Behavior Of Aqueous Solutions Research Articles

Estimation of Nanoparticle's Surface Electrostatic Potential in Solution Using Acid-Base Molecular Probes. III. Experimental Hydrophobicity/Hydrophilicity and Charge Distribution of MS2 Virus Surface.

MS2 bacteriophage is often used as a model for evaluating pathogenic viruses' behavior in aqueous solution. However, the questions of the virus surface's hydrophilic/hydrophobic balance, the charge distribution, and the binding mechanism are open. Using the dynamic light scattering method and laser Doppler electrophoresis, the hydrodynamic diameter and the ζ-potential of the virus particles were measured at their concentration of 5 × 1011 particles per mL and ionic strength 0.03 M. The values were found to be 30 nm and -29 or -34 mV (by Smoluchowski or Ohshima approximations), respectively. The MS2 bacteriophage surface was also investigated using a series of acid-base indicator dyes of various charge type, size, and structure. Their spectral and acid-base properties (pKa) are very sensitive to the microenvironment in aqueous solution, including containing nanoparticles. The electrostatic potential of the surface Ψ was estimated using the common formula: Ψ = 59 × (pKai - pKa) in mV at 25 °C. The Ψ values were -50 and +10 mV, respectively, which indicate the "mosaic" way of the charge distribution on the surface. These data are in good agreement with the obtained ζ-potential values and provide even more information about the virus surface. It was found that the surface of the MS2 virus is hydrophilic in solution in contrast to the commonly accepted hypothesis of the hydrophobicity of virus particles. No hydrophobic interactions between various molecular probes and the capsid were observed.

Evidence of Formation of Monolayer Hydrated Salts in Nanopores.

Despite much effort being devoted to the study of ionic aqueous solutions at the nanoscale, our fundamental understanding of the microscopic kinetic and thermodynamic behaviors in these systems remains largely incomplete. Herein, we reported the first 10 μs molecular dynamics simulation, providing evidence of the spontaneous formation of monolayer hexagonal honeycomb hydrated salts of XCl2·6H2O (X = Ba, Sr, Ca, and Mg) from electrolyte aqueous solutions confined in an angstrom-scale slit under ambient conditions. By using both the classical molecular dynamics simulations and the first-principles Born-Oppenheimer molecular dynamics simulations, we further demonstrated that the hydrated salts were stable not only at ambient temperature but also at elevated temperatures. This phenomenon of formation of hydrated salt in water is contrary to the conventional view. The free energy calculations and dehydration analyses indicated that the spontaneous formation of hydrated salts can be attributed to the interplay between ion hydration and Coulombic attractions in the highly confined water. In addition to providing molecular-level insights into the novel behavior of ionic aqueous solutions at the nanoscale, our findings may have implications for the future exploration of potential existence of water molecules in the saline deposits on hot planets.

Stabilization Effects Induced by Trehalose on Creatine Aqueous Solutions Investigated by Infrared Spectroscopy.

Creatine is a very popular amino acid widely utilized in the sports world due to its functions mainly related to muscle building and increasing performance. The present work investigates the behavior of creatine aqueous solutions and of creatine aqueous in the presence of trehalose as a function of time changes by means of Infrared spectroscopy. Infrared spectra have been gathered and studied over time for both the full spectrum and the intramolecular OH-stretching region for the two mixtures. This latter region was studied more specifically using a cutting-edge technique called Spectral Distance (SD). From this analysis of the spectral features of the investigated samples, it emerges that trehalose has a significant stabilizing effect on creatine aqueous solutions.

Layered silicate edge-linked perylene diimides: Synthesis, self-assembly and energy transfer

The control over intermolecular interactions between chromophores at nanomaterial interfaces is important for sensing and light-harvesting applications. To that aim, inorganic nanoparticles with anisotropic shape and surface chemistry can serve as useful supports for organic modification. Herein, novel asymmetric perylene diimides with aspartic acid and oleyl terminal groups were grafted to the edges of the layered silicate clay Laponite, a water-dispersible discoidal nanoparticle. The photophysical properties and solvent-dependent self-assembly of the nanoclay-grafted perylenes were investigated, revealing that the polarity of the terminating ligand dictates the aggregation behavior in aqueous solution, where increased water content generally led to the formation of perylene H-aggregates. The anionic basal surface of the nanoclay provided a binding site for a cationic fluorophore, leading to energy transfer from the face-bound donor to the edge-bound perylene acceptor. This study encourages further research on the use of functional ligands for the formation of organic–inorganic hybrids, particularly where inorganic template particles with specific surface chemistry can be exploited to study intermolecular interactions. Overall, these findings should advance further design and implementation of novel semiconducting ligands towards inorganic–organic hybrids, with potential applications in sensing and energy harvesting.

Sorption behavior of ethyl acetate aqueous solutions through a polyvinyl alcohol/tetraethoxysilane/perfluorosulfonic acid hybrid membrane: an experimental study

Sorption behavior of ethyl acetate aqueous solutions through a polyvinyl alcohol/tetraethoxysilane/perfluorosulfonic acid hybrid membrane: an experimental study

Molecular dynamics of preferential adsorption in mixed alkali-halide electrolytes at graphene electrodes.

Understanding the microscopic behavior of aqueous electrolyte solutions in contact with graphene and related carbon surfaces is important in electrochemical technologies, such as capacitive deionization or supercapacitors. In this work, we focus on preferential adsorption of ions in mixed alkali-halide electrolytes containing different fractions of Li+/Na+ or Li+/K+ and/or Na+/K+ cations with Cl- anions dissolved in water. We performed molecular dynamics simulations of the solutions in contact with both neutral and positively and negatively charged graphene surfaces under ambient conditions, using the effectively polarizable force field. The simulations show that large ions are often intuitively attracted to oppositely charged electrodes. In contrast, the adsorption behavior of small ions tends to be counterintuitive. In mixed-cation solutions, one of the cations always supports the adsorption of the other cation, while the other cation weakens the adsorption of the first cation. In mixed-cation solutions containing large and small cations simultaneously, adsorption of the larger cations varies dramatically with the electrode charge in an intuitive way, while adsorption of the smaller cations changes oppositely, i.e., in a counterintuitive way. For (Li/K)Cl mixed-cation solutions, these effects allow the control of Li+ adsorption by varying the electrode charge, whereas, for LiCl single-salt solutions, Li+ adsorption is nearly independent of the electrode charge. We rationalize this cation-cation lever effect as a result of a competition between three driving forces: (i) direct graphene-ion interactions, (ii) the strong tendency of the solutions to saturate the network of non-covalent intermolecular bonds, and (iii) the tendency to suppress local charge accumulation in any region larger than typical interparticle distances. We analyze the driving forces in detail using a general method for intermolecular bonding based on spatial distribution functions and different contributions to the total charge density profiles. The analysis helps to predict whether an ion is more affected by each of the three driving forces, depending on the strength of the ion solvation shells and the compatibility between the contributions of the charge density profiles due to the ion and water molecules. This approach is general and can also be applied to other solutions under different thermodynamic conditions.

Experimental and Theoretical Studies on the Phase Behavior of Aqueous Solutions of Structurally Controlled Hyperbranched Poly(N-isopropylacrylamide)s

Structurally controlled hyperbranched poly(N-isopropylacrylamide)s (HB-PNIPAMs) having different branching densities were systematically synthesized, and their phase behavior, i.e., lower critical solution temperatures (LCSTs), in water was studied. The branching significantly affects LCSTs, and they decrease with an increase in the branching density. The origin of the experimental results was theoretically analyzed on the basis of the concept of cooperative hydration, which is the sequential formation of hydrogen bonds between polymer chains and water molecules. Assuming that the cooperativity of hydration does not propagate beyond the branching points, we calculate the spinodal curves, binodal curves, and critical points and construct the phase diagrams. The degrees of hydration of the subchains, branching points, and end groups are also calculated to examine their hydration effect on the phase behavior. In this investigation, we consider the following two situations: (i) only subchains can be hydrated, and (ii) every part of HB polymers, including branching points and end groups, can be hydrated. We compare the theory with the reported observations of the cloud points of structurally well-controlled HB-PNIPAMs in water. Qualitative agreement is obtained by using the same value of cooperativity as the study of aqueous solutions of linear PNIPAMs. We also show that the hydration behavior of the end groups and the branching points strongly influences the phase behavior and illustrate that the binodal temperature is determined by the balance between the effect of promoting hydration by their hydration and suppressing hydration due to the inhibition of cooperative hydration by the branching points.

Reactive Extrusion Synthesis of Biobased Isocyanate-Free Hydrophobically Modified Ethoxylated Urethanes with Pendant Hydrophobic Groups.

Development of hydrophobically modified ethoxylated urethane (HEUR) rheology modifiers enabled the widespread application of waterborne paints and coatings, replacing their environmentally burdening solvent-based predecessors. However, the diisocyanates, required for the conventional synthesis of HEURs, pose severe eco-sustainability threats. In this paper, we demonstrate an innovative approach to avoiding toxic components in the preparation of rheology modifiers by obtaining a new class of water-soluble isocyanate-free hydrophobically modified ethoxylated poly(hydroxy-urethane)s (IFHEURs). The first step in the synthetic pathway was the preparation of CO2-based five-membered poly(ethylene glycol) bis(cyclic carbonate) and its subsequent aminolysis using 4,7,10-trioxa-1,13-tridecanediamine, yielding poly(hydroxy-urethane) (PHU) prepolymers terminated with cyclic carbonate groups. The PHU prepolymers were further extended in a reactive extrusion (REX) synthesis using biobased hydrophobic diamine PRIAMINE 1075. The REX technique made it possible to overcome the typical limitations of the aminolysis reaction and to reach the desired conversion within a moderate reaction time. IFHEURs have been structurally elucidated using FT-IR and NMR spectroscopy techniques, MALDI-ToF mass spectrometry, and SEC analysis and applied as rheology modifiers. The study of their associative behavior in aqueous solutions confirmed that the architectural flexibility of the obtained IFHEURs, containing terminal and pendant hydrophobic groups, opens a perspective for tuneable thickening performance.

Effect of Hydrogen Bonding on Dynamic Rheological Behavior of PVA Aqueous Solution.

The rheological behavior of polyvinyl alcohol (PVA) aqueous solution is crucial to optimizing the processing technology and performance of PVA products. In this paper, the dynamic rheological behavior of PVA aqueous solution was investigated in detail. PVA solution with a concentration of 10 wt% showed unnormal rheological behaviors, that is, the liquid-like behavior in the high frequency (ω) region and the solid-like behavior in the low ω region. A storage modulus (G′) plateau appears in the relatively low ω region as a gel with a network structure. Different from conventional hydrogel, this plateau has a low modulus, and the corresponding size of the relaxation unit is estimated to be 554 nm, being higher than the size of a whole PVA chain. It is believed that the network mesh is formed by the intermolecular hydrogen bonding interactions among PVA chains. The relaxation time of these meshes is longer than the reptation time of a PVA chain. Based on the relaxation spectrum and calculation analysis, it is found that the destruction of intermolecular hydrogen bonds, such as by heating up, adding sodium dodecyl sulfate, and shear operation, will make the relaxation unit (mesh) larger and lead to the left shift of the intersection of G′ and loss modulus (G″). In a PVA solution with a high concentration, multiple meshes of various sizes could be formed and thus generate multiple relaxation peaks. The large-sized meshes mainly contribute to the left shift of the intersection of G′ and G″, and the small-sized meshes contribute to the high plateau modulus. The results in this paper offer a new angle to analyze polymer solutions with strong intermolecular interaction.

Synthesis and thermoresponsive behavior of double hydrophilic graft copolymer based on poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline)

A recent challenge in polymer self-assembly is the utilization of double hydrophilic graft copolymers (DHGC) in view of biomedical applications. Here we describe, for the first time, a platform of biocompatible DHGC fully based on poly(2-alkyl-2-oxazoline) leading to stimuli-responsive self-assemblies. This original DHGC platform was composed of backbone poly(2-methyl-2-oxazoline-co-2-pentyl-2-oxazoline) (P(MeOx-co-PentOx)) and poly(2-ethyl-2-oxazoline) (PEtOx) grafts. A “grafting onto” approach based on the combination of cationic ring-opening polymerization (CROP) technique and “click chemistry” CuAAc reaction, was successfully used to synthesize poly(2-methyl-2-oxazoline-co-2-pentyl-2-oxazoline)-g-poly(2-ethyl-2-oxazoline) (P(MeOx-co-PentOx)-g-PEtOx) copolymer conjugates of varying backbone and side chain lengths. These purely hydrophilic copolymers demonstrated self-assembling behavior in aqueous solution, showing a characteristic double hydrophilic behavior originating from building blocks immiscibilities. Self-associated structures with spherical morphologies have been evidenced by DLS and cryo-TEM. The sizes and the efficiency of self-association were mainly controlled by the concentration of the graft copolymer and by the molar ratio of the different hydrophilic compounds. In addition, thermoresponsive properties of these copolymers were studied by turbidimetry and DLS. From purely hydrophilic at low temperature, the copolymers showed amphiphilic characters at temperatures close to the cloud points (CP). Interestingly, cloud points were not controlled by the PEtOx graft length as it has been reported for PEtOx homopolymers but it depended mainly upon the PEtOx content of the copolymer, with a critical value around 75 PEtOx wt%. Addition of a kosmotropic salt (Na2SO4) allowed to trigger CPs from 80 °C till 26 °C. The self-assembling properties of this family of hydrophilic and biocompatible copolymers may offer promising prospect in the field of biomedical applications as bioreactors.

The impact of chlorination on the tetracycline sorption behavior of microplastics in aqueous solution

Considering the large volumes of treated water and incomplete elimination of pollutants, wastewater treatment plants (WWTPs) remain a considerable source of microplastics (MPs). Chlorine, the most frequently used disinfectant in WWTPs, has a strong oxidizing impact on MPs. However, little is documented, to date, about the impact of chlorination on the transformation of MPs and the subsequent environmental behaviors of the chlorinated MPs when released into the aquatic environment. This study explored the response of the physicochemical properties of specific thermoplastics, namely polyurethane (TPU) MPs and polystyrene (PS) MPs, to chlorination and their emerging pollutant [tetracycline (TC)] adsorption behavior in aqueous solution. The results indicated that the O/C ratio of the MP surface did not significantly change, and that there were increases in the O-containing functional groups of the TPU and PS MPs, after chlorination. The surface area of the chlorinated TPU MPs increased by 45 %, and that of the chlorinated PS increased by 21 %, compared with the pristine ones, which contributed to the TC adsorption. The adsorption isotherm fitting parameters suggested that the chlorinated TPU fitted the multilayer adsorption, and the chlorinated PS was inclined to the monolayer adsorption. The relative abundance of the O-containing functional groups, on the TPU surface, led to the release of CHCl3 molecules, and the clear surface irregularities and fissures occurred after chlorine treatment. No fissures were found on the surface of the chlorinated PS MPs. The hydrophobicity and electrostatic adsorption were proved to be the major impacts on the TC adsorption of the chlorinated MPs, and the subsequently formed hydrogen bonds led to the stronger adsorption capacity of the chlorinated TPU than the chlorinated PS MPs.

Thermo-Responsive Polyion Complex of Polysulfobetaine and a Cationic Surfactant in Water

Poly(4-((3-methacrylamidopropyl)dimethylammonium)butane-1-sulfonate) (PSBP) was prepared via controlled radical polymerization. PSBP showed upper critical solution temperature (UCST) behavior in aqueous solutions, which could be controlled by adjusting the polymer and NaCl concentrations. Owing to its pendant sulfonate anions, PSBP exhibited a negative zeta potential of −7.99 mV and formed a water-soluble ion complex with the cationic surfactant cetyltrimethylammonium bromide (CTAB) via attractive electrostatic interaction. A neutral PSBP/CTAB complex was formed under equimolar concentrations of the pendant sulfonate group in PSBP and the quaternary ammonium group in CTAB. Transmittance electron microscopic images revealed the spherical shape of the complex. The stoichiometrically neutral-charge PSBP/CTAB complex exhibited UCST behavior in aqueous solutions. Similar to PSBP, the phase transition temperature of the PSBP/CTAB complex could be tuned by modifying the polymer and NaCl concentrations. In 0.1 M aqueous solution, the PSBP/CTAB complex showed UCST behavior at a low complex concentration of 0.084 g/L, whereas PSBP did not exhibit UCST behavior at concentrations below 1.0 g/L. This observation suggests that the interaction between PSBP and CTAB in the complex was stronger than the interpolymer interaction of PSBP.

Novel berberine-based pharmaceutical salts with fatty acid anions: Synthesis, characterization, physicochemical properties

Berberine (BBR), a quaternary isoquinoline alkaloid found in a Chinese herb medicine from Berberis species plants, was utilized to synthesize three new biocompatible berberine-based pharmaceutical salts, featuring three mid-chain fatty acid anions derived from animal and vegetable oils. Three salts [BBR][FA] were namely berberine caproate [BBR][CAP], berberine heptylate [BBR][HEP] and berberine octoate [BBR][OCT]. These compounds were characterized using 1H and 13C NMR, FTIR, ESI-MS, and thermogravimetric analyses. The solubility and octanol/water partition coefficient were evaluated in water and simulated body fluids (simulated gastric, simulated intestinal and simulated body fluids). The water solubility of [BBR][FA] was higher than that of salt precursor berberine chloride [BBR][Cl]. The minimum inhibitory concentration and minimum bactericidal or fungicidal concentration against three strains (Staphylococcus aureus, Bacillus subtilis and Candida albicans) were also examined. The results showed that they have similar antimicrobial activity to [BBR][Cl]. Furthermore, transport and volumetric properties (density and conductivity) were determined to investigate their aggregation and solvation behaviors in aqueous solution. The limiting molar conductivity, Ʌ0, critical micelle concentration, cmc, apparent molar volume at infinite dilution, V2,φ0, the apparent molar expansibility at infinite dilution, Eφ0, etc for [BBR][FA] were calculated. Effect of the length in alkyl chain of fatty acid anions in [BBR][FA] and temperature on the obtained properties as well as the nature of the interactions in aqueous [BBR][FA] solutions have been discussed.

Multi-responsiveness N-vinylpyrrolidone and methyl acrylate copolymer with wide tunable range of response temperature

• The LCST of the P(NVP-co-MA) copolymer can vary from 17 °C to 90 °C, showing a wide tunable range. • The P(NVP-co-MA) copolymer is temperature-responsive, salt-responsive, and pH-responsive. • The P(NVP-co-MA) copolymer is both biocompatible and multi-responsive. Copolymers of N-vinylpyrrolidone (NVP) and methyl acrylate (MA) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization, which exhibited typical lower critical solution temperature (LCST) behavior in aqueous solution. The molecular structure and composition of copolymer P(NVP-co-MA) were characterized by FTIR and NMR. The response behavior was investigated by UV transmittance tests. The LCST of the copolymer P(NVP-co-MA) can vary from 17 °C to 90 °C by adjusting the ratio of the two monomers, showing a wide tunable range. The dynamic light scattering (DLS) results showed that beyond LCST, the hydrodynamic size increased with increasing temperature, polymer molecular chains aggregated in solution, and solubility deteriorated, confirming its LCST responsiveness. In addition, the copolymer P(NVP-co-MA) is salt responsive as well as pH-responsive. The multi-responsive and biocompatible copolymer has a large potential application in the fields of materials and biomedicine.

Thermodynamic properties data of ternary system NH4Cl-NH4H2PO4-H2O at 298.15 K including the solubility data

• Determination of the thermodynamic properties of the system {yNH4Cl+(1-y)NH4H2PO4}(aq) at 25 °C. • Application of the PSC model to describe the thermodynamic behavior of aqueous solutions. • Calculation of NH4Cl and NH4H2PO4 activity coefficients in the system {yNH4Cl+(1-y)NH4H2PO4}(aq). • Prediction of NH4Cl and NH4H2PO4 solubilities in aqueous solution. The mixed aqueous electrolyte system ammonium chloride and ammonium di-hydrogen phosphate has been studied with the hygrometric method at the temperature 298.15 K. The water activities, osmotic coefficient and solubilities are deduced from measurements of relative humidities of this system against total molality ranging from 0.4 mol . kg −1 to about saturation, and for different ionic-strength fractions y of NH 4 H 2 PO 4 ( y = I N H 4 H 2 P O 4 / [ I N H 4 H 2 P O 4 + I N H 4 C l ]) of 0, 1/4, 1/3, 1/2, 2/3, 3/4 and 1. Experimental results are compared to Dinane rule by the Extended Compound Additivity Law (ECA), Leitzke-Stoughton (LS II) and Lin et al. equation. The obtained results were correlated using the PSC model to predict the solute activity coefficients in the mixture for different compositions of the system and are also used to calculate the solubility and excess Gibbs energy in the studied molality range.

An empirical model to represent the CMC behavior of aqueous solutions of homologous series of nonionic surfactants, related to its chemical constitution

• The Critical Micelle Concentration (CMC) is a fundamental property of surfactants. • An empirical model is presented based on the thermodynamics of micellization of a given homologous series of surfactants. • The reason for the observed increase and decrease in CMC value is explained. • The proposed model is compared with other empirical models and its quality to estimate the CMC is superior. Critical Micelle Concentration (CMC) is a fundamental property of surfactants in (aqueous) solution. The importance of defining the CMC of an aqueous surfactant solution is related to the different behavior and performance of the given system below and above its CMC, which has impact on the usage of this type of systems for different industrial applications. In this work, an empirical model is presented, based on the fundamental equation for the thermodynamics of micellization of a given homologous series of surfactants with the same chemical nature, to estimate the corresponding CMC. This simple model contains three adjustable parameters and allows predicting the log[CMC] of the nonionic surfactants polyoxyethylene alkyl ethers (C n E m ) in aqueous solution. The analysis of the three parameters showed that the hydrophobic characteristics play the major role in micelle formation. The polarity of the molecules is also important, but its effect is less pronounced. The proposed model is compared with other empirical models and its quality to estimate the CMC is superior.

Thickening behavior of thermo‐associative water soluble multiblock copolymers under redox RAFT polymerization

AbstractIn this study, the synthesis of thermo‐associative water soluble multiblock copolymers is reported. A trithiocarbonate functionalized polyacrylamide (PAM) was prepared and subsequently utilized in the preparation of three series of thermo‐associative copolymers by addition of N‐isopropylacrylamide (NIPAM) and acrylamide (AM) until reaching a nonablock copolymer with four thermo‐associative blocks distributed into the backbone of polymer. Reactions were performed at 25 °C using a tertbutyl hydroperoxyde (TBHP) and ascorbic acid (As.Ac.) as redox initiator, and S,S′‐Bis (α,α’‐dimethyl‐α”‐acetic acid)‐trithiocarbonate (DMAT) as chain transfer agent. The targeted molecular weight (MnTheo) of PAM was maintained constant (10,000 g/mol) while the expected Mntheo of polyN‐isopropylacrylamide (PNIPAM) was varied from 10,000, 15,000, and 20,000 g/mol, respectively. The synthesized copolymers were characterized by infrared (IR), nuclear magnetic resonance (NMR), size exclusion chromatography (SEC) for determining the structure of materials, whereas ultraviolet (UV) analysis allowed to get access to the cloud point temperature (Tcp) of polymers. Rheological analyses were carried out for examining the effect of thermo‐responsive block on the thickening behavior of aqueous polymer solutions. These analyses were performed at different concentration from 1 to 20 wt. % varying the temperature of measurements from 25, 30, 40, 50, 60, and 70 °C. Results confirmed the influence of the size of thermo‐responsive blocks on the viscosity of these copolymers.

Atomic-Scale Oxide Growth and Dissolution Kinetics on Ni-Cr Alloys

Passivation oxide formation is the key for corrosion control of metal alloys. The kinetics of competing oxide formation and dissolution determines alloy corrosion behaviors in aqueous solution. Despite the important role of the multi-component oxide evolution, little has been known on the kinetics from the atomistic level. To this end, we have built a computational framework that enables simulations of competing kinetic processes in multi-component oxides from first principles. The effects of applied voltage, pH and temperature on oxide growth, dissolution and reprecipitation can all be captured in this model. Combining with our experimental measurements on alloy 22, we identified three voltage regimes with distinct oxide thicknesses and compositions. In the low voltage regime, oxide growth is the dominating process. The Cr/Ni ratio in the oxide is close to that in the alloy. In the medium voltage regime, Ni dissolves from the mixed oxide, NixCryO, and reprecipitates back as Ni oxide, NixO, to achieve phase separation. The resulted oxide film is significantly thickened with a duplex structure formed. In the high voltage regime, Ni dissolution dominates, and the Cr/Ni ratio increases. The temperature and pH dependencies have also been simulated. Higher temperature moves the dissolution-reprecipitation to the lower voltage; lower pH suppresses Ni reprecipitation and results in a thinner oxide film. These trends are also in agreement with the experiments.The oxide energetics of various stoichiometries are calculated by the density functional theory (DFT). Then the obtained data are used to train a surrogate lattice Hamiltonian with the cluster expansion (CE) method. Finally, kinetic Monte Carlo (KMC) simulations are run with the cation hopping barriers calculated on-the-fly based on the local environments from the combination of the above Hamiltonian and the linear Brønsted−Evans−Polanyi (BEP) relation.

Characterizing Recast Nafion® Film Electrode Interface Diffusion and Kinetics in a Non-Aqueous System

The effect of recast Nafion® films on platinum working electrodes in acetonitrile will be characterized by cyclic voltammetry and rotating disk voltammetry. Until now, the behavior of recast Nafion® in a non-aqueous system has not been reported in this way. The behavior of recast Nafion® films in acetonitrile has been anecdotally observed to be different from the behavior in aqueous solutions, which have also been comprehensively studied1,2. The reversible redox couple of Tris(2,2′-bipyridine)ruthenium(II) hexafluorophosphate, Ru(bpy)3 2 ++, in an acetonitrile electrolyte solution will be compared between a bare platinum working electrode and a recast Nafion® film coated platinum working electrode by cyclic voltammetry. In cyclic voltammetry the convective mass transport of the species is limited only to the diffusion at the stationary electrode interface. In rotating the working electrode (RDE) the limitation on mass transport is extended beyond the stationary diffusion behavior. The current is dependent on and limited by the mass transport of the species to the electrode interface where it can undergo redox, the limiting current of both a bare platinum working electrode system and of a recast Nafion® film coated platinum working electrode will be observed by changing the rotation rate of the RDE. The diffusion interface of the electrode inside an acetonitrile solution of Ru(bpy)3 2 + and an electrolyte will be determined by rotating disk voltammetry at a bare platinum working electrode and at a recast Nafion® film coated platinum working electrode. The film solution interface thickness will be reported along with the effect on the diffusion of the interface between bare and recast Nafion® coated platinum working electrodes.1. S. K. Zecevic et al 1997 J. Electrochem. Soc. 144 29732. T. A. Zowodzinski, S. Gottesfeld et al 1997 Advances in Electrochemical Sciences and Engineering

Phase Equilibria, Thermodynamic Behavior, and Transport Properties of Aqueous Solutions of [BMPYR] Trifluoromethanesulfonate and [BMPYR] Tricyanomethanide

Phase Equilibria, Thermodynamic Behavior, and Transport Properties of Aqueous Solutions of [BMPYR] Trifluoromethanesulfonate and [BMPYR] Tricyanomethanide