid crystal cell was significantly enhanced when a C60-doped poly(9-vinylcarbazole) (PVK)/TiO2 nanocomposite was used in two photoconductive layers. The C60-doped PVK/TiO2 nanocomposite film was prepared by infiltrating C60-doped PVK into a highly ordered mesoporous TiO2 layer. The addition of the TiO2 layer to the C60-doped PVK layer increased the first-order Raman−Nath diffraction efficiency from 24% to 42.9%. This enhancement of diffraction efficiency is attributed to a blocking effect of charge recombination in the composite layer. The electron transfer from the PVK layer into the TiO2 layer would decrease the recombination of photogenerated charges in the PVK layer, while charges in the PVK layer could participate in the formation of a space-charge field

Shape-Deformable Thermoelectric Carbon Nanotube Doughs

In this study, shape-deformable thermoelectric p- and n-type doughs are fabricated by blending single-walled carbon nanotubes with excess amounts of nonvolatile liquid surfactants for efficient energy harvesting from diverse heat sources. The shape-deformable thermoelectric doughs exhibit touch-healing properties and can be easily molded into arbitrary shapes by simple shaping methods, such as those commonly used for rubber play dough. We used cube-shaped thermoelectric doughs to fabricate a vertical thermoelectric generator. Considering the shape-deformable properties of the thermoelectric doughs, a contraction strain of ∼2% in the through-plane direction of the thermoelectric generator can be applied for an effective application of ΔT. We show that the thermoelectric generator we built with eight p–n pairs exhibits a maximum output power of 2.2 μW at a vertical ΔT of 15 K. Our results demonstrate the energy harvesting capability of thermoelectric generators with shape-deformable p- and n-type doughs. Owing to the properties of this material, thermoelectric generators with various device geometries can be fabricated for energy harvesting from a diverse range of nonflat heat sources

Zero Energy Heating of Solvent with Network-Structured Solar-Thermal Material: Eco-Friendly Palladium Catalysis of the Suzuki Reaction

Solar-thermal materials absorb sunlight and convert it into heat, which is released into the surrounding medium. Utilization of solar energy for solvent heating can be a potential method of eco-friendly organic reactions. However, to date, significant heating of the entire volume of a solvent by 1 sun illumination has not been reported. In the present work, a network structure of solar-thermal materials has been proposed for zero energy heating of a solvent under 1 sun illumination. A network-structured solar-thermal material with an additional catalytic function was fabricated by sputtering palladium into a melamine sponge. The nanocrystalline palladium-decorated melamine sponge (Pd-sponge) has excellent sunlight absorption properties in the entire wavelength range that enable efficient solar-thermal conversion. The Pd-sponge can reduce heat loss to the surroundings by effectively blocking thermal radiation from the heated solvent. The temperature of the reaction solution with the ethanol–water mixture filled in the Pd-sponge increased from 23 to 59 °C under 1 sun illumination. The elevated temperature of the reaction solutions by solar-thermal conversion successfully accelerated the heterogeneous Pd-catalyzed Suzuki coupling reactions with high conversions. Easy and low-energy-consuming multicycle use of the solar-thermal and catalytic properties of the Pd-sponge has also been demonstrated

Foldable Thermoelectric Materials: Improvement of the Thermoelectric Performance of Directly Spun CNT Webs by Individual Control of Electrical and Thermal Conductivity

We suggest the fabrication of foldable thermoelectric (TE) materials by embedding conducting polymers into Au-doped CNT webs. The CNT bundles, which are interconnected by a direct spinning method to form 3D networks without interfacial contact resistance, provide both high electrical conductivity and high carrier mobility. The <i>ZT</i> value of the spun CNT web is significantly enhanced through two simple processes. Decorating the porous CNT webs with Au nanoparticles increases the electrical conductivity, resulting in an optimal <i>ZT</i> of 0.163, which represents a more than 2-fold improvement compared to the <i>ZT</i> of pristine CNT webs (0.079). After decoration, polyaniline (PANI) is integrated into the Au-doped CNT webs both to improve the Seebeck coefficient by an energy-filtering effect and to decrease the thermal conductivity by the phonon-scattering effect. This leads to a <i>ZT</i> of 0.203, which is one of the highest <i>ZT</i> values reported for organic TE materials. Moreover, Au-doped CNT/PANI web is ultralightweight, free-standing, thermally stable, and mechanically robust, which makes it a viable candidate for a hybrid TE conversion device for wearable electronics. When a 20 K temperature gradient is applied to the TE module consisting of seven p–n couples, 1.74 μW of power is generated

Surface Modification of a Polyimide Gate Insulator with an Yttrium Oxide Interlayer for Aqueous-Solution-Processed ZnO Thin-Film Transistors

We report a simple approach to modify the surface of a polyimide gate insulator with an yttrium oxide interlayer for aqueous-solution-processed ZnO thin-film transistors. It is expected that the yttrium oxide interlayer will provide a surface that is more chemically compatible with the ZnO semiconductor than is bare polyimde. The field-effect mobility and the on/off current ratio of the ZnO TFT with the YO_<i>x</i>/polyimide gate insulator were 0.456 cm²/V·s and 2.12 × 10⁶, respectively, whereas the ZnO TFT with the polyimide gate insulator was inactive

Modified Mesoporous Silica Gas Separation Membranes on Polymeric Hollow Fibers

Modified Mesoporous Silica Gas Separation Membranes on Polymeric Hollow Fiber