Range Of Reduction Potentials Research Articles

First and Second Reductions in an Aprotic Solvent: Comparing Computational and Experimental One-Electron Reduction Potentials for 345 Quinones.

Using reference reduction potentials of quinones recently measured relative to the saturated calomel electrode (SCE) in N,N-dimethylformamide (DMF), we benchmark absolute one-electron reduction potentials computed for 345 Q/Q•- and 265 Q•-/Q2- half-reactions using adiabatic electron affinities computed with density functional theory and solvation energies computed with four continuum solvation models: IEF-PCM, C-PCM, COSMO, and SM12. Regression analyses indicate a strong linear correlation between experimental and absolute computed Q/Q•- reduction potentials with Pearson's correlation coefficient (r) between 0.95 and 0.96 and the mean absolute error (MAE) relative to the linear fit between 83.29 and 89.51 mV for different solvation methods when the slope of the regression is constrained to 1. The same analysis for Q•-/Q2- gave a linear regression with r between 0.74 and 0.90 and MAE between 95.87 and 144.53 mV, respectively. The y-intercept values obtained from the linear regressions are in good agreement with the range of absolute reduction potentials reported in the literature for the SCE but reveal several sources of systematic error. The y-intercepts from Q•-/Q2- calculations are lower than those from Q/Q•- by around 320-410 mV for IEF-PCM, C-PCM, and SM12 compared to 210 mV for COSMO. Systematic errors also arise between molecules having different ring sizes (benzoquinones, naphthoquinones, and anthraquinones) and different substituents (titratable vs nontitratable). SCF convergence issues were found to be a source of random error that was slightly reduced by directly optimizing the solute structure in the continuum solvent reaction field. While SM12 MAEs were lower than those of the other solvation models for Q/Q•-, SM12 had larger MAEs for Q•-/Q2- pointing to a larger error when describing multiply charged anions in DMF. Altogether, the results highlight the advantages of, and further need for, testing computational methods using a large experimental data set that is not skewed (e.g., having more titratable than nontitratable substituents on different parent groups or vice versa) to help further distinguish between sources of random and systematic errors in the calculations.

Chemiluminescence and electrochemiluminescence of water-soluble iridium(III) complexes containing a tetraethylene-glycol functionalised triazolylpyridine ligand

BackgroundIridium(III) complexes, exhibiting high luminescence quantum yields and a wide range of emission colours, are promising alternatives to tris(2,2ʹ-bipyridine)ruthenium(II) for chemiluminescence (CL) and electrochemiluminescence (ECL) detection. This emerging class of reagent, however, is limited by the poor solubility of many iridium(III) complexes in aqueous solution, and lack of understanding of their remarkably variable selectivities towards different analytes. ResultsSeven [Ir(C^N)2(pt-TEG)]+ complexes, exhibiting a wide range of reduction potentials and emission energies, were examined with six model analytes. For CL, cerium(IV) was used as the oxidant. The alkylamine analytes generally produced greater CL and ECL with the more readily oxidised Ir(III) complexes (C^N = piq, bt, ppy), predominantly through the ‘direct’ pathway requiring oxidation of both metal complex and analyte. Aniline derivatives that did not also contain secondary or tertiary alkylamines elicited CL from the less readily oxidised complexes (C^N = df-ppy-CF3, df-ppy) via energy transfer. The most difficult to oxidise complexes (C^N = df(CF3)-ppy-Me, df(CN)-ppy) gave poor responses due to the limited potential window of the solvent and inefficiency of energy transfer to their high energy excited states. Greater CL and/or ECL intensities were generally obtained for each analyte with at least one Ir(III) complex than with [Ru(bpy)3]2+; superior limits of detection for two analytes were demonstrated. SignificanceThis exploration of CL/ECL in which the properties of luminophore, analyte and oxidant are all varied provides a new understanding of the influence of the metal-complex potentials and excited state energy on the light-producing and quenching pathways, and consequently, their distinct selectivity towards different analytes. These findings will guide the development of water-soluble Ir(III) complexes as CL and ECL reagents.

Symmetric dicyanobenzothiadiazole (DCBT) dyes with a 1.5 eV excited state reduction potential range.

Strong molecular photooxidants are important in many disciplines including organic synthesis and renewable energy. In these fields, strongly oxidizing chromophores are employed to drive various transformations from challenging bond formations to energy storage systems. A range of photooxidant strengths are needed to drive these processes. A series of 8 symmetrically bisarylated 5,6-dicyano[2,1,3]benzothiadiazole (DCBT) dyes were studied for their tunability toward breadth of light absorption and photooxidant strength. The dye oxidation strength and light absorption tunability is the result of appending various aryl substituents on the periphery of the DCBT core which shows remarkable tunability of the final chromophore. The dyes are studied via steady-state absorption and emission, time-correlated single photon counting, computational analysis, and cyclic voltammetry. In changing the peripheral aryl substituents via electronics, sterics, and π-conjugation length, a series of dyes are arrived at with a dramatic 1.5 eV range in oxidizing strength and >200 nm (0.95 eV) absorption maxima tunability. Furthermore, two dyes in the series exhibit strong oxidizing strength while still approaching red light absorbance (>650 nm onset) which provides unique opportunities for the use of lower energy light to affect chemical transformations. Ultimately, this series provides options for photooxidations that allow for energetic tuning and selectivity for a given chemical transformation.

Electrochemical Diagnosis of Urinary Tract Infection Using Boron-Doped Diamond Electrodes.

Efficient detection of sodium nitrite in human urine could be used to diagnose urinary tract infections rapidly. Here, we demonstrate a fast and novel method for the selective detection of sodium nitrite in different human urine samples using electrolysis with a bare boron-doped diamond electrode. The measurement is performed without adding any other species, such as enzymes, and uses a simple electrochemical approach with an oxidation step followed by reduction. In the present study, we pay attention to the reduction potential range for the measurement, which is substantially different from many previous literature reports that focus on the oxidation reaction. The determination of added sodium nitrite based on cyclic voltammetry or differential pulse voltammetry is employed for two pooled urine samples and three individual urine matrices. From this, the linear response ranges for sodium nitrite detection are 0.5-10 mg/L (7.2-140 μmol/L) and 10-400 mg/L (140-5800 μmol/L). The results from these urine samples convert well to the calibration curve, with a limit of detection established as 0.82 mg/L (R2 = 0.9914), which is clinically relevant.

Development of Coriander Honey loaded CeO2 for cyclic voltammetry, chemical sensor, dye purification, and antioxidant properties

BackgroundThe present study was involved the CH-doped CeO2 NPs using low-cost and environmental friendly like coriander honey (CH). Besides, CH-doped/CeO2 NPs was employed as sensor, electrochemical, and water treatment activities of the synthesized NPs. MethodsThe coriander honey was used as a supporting materials to synthsized CH-doped/CeO2 NPs by simple reflux method. Various spectroscopic techniques were used to analysed including UV-Vis, XRD, IR, SEM, and EDAX. Significant FindingsIt is exposed that was employed as the electrochemical analysis was performed using cyclic voltammetry with 3M KOH, which yielded a specific capacitance of 155.7 Fg−1 and proton diffusion coefficient results of about 1.89×10−4. The study also examined the composite material's sensing properties using some chemicals like mercury chloride, lead nitrate, and cow urine (gomutra) is an eco-friendly liquid, and found them to perform well within the oxidation and reduction potential range. Photocatalytic studies were conducted using methyl violet (MV) and Congo red (CR) dye, which showed a high degradation rate of 95.1 and 78.7%, respectively, demonstrating first-order kinetics with the coriander honey/CeO2 NPs composite. Finally, the antioxidant property of the composite material was tested using the free radical scavenging method with DPPH (2,2-diphenyl-1-picrylhydrazyl), yielding an activity of 79.37% and an IC50 value of 5581.157mg/mL.

Orchestrating copper binding: structure and variations on the cupredoxin fold.

A large number of copper binding proteins coordinate metal ions using a shared three-dimensional fold called the cupredoxin domain. This domain was originally identified in Type 1 "blue copper" centers but has since proven to be a common domain architecture within an increasingly large and diverse group of copper binding domains. The cupredoxin fold has a number of qualities that make it ideal for coordinating Cu ions for purposes including electron transfer, enzyme catalysis, assembly of other copper sites, and copper sequestration. The structural core does not undergo major conformational changes upon metal binding, but variations within the coordination environment of the metal site confer a range of Cu-binding affinities, reduction potentials, and spectroscopic properties. Here, we discuss these proteins from a structural perspective, examining how variations within the overall cupredoxin fold and metal binding sites are linked to distinct spectroscopic properties and biological functions. Expanding far beyond the blue copper proteins, cupredoxin domains are used by a growing number of proteins and enzymes as a means of binding copper ions, with many more likely remaining to be identified.

Deactivation and regeneration of a benchmark Pt/C catalyst toward oxygen reduction reaction in the presence of poisonous SO2 and NO

Adsorbed SO2 on Pt sites can be substituted by NO; adsorbed NO can be completely reduced to NH4+ and removed in a reduction potential range.

Estimating the Reducing Power of Carbon Nanotubes and Granular Activated Carbon Using Various Compounds

Determining the degree of the reducing power of multi-walled carbon nanotubes (MWCNTs) and granular activated carbon (GAC) enables their effective application in various fields. In this study, we estimate the reducing power of carbon nanotubes (CNTs) and GAC by measuring the reduction degree of various compounds with different reduction potentials. MWCNTs and GAC materials can reduce Cr(VI), Fe(III) and PMo12O403−, where the reduction potentials range from +1.33 V to +0.65 V. However, no reduced forms of PW12O403− and SiW12O404− compounds were detected, indicating that the reducing power of MWCNTs and GAC is insufficient for reduction potentials in the range +0.218 V to +0.054 V. MWCNTs exhibit a short reduction time (5 min), whereas GAC exhibits a gradually increasing reduction degree of all the compounds assessed until the end of the reaction. This indicates a higher reduction degree than that of MWCNTs systems. Acidic initial pH values favor reduction, and the reduction degree increases as the pH becomes lower than 4.0. Moreover, large quantities of MWCNTs and GAC increase the concentrations of the reduced compounds.

The Redox-Active Conopeptide Derived from the Venom Duct Transcriptome of Conus lividus Assists in the Oxidative Folding of Conotoxin.

The tetrapeptides Li504 and Li520, differing in the modification of the 4-trans-hydroxylation of proline, are novel conopeptides derived from the venom duct transcriptome of the marine cone snail Conus lividus. These predicted mature peptides are homologous to the active site motif of oxidoreductases that catalyze the oxidation, reduction, and rearrangement of disulfide bonds in peptides and proteins. The estimated reduction potential of the disulfide of Li504 and Li520 is within the range of disulfide reduction potentials of oxidoreductases, indicating that they may catalyze the oxidative folding of conotoxins. Conformational features of Li504 and Li520 include the trans configuration of the Cys1-Pro2/Hyp2 peptide bond with a type 1 turn that is similar to the active site motif of glutaredoxin that regulates the oxidation of cysteine thiols to disulfides. Li504- and Li520-assisted oxidative folding of α-conotoxin ImI confirms that Li520 improves the yield of the natively folded peptide by concomitantly decreasing the yield of the non-native disulfide isomer and thus acts as a miniature disulfide isomerase. The geometry of the Cys1-Hyp2 peptide bond of Li520 shifts between the trans and cis configurations in the disulfide form and thiol/thiolate form, which regulates the deprotonation of the N-terminal cysteine residue. Hydrogen bonding of the hydroxyl group of 4-trans-hydroxyproline with the interpeptide chain unit in the mixed disulfide form may play a vital role in shifting the geometry of the Cys1-Hyp2 peptide bond from cis to trans configuration. The Li520 conopeptide together with similar peptides derived from other species may constitute a new family of "redox-active" conopeptides that are integral components of the oxidative folding machinery of conotoxins.

Spectral Probe for Electron Transfer and Addition Reactions of Azide Radicals with Substituted Quinoxalin-2-Ones in Aqueous Solutions.

The azide radical (N3●) is one of the most important one-electron oxidants used extensively in radiation chemistry studies involving molecules of biological significance. Generally, it was assumed that N3● reacts in aqueous solutions only by electron transfer. However, there were several reports indicating the possibility of N3● addition in aqueous solutions to organic compounds containing double bonds. The main purpose of this study was to find an experimental approach that allows a clear assignment of the nature of obtained products either to its one-electron oxidation or its addition products. Radiolysis of water provides a convenient source of one-electron oxidizing radicals characterized by a very broad range of reduction potentials. Two inorganic radicals (SO4●−, CO3●−) and Tl2+ ions with the reduction potentials higher, and one radical (SCN)2●− with the reduction potential slightly lower than the reduction potential of N3● were selected as dominant electron-acceptors. Transient absorption spectra formed in their reactions with a series of quinoxalin-2-one derivatives were confronted with absorption spectra formed from reactions of N3● with the same series of compounds. Cases, in which the absorption spectra formed in reactions involving N3● differ from the absorption spectra formed in the reactions involving other one-electron oxidants, strongly indicate that N3● is involved in the other reaction channel such as addition to double bonds. Moreover, it was shown that high-rate constants of reactions of N3● with quinoxalin-2-ones do not ultimately prove that they are electron transfer reactions. The optimized structures of the radical cations (7-R-3-MeQ)●+, radicals (7-R-3-MeQ)● and N3● adducts at the C2 carbon atom in pyrazine moiety and their absorption spectra are reasonably well reproduced by density functional theory quantum mechanics calculations employing the ωB97XD functional combined with the Dunning’s aug-cc-pVTZ correlation-consistent polarized basis sets augmented with diffuse functions.

Biophysical Characterization of Iron-Sulfur Proteins.

Iron-sulfur proteins are primordial catalysts and biological electron carriers that today drive major metabolic pathways across all forms of life. They can access a diversity of oxidation states and can mediate electron transfer over an extended range of reduction potentials spanning more than 1 V. Depending on the protein micro-environment and geometry of ligand, co-ordination the iron-sulfur clusters can occur in different forms [2Fe-2S], [3Fe-4S], HiPIP [4Fe-4S], and [4Fe-4S]. There are several spectroscopic methods available to characterize the composition and electronic configuration of the iron-sulfur clusters, such as optical methods and electron paramagnetic resonance. This paper presents the protocols used to characterize the metal center of Coiled-Coil Iron-Sulfur (CCIS), an artificial metalloprotein containing one [4Fe-4S] cluster. It is expected that these protocols will be of general utility for other iron-sulfur proteins.

Theoretical design and exploration of low-valent uranium metallocenes via manipulating cyclopentadienyl substituent

Over a century of investigations on uranium complexes resulted in great progress in establishing their fundamental properties and developing applications. However, the in-depth understanding of uranium chemistry, particularly in record low + II valence, is still challenging due to rare crystallographically-identified U(II) complexes, extremely low stability and rigid synthetic conditions. Herein, to further expand experimental findings, various substituted-cyclopentadienyl uranium complexes, [U(CpX)3]n (X = Me, H, Cl, SiMe3 and 2SiMe3; n = -1 and 0), have been explored using relativistic density functional theory. It is shown that the reduction from [U(CpX)3] to [U(CpX)3]– slightly strengthens the U-Cp bonding, while the great enhancement is found in previously reported uranium arene analogues. The + III oxidation state is assigned to the metal of [U(CpX)3]; in contrast, it is approximately + II valence for [U(CpX)3]– because of non-negligible electron density residing on the CpX ligands, whose amount positively correlates with the electron-withdrawing ability of X substituent. Calculated reduction potentials range from −3.02 to −2.74 V while considering solvation and spin–orbit coupling effects. The largest value of the chloride complex couples is attributed to the better balance of electronic and steric effects.

Electro-Carboxylation of Furfural By CO2 in γ-Valerolactone

The continuous rise of global warming and depletion of fossil fuel resources has led to the development of new ways of valorization of non petro-sourced chemicals. In this objective, it is important to develop electrochemical valorization processes of CO2, a greenhouse gas, for the synthesis of valuable molecules. When the CO2 electroreduction is performed in aqueous media, the competitive HER will decrease the energetic efficiency and the rapid deactivation of reaction intermediates will lead to side products such as CO, formic acid, oxalic acid and small chain hydrocarbons [1]. To circumvent these issues and create value added chemicals, reductive electro-carboxylation reactions can be performed in polar aprotic solvents (DMF, DMSO, acetonitrile or NMP) in the presence of tetraalkylammonim bromide or chloride as electrolytes [2].In this work, we focused on non-aqueous bio-sourced solvent, the γ-valerolactone (GVL), to perform a carboxylation reaction of bio-sourced molecules like furfural by electroreduction of CO2. The reductive electro-carboxylation of furfural was studied at a Pt/C electrode was studied in a bio-sourced GVL with tributylmethylammonium chloride (TBMACl) as electrolyte. The solvent behavior in the CO2 reduction potential range was studied by in situ FTIRS measurements which indicated that GVL reacted at the electrode in the absence of furfural and/or of CO2, while the presence of furfural and/or of CO2 made the solvent much less reactive. The electrochemical study showed that the CO2 electroreduction started at from the high cathodic potential of −0.8 V vs SCE (saturated calomel electrode) and the coupling of electrochemistry with in situ FTIRS demonstrated that it reacted with furfural.The reductive electro-carboxylation was then performed in an electrolysis cell. The cell voltage was maintained at 2.0 V (corresponding to a cathode potential of -1.9 V vs. SCE) for 24 h. In absence of furfural, gas chromatography coupled with mass spectroscopy (GC–MS) analyses revealed the formation of oxalic acid (coupling reaction of CO2) as main reaction product. In the presence of furfural in the reaction medium, a new carboxylated specie, 2-furyl(hydroxy)acetic acid, was identified as the main reaction product. 1H NMR and LC-MS analyses further confirmed the formation of this compound, demonstrating the potentialities of bio-sourced solvents for reduction electro-carboxylation of a bio-sourced molecule by reduction of CO2[3].[1] Y. Hori, Electrochemical CO2 reduction on metal electrodes, in: C. Vayenas, R. White, M. Gamboa-Aldeco (Eds.), Modern Aspects of Electrochemistry, 42, Springer, NewYork 2008, pp. 89–189[2] R. Matthesses, J. Fransaer, K. Binnemans, D.E. De Vos, Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids, Beilstein J. Org.Chem. 10 (2004) 2484–2500.[3] Florent Boissou, S. Baranton, M. Tarighi, K. De Oliveira Vigier, C. Coutanceau, The potency of γ-valerolactone as bio-sourced polar aprotic organic medium for the electrocarboxlation of furfural by CO2. J. Electroanal. Chem. 848 (2019) 113257

The Type 1 Blue Copper Site: From Electron Transfer to Biological Function.

Cupredoxins host in their scaffold one of the most studied and interesting metal sites in biology: the type 1 (T1) or blue Cu center. Blue Cu proteins have evolved to play key roles in biological electron transfer and have the ability to react with a wide variety of redox partners. The inner coordination sphere of T1 Cu sites conserves two histidines and one cysteine with a short Cu-S(Cys) bond as ligands in a trigonal arrangement, with a variable axial ligand that modulates the electronic structure and reactivity. The structural, electronic and geometric features of T1 Cu centers provide the basis for a site that can be optimized by the protein structure for each biological function. This chapter highlights the properties that make this unique Cu center in biology an efficient and tunable electron transfer site. The contributions of the first coordination shell and the high covalency of the Cu-S(Cys) bond in the T1 Cu site to its distinctive geometric and spectroscopic features are discussed, as well as the role of the protein scaffold in imposing an 'entatic' state with a distorted tetrahedral geometry that minimizes geometric changes upon redox cycling. The analysis of naturally occurring perturbed blue Cu sites provides further insights into how the protein scaffold can tune the properties of the T1 Cu site. Blue Cu sites display a wide range of reduction potentials, as these are tuned to be consistent with their physiologically relevant electron donors and acceptors. The different properties of the protein matrix that play important roles in finetuning the reduction potential of T1 Cu sites are also discussed, including the nature of the axial ligand and outer coordination sphere effects. These concepts are further illustrated by the discussion of examples of biosynthetic blue Cu proteins. Finally, the different features of the T1 Cu site that make it an optimal site for electron transfer (ET) are discussed, in terms of Markus theory for intra- and inter-molecular ET. The active site in multicopper oxidases is used as an example to illustrate the contributions of the anisotropic covalency of the blue Cu site to an efficient ET, while the diverse reactivity of the T1 Cu sites in these enzymes is discussed to dissect the different properties provided by the protein that help tune these unique sites for biological ET.

Heterobimetallic Single-Source Precursors: A Springboard to the Synthesis of Binary Intermetallics

Intermetallics are atomically ordered crystalline compounds containing two or more main group and transition metals. In addition to their rich crystal chemistry, intermetallics display unique properties of interest for a variety of applications, including superconductivity, hydrogen storage, and catalysis. Because of the presence of metals with a wide range of reduction potentials, the controlled synthesis of intermetallics can be difficult. Recently, soft chemical syntheses such as the modified polyol and ship-in-a-bottle methods have helped advance the preparation of these materials. However, phase-segregated products and complex multistep syntheses remain common. Here, we demonstrate the use of heterobimetallic single-source precursors for the synthesis of 10–15 and 11–15 binary intermetallics. The coordination environment of the precursor, as well as the exact temperature used play a critical role in determining the crystalline intermetallic phase that is produced, highlighting the potential versatility of this approach in the synthesis of a variety of compounds. Furthermore, we show that a recently developed novel plasma-processing technique is successful in removing the surface graphitic carbon observed in some of the prepared compounds. This new single-source precursor approach is a powerful addition to the synthesis of atomically ordered intermetallic compounds and will help facilitate their further study and development for future applications.

Designing Redox-Active Oligomers for Crossover-Free, Nonaqueous Redox-Flow Batteries with High Volumetric Energy Density

Here we show how to design organic redox-active solutions for use in redox-flow batteries, with an emphasis on attaining high volumetric capacity electrodes that minimize active-material crossover through the flow cell’s membrane. Specifically, we advance oligoethylene oxides as versatile core motifs that grant access to liquid redox-active oligomers having infinite miscibility with organic electrolytes. The resulting solutions exhibit order-of-magnitude increases in volumetric capacity and obviate deleterious effects on redox stability. The design is broadly applicable, allowing both low potential and high potential redox centers to be appended to these core motifs, as demonstrated by benzofurazan, nitrobenzene, 2,2,6,6-tetramethylpiperidin-1-yl)oxyl, and 2,5-di-tert-butyl-1-methoxy-4-(2′-methoxy)benzene pendants, whose reduction potentials range from −1.87 to 0.76 V vs Ag/Ag+ in acetonitrile. Notably, the oligoethylene oxide scaffold minimizes membrane crossover relative to redox-active small molecules,...

Triplet-State Dissolved Organic Matter Quantum Yields and Lifetimes from Direct Observation of Aromatic Amine Oxidation.

Excited triplet state chromophoric dissolved organic matter (3CDOM*) is a short-lived mixture of excited-state species that plays important roles in aquatic photochemical processes. Unlike the study of the triplet states of well-defined molecules, which are amenable to transient absorbance spectroscopy, the study of 3CDOM* is hampered by it being a complex mixture and its low average intersystem crossing quantum yield (ΦISC). This study is an alternative approach to investigating 3CDOM* using transient absorption laser spectroscopy. The radical cation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), formed through oxidation by 3CDOM*, was directly observable by transient absorption spectroscopy and was used to probe basic photophysical properties of 3CDOM*. Quenching and control experiments verified that TMPD•+ was formed from 3CDOM* under anoxic conditions. Model triplet sensitizers with a wide range of excited triplet state reduction potentials and CDOM oxidized TMPD at near diffusion-controlled rates. This gives support to the idea that a large cross-section of 3CDOM* moieties are able to oxidize TMPD and that the complex mixture of 3CDOM* can be simplified to a single signal. Using the TMPD•+ transient, the natural triplet lifetime and ΦISC for different DOM isolates and natural waters were quantified; values ranged from 12 to 26 μs and 4.1-7.8%, respectively.

DFT modeling of structures and redox potentials of wild-type, Nickel-substituted and mutated (N47S/M121L, HPAz) Azurin

Azurin (Az) from Pseudomonas aeruginosa is a redox active protein belonging to the family of cupredoxins. Cupredoxins span a wide range of reduction potentials (E0) going from stellacyanin having the lowest potential of ca. 184mV to rusticyanin showing the higher potential of ca. 680mV. Several works have been devoted to the understanding of the factors influencing E0 by changing primary coordination sphere ligands or exploring secondary coordination sphere mutations. To this goal, a series of Az mutants have been designed and showed that E0 could be tuned over a very broad range (between 90mV and 640mV) without significantly perturbing the metal binding site. Among these mutants, the HPAz variant showed the highest E0 value (970mV) ever reported for Az while a significant lowering of E° value (−590mV) has been reached in a Ni-substituted Az. In this paper, we computed the B3LYP energies and Gibbs free energies of oxidized and reduced models of wild-type Az, Ni-substituted Az and two mutants (N47S/M121L and HPAz) of the protein Az to estimate their E0. The results show that the employed strategy is able to reproduce the experimental lowering or increasing of E0 among the studied Az proteins.

Physicochemical and corrosion properties of sono-electrodeposited Cu-Ni thin films

Cu-Ni thin films were electroplated from a bath containing fixed amount of Ni and three different concentration of copper in order to make Cu:Ni molar ratio of 1:10, 1:15 and 1:20 in static and ultrasonic condition. Electrochemical characterization i.e. cyclic voltammetry (CV) was done to know the reduction potential range for Cu-Ni co-deposition. Corrosion study revealed that films synthesized under static condition had better corrosion protective behavior as compared to films in ultrasonic condition. X-ray diffraction (XRD) patterns were recorded and it showed that alloying was better in presence of ultrasound. Surface morphology was examined by scanning electron microscopy, atomic force microscopy and composition analysis was done by energy dispersive spectroscopy (EDS) studies. Both morphology and composition showed a strong dependence on bath concentration and ultrasonic irradiation. EDS analysis showed that the films are Ni rich in static condition and Cu rich in presence of ultrasound. Hardness was tested by Micro-Vickers hardness tester where films in presence of ultrasound were found to have better hardness value due to refined grain size. Thickness and residual stress of the films were measured by Stylus surface profilometer. Film thickness varied from 1.98–2.16 μm in static condition which got increased to 2.69–3.59 μm in presence of sonication for equal period of deposition. Residual stress analysis reported a stress value ranging from 172.43 to 273.18 GPa in static condition which showed a remarkable decrease to 35.25–82.34 GPa in ultrasonic condition.

(Invited) Electrodeposition of Yttrium Alloy from Ionic Liquids for High Performance Oxygen Reduction Reaction Catalysts

The oxygen reduction reaction (ORR) can be greatly improved when the traditional used Pt catalyst is alloyed with yttrium. According to density functional theory calculations, the activity of polycrystalline Pt3Y electrodecan be enhanced relative to pure Pt by afactor of 6-10.[1] Experimental preparation of PtY alloy is limited to physical method such as gas aggregation[2] ormagnetron co-sputtering. [3] The mass activity of ORR at 0.9VRHE is as high as 3.05A mgPt -1obtained from a PtxY particle of 9nm in diameter.[2]However there is no firm evidence of the possibility of mass production of PtY alloy with high catalytic performance in ORR from chemical method because yttrium reacts with even trace amount of water and oxygen. To solve this problem, electrodeposition is considered to be a possibility. It is well known that yttrium is extremely basic metal with a reduction potential -2.43VRHE and electroplating of yttrium from aqueous solutions is believedto be unattainable due to intensive hydrogen evolution at such large over potentials. This problem can be solved using ionic liquids as solvent and electrolyte. They are appropriate medium for the electrodeposition of yttrium and its alloys, because the area of electrochemical stability of ionic liquids overlaps the range of reduction potentials of yttrium.[4] We selected 1-ethyl-3-methylimidazolium tetrafluoroborate to electrodeposit yttrium on glassy carbon substrate.[5]A controlled method is applied to form PtY alloy based on the electrodeposited yttrium. The ORR activity is evaluated by both half cell and full cell characterizations.