Conduction Mechanism in Acceptor- or Donor-Doped ZrO2 Bulk and Thin Films.

The leakage current in capacitors in future electronics should be highly suppressed to achieve low power consumption, high reliability, and fast data processing. Although considerable efforts have been directed at reducing the leakage current, fundamental studies on the effects of doping on bulk and thin-film materials have rarely been conducted. Herein, we investigated the effects of doping with acceptor and donor elements on the conduction of bulk and thin-film ZrO2 and elucidated the underlying charge conduction mechanism. In the case of bulk ZrO2, the electrical conductivity was reliably modulated by the type of dopant element, which is highly consistent with defect chemistry theory. However, unlike in the bulk material, in acceptor- and donor-doped thin-film ZrO2, the leakage current was suppressed, indicating that the factors determining the electrical property in thin films are different from those in bulk materials.

Propofol protects against lipopolysaccharide-induced inflammatory response in human amnion-derived WISH cells.

Background: Nonobstetric surgery is sometimes required during pregnancy, and neck abscess or facial bone fracture surgery cannot be postponed in pregnant women. However, dental surgery can be stressful and can cause inflammation, and the inflammatory response is a well-known major cause of preterm labor. Propofol is an intravenous anesthetic commonly used for general anesthesia and sedation. Studies investigating the effect of propofol on human amnion are rare. The current study investigated the effects of propofol on lipopolysaccharide (LPS)-induced inflammatory responses in human amnion-derived WISH cells. Methods: WISH cells were exposed to LPS for 24 h and co-treated with various concentrations of propofol (0.01-1 µg/ml). Cell viability was measured using the MTT assay. Nitric oxide (NO) production was analyzed using a microassay based on the Griess reaction. The protein expression of cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE 2), p38, and phospho-p38 was analyzed using western blotting. Results: Propofol did not affect the viability and NO production of WISH cells. Co-treatment with LPS and propofol reduced COX-2 and PGE2 protein expression and inhibited p38 phosphorylation in WISH cells. Conclusion: Propofol does not affect the viability of WISH cells and inhibits LPS-induced expression of inflammatory factors. The inhibitory effect of propofol on inflammatory factor expression is likely mediated by the inhibition of p38 activation.

Controlled Electrophoretic Deposition Strategy of Binder-Free CoFe2O4 Nanoparticles as an Enhanced Electrocatalyst for the Oxygen Evolution Reaction.

The kinetic-sluggish oxygen evolution reaction (OER) is the main obstacle in electrocatalytic water splitting for sustainable production of hydrogen energy. Efficient water electrolysis can be ensured by lowering the overpotential of the OER by developing highly active catalysts. In this study, a controlled electrophoretic deposition strategy was used to develop a binder-free spinel oxide nanoparticle-coated Ni foam as an efficient electrocatalyst for water oxidation. Oxygen evolution was successfully promoted using the CoFe2O4 catalyst, and it was optimized by modulating the electrophoretic parameters. When optimized, CoFe2O4 nanoparticles presented more active catalytic sites, superior charge transfer, increased ion diffusion, and favorable reaction kinetics, which led to a small overpotential of 287 mV for a current density of 10 mA cm-2, with a small Tafel slope of 43 mV dec-1. Moreover, the CoFe2O4 nanoparticle electrode exhibited considerable long-term stability over 100 h without detectable activity loss. The results demonstrate promising potential for large-scale water splitting using Earth-abundant oxide materials via a simple and cheap fabrication process.

An Innovative Way to Turn Catalyst into Substrate for Highly Efficient Water Splitting.

The energy-efficiency loss with high overpotential during hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as economic inefficiencies including high-cost materials and complicated processes, is considered the major challenge to the implementation of electrochemical water splitting applications. The authors present a new platform for electrocatalysts that functions in an unprecedented way to turn a catalyst into substrate. The NiFe alloy catalyzed substrate (NiFe-CS) described herein is substantially active and stable electrocatalyst for both HER and OER, with low overpotential of 33 and 191 mV at 10 mA cm-2 for HER and OER, respectively. This structure enables not only the maximization of electrochemically active sites, but also the formation of hydroxyl species on the surface as the active phase. These outstanding results provide a new pathway for the development of electrocatalysts used in energy conversion technology.

Cerium Oxide-Polysulfone Composite Separator for an Advanced Alkaline Electrolyzer.

The intermittent and volatile nature of renewable energy sources threatens the stable operation of power grids, necessitating dynamically operated energy storage. Power-to-gas technology is a promising method for managing electricity variations on a large gigawatt (GW) scale. The electrolyzer is a key component that can convert excess electricity into hydrogen with high flexibility. Recently, organic/inorganic composite separators have been widely used as diaphragm membranes; however, they are prone to increase ohmic resistance and gas crossover, which inhibit electrolyzer efficiency. Here, we show that the ceria nanoparticle and polysulfone composite separator exhibits a low area resistance of 0.16 Ω cm2 and a hydrogen permeability of 1.2 × 10-12 mol cm-1 s-1 bar-1 in 30 wt% potassium hydroxide (KOH) electrolyte, which outperformed the commercial separator, the Zirfon PERL separator. The cell using a 100 nm ceria nanoparticle/polysulfone separator and advanced catalysts has a remarkable capability of 1.84 V at 800 mA cm-2 at 30 wt% and 80 °C. The decrease in the average pore size of 77 nm and high wettability (contact angle 75°) contributed to the reduced ohmic resistance and low gas crossover. These results demonstrate that the use of ceria nanoparticle-based separators can achieve high performance compared to commercial zirconia-based separators.

Three-Dimensionally Printed Stretchable Conductors from Surfactant-Mediated Composite Pastes.

A stretchable conductor is a critical prerequisite to achieve various forms of stretchable electronics. In particular, directly printable stretchable conductors have gathered considerable attention with recent growing interest in a variety of large-area, deformable electronics. In this study, we have developed a chemical pathway of incorporating a surfactant with a moderate hydrophilic-lipophilic balance in formulating composite pastes for printed stretchable conductors, with a possibility of a vertically stackable, three-dimensional printing process. We demonstrate that the addition of a nonionic surfactant, sorbitane monooleate (commonly called SPAN 80) in Ag flake-based composite pastes, allows a critical reduction in resistance variation under an external strain. The four-layer stacked, surfactant-added composite conductors show a resistance variation of merely 1.6 at a strain of 0.6 and excellent cycling durability over 1000 cycles. The effectiveness of the methods suggested in this study is demonstrated with basic light-emitting diode circuits and the thermal heating characteristics of stretchable conductors.

Characterization of Tetrodes Coated with Au Nanoparticles (AuNPs) and PEDOT and Their Application to Thalamic Neural Signal Detection in vivo.

Tetrodes, consisting of four twisted micro-wires can simultaneously record the number of neurons in the brain. To improve the quality of neuronal activity detection, the tetrode tips should be modified to increase the surface area and lower the impedance properties. In this study, tetrode tips were modified by the electrodeposition of Au nanoparticles (AuNPs) and dextran (Dex) doped poly (3,4-ethylenedioxythiophene) (PEDOT). The electrochemical properties were measured using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). A decrease in the impedance value from 4.3 MΩ to 13 kΩ at 1 kHz was achieved by the modified tetrodes. The cathodic charge storage capacity (CSCC) of AuNPs-PEDOT deposited tetrodes was 4.5 mC/cm2, as determined by CV measurements. The tetrodes that were electroplated with AuNPs and PEDOT exhibited an increased surface area, which reduced the tetrode impedance. In vivo recording in the ventral posterior medial (VPM) nucleus of the thalamus was performed to investigate the single-unit activity in normal rats. To evaluate the recording performance of modified tetrodes, spontaneous spike signals were recorded. The values of the L-ratio, isolation distance and signal-to-noise (SNR) confirmed that electroplating the tetrode surface with AuNPs and PEDOT improved the recording performance, and these parameters could be used to effectively quantify the spikes of each cluster.

Elucidation of the Oxygen Surface Kinetics in a Coated Dual-Phase Membrane for Enhancing Oxygen Permeation Flux.

The dual-phase membrane has received much attention as the solution to the instability of the oxygen permeation membrane. It has been reported that the oxygen flux of the dual-phase membrane is greatly enhanced by the active coating layer. However, there has been little discussion about the enhancement mechanism by surface coating in the dual-phase membrane. This study investigates the oxygen flux of the Ce0.9Gd0.1O2-δ-La0.7Sr0.3MnO3±Î´ (GDC 80 vol %/LSM 20 vol %) composite membrane depending on the oxygen partial pressure (PO2) to elucidate the mechanism of enhanced oxygen flux by the surface modification in the fluorite-rich phase dual-phase membrane. The oxygen permeation resistances were obtained from the oxygen flux as a function of PO2 using the oxygen permeation model. The surface exchange coefficient (k) and the bulk diffusion coefficient (D) were calculated from these resistances. According to the calculated k and D values, we concluded that the active coating layer (La0.6Sr0.4CoO3-δ) significantly increased the k value of the membrane. Furthermore, the surface exchange reaction on the permeate side was more sluggish than that at the feed side under operating conditions (feed: 0.21 atm/permeate side: 4.7 × 10-4 atm). Therefore, the enhancement of the oxygen surface exchange kinetics at the permeate side is more important in improving the oxygen permeation flux of the thin film-based fluorite-rich dual-phase membrane. These results provide new insight about the function of the surface coating to enhance the oxygen permeation flux of the dual-phase membrane.

The effects of n-type doping on lithium storage in TiO2.

In this report, we discuss the Li-storage performance of niobium-doped TiO2 nanostructures (Ti(1-y)Nb(y)O(2+δ)), with a special focus on the effects of ionic/electronic charge carrier concentration (defect chemistry) on Li storage and transport properties. By Nb-doping, Li storage kinetics of titania electrode material is significantly improved mainly due to the increased electronic charge carrier concentration (n-type doping). However, it was found that there is a maximum beyond which further doping is rather detrimental to Li diffusion kinetics. Defect chemical analysis indicates that this limited doping effect is due to the trapping of free lithium ions by the critical electron-ion association reactions at room temperature such as Li(i)(•) + e' ⇌ Li(i)(×) and Nb(Ti)(•) + e' ⇌ Nb(Ti)(×).

Substantial Oxygen Flux in Dual-Phase Membrane of Ceria and Pure Electronic Conductor by Tailoring the Surface.

The oxygen permeation flux of dual-phase membranes, Ce0.9Gd0.1O2-δ-La0.7Sr0.3MnO3±Î´ (GDC/LSM), has been systematically studied as a function of their LSM content, thickness, and coating material. The electronic percolation threshold of this GDC/LSM membrane occurs at about 20 vol % LSM. The coated LSM20 (80 vol % GDC, 20 vol % LSM) dual-phase membrane exhibits a maximum oxygen flux of 2.2 mL·cm(-2)·min(-1) at 850 °C, indicating that to enhance the oxygen permeation flux, the LSM content should be adjusted to the minimum value at which electronic percolation is maintained. The oxygen ion conductivity of the dual-phase membrane is reliably calculated from oxygen flux data by considering the effects of surface oxygen exchange. Thermal cycling tests confirm the mechanical stability of the membrane. Furthermore, a dual-phase membrane prepared here with a cobalt-free coating remains chemically stable in a CO2 atmosphere at a lower temperature (800 °C) than has previously been achieved.

Measuring electrical properties of thin film fuel cell electrodes by in situ infrared spectroscopy.

The electrical conductivities of cathode films on a solid oxide fuel cell electrolyte can be determined quantitatively by in situ infrared spectroscopy over a wide range of temperatures and partial oxygen pressures. This method allows measurement of the electrical conductivity of an electrode film on the electrolyte excluding leakage current effects through the substrate.