Electrochemical Potential Difference Research Articles

Gate Tunable Hole Charge Qubit Formed in a Ge/Si Nanowire Double Quantum Dot Coupled to Microwave Photons.

A controllable and coherent light-matter interface is an essential element for a scalable quantum information processor. Strong coupling to an on-chip cavity has been accomplished in various electron quantum dot systems, but rarely explored in the hole systems. Here we demonstrate a hybrid architecture comprising a microwave transmission line resonator controllably coupled to a hole charge qubit formed in a Ge/Si core/shell nanowire (NW), which is a natural one-dimensional hole gas with a strong spin-orbit interaction (SOI) and lack of nuclear spin scattering, potentially enabling fast spin manipulation by electric manners and long coherence times. The charge qubit is established in a double quantum dot defined by local electrical gates. Qubit transition energy can be independently tuned by the electrochemical potential difference and the tunnel coupling between the adjacent dots, opening transverse (σ x) and longitudinal (σ z) degrees of freedom for qubit operation and interaction. As the qubit energy is swept across the photon level, the coupling with resonator is thus switched on and off, as detected by resonator transmission spectroscopy. The observed resonance dynamics is replicated by a complete quantum numerical simulation considering an efficient charge dipole-photon coupling with a strength up to 2π × 55 MHz, yielding an estimation of the spin-resonator coupling rate through SOI to be about 10 MHz. The results inspire the future researches on the coherent hole-photon interaction in Ge/Si nanowires.

Effect of Zr on Structure and Resistance to Intergranular Corrosion of Severely Deformed 2024 Aluminum Alloy

Effects of severe plastic deformation by isothermal сryorolling with a strain of e~2 and subsequent natural and artificial aging on the structure and resistance to intergranular corrosion (IGC) of the preliminary quenched 2024 aluminum alloy of standard and Zr modified compositions were investigated. Increasing the temperature of aging leads to decreasing the alloy IGC resistance due to precipitation of more stable strengthening S-phase (Al2CuMg), rising difference of electrochemical potentials at grain and subgrain boundaries. Zr additions, оn the opposite, significantly increased the alloy IGC resistance in both naturally and artificially aged conditions, reducing its depth and intensity. The main structural factor, influencing the alloy corrosion behavior, is excess phases: their composition, volume fraction and distribution.

SLC Family Transporters.

Solute carrier (SLC) family transporters utilize an electrochemical potential difference or an ion gradient generated by primary active transporters for transporting their substrates across biological membranes. These transporters are categorized as facilitated transporters or secondary active transporters. More than 300 SLC transporters have been identified. SLC transporters related to drug transport mainly include SLC21 gene subfamily (organic anion-transporting polypeptides, OATPs), SLC22A gene subfamily (organic anion transporters, OATs; organic cation transporters, OCTs; or organic cation/carnitine transporters, OCTNs), SLC15A gene subfamily (peptide transporters, PEPTs), and SLC47A gene subfamily (multidrug and toxin extrusion, MATEs). In general, OCTs transport organic cations, OATPs transport large and fairly hydrophobic organic anions, OATs transport the smaller and more hydrophilic organic anions, and PEPTs are responsible for the uptake of di-/tripeptides and peptide-like drugs. MATEs are responsible for efflux of organic cations. These transporters also transport some endogenous substances, indicating that the dysfunction of SLCs not only disrupts homeostasis but also largely impacts on the disposition of their substrate drugs. This chapter will discuss these SLC family transporters, with an emphasis on tissue distribution, substrate specificity, transporter physiology, and clinical significance.

Presentation and Verification of an Electrolytic Etching Technique for the Determination of prior Austenite Grain Boundaries in the Steel PH15-5

AbstractIn the field of hot working, modelling of austenite grain size makes a significant contribution to the prediction of future material properties. One of the difficulties when it comes to modelling is the detection of grain sizes at different recrystallization stages by means of etching methods. Especially with high-purity steels with a martensitic structure, imaging of prior austenite grain boundaries without simultaneous highlighting of lath martensite boundaries, is, in many cases, only possible to some extent when using etching technology. Due to small electrochemical potential differences, increased purity of the alloy causes a more uniform etching attack on grain and lath boundaries and thus leads to a poorer discrimination. An alternative technique for grain size determination is Electron Backscatter Diffraction (EBSD). However, this technique maps only a relatively small area of the sample and is also significantly more expensive than the combination of electrolytic etching and light microscopic analysis.Therefore, this work will present a novel electrolytic etching technique for light microscopic imaging of prior austenite grain boundaries in high-purity and corrosion-resistant grades of precipitation hardening steels. For this purpose, a series of tests was carried out on the alloy PH15-5 and the results were verified by correlative EBSD measurements.

Construction begins on Fukushima Hydrogen Energy Research Field

Since the scientific cause for a series of hydrogen explosions during the Fukushima accident has not been established, the author investigated his basic theory named “radiation-induced electrolysis (RIE)” by applying the estimation of the amounts of H2 generation during the active phase of the Fukushima accident. The author's theory was originally developed by including Faraday's law of electrolysis into the basic time-dependent material balance equation of radiation-chemical species for his study on accelerated corrosion phenomena which is widely observed in aged plants. As such this theory applies to the early phase of the accident before the loss of water levels in the reactor cores, although the simulations were performed from the time of seismic reactor trip to the hydrogen explosions in this paper.Through this mechanism as much as 29,400 m3-STP of hydrogen gas is estimated to be accumulated inside the PCV just prior to the hydrogen explosion which occurred one day after the reactor trip in 1F1. With this large volume of hydrogen gas the explosion was a viable possibility upon the “venting” operation. In view of this observation, hydrogen generation from the spent fuel pools was also investigated.For the investigation of the 1F4 SFP, the pool water temperature and flow velocity due to natural circulation were changed widely to identify conditions of large hydrogen generation. During the trial calculations it was discovered that SBO induced a rapid initiation of electrolysis when the pool water temperature surpassed 40 °C with a range of low water flow velocity through the spent fuels.With a mix of different levels of radioactivity of spent fuel, a difference in the absorbed dose rate of water through γ-decay heat should have existed. This configuration induced an electrochemical potential difference between the highly radioactive region where there was spent fuel stored by evacuating the core and less radioactive fuels stored for several years. The spent fuel was stored in racks placed at the bottom of the pool where the wall was covered with a stainless steel lining. The metallic contacts enabled electric conduction between the highly radioactive fuel assemblies and the cooled spent fuel.

Increased yield of MoS2 monolayer exfoliation through the bimetallic corrosion of aluminum

In this paper, we propose a corrosion assisted exfoliation method as an improvement to the traditional tape exfoliation to obtain transition-metal dichalcogenide monolayers. Our method primarily relies on the electrochemical potential difference between transition metals and aluminum. The assistance of bubbles resulting from the bimetallic corrosion increases the yield of the exfoliation process for monolayers by 30-fold while boosting the probability of obtaining isolated monolayers. We use Raman measurements and a statistical comparison of the improved method with tape exfoliation to lay the evidence for our findings.

Discovery, Mechanism, and Application of Antigalvanic Reaction.

Among many outstanding findings associated with the quantum size effect, one of the most exciting is the discovery of the antigalvanic reaction (AGR), which is the opposite of the classic galvanic reaction (GR) that has a history of nearly 240 years. The GR, named after Italian scientist Luigi Galvani, involves the spontaneous reduction of a noble-metal cation by a less noble metal in solution driven by the difference in electrochemical potentials. Classic galvanic reduction has been widely applied and has recently received particular interest in nanoscience and nanotechnology. However, the opposite of GR, that is, reduction of metal ions by less reactive (or more noble) metals, has long been regarded as a virtual impossibility until the recent surprising findings regarding atomically precise ultrasmall metal nanoparticles (nanoclusters), which bridge the gap between metal atoms (complexes) and metal nanocrystals and provide opportunities for novel scientific findings due to their well-defined compositions and structures. The AGR is significant not only because it is the opposite of the classic galvanic theory but also because it opens extensive applications in a large range of fields, such as sensing and tuning the compositions, structures, and properties of nanostructures that are otherwise difficult to obtain. Starting with the proposal of the general AGR concept in 2012 by Wu, a new era began, in which AGR received widespread attention and was extensively studied. After years of effort, great advances have been achieved in the research on AGR, which will be reviewed below. In this Account, we first provide a short introduction to the AGR concept and then discuss the driving force of the AGR together with the effecting factors, including the ligand, particle size, solvent, metal ion precursor, and ion dose. Subsequently, the application of the AGR in engineering atomically precise alloy (bimetallic and trimetallic) and monometallic nanoclusters is described, and tuning the properties of the parent nanoclusters is also included. In particular, four alloying modes (namely, (i) addition, (ii) replacement, (iii) replacement and structural transformation, and (iv) nonreplacement and structural transformation) associated with the AGR are discussed. After that, the applications of the AGR in metal ion sensing and antioxidation are reviewed. Finally, future prospects are discussed, and some challenging issues are presented at the end of this Account. It is expected that this Account will stimulate more scientific and technological interests in the AGR, and exciting progress in the understanding and application of the AGR will be made in the coming years.

Mg-Mg2X (X=Cu, Sn) eutectic alloy for the Mg2X nano-lamellar compounds to catalyze hydrolysis reaction for H2 generation and the recycling of pure X metals from the reaction wastes

The hydrogen generating characteristics of typical Mg-Mg2X (Cu, Sn) eutectic alloys in the hydrolysis of seawater were investigated. Cu and Sn are cheaper than Nd, Ni, Co, and rare earth elements, and these were used as catalysts in the rapid (30 min) formation of Mg-Mg2X (Cu, Sn) eutectic alloy in an induction furnace. Hydrogen was evolved in 3.5 wt % NaCl solution (to mimic seawater). Both bulk Mg-Mg2Cu and Mg-Mg2Sn eutectic alloys reacted until the Mg ran out. This typical process involves the unique eutectic lamellar structure of multi-layered Mg2X (as the cathode) stock with Mg (as the anode). This eutectic structure creates numerous nano galvanic-cells in the alloy matrix that accelerates the hydrolysis reaction. The better hydrogen evolution performance was achieved using Mg-Mg2Cu eutectic alloy because it has the highest electrochemical potential difference (Mg vs. Mg2Cu:0.32 V > Mg vs. Mg2Sn:0.17 V). The by-product of hydrolysis was not wasted: an extraction method for recycling the valuable metals (Cu and Sn) at room temperature was developed.

Thermodynamic and Structural Study of the Copper-Aluminum System by the Electrochemical Method Using a Copper-Selective Beta″ Alumina Membrane

The liquid phase thermodynamics of mixing of the copper-aluminum binary system are investigated as a function of temperature and composition using the electrochemical potential difference method. A copper-selective beta″ alumina is used as a solid electrolyte, synthesized through ion exchange, sintering from base oxide powders, and the floating zone method of crystal growth. Measured thermodynamics of mixing data were used to inform short-range ordering in copper-aluminum melts through Darken’s factor for excess stability and Bhatia–Thornton structure factors, revealing a strong departure from ideality and pronounced ordering. Mixing properties were used to predict viscosity and self-diffusion coefficients. Features observed in calculated electronic entropy of mixing for copper-aluminum were compared with trends in viscosity, demonstrating the utility of electronic properties of mixing in the description of structure–properties in this liquid binary system.

Effect of acid–base reaction on the electrophoretic deposition of hydroxyapatite nanostructured coatings in isopropanol

Triethanolamine (TEA) was added along with acetic acid (AA) to enhance the stability of hydroxyapatite (HA) nanoparticles in isopropanol. H+TEA ions generated by AA and TEA reaction were adsorbed on particles and increased their zeta potential. Zeta potential increased to the maximum value at optimum concentration of AA (AA*) and then decreased with its further addition. Kinetics of EPD increased with AA addition into the TEA containing suspensions. Detachment of particles from deposits into the suspensions was the fastest at AA* due to the highest electrochemical potential difference at the interface. Sticking parameter (f factor) was the minimum at AA*. Corrosion rate of substrate considerably decreased in simulated body fluid (SBF) at 37 °C as the HA coating was applied on it. Apatite layer grew on the coating after its soaking in SBF at 37 °C for 1 week.

Electrophoretic deposition of hydroxyapatite nanoparticles: effect of suspension composition on the electrochemical potential difference at deposit/suspensions interface

Suspensions of HA nanoparticles were prepared in different alcohols using triethanolamine (TEA) as dispersant. Optimum concentration of TEA increased with molecular weight of alcohol: 0.67, 0.67 and 8 ml L−1, respectively, in methanolic, ethanolic and butanolic suspensions. Current density increased during EPD from TEA containing methanolic and ethanolic suspensions due to desorption of H+TEA ions from deposited HA nanoparticles under the influence of applied electric field. Particles were detached from deposits into the suspensions at the interface after switching off the voltage due to the generation of an electrochemical potential difference there. The rate of detachment decreased continuously in all methanolic suspensions and ethanolic suspensions with 4 ml L−1 ≤ TEA due to the continuous reduction in the electrochemical potential difference at the interface caused by the effective diffusion of high concentration of free TEA and H+TEA species present in the liquid phase of deposits into the suspension. However, the rate of detachment remained constant in ethanolic suspensions with TEA < 4 ml L−1 and in all butanolic suspensions. The mass flow of TEA and H+TEA species from deposit into the suspensions is negligible in these suspensions so that the electrochemical potential difference and so detachment rate remain constant.

Origin of symmetry breaking in the seed-mediated growth of bi-metal nano-heterostructures

Seed-mediated growth is the most general way to controllably synthesize bimetal nano-heterostructures. Despite successful instances through trial and error were reported, the way for second metal depositing on the seed, namely whether the symmetry of resulted nano-heterostructure follows the original crystal symmetry of seed metal, remains an unpredictable issue to date. In this work, we propose that the thermodynamic factor, i.e., the difference of equilibrium electrochemical potentials (corresponding to their Fermi levels) of two metals in the growth solution, plays a key role for the symmetry breaking of bimetal nano-heterostructures during the seed-mediated growth. As a proof-of-principle experiment, by reversing the relative position of Fermi levels of the Pd nanocube seeds and the second metal Au with changing the concentration of reductant (L-ascorbic acid) in the growth solution, the structure of as-prepared products successfully evolved from centrosymmetric Pd@Au core-shell trisoctahedra to asymmetric Pd-Au hetero-dimers. The idea was further demonstrated by the growth of Ag on the Pd seeds. The present work intends to reveal the origin of symmetry breaking in the seed-mediated growth of nano-heterostructures from the viewpoint of thermodynamics, and these new insights will in turn help to achieve rational construction of bimetal nano-heterostructures with specific functions.

Deposition mechanism of aluminum on uranium in AlCl3-1-ethyl-3-methylimidazolium chloride ionic liquid by galvanic displacement

Aluminum (Al) coatings, which are found to be dendrites, have been deposited on uranium (U) substrate in ionic liquid via galvanic displacement. Interestingly, a dense Al nano-layer has formed between the Al dendrites and the U substrate. In this work, the growth mechanism of the Al coating has been investigated by ultraviolet–visible spectroscopy, scanning electron microscopy, grazing incidence X-ray diffraction, and electrochemical measurements: the galvanic reaction sees the oxidation of U from the substrate while Al2Cl7− are reduced on its surface, driven by the electrochemical potential difference between Al and U. Furthermore, we have found that the Al nano-layer passivates the uranium surface, which is proved to be the rate limiting step in the galvanic deposition process; the observation of the interface morphology evolution process indicates that this Al nano-layer grows in a three-dimensional mode. This work demonstrates a convenient approach to deposit dense Al nano-layer on U, without any external power source.

Influence of the Chalcogen Element on the Filament Stability in CuIn(Te,Se,S)2/Al2O3 Filamentary Switching Devices.

In this paper, we report on the use of CuInX2 (X = Te, Se, S) as a cation supply layer in filamentary switching applications. Being used as absorber layers in solar cells, we take advantage of the reported Cu ionic conductivity of these materials to investigate the effect of the chalcogen element on filament stability. In situ X-ray diffraction showed material stability attractive for back-end-of-line in semiconductor industry. When integrated in 580 μm diameter memory cells, more volatile switching was found at low compliance current using CuInS2 and CuInSe2 compared to CuInTe2, which is ascribed to the natural tendency for Cu to diffuse back from the switching layer to the cation supply layer because of the larger difference in electrochemical potential using Se or S. Low-current and scaled behavior was also confirmed using conductive atomic force microscopy. Hence, by varying the chalcogen element, a method is presented to modulate the filament stability.

Comment on “Optical Imaging of Light-Induced Thermopower in Semiconductors”

In a recent article [Phys. Rev. Applied 5, 024005 (2016)], Gibelli and coworkers proposed a method to determine the thermopower, i.e. the Seebeck coefficient, using photoluminescence measurements. The photoluminescence spectra are used to obtain the local gradients of both the electrochemical potential difference between electron and holes and the temperature of the electron-hole plasma. However, the definition of the thermopower given in that article seems erroneous due to a confusion between the different physical quantities needed to derive this parameter.

Irreversible thermodynamics and Shockley recombination velocity: Application to photoabsorption near a surface

We apply the method of irreversible thermodynamics to obtain, for a semiconductor with electron and hole carriers adjacent to a single-carrier material, the recombination velocity and the rate of surface heating. The lack of equilibrium across the interface drives both a charged number current flux (the difference between electron and hole fluxes) and an uncharged number current flux (the sum of electron and hole fluxes). The latter provides a generalization of Shockley's recombination velocity. There are two contributions to the surface heating rate, one proportional to the charged number current flux times a difference in electrochemical potentials across the interface, and the other proportional to the uncharged number current flux times its associated difference in electrochemical potential. We apply our results to photoabsorption at a uniform volume rate $G$ within a distance $d$ of a vacuum semiconductor surface, finding the distributions of number current density, charge, and voltage as a function of position.

Role of Metallurgy in the Localized Corrosion of Carbon Steel

Localized residual strain develops within the metallurgical texture of 1018 carbon steel from metallurgical processes, such as fabrication, annealing, and shaping. This residual strain results in accelerated localized pitting due to the formation of anodic sites at these locations. Once initiated, micron-sized corrosion pits can coalesce to form sites of potential catastrophic failure. In this contribution, we focus on the localized biocorrosion which initiates and grows in areas of localized strain such as the interfaces between manganese sulfide (MnS) inclusions and ferrite grains in the steel, at grain boundaries between ferrite grains with different crystallographic orientations and at pearlite grains (intergrown cementite (Fe3C) and ferrite), which are readily found in 1018 carbon steel. Here we hypothesize and show experimentally that accelerated biocorrosion in 1018 carbon steel finds its roots in the electrochemical potential difference (micro galvanic cells) generated between the unstrained ferrite iron (α - Fe) and the lattice defects, dislocations and mismatches found at interfaces formed between α - Fe and secondary phases i.e. MnS inclusions, cementite lamellar structures and grain boundaries distributed throughout the 3D network of the carbon steel. This hypothesis is supported by results from multiple micro- and nanoscale imaging and analytical methods obtained from field emission scanning electron microscopy, energy dispersive spectroscopy, electron backscattered diffraction and Auger nanoprobe electron spectroscopy. The morphology and composition of grains in the steel coupons were characterized before and after exposure to suboxic and sulfidogenic environments dominated by aerobic and anaerobic marine organisms. Corrosion processes are demonstrated to initiate in localized areas of high residual strain.

Direct observation of the nanoscale Kirkendall effect during galvanic replacement reactions

Galvanic replacement (GR) is a simple and widely used approach to synthesize hollow nanostructures for applications in catalysis, plasmonics, and biomedical research. The reaction is driven by the difference in electrochemical potential between two metals in a solution. However, transient stages of this reaction are not fully understood. Here, we show using liquid cell transmission electron microscopy that silver (Ag) nanocubes become hollow via the nucleation, growth, and coalescence of voids inside the nanocubes, as they undergo GR with gold (Au) ions at different temperatures. These direct in situ observations indicate that void formation due to the nanoscale Kirkendall effect occurs in conjunction with GR. Although this mechanism has been suggested before, it has not been verified experimentally until now. These experiments can inform future strategies for deriving such nanostructures by providing insights into the structural transformations as a function of Au ion concentration, oxidation state of Au, and temperature.

Ultrafast synthesis of Te nanorods as cathode materials for lithium-tellurium batteries

Recently, tellurium has been regarded as a promising cathode material for rechargeable lithium-ion batteries due to its high theoretical volumetric capacity. However, a plethora of research are focusing on impregnating the tellurium into porous carbon materials by the thermal-diffusion method, which would consume large amounts of energy and take prolonged time. Herein, a carbon and binder-free cathode with 100% Te is fabricated by a facile galvanic replacement method on a nickle foam. Driven by the large electrochemical potential difference between Ni and Te, desirable amounts of Te can be obtained in just 10 min with no need of energy input. Li-Te batteries constructed by the as-obtained cathode show relatively good performance in DMSO solvent. To further elevate the performance of this battery especially at low current density, commercial carbon cloth is added between the separator and Te electrode as an interlayer. The cell with interlayer delivers a gravimetric capacity of 116.2 mAh g−1 after 70 cycles at the current density of 100 mA g−1, which is 2.8 times as high as that of a cell without interlayer (40.4 mAh g−1).

Reverse Electrodialysis-Assisted Solar Water Splitting

Photoelectrochemical (PEC) water splitting provides an attractive route for large-scale solar energy storage, but issues surrounding the efficiency and the stability of photoelectrode materials impose serious restrictions on its advancement. In order to relax one of the photoelectrode criteria, the band gap, a promising strategy involves complementing the conventional PEC setup with additional power sources. Here we introduce a new concept: solar water splitting combined with reverse electrodialysis (RED). RED is a membrane-based power generation technology that produces an electrochemical potential difference from a salinity gradient. In this study, the RED stack serves not only as a separator, but also as an additional tunable power source to compensate for the limited voltage produced by the photoelectrode. A hybrid system, composed of a single-junction p-Si and a RED stack, successfully enables solar water splitting without the need for an external bias. This system provides flexibility in photoelectrode material selection.