Electrochemical Potential Energy Research Articles

Mitochondrial-uncoupling nanomedicine for self-heating and immunometabolism regulation in cancer cells

Developing endogenous hyperthermia offers a promising strategy to address challenges with current exogenous hyperthermia techniques in clinics. Herein, a CD44-targeted and thermal-responsive nanocarrier was developed for the simultaneous delivery of 2,4-dinitrophenol and syrosingopine. The objective was to induce endogenous hyperthermia and regulate immunometabolism, ultimately augmenting anti-tumour immune responses. Dinitrophenol as mitochondrial uncoupler can convert electrochemical potential energy of inner mitochondrial membrane into heat, facilitating endogenous hyperthermia. Meanwhile, syrosingopine not only inhibits excessive lactate efflux caused by dinitrophenol but also downregulates tumour cell glycolysis, thus alleviating immunosuppression and heat shock protein (HSP)-dependent thermo-resistance through immunometabolism regulation. The synergistic effects of endogenous hyperthermia and immunometabolism regulation by this nanomedicine have potential to enhance tumor immunogenicity, reshape the tumour immune microenvironment, and effectively suppress the growth of subcutaneous tumours and patient-derived organoids in triple-negative breast cancer. Therefore, the endogenous hyperthermia strategy developed in this study would revolutionize hyperthermia for cancer treatment.

Sedimentation of a Charged Soft Sphere within a Charged Spherical Cavity.

The sedimentation of a soft particle composed of an uncharged hard sphere core and a charged porous surface layer inside a concentric charged spherical cavity full of a symmetric electrolyte solution is analyzed in a quasi-steady state. By using a regular perturbation method with small fixed charge densities of the soft sphere and cavity wall, a set of linearized electrokinetic equations relevant to the fluid velocity field, electrical potential profile, and ionic electrochemical potential energy distributions are solved. A closed-form formula for the sedimentation velocity of the soft sphere is obtained as a function of the ratios of core-to-particle radii, particle-to-cavity radii, particle radius-to-Debye screening length, and particle radius-to-porous layer permeation length. The existence of the surface charge on the cavity wall increases the settling velocity of the charged soft sphere, principally because of the electroosmotic enhancement of fluid recirculation within the cavity induced by the sedimentation potential gradient. When the porous layer space charge and cavity wall surface charge have the same sign, the particle velocity is generally enhanced by the presence of the cavity. When these fixed charges have opposite signs, the particle velocity will be enhanced/reduced by the presence of the cavity if the wall surface charge density is sufficiently large/small relative to the porous layer space charge density in magnitude. The effect of the wall surface charge on the sedimentation of the soft sphere increases with decreases in the ratios of core-to-particle radii, particle-to-cavity radii, and particle radius-to-porous layer permeation length but is not a monotonic function of the ratio of particle radius-to-Debye length.

Electrophoretic Mobility and Electric Conductivity of Salt-Free Suspensions of Charged Soft Particles

A unit cell model is employed to analyze the electrophoresis and electric conduction in a concentrated suspension of spherical charged soft particles (each is a hard core coated with a porous polyelectrolyte layer) in a salt-free medium. The linearized Poisson–Boltzmann equation applicable to a unit cell is solved for the equilibrium electrostatic potential distribution in the liquid solution containing the counterions only surrounding a soft particle. The counterionic continuity equation and modified Stokes/Brinkman equations are solved for the ionic electrochemical potential energy and fluid velocity distributions, respectively. Closed-form formulas for the electrophoretic mobility of the soft particles and effective electric conductivity of the suspension are derived, and the effect of particle interactions on these transport characteristics is interesting and significant. Same as the case in a suspension containing added electrolytes under the Debye–Hückel approximation, the scaled electrophoretic mobility in a salt-free suspension is an increasing function of the fixed charge density of the soft particles and decreases with increases in the core-to-particle radius ratio, ratio of the particle radius to the permeation length in the porous layer, and particle volume fraction, keeping the other parameters unchanged. The normalized effective electric conductivity of the salt-free suspension also increases with an increase in the fixed charge density and with a decrease in the core-to-particle radius ratio, but is not a monotonic function of the particle volume fraction.

Electrophoresis and electric conduction in a salt-free suspension of charged particles.

The electrophoresis and electric conduction of a suspension of charged spherical particles in a salt-free solution are analyzed by using a unit cell model. The linearized Poisson-Boltzmann equation (valid for the cases of relatively low surface charge density or high volume fraction of the particles) and Laplace equation are solved for the equilibrium electric potential profile and its perturbation caused by the imposed electric field, respectively, in the fluid containing the counterions only around the particle, and the ionic continuity equation and modified Stokes equations are solved for the electrochemical potential energy and fluid flow fields, respectively. Explicit analytical formulas for the electrophoretic mobility of the particles and effective electric conductivity of the suspension are obtained, and the particle interaction effects on these transport properties are significant and interesting. The scaled zeta potential, electrophoretic mobility, and effective electric conductivity increase monotonically with an increase in the scaled surface charge density of the particles and in general decrease with an increase in the particle volume fraction, keeping each other parameter unchanged. Under the Debye-Hückel approximation, the dependence of the electrophoretic mobility normalized with the surface charge density on the ratio of the particle radius to the Debye screening length and particle volume fraction in a salt-free suspension is same as that in a salt-containing suspension, but the variation of the effective electric conductivity with the particle volume fraction in a salt-free suspension is found to be quite different from that in a suspension containing added electrolyte.

Solid-state electrolytes: Advances and perspectives

All-solid-state Li batteries (ASSLiBs) that use solid-state electrolytes (SSEs) to replace liquid organic electrolytes are considered as promising next-generation energy storage devices because of their wide electrochemical potential windows, high safety, and high energy density. Therefore, ASSLiBs have attracted a lot of attention in recent years. In this review, we focus on the main challenges on the synthesis and the electrochemical properties of the SSEs including (i) crystal structures and modification of kinetics of Li-ion migration through doping technology, (ii) synthesis technologies and its effect on the electrochemical performances of the SSEs, and (iii) ambient condition stability and degration of SSEs. Finally, perspectives of future researches on the SSEs are presented.

Modeling the Electron Transfer Chain in an Artificial Photosynthetic Machine.

The development of efficient artificial leaves relies on the subtle combination of molecular assemblies able to absorb sunlight, converting light energy into electrochemical potential energy and finally transducing it into accessible chemical energy. The electronic design of these charge transfer molecular machines is crucial to build a complex supramolecular architecture for the light energy conversion. Here, we present an ab initio simulation of the whole decay pathways of a recently proposed artificial molecular reaction center. A complete structural and energetic characterization has been carried out with methods based on density functional theory, its time-dependent version, and a broken-symmetry approach. On the basis of our findings we provide a revision of the pathway only indirectly postulated from an experimental point of view, along with unprecedented and significant insights on the electronic and nuclear structure of intramolecular charge-separated states, which are fundamental for the application of this molecular assembly in photoelectrochemical cells. Importantly, we unravel the molecular driving forces of the various charge transfer steps, in particular those leading to the proton-coupled electron transfer final product, highlighting key elements for the future design strategies of such molecular assays.

Simultaneous promotion of photosynthesis and astaxanthin accumulation during two stages of Haematococcus pluvialis with ammonium ferric citrate

To simultaneously promote biomass yield and astaxanthin content of Haematococcus pluvialis, ammonium ferric citrate (AFC) was employed to stimulate light harvest in photosynthesis during the green stage and oxidation induction in astaxanthin accumulation during the red stage. AFC not only improved chlorophyll synthesis by 22.5% to provide more electrochemical potential energy in the green stage, but also alleviated photosystem II damage to maintain a high level of effective quantum yield by enhancing carotenoid production. The citrate derived from AFC stimulated acetyl-CoA and NADPH production through citric acid cycle and transaminase cycle during the red stage, resulting in an increased lipid content by 1.77-fold. The astaxanthin content in H. pluvialis cells cultivated with 5 μM AFC was 12.5% higher than that without AFC, which was attributed to severe oxidative stress caused by AFC through Haber-Weiss reaction. These results provided a new approach to reduce emission of greenhouse gasses with producing high-value products.

Results and model for single-gate ratchet charge pumping

We show experimentally that, in the same Si devices, we can demonstrate multiple two-gate pumping modes but not single-gate mode. We contrast this with GaAs devices, which do show single-gate pumping at a high yield. We propose four mechanisms to explain the lack of plateaus in the Si devices in single-gate ratchet mode: operating the dot with a large number of electrons, a large ratio between the change in electrochemical potential energy and the change in the energy of the barrier (plunger-to-barrier ratio, Δptb) compared to the charging energy (Δptb/EC), nonlinear tunnel barriers, and phase offset leading to nonequilibrium heating. Our analysis shows that each of these could contribute to the lack of plateaus in single-gate ratchet pumping on Si devices but allow two-gate pumping methods to work with robust plateaus. It is easier for GaAs pumps to avoid these failure mechanisms due to their different architectures and cleaner gate turnoff curves. We propose several methods to reduce these sources of error, including reducing cross capacitances between gates. These recommendations may prove useful to other researchers in producing more robust, higher yield single-gate ratchet pumps.

Solid State Battery Cells for in Operandi Diffusion Measurements Using µ+sr Spectroscopy

Solid state lithium ion batteries (SSBs) have been widely tipped to revolutionise energy storage technology. The combination of increased safety, longer lifetime, larger electrochemical potential window and higher energy density offered has led to sustained global research into their development. One important aspect of that development is the dynamics of ion diffusion, particularly through the bulk solid electrolyte but also at the electrode/electrolyte interface. Ion diffusion rates can limit how fast batteries can be charged/discharged, with charge movement across the electrode/electrolyte boundary especially key in SSBs, which can experience poor interfacial contact. An increased understanding of microscopic level ion behaviour at these boundaries will prove valuable, but has so far been elusive with techniques such as NMR and impedance spectroscopy yielding inconsistent results.1,2 Muon spin relaxation (µ+SR) spectroscopy is a relatively new technique used to investigate Li+ migration mechanisms, using spin-polarised positive muons created using a synchrotron. The muons can be controlled to stop at any point within a battery, acting as an atomic scale probe of charge movement in a particular area within the crystal structure. This occurs as an implanted muon’s spin is perturbed by the magnetic field of nearby diffusing ions. After an average lifetime of 2.2 µs the muon will decay into a positron, emitted preferentially along the direction of the muon spin at the instant of decay. Detection of the asymmetry of emitted positrons gives a time evolution of the muon ensemble’s spin polarisation, yielding information on ion diffusion dynamics and activation energies. µ+SR has been proven a successful technique to study in situ batteries, producing accurate measurements that are consistent with first-principle calculations.2,3 This research will focus on the study of the promising solid-state battery electrolyte material Al-doped LLZO (Li7La3Zr2O12), using µ+SR spectroscopy as a reliable and reproducible probe. The anode and cathode materials used will be Li4Ti5O12 and LiCoO2 to complete the cell. This cell will be tested in situ from room temperature to around 80ºC on the EMU beamline at ISIS Pulsed Neutron and Muon Source. Any insights gained will be translated back to design principles to optimise battery performance. Power Source, 2014, 268, 153–162Mater. Chem. A, 2017, 5, 8653Mater. Chem. A, 2016, 4, 1729Phys. Scr., 2013, 88, 068509

Sedimentation Velocity and Potential in Dilute Suspensions of Charge-Regulating Porous Spheres.

The sedimentation of a charge-regulating porous sphere surrounded by an arbitrary electric double layer, which usually models a permeable polyelectrolyte coil or an aggregate of nanoparticles, is analyzed for the first time. The hydrodynamic frictional segments and ionogenic functional groups uniformly distribute in the porous sphere, and a regulation mechanism for the dissociation and association reactions occurring at these functional groups linearly relates the local electric potential to fixed charge density. The linearized electrokinetic equations governing the ionic concentration (or electrochemical potential energy), electric potential, and fluid velocity fields are solved for the case of a small basic fixed charge density by the regular perturbation method. Analytical formulae for the sedimentation velocity of a porous sphere and sedimentation potential of a dilute suspension of porous spheres are then obtained. The charge regulation tends to reduce the electrokinetic retardation to sedimentation velocity and the sedimentation potential (can be as much as 50 and 25%, respectively) compared to the case that the fixed charge density is a constant. Both the electrokinetic retardation to sedimentation velocity and the sedimentation potential vanish at the isoelectric point of the particles. The increase in the bulk concentration of the potential-determining ions crossing the isoelectric point changes signs of the fixed charges and thus causes a reversal in the direction of the sedimentation potential. The effects of charge regulation on the sedimentation of porous particles differ substantially from those of hard particles.

Average Current Through a Single-electron Transistor Under Fluctuations of an Observer’s Frame of Reference

The average current through a single-electron transistor (SET) under fluctuations of an observer’s frame of reference (OFR) is reported. To date, the average current through a SET has been studied under the assumption that an OFR remains constant throughout the performance of measurements of the current; thus, it remains an unsolved problem as to what is measured of the current when the OFR is assumed to fluctuate. In this paper, a SET comprising a source, drain, and single channel is considered, where an OFR is assumed to be matched to the electrochemical potential energy of the drain of the SET. The average current through the SET for two types of OFR fluctuation is formulated: periodic-square-wave fluctuation and periodic-sawtooth-wave fluctuation, in time representations. Under these types of fluctuation, the average current exhibits a zero-bias Coulomb peak—the amplitude of which gradually increases with the amplitude of the fluctuation type divided by temperature. The amplitude of the zero-bias Coulomb peak is greater in the case of periodic-square-wave fluctuations. Therefore, the amplitude of the zero-bias Coulomb peak together with a varying of both the energy of the channel and the temperature has the potential to reveal the distribution of fluctuations of an OFR.

Sedimentation Velocity and Potential in Dilute Suspensions of Charged Porous Shells

The sedimentation of a charged spherical porous shell with arbitrary inner and outer radii, which can model a permeable microcapsule or vesicle, in a general electrolyte solution is analytically examined. The relaxation effect in the electric double layers of arbitrary thickness around the porous shell is considered. The differential equations governing the electric potential profile, ionic electrochemical potential energy (or concentration) distributions, and fluid velocity field are linearized by taking the system to be only slightly distorted from equilibrium. These linearized equations are solved using a perturbation method with the density of the fixed charge of the porous shell as the small perturbation parameter. Closed-form formulas for the sedimentation velocity of a porous shell and sedimentation potential in a suspension of porous shells are obtained from a force balance and a zero current requirement, respectively. Both the charge-induced sedimentation velocity retardation and sedimentation potential are monotonic increasing functions of the relative shell thickness, and these increases are substantial if the shell is thin. The sedimentation velocity and potential are complex functions of the electrokinetic radius and normalized flow penetration length of the porous shell. In the limit of the porous shells with zero inner radius, our formulas for the sedimentation velocity and potential reduce to the results obtained for the intact porous spheres.

(Invited) Biomimetic Proton Conductive Polymer Electrolyte

Proton conductive polymer electrolyte is one of the key components to fabricate an efficient fuel cell. Perfluorosulfonic acid polymers, such as Nafion are widely used because of their high proton conductivity. It has been considered that a strong acid is important for high proton conductivity therefore many group synthesized acid contain polymer from the viewpoint of how much strong acid can be added with keeping the polymer mechanical strength. On the other hand, living cell, mitochondria also used proton to produce energy. The difference in proton concentration across a membrane produce electrochemical potential energy, which drives the synthesis of ATP. Mitochondria does not contain strong acid and the protons are transferred using weak acid and base, whereas efficient proton conduction occurred at the bilayer membranes. Although the detailed mechanism for the proton conduction at the membrane is still controversial, several groups suggested that protons efficiently conduct through the membrane surface [1]. In this paper, we present a polymer proton conductive membrane which mimic the proton conduction at the bilayer membrane [2]. The polymer membrane was prepared by deposition of poly(N-dodecylacrylamide-co-acrylic acid) monolayer formed at an air-water interface using the Langmuir-Blodgett technique. The membrane was formed by multilayer film of the monolayer, in which formed a clear lamellar structure composed of hydrophobic alkyl side chains and hydrophilic amide and carboxylic acid regions. The hydrophilic region created 2D proton conductive nanospace, which resembles to the bilayer membrane surface. The proton conductivity in the 2D proton nanospace of the biomimetic polymer membrane reached to 5.9×10-2 S/cm, which is comparable to strong acid polymer electrolyte. The achievement of high proton conductivity even using weak acid as a proton source clearly indicates an efficient proton conduction in 2D nanospace. Moreover, we found that acrylic acid groups should be located in a proper distance to achieve the high proton conductivity. The mechanism of proton conduction at the 2D nanospace will be discussed using reported works of theoretical calculation.

Diffusiophoresis of a charged porous shell in electrolyte gradients

The diffusiophoresis of a charged spherical porous shell or permeable microcapsule with arbitrary inner and outer radii, fluid permeability, and electric double layer thickness in an ionic solution is analyzed. With the assumption that the imposed electrolyte concentration gradient is relatively weak and the transport system is only perturbed slightly from equilibrium, the electrostatic potential, ionic concentration (electrochemical potential energy), and fluid velocity fields are determined as power-series expansions of the small fixed charge density of the porous shell by solving the relevant linearized electrokinetic equations. An explicit expression for the diffusiophoretic velocity of the porous shell correct to the second order of the fixed charge density results from balancing the exerted electrostatic and hydrodynamic forces. Both the electrophoretic (first-order) and chemiphoretic (second-order) mobilities increase with an increase in the normalized thickness of the porous shell, and these increases are significant when the porous shell is thin. However, the diffusiophoretic velocity of the porous shell, which is the sum of the electrophoretic and chemiphoretic velocities, may not be a monotonic function of its normalized thickness. The variation in the normalized fixed charge density of the porous shell from negative to positive values can lead to more than one reversals in the direction of the diffusiophoretic velocity.

Electrochemical synthesis and potential electrochemical energy storage performance of nodule-type polyaniline

Nodule-type polyaniline (PAni) has been successfully electrosynthesized onto conducting substrate and envisaged in electrochemical supercapacitor (ES) application as a potential energy storage electrode. Various bands are confirmed from the X-ray photoelectron and Fourier transform infrared spectra. Each nodule is of ∼100–200nminlength and 20–80nmindiameter. The ∼45° surface water contact angle with water of PAni surface can be beneficial for accessing an entire electrode area with minimum interfacial resistance loss when is in contact with the aqueous electrolyte for ES application. The PAni nodule-type electrode when electrochemically characterized using cyclic-voltammetry and galvanostatic charge–discharge measurements has demonstrated a specific capacitance of ∼508Fg−1, a specific energy of 32.12Whkg−1, a specific power of 13.39kWkg−1 and a Coulombic efficiency of 100% in 1MH2SO4 electrolyte solution. An occurrence of 70% retention of initial capacity even after 5000 cycles is supporting for energy-storage application. Two separate redox reaction behaviors are confirmed in the discharge measurement.

Electrophoretic mobility of charged porous shells or microcapsules and electric conductivity of their dilute suspensions

Abstract An analysis is presented for the electrophoresis and electric conduction in a dilute suspension of charged spherical porous shells or permeable microcapsules with electric double layers of arbitrary thickness in an electrolyte solution. With the assumption that the system is slightly perturbed from equilibrium, the linearized electrokinetic equations governing the ionic electrochemical potential energy and fluid velocity distributions are solved as series expansions in the small fixed charge density of the porous shells. Explicit formulas for the electrophoretic mobility of the porous shells and effective electric conductivity of the suspension are derived. Both the electrophoretic mobility and the effective conductivity decrease monotonically with a decrease in the relative thickness of the porous shells, but these decreases are not conspicuous until the porous shells are quite thin. When the fluid permeability of the porous shells is smaller or the electric double layers are thicker, the effect of this relative thickness on the electrophoretic mobility and effective conductivity becomes more significant. In the limiting case of zero inner radius of the porous shells, our formulas reduce to the corresponding results obtained for the electrophoresis and electric conduction in a suspension of charged porous spheres.

Experimental Validation of the Elimination of Dendrite Short-Circuit Failure in Secondary Lithium-Metal Convection Cell Batteries

Sustained cycling of metallic lithium negative electrodes is possible without dendrite failure in the convection battery due to the ability to effectively lower concentrations within the separator region during charge by flowing electrolyte through the negative electrode first, where lithium ions are consumed, prior to entering the separator. Consumption of lithium ions prior to entering the separator region results in a lowered concentration and reduced electrochemical potential. Additionally, convective flow reduces overall concentration gradients therefore lowering concentration overpotentials. At these lowered concentrations, dendrite formation is not thermodynamically favored as shown through the relationship between concentration, electrochemical potential and Gibbs free energy. This work presents theory, experimental validation, and autopsy (visual) verification of how the pumping of electrolyte between counter-electrodes eliminates dendrite short-circuit through the separator. Experimental validation included establishing a control using lithium particles as the negative electrode. The control consistently failed due to dendrite-based short circuit when operated without the flow of electrolyte. For the same experimental system operated with flow, the battery operated for 10 cycles (limit of study), exhibiting characteristic capacity fade at these rates. Imagery confirmed that dendrite crystals were not forming in the separator when operated during flow and that crystals did form without flow.

Prediction of quantum dot characteristics through universal scaling relations

We derive scaling relations for the electrochemical potential and addition energy of 2D quantum dots charged with N electrons. In the derivation we apply the Thomas–Fermi theory for the harmonic model of a quantum dot in the effective mass approximation. We demonstrate that the resulting scaling relations yield excellent agreement with measured chemical potentials and addition energies for both lateral and vertical quantum dots. Moreover, we show that the scaling relation has predictive power in estimating the confinement strength and the number of electrons trapped in the quantum dot.

Sedimentation of a Charged Porous Particle in a Charged Cavity

The sedimentation of a charged porous sphere at the center of a charged spherical cavity filled with an electrolyte solution is analyzed. The thickness of the electric double layers around the particle and cavity wall is arbitrary, and their relaxation effect is considered. Through the use of a set of linearized electrokinetic equations and a perturbation method, the ionic electrochemical potential energy, electric potential, and velocity fields in the fluid are solved with the fixed space charge density of the particle and surface charge density of the cavity as the small perturbation parameters, and an explicit formula for the sedimentation velocity is obtained. Due to the electroosmotic enhancement on the fluid recirculation in the cavity caused by the sedimentation-induced electric field, the presence of the surface charges on the cavity wall increases the sedimentation velocity of the porous particle. For the sedimentation of a porous particle in a cavity with their fixed charges of the same sign, the effect of electric interaction between the particle and cavity wall in general increases the sedimentation velocity. For the case of their fixed charges with opposite signs, the sedimentation velocity is increased/reduced if the magnitude of the fixed charge density of the cavity wall is relatively large/small. The effect of the surface charges at the cavity wall on the sedimentation of the porous particle increases with an increase in the permeability for fluid flow within the particle and with a decrease in the particle-to-cavity radius ratio (i.e., an increase in the surface area of the cavity wall relative to a given size of the particle, which enhances the fluid recirculation effect).

Copper(I) and Iron(II) Complexes of a Novel Tris(pyridyl)­ethane‐Derived N4 Ligand: Aspects of Redox Behaviour and Bioinorganic Physicochemistry

AbstractThe N4 ligand 1‐{6‐[1,1‐bis(pyridin‐2‐yl)ethyl]pyridin‐2‐yl}‐N,N‐dimethylmethanamine (L) is presented. It has been used to obtain the copper(I) complex [CuL(MeCN)]PF6 and the iron(II) complex [Fe(CN)2L]. Aerobic oxidation of the copper(I) complex is unspecific at room temperature. Anaerobic oxidation in solution, which is very sluggish, occurs with formation of the copper(II) complex [CuIIFL]PF6, suggesting concomitant hydrolysis of hexafluorophosphate initiated by traces of water. The iron(II) complex adsorbed at a TiO2 surface is an efficient photosensitiser of the support. Photoelectrochemical photocurrent switching (PEPS), which can be initiated by changing the electrochemical potential and photon energy, is very pronounced. The construction of a simple photoelectrochemical NOR logic gate has been demonstrated.