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We have successfully synthesized the composites of Ag-doped zinc antimonide (Ag-ZnSb) and few-layer-graphene (FLG) by high-energy-mechanical milling and spark plasma sintering using Ag-ZnSb ingot and FLG as raw materials. The FLG/Ag-ZnSb shows 22%-reduced lattice thermal conductivity by increased phonon boundary scattering due to embedded FLG. The electrical conductivity of the composites was decreased due to reduced carrier concentration, while the Seebeck coefficient of the composites was increased by electron donating effect of FLG. The maximum figure of merit, ZT , of 0.86 was observed at 630 K. The peak ZT temperature in the FLG/Ag-ZnSb cases (~630 K) were higher than the pristine Ag-ZnSb compound (~580 K) resulting in advantages for the higher temperature power generation.

p-Type Nd1–z Yb z Fe4–x Co x Sb12 (z = 0.25, 0.5, 0.75 and x = 0, 0.5, 1.0) skutterudites were synthesized by using encapsulated melting and hot pressing. The effects of Nd/Yb double filling and Co substitution for Fe (charge compensation) on the microstructure, the charge transport, and the thermoelectric properties of the skutterudite specimens were investigated. All specimens were transformed to the skutterudite phase by the annealing process, and a few secondary phases such as marcasite FeSb2 were formed together with the skutterudite phase, although their formation was suppressed with increasing Co content. The lattice constant changed with the filling ratio of Nd/Yb and Fe/Co substitution, which meant that the double filling of Nd/Yb and the substitution of Co for Fe were successfully performed. All specimens showed p-type conduction at temperatures ranging from 323 K to 823 K and exhibited degenerate semiconductor characteristics, in which the electrical conductivity decreased and the Seebeck coefficient increased with increasing temperature. The Seebeck coefficient increased with increasing Nd and Co contents due to the decreased carrier concentration while the electrical conductivity and the thermal conductivity decreased. The maximum Seebeck coefficient was obtained at temperatures in the range from 723 K to 823 K, and the thermal conductivity significantly increased at temperatures above 623 K due to bipolar conduction. The dimensionless figure of merit, ZT, showed maximum values at temperatures ranging from 723 K to 823 K due to the decrease in the Seebeck coefficient (or the decrease in the power factor) and the increase in the thermal conductivity at high temperatures. The maximum ZT = 0.81 was obtained for Nd0.75Yb0.25Fe4Sb12 at 823 K and for Nd0.75Yb0.25Fe3CoSb12 at 723 K.

The ultrafast bouncing motion of a liquid droplet has been investigated for droplet manipulation with a single droplet actuator using an electrostatic force for the first time. Under an electrostatic field, various kinds of liquid droplets (e.g. deionized water and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) solution) were rapidly bounced between two superhydrophobic electrodes, one from a capacitive electrode and another from a stage electrode. They were formed by sequential processes of a galvanic displacement method and the coating of a self-assembled monolayer on circular-patterned Cu films on a printed circuit board substrate. The frequency of the bouncing motion of the droplets reached up to 0.57 kHz and 0.71 kHz for water and PEDOT:PSS solution, respectively. Furthermore, the effects of the droplet volume, different types of liquid material such as water and conducting polymer solution, and applied voltages on the droplet bouncing motion were fully analyzed. A charge transfer between the droplet surface and the super-hydrophobic electrodes leads to droplet bouncing and its repetitive charging/discharging process across two electrodes results in a continuous bouncing operation. We successfully measured the transferred current of nA level from several single droplets under rapidly-bouncing motion via the stage electrode. This rapidly-bouncing droplet actuator using electrostatic force can be effectively used for various chemical and biological applications due to its high-speed, contamination-free and facile method.

The reproducibility problem is one of the central issues in n-type Bi2Te3-based thermoelectric materials. We herein investigate the effects of doping on the positional uniformity of the electronic transport properties of spark-plasma-sintered Bi2Te2.7Se0.3 polycrystalline bulks. Both the electrical conductivity and the Seebeck coefficient showed severe deviations with position in the pristine Bi2Te2.7Se0.3 bulk due to the variation in carrier concentration originating from the formation of Te- and Se-site vacancies. This non-uniformity problem could be significantly improved by the addition of excess elemental Cu and Te. Uniformity enhanced by Cu addition might be considered to be related with the suppression of Te/Se evaporation in the presence of intercalated Cu atoms. A maximum power factor value of ∼2.72 mW/mK2 at 300 K was obtained for Cu0.01Bi2Te2.7Se0.3.

We fabricated and studied the operation characteristics of light emitting devices (LEDs) based on green CdSe/ZnS quantum dots (QDs). A series of devices with different concentrations of QDs in toluene showed typical electroluminescence (EL) peaks that are consistent with green photoluminescence of colloidal QDs emitting layer (EML), but their bandwidth were varied due to the parasitic emission originating from the adjacent organic layers. Upon the increase of the QD concentration, the contribution of the color contamination to emission light from QD-LED (QLED) devices was decreased resulting in the narrowing of EL spectra. On the other hand, the maximum efficiency of QLEDs increased in the lower QD concentration range, while decreased in the higher range. The optimum luminous efficiency of 1.22 cd/A and the external quantum efficiency of 0.43% at standard video brightness (200 cd/m2) was observed from the device with a QD concentration of 6 mg/ml which can be attributed to the enhanced charge recombination in QD EML.

Iron (Fe) powders with high-purity and controlled primary and secondary assembled particles were synthesized with reduction process to control the particle shape and thereby variation of its electromagnetic properties. Iron precursors, such as iron hydroxide and iron oxide powder precursors, with fine-sized and acicular or spherical/cubic morphology, were prepared by co-precipitation and hydrothermal processes and then reduced at different reducing atmospheres by using a hydrogen/argon mixed gas. The electromagnetic properties were evaluated by dielectric permittivity and magnetic permeability and their loss measurements. The reduced Fe powders showed different particle shapes and sizes with different reduction conditions, which affected both primary and secondary particles and thereby electromagnetic properties. The morphology of the Fe powders strongly depended on the reduction conditions and precursor's morphology. The electromagnetic properties were varied with different shapes and sizes of primary and secondary particles. It was found that the permeability is better for interconnected secondary particles with smaller primary particle size, and the dielectric permittivity is much more variable than the magnetic permeability with different parameters mentioned above.

The effects of eco-friendly (BiNa0.84K0.16)0.48Sr0.04TiO3 (BNKS)-content in 0.65Bi1.05FeO3–0.35BaTiO3 (BFBT) dielectrics were investigated by following simple solid state fabrication route. By the introduction of BNKS in BFBT matrix the average grain size was significantly reduced, with relatively high dense microstructure (relative density > 94%). The BNKS-modified BFBT dielectrics demonstrated thermally-stable er (670–1005, from 30 °C to 500 °C), high Tmax (424 °C–465 °C), colossal er-max (58880–69226), and er-mid (2891–5652 ± 15%) across the broad range of temperature from 244 °C to 500 °C. At the optimum composition (x = 0.10) the temperature-dependent (30 °C–150 °C) substantially high energy-storage density (Wstore ∼ 0.81 J/cm3) and efficiency (η > 60%) in bulk ceramics were observed. The thermally-stable dielectric and energy storage properties suggest that present investigated dielectrics can be promising candidates for high temperature dielectric applications and power electronics.

Point defect or doping in Strontium titanium oxide (STO) largely determines the thermoelectric (TE) properties. So far, insufficient knowledge exists on the impact of double Schottky barrier on the TE performance. Herein, we report a drastic effect of double Schottky barrier on the TE performance in undoped STO. It demonstrates that incorporation of Reduced Graphene Oxide (RGO) into undoped STO weakens the double Schottky barrier and thereby results in a simultaneous increase in both carrier concentration and mobility of undoped STO. The enhanced mobility exhibits single crystal-like behavior. This increase in the carrier concentration and mobility boosts the electrical conductivity and power factor of undoped STO, which is attributed to the reduction of the double Schottky barrier height and/or the band alignment of STO and RGO that allow the charge transfer through the interface at grain boundaries. Furthermore, this STO/RGO interface also enhances the phonon scattering, which results in low thermal conductivity. This strategy significantly increases the ratio of σ/κ, resulting in an enhancement in ZT as compared with pure undoped STO. This study opens a new window to optimize the TE properties of many candidate materials.

We demonstrated imaging of the depletion layer in a MoS

It has been a difficulty to form well-distributed nano- and mesosized inclusions in a Bi

In this work, the effects of niobium (Nb) doping on thermoelectric properties of n-type half-Heusler (Hf0.25Zr0.25Ti0.5)1-xNbxNiSn (x = 0, 0.005, 0.01, 0.015, 0.02, and 0.025) compounds were investigated. The samples were synthesized by arc-melting method and followed by annealing, mechanical grinding and spark plasma sintering (SPS) process. The electrical conductivity, the Seebeck coefficient, the thermal conductivity, and the Hall coefficient measurements were performed in the range of temperature from room temperature to 923 K. By changing Nb-doping amount, the electrical conductivity increased with increasing the doping level, while the Seebeck coefficient relatively less decreased at high temperatures, resulting in the highest power factor of 36 × 10−4 (W/K2m) at 773 K with x = 0.02 sample. Furthermore, a significant reduction in the lattice thermal conductivity is attributed to anharmonic phonon-phonon interactions by aliovalent substitution into multi-element site and higher degree of phase separation, which was achieved through the synthesis process of these compounds. The enhancement of the power factor combined to low thermal conductivity leads to ∼20% increase of the dimensionless figure of merit (ZT, ∼1.0 at 773 K) in comparison to the parent Hf0.25Zr0.25Ti0.5NiSn compound. It is believed that this is attributed to a decoupling between the electrical conductivity, thermopower, and phonon transport by Nb-doping. The Nb-doped compounds also showed high stability of the power factor up to 873 K.

The n -type Hf0.25Zr0.25Ti0.5NiSn0.998Sb0.002 Half-Heusler (HH) alloy composition was prepared by using the induction melting method in addition to the mechanical grinding, annealing, and spark plasma sintering processes. Analysis of X-ray diffraction (XRD) results indicated the formation of a pure phase HH structured compound. The electrical and thermal properties at temperatures ranging from room temperature to 718 K were investigated. The electrical conductivity increased with increasing temperatures and demonstrated nondegenerate semiconducting behavior, and a large reduction in the thermal conductivity to the value of 2.5 W/mK at room temperature was observed. With the power factor and thermal conductivity, the dimensionless figure of merit was increased with temperature and measured at 0.94 at 718 K for the compound synthesized by the induction melting process.

We fabricated high efficiency yellow-color organic light-emitting diodes (OLEDs) by co-doping 2,8-di(t-butyl)-5,11-di[4-(t-butyl)phenyl]-6,12-diphenylnaphthacene (TBRb) and tris(8-hydroxyquinolinato)aluminum (Alq 3 ) guests in a N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) host. Co-doping of electron-transporting Alq 3 with yellow dopant TBRb in hole-dominant NPB layers resulted in substantial luminance-yield improvement compared to TBRb-only counterparts without color contamination from Alq 3 green emission. The luminance yield of 11.4 cd/A, corresponding to the co-doping of 8% TBRb and 2% Alq 3 , is larger than previously reported luminance-yield values of conventional TBRb-based yellow OLEDs. Another advantage of the TBRb-Alq 3 co-doped OLEDs is an insignificant roll-off of efficiency at high current-density and/or brightness levels.

Bi2Te3-ySey (y = 0 - 0.6) solid solutions were prepared by using mechanical alloying and hot pressing. The lattice constants decreased with increasing Se content, which revealed the successful formation of solid solutions by using a planetary mill. The relative densities of hot-pressed specimens were higher than 96%. All specimens indicated n-type conductions in the measuring temperature range from 323 K to 523 K, and the electrical conductivity slightly decreased with increasing temperature. The Seebeck coefficient increased with increasing Se content, and the electrical and the thermal conductivities decreased; thus, the dimensionless figure of merit was improved. A maximum dimensionless figure of merit of 0.76 was obtained at 473 K for Bi2Te2.55Se0.45.

Lead-free piezoelectric 0.97(Bi0.5Na0.5Ti1−xNbx)O3-0.03BaZrO3 (BNT-BZ3) ceramics (x = 0 ~ 0.03) were prepared by a conventional solid-state reaction method. X-ray diffraction patterns revealed the formation of single-phase perovskite structure with x ≤ 0.015. The depolarization temperature and the dielectric constant decreased with increasing Nb content. The remanent polarization (Pr) and the piezoelectric constant (d33) increased from 28 μC/cm2 and 98 pC/N for x = 0 to 31 μC/cm2 and 128 pC/N for x = 0.005, respectively. In addition, the electric field induced strain was enhanced with a maximum value Smax = 0.17% with a normalized piezoelectric coefficient of d*33 = 283 pm/V at an applied electric field of 6 kV/mm for x = 0.015.

A significant challenge in nano and biophotonics is to demonstrate fully biocompatible nano-optics devices that can perform biofunctions in vivo. Here we present a scalable, cost-effective, and large-area nanofabrication method for creating a quasi-3D plasmonic crystal using poly(ethylene glycol) (PEG) and gold (Au), both biocompatible materials. The plasmonic crystal was prepared by depositing an Au layer on the upper hemisphere of the replicated PEG nanospheres array. Additionally we demonstrated that the fabricated plasmonic crystal can behave as a label-free glucose sensor with sensitivity and figure-of-merit values comparable to other plasmonic crystal based sensors.

Adhesion control of various liquid droplets on a liquid-repellent surface is a fundamental technique in novel open channel microfluidic systems. Herein, we demonstrate reversible liquid droplet adhesion switching on superamphiphobic Pd-decorated Ag dendrites (Pd/Ag dendrites). Although adhesion between liquids and the superamphiphobic surfaces was extremely low under ambient air, high adhesion was instantly achieved by exposure of the dendrites to 8% hydrogen gas. Transition from low to high adhesion and the reverse case were successfully repeated more than 10 times by switching from atmospheric ambient air to 8% hydrogen gas. This is the first technique that allows real-time reversible adhesion change with various liquid droplets to a surface using gas-induced structural changes and can potentially be used to realize various functions for droplet-based microfluidics.

We used electrostatic force microscopy (EFM) to investigate local conducting states of atomically thin individual graphene oxide (GO) sheets and monitor the spatial evolution of their conducting properties during the reduction process. Because of the thinness of the GO sheets and finite carrier density, the electric field is partially screened in the reduced GO, which is manifested in the EFM phase signals. We found inhomogeneous oxidation states in as-prepared GO sheets and followed the evolution of reduction process in the individual GO sheets during both thermal and chemical reduction. We also compared the EFM measurement results with simultaneous IV characteristics to assess correlations between two measurements.

With poly(3-hexylthiophene) (P3HT) nanowire (NW) inclusion in active layers (ALs), organic solar cells (OSCs) based on P3HT donor and indene-C60 bisadduct (ICBA) acceptor showed power conversion efficiency (PCE) improvements for both bulk heterojunction (BHJ)- and bilayer (BL)-structure AL devices. The PCE increase was approximately 14 % for both types of P3HT:ICBA OSCs. However, improvements in short-circuit current density (Jsc ) were about 4.4 and 6.4 % for BHJ- and BL-type AL devices, respectively. A systematic study showed that the addition of P3HT NWs did not result in enhanced internal quantum efficiencies for either type of device. However, the difference in light-harvesting efficiency was important in accounting for Jsc variations. Interestingly, there was no correlation between Jsc and PCE variations, whereas the open-circuit voltage (Voc ) and fill factor (FF) showed correlations with the PCE. The variation in FF is discussed in terms of Voc and equivalent-circuit parameters based on a nonideal diode model.

Reliability tests for thermoelectric unicouples were carried out to investigate the adhesion properties of CoSb3/Ti/Mo(Cu) interfaces. The n-type In0.25 Co3.95Ni0.05Sb12 and p-type In0.25Co3FeSb12 bulks were prepared for fabricating a thermoelectric unicouple (one p–n couple) by an induction melting and a spark plasma sintering process. Mo-Cu alloy was selected as an electrode for the unicouples due to its high melting temperature and proper work function value. Many thermoelectric unicouples with the CoSb3/Ti/Mo(Cu) interfaces were fabricated with the proper brazing materials by means of a repeated firing process. Reliability of the unicouples with the interfaces was evaluated by a vibration test and a thermal cycling test. After the thermal cycling and vibration tests, the power-generation characteristics of the unicouples were compared with the unicouples before the tests. Even after the vibration test, electrical power with a power density of 0.5 W/cm2 was generated. The Ti-interlayer is considered as a possible candidate for making a reliable unicouple with high adhesion strength. With the thermal cycling test, the resistance of the unicouple increased and the electrical power from the unicouple decreased. A failure mode by the thermal cycling test was ascribed to a complex effect of micro-cracks originated from the thermal stress and oxidation problem of the thermoelectric materials; that is, a thick oxide layer more than 300 μm was detected after a high-temperature durability test of n-type In0.25Co3.95Ni0.05Sb12 material at 773 K in air for 7 days.

Textured Ca3Co4O9 ceramics were prepared by spark plasma sintering (SPS) from commercial CaCO3 and Co3O4 powders to investigate the thermoelectric anisotropy of Ca3Co4O9. The degree of orientation of the textured specimens was evaluated by using the Lotgering factor method, and the SPS process was confirmed to be an effective technology to prepare textured Ca3Co4O9 ceramics. Both the power factors and the thermal conductivities were measured in two different directions, parallel (out-of-plane) and perpendicular (in-plane) to the SPS press axis. The difference in anisotropy between the electrical conductivity and the thermal conductivity was investigated for the textured Ca3Co4O9 ceramics. The maximum figure of merit (ZT) value along the direction perpendicular to the SPS press axis was more than 20% higher than it was along the direction parallel to the SPS press axis. It is noted that the strong thermoelectric anisotropy can give rise to an overestimates of ZT when preparing samples in different directions for power factor and thermal conductivity measurements.

Lead-free piezoelectric ceramics (1−x) [(0.97Bi0.5Na0.5TiO3)]-0.03BaZrO3-xLiNbO3 (BNT-BZ3-xLN) with x = (0–0.07) were synthesized using the conventional solid-state reaction method, and their crystal structure, microstructure, and dielectric, ferroelectric and piezoelectric properties were investigated as a function of the LN content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNT-BZ ceramics in this study. The results indicate that the LN substitution into BNT-BZ3 induces a transition from a ferroelectric to a diffuse and/or relaxor state accompanying a field-induced strain of 0.20% for x = 0.05 at an applied field of 6 kV/mm. The corresponding dynamic piezoelectric coefficient for this composition was (S max/E max = 333 pm/V). A significant reduction of the coercive field (E c) and enhancement of the piezoelectric constant (d 33) from 98 pC/N for x = 0 to 117 pC/N x = 0.01 was observed.

A multi-inlet-multi-outlet (MIMO) superhydrophobic droplet guiding track was demonstrated for water droplet manipulation using an electrostatic force-induced trajectory switching system. Without applying an external electrostatic field, the water droplet rolled along the superhydrophobic guiding track due to its extreme water repellent properties and gravitational force. By applying a DC bias to a capacitor above the guiding track, the trajectory of the water droplet can be easily controlled by the electrostatic attraction. Electrostatically-induced trajectory switching was successfully achieved when the electrostatic and gravitational forces exerted on the water droplet were properly balanced. On a MIMO superhydrophobic droplet guiding track with three inlets and four outlets, the water droplet was guided along the intended trajectory.

Early and active management of cancer pain is important for improving patients’ satisfaction with treatment and quality of life. The efficacy and tolerability of osmotic release oral system (OROS®) hydromorphone was evaluated in opioid-naive cancer patients experiencing moderate to severe cancer pain. The authors believe the results of this study will provide meaningful information regarding the clinical benefit of OROS hydromorphone as front-line therapy in opioid-naive cancer patients., BACKGROUND: Osmotic release oral system (OROS®) hydromorphone is a potent, long-acting opioid analgesic, effective and safe for controlling cancer pain in patients who have received other strong opioids. To date, few studies have examined the efficacy of hydromorphone for pain relief in opioid-naive cancer patients. OBJECTIVES: A prospective, open-label, multicentre trial was conducted to determine the efficacy and tolerability of OROS hydromorphone as a single and front-line opioid therapy for patients experiencing moderate to severe cancer pain. METHODS: OROS hydromorphone was administered to patients who had not previously received strong, long-acting opioids. The baseline evaluation (visit 1) was followed by two evaluations (visits 2 and 3) performed two and 14 weeks later, respectively. The starting dose of OROS hydromorphone was 4 mg/day and was increased every two days when pain control was insufficient. Immediate-release hydromorphone was the only accepted alternative strong opioid for relief of breakthrough pain. The efficacy, safety and tolerability of OROS hydromorphone, including the effects on quality of life, and patients’ and investigators’ global impressions on pain relief were evaluated. The primary end point was pain intensity difference (PID) at visit 2 relative to visit 1 (expressed as %PID). RESULTS: A total of 107 patients were enrolled in the present study. An improvement in pain intensity of >50% (≥50% PID) was observed in 51.0% of the full analysis set and 58.6% of the per-protocol set. The mean pain score, measured using a numerical rating scale, was significantly reduced after two weeks of treatment, and most adverse events were manageable. Quality of life also improved, and >70% of patients and investigators were satisfied with the treatment. CONCLUSIONS: OROS hydromorphone provided effective pain relief and improved quality of life in opioid-naive cancer patients. As a single and front-line treatment, OROS hydromorphone delivered rapid pain control.

We demonstrate the development of an effective technique to remove the poly methyl methacrylate (PMMA) layer used for transferring graphene synthesized by a chemical vapor deposition (CVD). This was achieved utilizing electron-beam bombardment and following developing processes, prior to the use of conventional organic solvents. Field-effect transistors were fabricated on the transferred graphene in order to explore their Dirac points and carrier motilities in the ambient condition - the results were then compared with those from the conventional wet chemical treatment. It was found that the Dirac points were located close to the zero gate bias when compared to those from the acetone and the acetic acid treatments. Most significantly, the field-effect mobility reached as high as 6770 cm2/Vs and 7350 cm2/Vs on average for holes and electrons, respectively, which is more than seven times improvement in comparison to conventional acetone treatments for CVD-grown graphene devices.

Gradient-layered $i$ a-Si:H passivation is shown to enhance minority carrier lifetimes in silicon heterojunction solar cells compared to single or dual-layer passivation structures. The gradient layered passivation contains optimized interfacial and capping layers for passivating the $i$ a-Si:H/c-Si interface and a gradient layer for suppressing charge traps in bulk $i$ a-Si:H. Gradient layers were obtained by changing the hydrogen dilution ratio continuously during deposition of $i$ a-Si:H. The minority carrier lifetime of the c-Si substrate using gradient-layered passivation was as high as $2451\mu \mathbf{s}$ , compared to 1831 μs for dual-layered passivation at $2\times 10^{15}$ cm−1injection level. JV characteristics of Silicon heterojunction (SHJ) solar cell employing these gradient passivation schemes will also be discussed. When the gradient-layered passivation was implied to interdigitated back contact (IBC) SHJ solar cells, there was an improvement in efficiency, compared to other passivation schemes such as single and dual passivation.

The band alignment at an Al2O3/SrTiO3 heterointerface forming a two-dimensional electron gas (2DEG) was investigated using scanning photocurrent microscopy (SPCM) in an electrolyte-gated environment. We used a focused UV laser source for above-the-bandgap illumination on the SrTiO3 layer, creating electron-hole pairs that contributed to the photocurrent through migration towards the metal electrodes. The polarity of the SPCM signals of a bare SrTiO3 device shows typical p-type behavior at zero gate bias, in which the photogenerated electrons are collected by the electrodes. In contrast, the SPCM polarity of 2DEG device indicates that the hole carriers were collected by the metal electrodes. Careful transport measurements revealed that the gate-dependent conductance of the 2DEG devices exhibits n-type switching behavior. More importantly, the SPCM signals in 2DEG devices demonstrated very unique gate-responses that cannot be found in conventional semiconducting devices, based on which we were able to perform detailed investigation into the electronic band alignment of the 2DEG devices and obtain the valence band offset at the heterointerface.

Scientific Reports 6: Article number: 35994; published online: 27 October 2016; updated: 16 March 2017. Ujwal Thakur was omitted from the author list in the original version of this Article. This has been corrected in the PDF and HTML versions of the Article, as well as the Supplementary Informationfile.

We report the synthesis and thermoelectric properties of a new p-type oxide thermoelectric material (Li1−xNbO2, with x = 0–0.6), in which Li-vacancies play a significant role in the enhancement of the thermoelectric performance. The electrical conductivity drastically increases due to Li-vacancies, resulting in an increase in the hole carrier concentration. A remarkable enhancement in the power factor is observed, which is comparable to well-known oxide thermoelectrics. The carrier concentration was not significantly dependent on the temperature, while the Hall mobility shows negative temperature-dependence. The Seebeck coefficient is linearly proportional to temperature, and the density of the state effective mass Image ID:c7ra10557f-t1.gif was estimated by using the Pisarenko relation. The thermal conductivity was substantially reduced by Li-vacancies and Li-vacancy induced localized double phonon scattering. Density functional theory (DFT) calculations reveal that the enhancement of the thermoelectric properties is mainly due to the increase in the electronic density of states (DOS) at the Fermi energy, which increases with hole concentration. All of the samples after high-temperature measurements are highly stable, which suggests that the well-synthesized nonstoichiometric Li1−xNbO2 could be a new promising candidate material for high temperature thermoelectric applications., This work was partially supported by the Industrial Technology Innovation Program (Industrial Materials Core Technology Development Program) funded by the Ministry of Trade, Industry and Energy, Republic of Korea (10052977). The coauthor, V. M. Garcia-Suarez, thanks the Spanish Ministerio de Economía y Competitividad for funding (FIS2015-63918-R) and Banco Santander for a Mobility Excelence Grant.

We fabricated plasmonic devices operating in the terahertz (THz) frequency range using silver nanowire (AgNW) network films. AgNW films exhibit high conductivity and good transparency in the visible range, with a figure of merit comparable to that of conventional transparent conducting oxide films. The THz conductivity of AgNW films can be improved by post-treatment procedures such as welding using graphene oxide flakes. Using photolithography, we fabricated the slot antenna arrays whose resonance behaviors are determined by geometric parameters such as the length of individual elements. The plasmonic resonance varied with the sheet resistances of the film, enabling us to manipulate the quality factors and the peak position of the resonance, in particular, by controlling the films thickness and by the post-procedures such as the chemical vapor treatment. (C) 2017 Optical Society of America

The thermal stability of the La0.9Fe3CoSb12 skutterudite was examined by varying the aging conditions of temperature, time, and atmosphere (air and vacuum). Thermogravimetry, differential scanning calorimetry and x-ray diffraction analyses revealed that the La0.9Fe3CoSb12 was significantly oxidized at temperatures above 673 K in air. The Sb-based oxides were preferably formed when aged at high temperatures in air. The thickness of the oxide layers was found to increase with increasing aging temperature and time, while the activation energy for the oxidation of the Fe-Sb-based skutterudite was lower than that of the Co-Sb-based skutterudites. However, when the analysis was performed in a vacuum, the La0.9Fe3CoSb12 skutterudite was stable, and no oxide layers were observed after aging at 823 K for 100 h. These results suggest that a protective coating for the skutterudite materials or the encapsulated packaging of the skutterudite modules is required for high-temperature applications.

In the present study, we visualize ultrafast carrier dynamics in one-dimensional nanoscale devices, such as Si nanowire and carbon nanotube transistors using femtosecond photocurrent microscopy. We investigate transit times of ultrashort carriers that are generated near one metallic electrode and subsequently transported toward the opposite electrode based on drift and diffusion motions. Conversely, pure diffusion motion is observed when the pump pulse is located in the middle of the nanowires. Carrier dynamics have been addressed for various working conditions, in which we found that the carrier velocity and pulse width can be manipulated by the external electrodes. In particular, the carrier velocities extracted from transit times increase for a larger negative gate bias because of the increased field strength at the Schottky barrier.

We report fully solution-processed fabrication of transparent conducting oxide-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) by combining spray-coating of single-wall carbon nanotubes (SWCNTs) and chemical reduction of chloroplatinic acid precursor to platinum nanoparticles (Pt NPs) with formic acid. The power conversion efficiency of a semitransparent DSSC with such SWCNT-based CE loaded with Pt NPs is comparable to that of a control device with a conventional CE. Quantification of Pt loading shows that network morphology of entangled SWCNTs is efficient in forming and retaining chemically reduced Pt NPs. Moreover, electron microscopy and electrochemical impedance spectroscopy results show that mainly Pt NPs, which are tens of nanometers in diameter and reside at the surface of SWCNT CEs, contribute to electrocatalytic activity for triiodide reduction, to which we attribute strong correlation between power conversion efficiency of DSSCs and time constant deduced from equivalent-circuit analysis of impedance spectra.

We fabricated hybrid light emitting devices based on colloidal CdSe/ZnS core/shell quantum dots and a solution-processed NiO layer. The use of a sol-gel NiO layer as a hole injection layer (HIL) resulted in overall improvement in device operation compared to a control device with a more conventional poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) HIL. In particular, luminous efficiency increased substantially because of the suppression of excessive currents and became as large as 2.45 cd/A. To manifest the origin of current reduction, temperature- and electric field-dependent variations of currents with respect to bias voltages were investigated. In a low bias voltage range below the threshold for luminance turn-on, the Poole-Frenkel (PF) emission mechanism was responsible for the current-density variation. However, the space-charge-limited current modified with PF-type mobility ruled the current-density variation in high bias voltage range above the threshold.

La-filled skutterudites LazCo4Sb12 (z = 0, 0.1, 0.2, 0.3, 0.4) were prepared by encapsulated melting and hot pressing. The filling effects of La on the transport and the thermoelectric properties of skutterudites were examined. All specimens were transformed to skutterudite phases through subsequent annealing. The intrinsic CoSb3 had a high positive Seebeck coefficient, but a thermoelectric figure of merit, ZT, of lower than 0.1 due to its low electrical conductivity and high thermal conductivity. However, La-filled CoSb3 showed degenerate semiconductor behavior and high electrical conductivity, and exhibited n-type conduction because of the excess electrons donated from the La fillers. The Seebeck coefficient increased and then decreased slightly with increasing temperature, and it decreased with increasing La filling content due to increased carrier concentration. The thermal conductivity was reduced significantly by La filling, mainly due to the decrease in the lattice thermal conductivity. ZT = 0.35 was obtained in the temperature range from 623 to 823 K for La0.2Co4Sb12.

Rare-earth-filled skutterudites R z Fe4−x Co x Sb12 (R: Yb, La, Ce) were prepared, and their transport and thermoelectric properties were examined. All specimens showed p-type conduction and exhibited a degenerate semiconductor behavior. R0.9Fe3CoSb12 had lower electrical conductivities and higher Seebeck coefficients than RFe4Sb12, which meant that Co led to charge compensation through electron donations. All specimens had positive Hall coefficients, and their carrier concentrations were decreased by charge compensation with increasing Co substitution. The thermal conductivities of R0.9Fe3CoSb12 were lower than those of RFe4Sb12 due to the decreased carrier concentration, as well as the lattice scattering induced by the substitution of Co for Fe. Yb-filled and La-filled skutterudites showed enhanced thermoelectric figures of merit through charge compensation with Co, but Ce-filled skutterudites did not. Yb2∼3+ and La3+ ions required charge compensation to stabilize their skutterudite phases, but Ce3∼4+ ions did not.

We report the fabrication of efficient indium-tin-oxide-free organic solar cells based on poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM). All layers of the devices from the lowermost silver nanowire cathode to the uppermost conducting polymer anode are deposited from solution and processed at plastic-compatible temperatures

P-type Ce-filled skutterudites CezFe4−xCoxSb12 (z = 0.3–1, x = 1–3) were prepared, and their thermoelectric properties were examined at temperatures between 500 K and 800 K. Specimens were synthesized by encapsulated melting at 1323 K for 10 h and were hot pressed after annealing at 873 K for 24 h. Stable skutterudite phases could be obtained by the incorporation of Ce filling and charge compensation with Co for Fe. The electrical conductivity decreased slightly with increasing temperature and Co content. The Seebeck coefficient had positive values (p-type conductivity), increased with increasing temperature until a specific temperature, and then decreased thereafter. The thermal conductivity decreased through the further lattice scattering induced by substituting Co at Fe sites and by Ce filling. The thermoelectric performance of Fe-rich skutterudites was superior to that of Co-rich skutterudites. A dimensionless figure of merit of ZTmax = 0.7 was achieved at 823 K for CeFe4Sb12.

In this work, the lead-free piezoelectric ceramic (1-x)[0.65Bi1.05FeO3–0.35BaTiO3] – xBiAlO3, (BFBT-xBA) (where x = 0, 0.010, 0.015, 0.020, 0.025, and 0.030), were synthesized by a solid-state reaction method, followed by air quenching process. The effects of BiAlO3 (BA) on the crystal structure, morphology and electrical properties of 0.65Bi1.05FeO3-0.35BaTiO3 (BF-BT) ceramics have been investigated. With the incorporation of BA-content (x = 0.010) the coexistence of rhombohedral and pseudocubic phases were observed. Scanning electron microscope (SEM) micrographs revealed that the average grain size of BF-35BT ceramics increased with the addition of BA. Well-saturated ferroelectric (P–E) hysteresis loops with definite remnant polarization (Pr) and coercive field (Ec) were observed. As a result, improvements in ferroelectric and piezoelectric properties with relative high Curie temperature (TC) were obtained at the optimum composition (x = 0.010). In addition, the static piezoelectric coefficient (d33) was enhanced from 97 pC/N for the base composition (x = 0) to 210 pC/N for the optimum (x = 0.010) composition.

The effect of thermal quenching on physical properties of morphotropic phase boundary BiFeO3-0.35PbTiO3 composition, composed of Pnma, R3c and P4mm phases, has been investigated in detail. We detected and quantified role of quenching through investigation of magnetic, dielectric and ferroelectric anomalies. Quenching significantly i) enhances the tetragonal phase percentage (hence affects domain structure), ii) reduces domain wall clamping with a large increase in electrical polarization, iii) increases magnetization at the structural phase transition temperature (tunable magneto-electric coupling), iv) magnifies intrinsic property i.e. intra grain relaxation dynamics (which are otherwise suppressed due to the pinning of the defect dipoles), etc. All these findings clearly verify the role of quenching which noticeably enhances multiferroic properties at the well-known morphotropic phase boundary.

We demonstrate the fabrication of plasmonic and metamaterials devices, operating in the terahertz frequency range, by using highly conductive, single-walled carbon nanotube (SWNT) network films. We fabricated various patterns on the SWNT films using photolithography or laser machining techniques, whose resonance behaviors are determined by geometric parameters such as the periodicity of the array patterns or the shape of the individual elements. The excellent mechanical properties of SWNT films enabled us to fabricate free-standing and highly flexible devices. More importantly, using postprocessings such as chemical treatments and nanoparticle coatings, we were able to engineer the dielectric constants of the SWNT films, such as enhancing or degrading the conductive properties. As a result of the postprocessings, the resonance peak of the plasmonic devices was suppressed or retrieved, which is not achievable in conventional metal films. In particular, we were able to control the metamaterials resonances, ...

The ionic and electronic conductivities of nonstoichiometric BaTiO 3 (undoped, Ca-doped, and Zr-doped BaTiO 3–δ ) ceramics were investigated through high temperature equilibrium conductivity (HiTEC) and in-situ impedance measurements at various equilibrium conditions with different oxygen partial pressures over a temperature range of 950–1050 °C. Contribution of mobile oxygen vacancies on the electrical conductivity has been determined by HiTEC measurement as a function of oxygen partial pressure; the electrical conductivity with mobile oxygen vacancies shows a broad transition from p -type to n -type, and thereby there is an increase of the minimum conductivity at the n – p transition point. Through combining in-situ impedance spectroscopy measurements with the HiTEC measurements, it was confirmed clearly that the mobile oxygen vacancy contributes to the total conductivity, and the oxides become mixed conductors around the n – p transition regime (minimum electronic conductivity regime). It was found that Warburg impedance can be observed at the condition of t ion /t electronic ≳ 0.05 in the temperature range of 950–1050 °C and p O 2 range of 0.95–10 − 16 atm. The ionic conductivity varied with the concentration of extrinsic oxygen vacancies and dopants, and the activation energy for mobility of oxygen vacancy in Ca-doped BaTiO 3–δ was found to be 1.04 ± 0.05 eV using the two techniques in a very good agreement.

We report the characterization of individual carbon nanotube and Si nanowire field-effect transistors through high-speed scanning photocurrent microscopy with a scanning speed of 1 frame/s and a photocurrent sensitivity of less than 1 pA. This enables us to record photocurrent images that are free from hysteresis effects that modify the field configurations applied by the gate bias voltage. We can clearly resolve the photocurrent signals with polarity inversion near the metallic contacts under gate bias conditions which cause severe hysteresis effects in the nanowire devices. We also studied the dynamics of the hysteresis effects for different gate bias configurations. This high-speed photocurrent imaging technique is particularly useful for obtaining two-dimensional, localized optoelectronic characteristics and their correlation with overall device performance without encountering undesired dynamic responses.

We report here a case of oral myiasis in the Republic of Korea. The patient was a 37-year-old man with a 30-year history of Becker's muscular dystrophy. He was intubated due to dyspnea 8 days prior to admission to an intensive care unit (ICU). A few hours after the ICU admission, 43 fly larvae were found during suction of the oral cavity. All maggots were identified as the third instars of Lucilia sericata (Diptera: Calliphoridae) by morphology. We discussed on the characteristics of myiasis acquired in Korea, including the infection risk and predisposing factors.

Bio-inspired superhydrophobic surfaces have attracted considerable attention due to their potential applications. Although various techniques to fabricate artificial superhydrophobic surfaces have been demonstrated, most of the methods lack water adherence or controllable wetting properties of the surfaces, which hinders their practical usage. In this paper, we present a simple approach to fabricate water-adhesive superhydrophobic silicon nanowire (Si NW) surfaces by applying a thermal annealing treatment in oxygen ambient. The Si NW arrays were fabricated using a metal assisted chemical etching method. After the cycled rapid thermal annealing (RTA) process at 1000 °C under oxygen ambient, the water contact angle of the Si NW surface changed dramatically from 0 to 154.3° with high water-adhesive properties. This drastic change of the wettability could be attributed to the formed siloxane groups (− Si–O–Si–) on the thermally-treated Si NW surfaces; H 2 O is released from two adjacent silanol groups (–Si–O–H) to form siloxane groups during the RTA process. When the annealed Si NW was exposed in air, the wettability of the superhydrophobic Si NW was reconverted due to the re-formation of silanol groups (–Si–O–H). The wettability conversion of Si NW between superhydrophilic and superhydrophobic was repeated with good reversibility.

Bulk nanostructured materials are important as energy materials. Among thermoelectric materials, the skutterudite system of CoSb3is a representative material of bulk nanostructured materials. Filling a skutterudite structure with atoms that have different localized frequencies (also known as triple filling) was reported to be effective for lowering thermal conductivity. Among studies representing superior power factors, In-filled skutterudite systems showed higher Seebeck coefficients. This study sought to optimize the composition ratio among the triple-filled atoms in anIn0.3-x-yBaxCeyCo4Sb12system. The composition dependence of the thermoelectric properties was investigated for specimens with different ratios among the three kinds of filler atoms in theIn0.3-x-yBaxCeyCo4Sb12system. In addition, the process variables were carefully optimized for filled skutterudite systems to obtain a maximumZTvalue.