Communication: Evidence of hydrated electrons injected by a metallic electrode in a high voltage system

In this work it a strong evidence of the hydrated electrons production was shown in a film of condensed water, by directing the injection of electrons in localized and/or delocalized water electronic states using a system of high voltage made in laboratory. The results show that the water layers on the silica particles are electrically charged by injection of electrons from a metal electrode when silica is placed in high electric field. This charging process also appears to depend on the thickness of these water layers and of the spatial arrangement required by the silica surface.     

Preparation of chitosan microspheres by ionotropic gelation under a high voltage electrostatic field for protein delivery

Biodegradable microspheres have been widely used in drug/protein delivery system. In this paper, a modified ionotropic gelation method combined with a high voltage electrostatic field was developed to prepare protein-loaded chitosan microspheres. Bovine serum albumin (BSA) was chosen as a model protein. The preparation process and major parameters were discussed and optimized. The morphology, particle size, encapsulation efficiency and in vitro release behavior of the prepared microspheres were investigated. The results revealed that the microspheres exhibited good sphericity and dispersity when the mixture of sodium tripolyphosphate (TPP) and ethanol was applied as coagulation solution. Higher encapsulation efficiency (>90%) was achieved for the weight ratio of BSA to chitosan below 5%. 35% of BSA was released from the microspheres cured in 3% coagulation solution, and more than 50% of BSA was released from the microspheres cured in 1% coagulation solution at pH 8.8. However, only 15% of BSA was released from the microspheres cured in 1% coagulation solution at pH 4. The results suggested that ionotropic gelation method combined with a high voltage electrostatic field will be an effective method for fabricating chitosan microspheres for sustained delivery of protein.     

Quinoidal oligoquinoline: a novel quinodimethane exhibiting high electroluminescence efficiency and p-channel field effect charge transport

A novel tetraphenylquinodimethane based on electron-deficient 4-phenylquinoline oligomer displayed an unusually low ionization potential and was used as a p-channel semiconductor in thin-film transistors and as an emitter to achieve very bright and high efficiency green light-emitting diodes.     

Electrostatic potentials,fields and field gradients from a general crystalline charge density

Explicit expressions for the electrostatic potential, the electric field and the electric field gradient at the nuclear positions of a crystalline lattice are presented. They are derived for a charge density given as an expansion in terms of spherical harmonics around the nuclear sites and as a Fourier series in the interstitial. These expressions can be decomposed into contributions from the spherical region centered around the lattice site of interest, from spherical regions surrounding all the other lattice sites and a contribution from the interstitital region.     

Copper uptake by silica and iron oxide under high surface coverage conditions: surface charge and sorption equilibrium modeling

A sorption modeling approach based on surface complexation concepts was applied to predict copper uptake and its effects on the surface electrostatic potential of ferric oxide and silica colloids. Equilibrium modeling of copper uptake by ferric oxide using the traditional surface complexation model (SCM) was reasonably successful with some discrepancies especially in the acidic pH ranges and high colloid concentration cases. Good predictions of the ferric oxide charge reversals during uptake were obtained from the modeling. Based on the SCM predictions, copper removal from solution is due to the outer-sphere complexation of the first hydrolysis product, resulting in the surface-metal complex SO(-)CuOH(+). The SCM was found to be insufficient to describe copper uptake by silica particles. To address discrepancies between experimental data and SCM predictions, the SCM was modified to include attributes of the surface polymer model (SPM), which incorporates sorption of the dimeric copper species Cu(2)(OH)(2)(2+). The continuum model (CM) was also studied as a second modification to the SCM to include formation of surface precipitates. Both the SPM and the CM were successful in modeling copper uptake and zeta potential variations as a function of pH at various solution conditions and colloid concentrations. From the SPM and CM predictions, it was concluded that for systems with high surface loadings, copper removal from solution occurs due to the formation of both monomeric and dimeric surface complexes, as well as through precipitation mechanisms.     

Molecular wiring of insulators: charging and discharging electrode materials for high-energy lithium-ion batteries by molecular charge transport layers

Self-assembled monolayers (SAMs) of redox-active molecules on mesoscopic substrates exhibit two-dimensional conductivity if their surface coverage exceeds the percolation threshold. Here, we show for the first time that such molecular charge transport layers can be employed to electrochemically address insulating battery materials. The widely used olivine-structured LiFePO4 was derivatized with a monolayer of 4-[bis(4-methoxyphenyl)amino]benzylphosphonic acid (BMABP) in this study. Fast cross-surface hole percolation was coupled to interfacial charge injection, affording charging and discharging of the cathode material. These findings offer the prospect to greatly reduce the amount of conductive carbon additives necessary to electrochemically address present metal phosphate cathode materials, opening up the possibility for a much improved energy storage density. When compared at equal loading, the rate capability is also enhanced with respect to conventional carbon-based conductive additives.     

Single nucleotide polymorphism analysis by chip-based hybridization and direct current electrical detection of gold-labeled DNA

Single nucleotide polymorphism (SNP) analysis at the point of care requires a low cost detection technology that is capable of miniaturization, multiplexing, and high sensitivity. Direct current electrical detection (DCED) of DNA following nanoparticle labeling and silver enhancement is a promising candidate technology for point-of-care diagnostics. In this work we present, for the first time, SNP analysis in PCR products from patient samples using DCED, taking this platform technology a step closer to practical application. We developed a silane functionalized polymer for coating of biochip surfaces. This polymeric coating is stable under harsh conditions and has exceptionally high binding capacity. Allele-specific oligonucleotide probes were immobilized on chips coated with this polymer. Biotinylated PCR products of the human cholesteryl ester transfer protein gene from different patients were hybridized to the chips, labeled with gold nanoparticles, and autometallographically enhanced. The chips were scanned for DC electrical resistance by applying movable electrodes to the surface. Eighteen of nineteen patient samples were assigned the correct genotype. Our results demonstrate that SNP analysis of patient samples is feasible with DCED.     

Drop-to-drop microextraction across a supported liquid membrane by an electrical field under stagnant conditions

Electromembrane extraction (EME) of basic drugs from 10 μL sample volumes was performed through an organic solvent (2-nitrophenyl octyl ether) immobilized as a supported liquid membrane (SLM) in the pores of a flat polypropylene membrane (25 μm thickness), and into 10 μL 10 mM HCl as the acceptor solution. The driving force for the extractions was 3–20 V d.c. potential sustained over the SLM. The influence of the membrane thickness, extraction time, and voltage was investigated, and a theory for the extraction kinetics is proposed. Pethidine, nortriptyline, methadone, haloperidol, and loperamide were extracted from pure water samples with recoveries ranging between 33% and 47% after only 5 min of operation under totally stagnant conditions. The extraction system was compatible with human urine and plasma samples and provided very efficient sample pretreatment, as acidic, neutral, and polar substances with no distribution into the organic SLM were not extracted across the membrane. Evaluation was performed for human urine, providing linearity in the range 1–20 μg/mL, and repeatability (RSD) in average within 12%.     

Electric response properties of a confined gas of independent particles acted upon by a direct current electric field

Exact results for linear and nonlinear electric response properties of a non-interacting ensemble of charged particles, confined within an impenetrable box and subjected to a static, homogeneous electric field, are derived and discussed. Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 5 June 2000     

Differences in the electrorheological response of a particle suspension under direct current and alternating current electric fields

We have observed an unusual reduction of shear stress with increasing shear rate under direct current electric fields, for an electrorheological fluid composed of sulfonated poly(styrene-co-divinylbenzene) particles dispersed in silicone oil. At all shear rates, the shear stress under the electric field is larger than that in the absence of the field, indicating that there is still some field-induced agglomeration of the particles. In contrast, the behavior under alternating current electric fields is the Bingham-fluid-type response commonly observed with electrorheological fluids. It is suggested that the conventional dipole–dipole interaction approach based on simplified microstructural models would be unable to explain these phenomena. Received: 27 November 2000 Accepted: 22 May 2001     

Determining the radius and the apparent charge of a micelle from electrical conductivity measurements by using a transport theory: explicit equations for practical use

We propose here a procedure which combines experiments and simple analytical formulas that allows us to determine good estimations of the size and charge of ionic micelles above the critical micellar concentration (cmc). First, the conductivity of n-tetradecyltrimethylammonium bromide and chloride (TTABr and TTACl, respectively) aqueous solutions was measured at 25 degrees C, before and above their cmc. Then, an analytical expression for the concentration dependence of the conductance of an ionic mixture with three species (monomers, micelles, and counterions) was developed and applied to the analysis of the experiments. The theoretical calculations use the mean spherical approximation (MSA) to describe equilibrium properties. Here, we propose new expressions for the electrical conductivity, adapted to the case of electrolytes that are dissymmetric in size, and applicable up to a total surfactant concentration of 0.1 mol L(-1). Moreover, we show that they are good approximations of the corresponding numerical results obtained from Brownian dynamics simulations. Since the analytical formulas given in the present paper involve a small number of unknown parameters, they allow one to derive the size and charge of macroions in solution from conductivity measurements.     

Polymer electrolyte-gated organic field-effect transistors: low-voltage, high-current switches for organic electronics and testbeds for probing electrical transport at high charge carrier density

We report the fabrication and extensive characterization of solid polymer electrolyte-gated organic field-effect transistors (PEG-FETs) in which a polyethylene oxide (PEO) film containing a dissolved Li salt is used to modulate the hole conductivity of a polymer semiconductor. The large capacitance (approximately 10 microF/cm2) of the solution-processed polymer electrolyte gate dielectric facilitates polymer semiconductor conductivities on the order of 103 S/cm at low gate voltages (<3 V). In PEG-FETs based on regioregular poly(3-hexylthiophene), gate-induced hole densities were 2 x 10(14) charges/cm2 with mobilities >3 cm2/V.s. PEG-FETs fabricated with gate electrodes either aligned or intentionally nonaligned to the channel exhibited dramatically different electrical behavior when tested in vacuum or in air. Large differences in ionic diffusivity can explain the dominance of either electrostatic charging (in vacuum) or bulk electrochemical doping (in air) as the device operational mechanism. The use of a larger anion in the polymer electrolyte, bis(trifluoromethanesulfonyl)imide (TFSI-), yielded transistors that showed clear current saturation and square law behavior in the output characteristics, which also points to electrostatic (field-effect) charging. In addition, negative transconductances were observed using the PEO/LiTFSI electrolyte for all three polymer semiconductors at gate voltages larger than -3 V. Bias stress measurements performed with PEO/LiTFSI-gated bottom contact PEG-FETs showed that polymer semiconductors can sustain high ON currents for greater than 10 min without large losses in conductance. Collectively, the results indicate that PEG-FETs may serve as useful devices for high-current/low-voltage applications and as testbeds for probing electrical transport in polymer semiconductors at high charge density.     

The electrical double layer charge and associated dimensional changes of high surface area electrodes as detected by more deflectometry

Due to the high surface to volume ratio, the interfacial tension of porous solids affects their outer dimensions by a minute, but detectable amount. Changes in the interfacial tension of a high surface area graphite electrode could be monitored adopting the moire deflectometry, a new optical technique for ray deflection mapping, by which the resolution in relative length changes of th e electrode was less than 1 microstrain.The strain vs. potential curves are typically pseudo-parabolic. Within the double layer potential range, their slope is a linear function of the electronic charge delivered to the electrode. Unlike the double layer charge, faradaic currents are not recognized as a strain change of the electrode, thus the method may serve to distinguish between faradaic and double layer processes. Hysteresis takes place in curves of charge or strain vs. electrode potential, but not for charge vs. strain curves. The minimum in the strain-potential plot, attributed to the potential of zero charge occurs at about –350 mV vs. SCE, corresponding to a surface group free carbon (or graphite) electrode.     

Large-scale cubic InN nanocrystals by a combined solution- and vapor-phase method under silica confinement

Large-scale cubic InN nanocrystals were synthesized by a combined solution- and vapor-phase method under silica confinement. Nearly monodisperse cubic InN nanocrystals with uniform spherical shape were dispersed stably in various organic solvents after removal of the silica shells. The average size of InN nanocrystals is 5.7 ± 0.6 nm. Powder X-ray diffraction results indicate that the InN nanocrystals are of high crystallinity with a cubic phase. X-ray photoelectron spectroscopy and energy-dispersive spectroscopy confirm that the nanocrystals are composed of In and N elements. The InN nanocrystals exhibit infrared photoluminescence at room temperature, with a peak energy of ~0.62 eV, which is smaller than that of high-quality wurtzite InN (~0.65-0.7 eV) and is in agreement with theoretical calculations. The small emission peak energy of InN nanocrystals, as compared to other low-cost solution or vapor methods, reveals the superior crystalline quality of our samples, with low or negligible defect density. This work will significantly promote InN-based applications in IR optoelectronic device and biology.     

Study of human blood under influence of magnetic field by AC dielectric and thermally stimulated discharge current methods

Journal of Thermal Analysis and Calorimetry - The aim of the present work is to study the effect of magnetic field on thermally stimulated discharge current (TSDC) characteristics and dielectric...     

Charge carrier transport in high purity perylene single crystal studied by time-of-flight measurements and through field effect transistor characteristics

Electronic transport has been studied by measuring the characteristics of field effect transistors using high purity perylene and the results have been compared with those from time-of-flight measurements. The purity of the material has been monitored by carrier trapping time and delayed fluorescence lifetime. Three types of field effect transistors have been studied: (1) thin film transistor, (2) transistor prepared by placing a single crystal flake on a substrate and (3) transistor fabricated on a single crystal by depositing electrodes and insulating layer onto it. Compared to thin film transistors prepared by evaporating perylene onto a SiO₂/Si substrate, higher mobility values were obtained with transistors using single crystals, but the electrical characteristics of the transistors were far from ideal: large threshold gate voltage observed in the second class of FETs indicated that a high density of traps are present at the interface between the organics and the insulator. A transistor of the third class showed that it functioned indeed as a FET with a reasonably high mobility, but the operation was not stable enough to allow reliable measurements. Much remains to be improved in the design and construction of a perylene FET before the potentiality of the material is fully developed. Also, it remains to be explored to what extent the bulk purity and the molecular order at the organics/insulator interface influence the transport of the charge carriers in an organic FET.     

Gene transfer and protein release of fission yeast by application of a high voltage electric pulse

A high voltage electric pulse can be applied to induce the uptake of DNA into cells and the release of protein from cells. In transformation procedures, electroporation is widely used since the technique is simple, rapid, reproducible, and highly efficient. In extraction of protein, on the other hand, electroextraction has many advantages over other conventional extractions. We have developed a highly efficient method for the electroporation of fission yeast. In particular, application of a high voltage electric pulse to fission yeast improves the cellular uptake and release of macromolecules controlled by both osmotic conditions and electric field strength.

Proton sponge-functionalized silica as high performance adsorbents for solid-phase extraction of trace perfluoroalkyl sulfonates in the environmental water samples and their direct analysis by MALDI-TOF-MS

1,8-Bis(dimethylamino)naphthalene (DMAN), a classical 'proton sponge', was functionalized on silica particles as a novel solid-phase extraction (SPE) adsorbent (DMAN@silica) for extracting perfluoroalkyl sulfonates (PFSs). High reproducibility and excellent extraction capability for PFSs were obtained in a wide pH range (3.0~8.5). The adsorbed PFSs on DMAN@silica sorbents could be efficiently eluted by 1,8-bis(tetramethylguanidino)naphthalene (TMGN) solution which is a proton sponge with higher proton affinity than DMAN. The elution could be directly analyzed by MALDI-TOF-MS using TMGN as matrix. Clear mass spectra for the PFSs were obtained due to no matrix ions interference observed. Furthermore, a novel strategy based on the DMAN@silica-SPE enrichment, followed by MALDI-TOF-MS analysis, was proposed and applied for PFSs quantification in environmental water samples. The calibration curves of each of the target analytes showed a wide linear dynamic range of response (0.1-10 ng L(-1) for perfluorooctane sulfonate (PFOS), perfluorohexyl sulfonate (PFHxS) and perfluorobutylsulfonate (PFBS)), which were over 2 orders of magnitude. The detection limits for PFOS, PFHxS, and PFBS were 0.021, 0.016, and 0.013 ng L(-1), respectively (S/N = 3). Recoveries of PFOS, PFHxS, and PFBS are in the ranges of 92-104%, 95-102%, and 98-109% for spiked river water samples. These results indicated that the prepared DMAN@silica adsorbents could efficiently enrich PFSs and that the proposed method is reliable.     

Synthesis and field emission properties of carbon nanotube films modified with amorphous carbon nanoparticles by a simple electrodeposition method

Amorphous carbon nanoparticles （a-CNPs） on a multi-walled carbon nanotube （MWCNT） film, deposited on a silicon substrate, were synthesized using an electrodeposition combination from a methanol suspension of polydiallyldimethylammonium chloride-modified MWCNTs. A low-voltage electropho- retic deposition of the MWCNTs and a high-voltage electrochemical deposition of the a-CNPs were carried out to yield homogenously attached a-CNPs on the surfaces of the MWCNTs, and form a composite film with good adhesion to the substrate. This scalable technology can produce a large area of a-CNP/MWCNT film. And the field emission investigations show that the a-CNP/MWCNT film has turn- on electric field of 3.17 V μm- 1 （at 10 μA cm-2） and threshold field of 4.62 V μm-1 （at 1 mA cm-2）, which are lower than those of the MWCNT film. The a-CNP/MWCNT film can be deposited simply with large areas and may be a promising cathode material applied in field emission displays.     

Surface chemistry of PVD (Cr,Al)N coatings deposited by means of direct current and high power pulsed magnetron sputtering

(Cr,Al)N protective coatings were deposited using direct current (DC) and high power pulse magnetron sputtering (HPPMS) technology. The chemical analysis of the surface near region of the coatings was performed by means of X‐ray photoelectron spectroscopy (XPS) and was correlated to the deposition parameters and resulting coating morphology. A surface oxidation process was observed by means of angle resolved XPS studies and XPS sputter profiles. Both DC and HPPMS coatings showed a non‐stoichiometric chemical composition with a significant excess of cations (chromium and aluminum) in the bulk structure, leading to a metastable phase. The passivation reaction of the surface near region leads to an anion to metal ratio which goes along with an enrichment of aluminum in the surface near region as a thermodynamically favored composition in equilibrium with the ambient atmosphere. Interestingly, the variation of the pulse duration of the HPPMS process, which led to a change of the peak current, had a strong influence on the resulting composition of the surface near region. Copyright © 2013 John Wiley & Sons, Ltd.