Correlation between wetting properties and electrical performance of solution processed PEDOT:PSS/CNT nano-composite thin films

Nano-composite thin films of poly(3,4-ethylenedioxythiophene) poly(styrene-sulfonate) (PEDOT:PSS) with different loading concentrations of multi-walled carbon nanotubes (MWCNT) were deposited on glass substrates using inkjet printing and spin coating techniques. The surface energy of the substrate was modified using an oxygen plasma to achieve different degrees of wetting by the composite solution. We show that the electrical properties strongly depend on the wetting of the substrate and by controlling the wettability, the conductivity of the nano-composite samples can be improved. Based on polymer conductivity, the electrical conductivity of the composite film can be improved or degraded by orders of magnitude with the incorporation of the same concentration of MWCNT. Moreover, electrical measurements show strong correlation between the conductivity of the carbon nanotube network and the resulting nano-composite films. The dependence of electrical properties on the wettability and the conductivity of the composite components could explain the diversity in the electrical behaviour reported in the literature for PEDOT:PSS/MWCNT nano-composite thin films.

Self‐Supported Cu3P Nanowire Arrays as an Integrated High‐Performance Three‐Dimensional Cathode for Generating Hydrogen from Water

Searching for inexpensive hydrogen evolution reaction (HER) electrocatalysts with high activity has attracted considerable research interest in the past years. Reported herein is the topotactic fabrication of self‐supported Cu₃P nanowire arrays on commercial porous copper foam (Cu₃P NW/CF) from its Cu(OH)₂ NW/CF precursor by a low‐temperature phosphidation reaction. Remarkably, as an integrated three‐dimensional hydrogen‐evolving cathode operating in acidic electrolytes, Cu₃P NW/CF maintains its activity for at least 25 hours and exhibits an onset overpotential of 62 mV, a Tafel slope of 67 mV dec^?1, and a Faradaic efficiency close to 100 %. Catalytic current density can approach 10 mA cm^?2 at an overpotential of 143 mV.     

Mg and Ni Incorporated ZnO Diluted Magnetic Semiconductor for Magnetic and Photo-Catalytic Applications

Zinc oxide is recently being used as a magnetic semiconductor with the introduction of magnetic elements. In this work, we report phase pure synthesis of Mg and Ni co-substituted ZnO to explore its structure, optical, magnetic and photo-catalytic properties. X-ray diffraction analysis reveals the hexagonal wurtzite type structure having P63mc space group without any impurity phase. UV-Vis spectrophotometry demonstrates the variation in bandgap with the addition of Mg and Ni content in ZnO matrix. Magnetic measurements exhibit a clear boosted magnetization in Ni and Mg co-doped compositions with its stable value of bandgap corroborating the structural stability and magnetic tuning for its advanced applications in modern-day spintronic devices. Photo-catalytic measurements performed using methyl green degradation demonstrate an enhanced trend of activity in Mg and Ni co-doped compositions.     

One-pot hydrothermal preparation of hierarchical manganese oxide nanorods for high-performance symmetric supercapacitors

An eco-friendly, new, and controllable approach for the preparation of manganese oxide(a-MnO₂) nanorods has been introduced using hydrothermal reaction for supercapacitor application. The in-depth crystal structure analysis of α-MnO₂ is analyzed by X-ray Rietveld refinement by using Full Prof program with the help of pseudo-Voigt profile function. The developed a-MnO₂ electrode attains a remarkable capacitance of 577.7 F/g recorded at a current density value of 1...     

Extremely cold antiprotons for antihydrogen production

The possibility to produce, trap and study antihydrogen atoms rests upon the recent availability of extremely cold antiprotons in a Penning trap. Over the last five years, our TRAP Collaboration has slowed, cooled and stored antiprotons at energies 10¹⁰ lower than was previously possible. The storage time exceeds 3.4 months despite the extremely low energy, which corresponds to 4.2 K in temperature units. The first example of measurements which become possible with extremely cold antiprotons is a comparison of the antiproton inertial masses which shows they are the same to a fractional accuracy of 4×10⁻⁸. (This is 1000 times more accurate than previous comparisons and large additional increases in accuracy are anticipated.) To increase the number of trapped antiprotons available for antihydrogen production, we have demonstrated that we can accumulate or “stack” antiprotons cooled from successive pulsed injections into our trap.     

Simulated mixed absorbers and effective atomic numbers for γ attenuation

The total γ-ray interaction cross-sections on mixed absorbers were determined at 662 keV with a view to study the effective atomic numbers for γ-ray absorption under narrow beam good geometry set-up. The measurements were taken for the combination of metallic absorbers like aluminium, copper, lead and mercury and also for the simulated absorbers by rotating the targets. ORTEC HPGe and NaI(Tl) detectors were used for detection of γ-rays. The experimental results compare favourably with theoretical values derived from XCOM package and suggest the usefulness of the concept of effective atomic numbers and the utility of the rotating absorbers technique.     

Polarization and spatial-mode behavior of short-wavelength VCSELs

We have investigated the packaging introduced feedback and resulting variations in the characteristics of Vertical-cavity surface-emitting lasers (VCSELs). An integrated test and characterization method was developed for both the packaged and bare dies as well as on-wafers chips. Using an ‘integrated test bench (ITB)’ for characterization, packaged and ‘un-packaged’ VCSELs from multiple sources were studied. ITB was used to monitor and measure simultaneously several beam-parameters under various bias conditions including both dc and high-speed pulsed pumping at room-temperature, or at higher-/lower-temperatures that are thermo-electrically controlled. Typical beam parameters included state of polarization (SOP), transverse (spatial) modes, wavelength spectra, and output power. A common observation was that majority of devices are affected by the presence of optical windows capping the package. A shift in longitudinal mode was noticeable in packaged versus ‘un-packaged’ (window-removed) devices. But, SOP and transverse modes in various devices are affected severely and in an unpredictable fashion.     

Spin quenching of Mn in complexes and CO binding with Mn deposited on MgO and CaO supports: DFT calculations

An attempt has been made to analyze the spin quenching properties of Mn, as a representative of transition metals, in Mn·MgO, Mn·CaO, OC·Mn·MgO, and OC·Mn·CaO complexes formed at the regular (001) surfaces of MgO and CaO, as well as the adsorption of CO on Mn deposited on MgO and CaO by means of hybrid density functional theory calculations and embedded cluster model. Clusters of moderate sizes were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. A test has been made to examine the effect of artificial flow of charge. While the spin states of Mn in Mn·MgO and Mn·CaO complexes are preserved, the combined effects of adsorbate and substrate in OC·Mn·MgO and OC·Mn·CaO complexes are strong enough to favor the low spin states and to quench the spin. The deposited Mn atoms enhance the adsorption of CO on MgO and CaO surfaces. The significant weakening of bond strength between OC and Mn in complexes supports the concept of bond order conservation. The relation between the strength of CO adsorption and the basicity of the support is verified. The natural bond orbital analysis reveals that the electronic structure of the adsorbed metal represents a qualitative change with respect to that of the free metal. The effects of spin contamination on the geometry, Mulliken charges, and adsorption energy are examined. The binding of CO precursor is dominated by the E(i)^Mn···CO pairwise additive components in MgO and CaO complexs, and the role of the support is not restricted to supporting the metal. The adsorbed CO molecules exhibit no remarkable deviation from linearity. Finally, relations are established between the process of spin quenching and the energy gaps between frontier orbitals. The results show that the spin state of adsorbed metal atoms on oxide supports and the role of precursor molecules on the magnetic and binding properties of complexes need to be explicitly taken into account. © 2012 Wiley Periodicals, Inc.     

A glutathione biosensor based on a glassy carbon electrode modified with CdO nanoparticle-decorated carbon nanotubes in a nafion matrix

A nanocomposite consisting of cadmium oxide decorated with carbon nanotubes (CdO.CNT NC) was prepared by a wet-chemical technique, and its optical, morphological, and structural properties were characterized by FTIR, UV/Vis, FESEM coupled to XEDS, XPS, and XRD methods. A flat glassy carbon electrode was modified with the nanocomposite to obtain a sensor for L-glutathione (GSH) which displays improved sensitivity, a large dynamic range and good long-term stability. The calibration plot (best acquired at a voltage of 0.5 V) is linear (r ² = 0.99) in the 0.1 nM to 0.01 M GSH concentration range. The detection limit is as low as 30.0 pM, and the sensitivity is ~9.49 μA?μM^?1?cm^?2. To the best of our knowledge, this is the first report on the determination of GSH using such a modified glassy carbon electrode (GCE) in combination with I-V method. The GCE was applied to the selective determination of GSH in spiked rabbit serum samples and gave acceptable results.

Open image in new window

Graphical abstract A selective glutathione biosensor based on wet-chemically prepared CdO.CNT/Nafion/GCE was fabricated by reliable I-V method and shows good analytical parameters such as high sensitivity, low detection limit, long-term stability, and large dynamic range.