High spin polarization induced by the interface hybridization in Co/C composite films

Co/C composite films with 10 at.% Co were fabricated by facing-target sputtering and postannealed in vacuum at 300–650 °C for 1.5 h. Co nanoparticles are dispersed in amorphous carbon matrix and Co–C compounds exist at the interface between Co nanoparticles and carbon matrix. Negative magnetoresistance was observed in the Co/C films and its maximum value of ?19% was measured at 3.98 × 10⁶ A/m and 5 K for the as-deposited film. Besides cotunneling effect, higher interfacial spin polarization, which is probably induced by the hybridization between Co 3d and C 2p electrons and consequently the preferred d-electron conduction and interfacial spin-filtering effect, also contributes to the large negative magnetoresistance. Postannealing treatment damages the interface hybridization, and thus leads to the disappearance of the higher interfacial spin polarization and large negative magnetoresistance.     

Enhanced Thermal and Mechanical Properties in Polyurethane/Au Nanocomposites

Summary: We have prepared waterborne polyurethane (WBPU) thin films containing gold nanoparticles by casting WBPU/Au solutions. The effect of the Au nanoparticle contents on the microstructure and properties of the composite films was investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), field emission scanning electron microscopy (FESEM), transmittance electron microscopy (TEM), FTIR spectroscopy (FTIR) and dynamic mechanical analysis (DMA). The Au nanoparticles initially in the WBPU solution were well dispersed in the WBPU films cast and dried at 60 °C. The thermostability and mechanical properties of the polymer increased with Au contents up to 4.35 × 10^?2 wt.‐%, which was believed to be a result of induced crystallization in the presence of Au nanoparticles. The Au/WBPU nanocomposite containing with 6.5 × 10^?2 wt.‐% of Au resulted in the aggregation of Au particles, which leads to a worsening of the thermal and mechanical properties.

TEM micrograph of nanocomposites filled with 4.35 × 10^?2 wt.‐% of Au nanoparticles.     

Nonvolatile memory devices based on Au/graphene oxide nanocomposites with bilateral multilevel characteristics

Current–voltage measurements on the Al/self-assembled Au nanoparticles inserted in graphene-oxide (GO) layer/indium-tin-oxide/glass devices at 300 K showed bilateral current bistabilities with four current states in a cell. The multilevel behaviors with four current states were obtained by applying different erasing voltages of −6, −12, and −18 V with a writing voltage of 3 V or different erasing voltages of 8, 14, and 18 V with a writing voltage of −5 V. The resistive memory devices demonstrated bilateral multilevel characteristics due to a nanocomposite consisting of Au nanoparticles inserted in a GO layer. The stabilities of the four current states with 1 × 10⁻¹, 1 × 10⁻⁴, 1 × 10⁻⁶, and 1 × 10⁻⁸ A achieved for the devices by using different erasing voltages were maintained for retention cycles larger than 1 × 10⁴ s under a continuous reading test. Memory operating mechanisms and multilevel characteristics based on the I–V curves were described by using the carrier-capture in the self-assembled Au nanoparticles and the local filament-path on the surface between the electrode and the GO layer.     

Taguchi optimization of device parameters for fullerene and Poly (3-octylthiophene) based heterojunction photovoltaic devices

Photovoltaic devices were fabricated with the structure ITO/fullerene/Poly (3-octylthiophene)/Au and device parameters were optimized using Taguchi optimization technique. Optimized parameter such as fullerene and Poly (3-octylthiophene) film thickness, annealing temperature and annealing duration are found to be as 110 nm, 45 nm, 120° C and 15 min respectively. Fabricated device with optimized parameters shows short circuit current density (J_sc), open circuit voltage (V_oc) and fill factor (FF) as 2 × 10^− 4 mA/cm², 0.47 V and 0.25 respectively. Effect of solvent casting on C₆₀ layer was studied which shows formation of uneven surface providing large interfacial area.     

Electrical contacts to nitrogen incorporated nanocrystalline diamond films

The effect of surface plasma treatment on the nature of the electrical contact to the nitrogen incorporated nanocrystalline diamond (n-NCD) films is reported. Nitrogen incorporated NCD films were grown in a microwave plasma enhanced chemical vapor deposition (MPECVD) reactor using CH₄ (1%)/N₂ (20%)/Ar (79%) gas chemistry. Raman spectra of the films showed features at ∼ 1140 cm^− 1, 1350 cm^− 1(D-band) and 1560 cm^− 1(G-band) respectively with changes in the bonding configuration of G-band after the plasma treatment. Electrical contacts to both untreated and surface plasma treated films are formed by sputtering and patterning Ti/Au metal electrodes. Ohmic nature of these contacts on the untreated films has changed to non-ohmic type after the hydrogen plasma treatment. The linear current–voltage characteristics could not be obtained even after annealing the contacts. The nature of the electrical contacts to these films depends on the surface conditions and the presence of defects and sp² carbon.     

Gradual modification of the YSZ structures by Au ion implantation and high-energy Si ion irradiation

Gold nanoparticles (Au-NPs) were created in crystalline yttria-stabilized zirconia (YSZ). (100)-, (110)- and (111)-oriented YSZ samples were implanted by 1 MeV Au⁺ ions at room temperature and fluences ranging from 1.5 × 10¹⁶ cm⁻² to 7.5 × 10¹⁶ cm⁻². The prepared Au: YSZ structures were annealed at 1100 °C for 1 h on air to support the Au-NPs coalescence and YSZ structure recovery. Subsequent irradiation with the 10 MeV Si³⁺ ions with a fluence of 5.0 × 10¹⁴ cm⁻² was performed to enable gradual modification of Au-NPs. Au-depth profiles and YSZ structure modification in the produced samples were analysed via Rutherford backscattering spectrometry in channelling mode (RBS-C) and X-ray diffraction (XRD). RBS-C showed the gold distributed in the region of about 50–300 nm below the YSZ surface. The disorder was accumulated in the region with Au-NPs and the concentration of the disorder increases as a function of ion implantation fluence. The Zr-disorder was partially decreased after the annealing, while the subsequent Si-ion irradiation increased Zr-disorder again, however, the disorder does not reach values before the annealing. XRD measurement evidenced elastic deformation of the YSZ host lattice in the Au-implanted samples. Optical absorbance showed the appearance of the new absorption band at 550 nm for the Au-ion fluences above 5.0 × 10¹⁶ cm⁻² ascribed to the Au-NPs formation. After the annealing, the absorption band is shifted to the wavelength of 580 nm which could be connected to the proceeding clustering of Au. The maximum absorption peak intensity increases which is connected to the increasing amount of the Au-NPs. Transmission electron microscopy (TEM) with Energy dispersive spectroscopy (EDS) confirmed the presence of Au-NPs in the implanted layer after the annealing. The subsequent Si-ion irradiation did not change the Au-NP shape which remained spherical with a slight size increase.     

Electroluminescent Characteristics of DBPPV–ZnO Nanocomposite Polymer Light Emitting Devices

We have demonstrated that fabrication and characterization of nanocomposite polymer light emitting devices with metal Zinc Oxide (ZnO) nanoparticles and 2,3-dibutoxy-1,4-poly(phenylenevinylene) (DBPPV). The current and luminance characteristics of devices with ZnO nanoparticles are much better than those of device with pure DBPPV. Optimized maximum luminance efficiencies of DBPPV–ZnO (3:1 wt%) before annealing (1.78 cd/A) and after annealing (2.45 cd/A) having a brightness 643 and 776 cd/m² at a current density of 36.16 and 31.67 mA/cm² are observed, respectively. Current density–voltage and brightness–voltage characteristics indicate that addition of ZnO nanoparticles can facilitate electrical injection and charge transport. The thermal annealing is thought to result in the formation of an interfacial layer between emissive polymer film and cathode.     

Radiation-induced polymerization of ethylene in pilot plant. III. Heavy-phase recycling process

Radiation-induced polymerization of ethylene using aqueous tert-butyl alcohol as medium was carried out in a large-scale pilot plant with a 50-liter central source-type reactor at a pressure of 105 to 395 kg/cm², temperature of 30° to 80°C, mean dose rate of 4.5 × 10⁴ to 1.9 × 10⁵ rads/hr, ethylene feed rate of 5.5 to 23.5 kg/hr, and medium feed rate of 21 to 102 l./hr. The space–time yield and molecular weight of the polymer were in the range of 4.7 to 16.8 g/l.-hr and 1.3 × 10⁴ to 8.9 × 10⁴, respectively. The space–time yield and molecular weight increased with mean residence time at 30°C, whereas at 80°C they became almost independent of the time. The space–time yield increased with pressure and dose rate, slightly decreased with temperature, and was maximum at ethylene molar fraction of 0.5. The polymer molecular weight increased with pressure and ethylene molar fraction, and decreased with dose rate and temperature. The total amount of deposited polymer on the reactor wall, source case wall, and scraping blades was usually less than 1 kg, which was negligibly small for the analysis of polymerization. Continuous discharge of the polymer slurry and production of fine-powder polyethylene were successfully carried out. In the central source-type reactor, a dose rate of 1.9 × 10⁵ rads/hr was obtained with a ⁶⁰Co source of ca. 12 kCi.     

Preparation of block copolymers via metal‐free visible‐light‐induced ATRP for the detection of lead ions

Polyacrylamide‐b‐poly(methacrylic acid) was prepared on the surface of Au electrode (Au/PAM/PMAA) for Pb²⁺ ion electrochemical sensing via metal‐free visible‐light‐induced atom transfer radical polymerization, which was very simple, convenient, and environmentally friendly. Au/PAM/PMAA was carefully examined by cyclic voltammetry, electrochemical impedance spectroscopy, and X‐ray photoelectron spectroscopy. Further, Au/PAM/PMAA was successfully used for the determination of Pb²⁺ ion by differential pulse anodic stripping voltammetry. Under the optimal conditions, a linear response from 1.0 × 10^?11 to 1.0 × 10^?4 mol/L with detection limit of 2.5 × 10^?12 mol/L (S/N = 3) was achieved from the results of experiments. Comparing with similar Pb²⁺ sensors, the broader linear range and lower detection limit suggested the promising prospect of Au/PAM/PMAA. In a word, the work of this article had an important significance for the polymer‐modified electrodes and the sensitive detection of Pb²⁺. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45863.     

The H+/H2 equilibrium potential dependence on H2 partial pressure on gold electrodes

Equilibrium behavior for the H⁺/H₂ couple has been verified at gold electrodes from partial pressures of 1 to about 6 × 10^?4 atm. The study was conducted in a high-purity, tight, electrochemical system in which the P_o2 above the cell solution was ×<10^?9 atm. To assure reversible behavior, solution wetting inside the gold/glass seal had to be prevented. Techniques for preparing clean reversible Au electrodes, cell cleaning, gas purification and high-purity electrolyte preparation are described.     

Multi-purpose ionization gas sensing devices using carbon nanofibers on plastic substrates

The authors present the study of carbon-nanofiber-based (CNF) ionization gas sensing devices on plastic substrates. The device is configured as diode structure with a Cu plate and a CNF film as anode and cathode respectively. The lowest breakdown voltage for He, Ar, air, N₂, N₂O, O₂ and C₂H₂ is 215, 270, 400, 490, 540, 574 and 613 V with 5% of variations, respectively. For a fixed applied voltage of 600 V, the ionization current of the device exhibits two regions of linearity with respect to gas pressure below and above 5 Pa, suggesting that the device can be employed as vacuum ion gauge. If the CNF films were used for both cathode and anode, there is no significant different in term of breakdown voltage of air, however, the voltage fluctuation increased to about 10%. The gas ionization device is very robust even after more than 1 month of repeated operations and with no signs of degradation.     

Plasmonic organic bulk–heterojunction solar cells based on hydrophobic gold nanorod insertion into active layers

In this work, we fabricated plasmonic organic bulk–heterojunction solar cells by inserting hydrophobic gold nanorods (GNRs) into the active layers. Power conversion efficiency was improved from 7.43% to 8.22% because the plasmonic effect of GNRs improved the light harvesting efficiency. Maximum exciton generation rate was increased from 1.35 × 10⁻²⁶ to 1.51× 10⁻²⁶m⁻³ s⁻¹, and the electron mobility was also increased from 8.6 × 10⁻⁵ to 1.5× 10⁻⁴cm⁻² V⁻¹ s⁻¹. As a result, the short circuit current density was improved from 15.5 to 16.7 mA cm⁻²—the dominant reason for performance enhancement. The open circuit voltage and fill factor were improved simultaneously. The plasmonic device showed a highest PCE of 8.43%, indicating that doping GNRs into active layers is a simple and effective way to fabricate high‐performance organic solar cells. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45920.     

Magnetoresistance of boron-doped chemical vapor deposition polycrystalline diamond films

The electrical properties and magnetoresistance of boron-doped polycrystalline diamond films grown on p-typed Si (100) by hot filament chemical vapor deposition have been investigated. As the atomic boron concentration increases from 3×10¹⁷ to 3×10¹⁹ cm⁻³, and grain size from 5 to 15 μm, the quality of diamond is improved, which causes the carrier mobility μ and longitudinal magnetoresistance change rate Δρ_///ρ₀ to increase. For a magnetic field (B) of 20 tesla and temperature 300 K, the longitudinal resistance change rate Δρ_///ρ₀ is up to 20%. Meanwhile, Δρ_///ρ₀ is proportional to μ²B² in a low field and proportional to μ^1.5B in a high field. It is the first time that a result is obtained in a high field.     

A study on the reaction kinetics of HCl removal from high-temperature coal gas

A study on chloride removal from high-temperature coal gas shows that all the tested sorbents can rapidly react with HCl vapor and reduce the HCl vapor concentration to less than 1×10⁻⁶ in a fixed-bed reactor. The ECl1 sorbent lab-made has the highest chloride capacity. The experimental data obtained were analyzed by a model based on fixed-bed reactor and shrinking core models, It is found that reaction between sorbent and HCl vapor is of first-order with respect to initial HCl concentration. The reaction is governed by combination of the chemical reaction and product layer diffusion.     

Gold nanoparticle ensemble on polydopamine/graphene nanohybrid as a novel electrocatalyst for determination of baicalein

A facile and green approach is used to synthesize polydopamine (PDA) functionalized reduced graphene oxide (RGO) via the self‐polymerization of dopamine (DA) under alkaline conditions. The obtained reduced RGO/PDA composite facilitate Au precursor adsorption. Then Au nanoparticles are reduced and assemble onto the surface of RGO/PDA composite form reduced RGO/PDA/gold (RGO/PDA/Au) nanocatalysts. After that, a sensitive electrochemical sensor for baicalein is fabricated based on RGO/PDA/Au nanocatalysts. In this method, the hydroxyl units of PDA can form hydrogen bonding with the phenolic hydroxyl groups of baicalein, making baicalein easily adsorb on the modified electrode surface to enhance the electrochemical response. The electrochemical mechanism of baicalein on the RGO/PDA/Au nanocatalysts modified GCE is thoroughly investigated by cyclic voltammetry. The fabricated electrochemical sensor show good electrochemical activity for baicalein. The linear range of baicalein is 1 × 10^?8 to 15 × 10^?6 mol L^?1 with the detection limit of 3.1 × 10^?9 mol L^?1. Furthermore, the proposed electrochemical sensor can be used to detect real sample. The results reveal that this method provides a new avenue for electrochemical investigation of baicalein in biochemical, pharmaceutical, and clinical research. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 46720.     

Improving the fabrication uniformity of ZnO nanowire UV sensor by step-corner growth mode

Uniformity in mass-fabrication of nanostructured device is important for its practical application. In this paper, we developed a step-corner growth mode to on-chip fabricate uniform oblique-bridged ZnO nanowire UV sensor. By strictly controlling the microelectronic processing including photolithography and magnetron sputtering procedures during the seed layer deposition and electrode fabrication, ZnO NW array could nucleate at the upper step-corner of the seed layer due to the high catalytic activities at the surface steps and kinks, and then grow in a distribution of circular sector to form an oblique bridging configuration, which guaranteed the device performance and uniformity at the same time. For the within-chip uniformity, in a 4?×?4 sensor array that randomly chosen under the 365?nm UV light of 2.5?mW/cm² and at the bias voltage of 1?V, the light-to-dark current ratio all kept in the level of 10⁶ with the average value of 1.84?×?10⁶. There were 75% of them in the range of 1.1?×?10⁶ ~ 3?×?10⁶. The detectivity all kept in the level of 10¹⁵Jones with the average value of 3.53?×?10¹⁵Jones. There were 75% of them in the range of 2?×?10¹⁵ ~4?×?10¹⁵Jones. For the chip-to-chip uniformity, in 12 packaged devices that randomly chosen from three fabrication lots, the light-to-dark current ratio all kept in the level of 10⁶ with the average value of 2.70?×?10⁶. There were 75% of them in the range of 1?×?10⁶~ 3?×?10⁶. The detectivity all kept in the level of 10¹⁵Jones with average value of 3.69?×?10¹⁵Jones. There were 75% of them in the range of 1?×?10¹⁵ ~ 4?×?10¹⁵Jones. The uniformity would deteriorate if the step height of seed layer was short, because NW would nucleate at the lower corner of the step and difficult to form the oblique bridge. Fabrication uniformity was also influenced by the step exposure degree, the compactness of the seed layer and the flatness of the substrate.     

Fiber laser annealing of brush-painted ITO nanoparticles for use as transparent anode for organic solar cells

We report on a fiber laser annealing process for brush-painted ITO nanoparticles, for use as transparent anodes in cost-efficient printable organic solar cells (OSCs). By simple brushing of ITO nanoparticle ink onto glass substrates followed by direct fiber laser annealing, we fabricated solution-processed ITO anodes with a sheet resistance of 56.79 Ω/square and an optical transmittance of 85.77%. The electrical, optical, and structural properties of ITO nanoparticle electrodes were investigated as a function of laser scan speed under a nitrogen ambient. In addition, the detailed microstructure of the laser-annealed ITO electrode was examined to explain the conduction mechanism. OSCs fabricated on laser-annealed ITO electrodes exhibit an open circuit voltage of 0.59 V, short circuit current of 9.02 mA/cm², fill factor of 53.30%, and power conversion efficiency of 2.81%. Successful operation of those OSCs with laser-annealed ITO electrode indicates that fiber laser annealing is a simple and cost-effective option to replace conventional energy-intensive furnace-based annealing processes.     

Polydopamine modified Au/FAU catalytic membrane for CO preferential oxidation

A hollow-fiber-supported stable Au/FAU catalytic membrane was successfully synthesized through a polydopamine coating modification-removal strategy and used as a flow-through catalytic membrane reactor for preferential oxidation of CO. Small Au nanoparticles can be efficiently isolated by dopamine and the dopamine-derived carbon shells. The interactions between Au nanoparticles and zeolite layer support are enhanced during annealing at high temperature under an inert atmosphere. A zeolite membrane supported Au nanoparticle catalyst was obtained after the removal of carbon shells, which showed high catalytic activity and stability for the removal of CO from hydrogen.     

The role of kinetics in the design of plasma microreactors

Miniaturization of plasma reactors has the potential of low power operation. In general, the electric field strength in the gap between two electrodes increases proportionate to inverse of the gap width, so that it is possible to overcome the first ionization potential of the gas with a low voltage. However, plasmas are extinguished primarily by recombination at the walls. Wall collisions are enhanced by the greater surface area to volume ratio in microchannels, which also increases proportionate to the inverse of the gap width. If the plasma were well mixed, then the plasma creation in the bulk would be balanced by extinction at the wall, providing no particular advantage with regard to low voltage/low power operation. However, the plasma is transferred from the bulk to the wall by ambipolar diffusion. If the operation of the plasma microreactor is essentially transient or batch, whether or not the reaction kinetics are comparable to or faster than ambipolar diffusion determines if there is a regime of operation in which a low voltage plasma discharge can generate a high yield of product. In this paper, this question is investigated with regards to the ozone formation reaction and a particular design of a microchannel plasma reactor, with parameters so chosen to arguably achieve low voltage operation. The focus of this paper is the simulation of the kinetics of the plasma reactions leading to ozone formation, which shows a time to completion that is comparable (10^?2 s) or faster than the estimate of ambipolar diffusion time at these length scales. Preliminary results of a microchip reactor are consistent with this prediction.     

A new electrochemical biosensor for hydrogen peroxide using HRP/AgNPs/cysteamine/p-ABSA/GCE self-assembly modified electrode

An electrochemical hydrogen peroxide biosensor was designed by immobilizing horseradish peroxidase (HRP) on Ag nanoparticles/cysteamine/p-aminobenzene sulfonic acid/glassy carbon (GC) electrode. Ag nanoparticles can act as tiny conduction centers on electrodes that adsorb redox enzymes, facilitating the transfer of electrons with no requiring any loss of biological activity. The forerunner film was first electropolymerized on the glassy carbon electrode with p-aminobenzene sulfonic acid (p-ABSA) by cyclic voltammetry. The cysteamine (CA) was bound on the surface of the film by electrostatic force, then Ag nanoparticles were immobilized on the cysteamine monolayer, and lastly HRP was adsorbed onto the surfaces of the Ag nanoparticles. A dramatic decrease in the overvoltage of H₂O₂ was observed with improved sensitivity, which makes the modified electrodes of great promise for oxidase-based amperometric biosensors. The biosensor responded to H₂O₂ in the linear range from 1.2×10⁶ mol/L to 9.8×10³ mol/L with a detection limit of 1.1×10⁸ mol/L. Moreover, the obtained biosensor exhibited good accuracy and high sensitivity.