Polycrystalline Gold Electrode Research Articles

Mechanistic Analysis of Hydrogen Evolution Reaction on Stationary Polycrystalline Gold Electrodes in H2SO4 Solutions

An impedance model based on the Volmer–Heyrovsky–Tafel mechanism was developed to study the kinetics of the hydrogen evolution reaction on polycrystalline gold electrodes at moderate overpotentials in aqueous H2SO4 (0.5 and 1.0 M) solutions. The model was optimized on data from potentiodynamic polarization and electrochemical impedance spectroscopy, and model parameters were extracted. Consistent with expectations, the magnitude of the impedance data indicated a higher rate of hydrogen evolution at lower pH. Also, the fractional surface coverage of adsorbed hydrogen (θHads) increases with increasing overpotential but the small value of θHads indicates only weak adsorption of H on gold. Tafel slopes and exchange current densities were estimated to be in the range of 81–124 mV/dec, and 10−6 and 10−5 A/cm2 in H2SO4 (0.5 and 1.0 M), respectively. The results show that the model accounts well for the experimental data, such as the steady-state current density. Sensitivity analysis reveals that the electrochemical parameters (α1, α2, k10, k−10, and k20) associated with the kinetics of the hydrogen evolution reaction have a major impact on the calculated impedance but the standard rate constant for hydrogen oxidation reaction (k−20) does not strongly affect the calculated impedance.

Redox Behavior of Arsenic (III) and Copper (II) Mixtures on Ultraflat Au (111) Thin Film Electrodes

The electrochemical behavior of arsenic on gold (Au) electrodes surfaces is of great interest as As is well-recognized as a highly toxic and relatively ubiquitous ground water species. The United States Environmental Protection Agency (USEPA) and World Health Organization (WHO) drinking water standards for arsenic are 10 PPB, or 𝜇g L-1 [1]. These minute ion concentrations necessitate the use of analytical methods with high sensitivity and a low susceptibility to cross interferences. Electrochemical stripping voltammetry is a well-established electroanalytical method for arsenic ions [2]. Polycrystalline gold electrodes are often used due to their high redox stability and relatively low overpotential for hydrogen evolution. We recently explored the use of ultra-flat, thin film, Au(111) electrodes to replace polycrystalline Au for As stripping voltammetry. Previous studies on oriented single crystals showed relatively narrow stripping peaks with greatly improved peak to background ratios on the (111) surfaces [3]. We observed comparatively similar or better stripping behavior on the Au(111) thin film electrodes with correspondingly far less gold usage per electrode. Unfortunately, copper is a known interference for arsenic stripping electroanalysis, with a strong affinity for UPD deposition on gold. We therefore studied the deposition behavior of Cu on Au(111) thin film electrodes and the co- deposition of Cu and As on the Au(111) thin film electrodes to evaluate cross interference effects. Copper redox behavior in 0.5M H2SO4 was characterized by cyclic voltammetry, electro- deposition and linear stripping voltammetry (LSV) measurements. Strong Cu UPD behavior was observed on Au(111) thin films with sharper, better defined redox peaks than polycrystalline electrodes. Arsenic and Cu ions were also co-deposited over a wide range of Cu (II) and As (III) concentrations. Complex redox behavior was observed with strong indications of Cu-As alloy formation. This was confirmed via angle resolved, X-ray Photoemission Spectroscopy (XPS) measurements. Our results also indicate that the electrodeposition efficiency during LSV of As is increased by the co-deposition of Cu. The results of this study have important implications for understanding the nature of Cu (II) interference with electrochemical detection of trace As (III) in water.[1] USEPA. National Secondary Drinking Water Regulations. 2009. https://www.epa.gov/sdwa/drinking-water- regulations-and-contaminants (accessed.[2] USEPA. METHOD 7063: ARSENIC IN AQUEOUS SAMPLES AND EXTRACTSBY ANODIC STRIPPING VOLTAMMETRY (ASV). 1996.[3] Casuse-Driovínto, T. Q.; Rizo, R.; Benavidez, A.; Brearley, A. J.; Cerrato, J. M.; Garzon, F. H.; Herrero, E.; Feliu, J. M. Increased Sensitivity and Selectivity for As(III) Detection at the Au(111) Surface: Single Crystals and Ultraflat Thin Films Comparison. The Journal of Physical Chemistry C 2022, 126 (48), 20343-20353. DOI: 10.1021/acs.jpcc.2c05541.

(Keynote) Iridium Deposition By Galvanic Displacement of Cu on a One-Pot Configuration

Water electrolysis with proton exchange membranes (PEMWE) is expected to play a vital role in the future hydrogen infrastructure. The hydrogen evolution is effectively catalyzed by platinum, and iridium oxide is a highly active and reasonably stable catalyst for the oxygen-evolution reation (OER) [1]. However, iridium is costly and scarce, and efficient utilization of it is necessary for large-scale deployment of PEMWE technology. This can be achieved in various ways, such as dilution with other and cheaper compounds such as Ta2O5 [2] and alloying with more abundant metals followed by post-synthesis-treatment such as de-alloying or surface enrichment [3]. A possible solution is the application of ultra-thin layers of iridium oxide on a less costly substrate. A suitable method for achieving such layers is that of surface-limited galvanic displacement [4], i.e. the underpotential deposition of a metal M followed by its oxidation by another and more noble metal N.In this work we have investigated Ir plating onto a polycrystalline gold electrode by successive galvanic displacement of Cu monolayers in a one-pot method, i.e by performing the Cu underpotential-deposition step in a solution also containing iridium precursors. The process is indicated in the figure. By using low concentrations of the precursors H2IrCl6 and IrCl3 in H2SO4, Cu submonolayers could be formed on a Au(poly) rotating disc electrode by underpotential deposition without any significant direct electrochemical formation of Ir or IrO2. The Cu submonolayer formed was then available for reaction with the Ir precursor before a new Cu submonolayer was formed. By evaluating the amount of Cu deposited in each submonolayer and the resulting Ir deposit, our results indicate that H2IrCl6 is reduced onto the Au electrode as metallic Ir via the formation of Ir(III). Due to transport of Ir(III) away from the reaction surface, this resulted in a low yield. No Ir deposited was achieved from IrCl3 solutions, possibly due to adsorption of irreducible species onto the Au surface.The results will be discussed in terms of possible reaction paths and the relative stability of iridium complexes in chloride-containing solutions. Acknowledgements This work was performed within the project "Metal(-oxide) catalyst-monolayer as cost-effective electrocatalysts for PEM water electrolysis" funded by the Research Council of Norway, contract no. 254976/E20. References Carmo, D. L. Fritz, J. Mergel, and D. Stolten, “A comprehensive review on PEM water electrolysis,” Int. J. Hydrogen Energy, 38, pp. 4901–4934, 2013.Comninellis and G. P. Vercesi, “Characterization of DSA®-type oxygen evolving electrodes: Choice of a coating,” J Appl Electrochem, 21, pp. 335–345, 1991.N. Nong, L. Gan, E. Willinger, D. Teschner, and P. Strasser, “IrOx core-shell nanocatalysts for cost- and energy-efficient electrochemical water splitting,” Chem. Sci., 5, pp. 2955–2963, 2014.Brankovic, J. X. Wang, and R. R. Adžic, “Metal monolayer deposition by replacement of metal adlayers on electrode surfaces,” Surface Science, vol. 474, L173–L179, 2001. Figure 1

Innovative and efficient electroanalytical approach for determining persulfate in aqueous solutions using a gold electrode

Persulfate (PDS), peroxodisulfate, peroxydisulfate, peroxodisulfuric acid, is an oxidant that can be generated by direct oxidation of sulfate ions or indirectly via reaction with hydroxyl radicals in anodes with high oxygen overpotential. Quantitative methods for determining/quantifying PDS in the presence of other strong oxidants or other anions in eco-friendly applications do not give reliable results because of these interferents. Therefore, an additional method is needed to improve the efficacy to determine/quantify the PDS concentration in oxidative environments. In this frame, an alternative sensing approach was developed based on the electroreduction of PDS in the polycrystalline gold electrode using the square wave voltammetry (SWV) technique for its detection and quantification. Then, the procedure was evaluated in terms of its effectiveness for determining PDS in complex matrices, such as in the electrolysis of sulfate ion precursor solutions using anodes with high oxygen overpotential (e.g.: diamond electrode) capable of generating other strong oxidants. Based on the results obtained, it was confirmed that only the direct electron transfer step is attained when PDS is electrochemically synthetized at the surface of the polycrystalline gold electrode, contributing to its detection and quantification by SWV. It was also observed that at acidic conditions, the PDS electroreduction process is controlled by mass transfer while that the sensitivity for PDS detection is improved, achieving detection limits of about 14 and 19 μM for perchloric and sulfuric acids medium, respectively. When the electrolysis of sulfate-based solution at acidic conditions was performed to determine the electrochemical production of PDS by SWV approach with Au sensor, the concentration of PDS was effectively determined and no interferences were assessed by other strong oxidants generated during the electrolysis. Conversely, the spectrophotometric method showed that, the results of the PDS concentration were overestimated and other strong oxidants significantly interfere with its determination during the electrolysis of sulfuric acid solutions. Therefore, the electroanalytical method presented here is a suitable alternative for determining PDS during the applicability of the environmental-electrochemical technologies.

Self-assembled aminothiols: Platforms for ultra-sensitive electrochemical detection of triclosan via surface azo coupling

Extensive use of triclosan (TCS) in commercially available personal and health care products has led to its abundance in environment (water, soil), resulting in adverse impact on aquatic, marine, animal and human life. The present work is intended towards the development of simple and fast electrochemical sensors for trace level detection of TCS in aqueous media. The working of sensors is based on surface diazotization of self-assembled monolayers (SAMs) of two aminothiols, 4-aminothiophenol (4-ATP) and 5-amino-2-mercaptobenzimidazole (AMB) on polycrystalline gold electrodes. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), self-assembly of two aminothiols was confirmed as both offered significant impedance to [Fe(CN)6]3-/4− redox probe. The exposed amino groups of two self-assembled aminothiols were subjected to diazotization and diazo derivatives so formed were utilized as platform for impedimetric sensing of TCS through azo coupling. The step-by-step study of self-assembly, diazotization and azo coupling was conducted using different techniques such as FTIR, UV-visible, NMR, FESEM and EDX. The proposed ATP and AMB based EIS sensors exhibited sensitivity towards TCS in wide linear concentration range of 1.0 × 10-10 M – 1.0 × 10-2 M and 1.0 × 10-12 M – 1.0 × 10-4 M with lower detection limits of 5.6 × 10-11 M and 7.9 × 10-13 M, respectively. A good selectivity was observed in the presence of common metal ions (Na+, K+, Ca2+, Mg2+, Cu2+, Fe3+, Zn2+, Co2+) and surfactants (SDS, Triton X-100, Triton X-114). Using proposed EIS sensors, the estimation of TCS in personal care products (soap, facewash, handwash) and water samples (surface and groundwater) has been successfully achieved.

Investigation of copper underpotential deposition on polycrystalline gold electrodes

A combination of cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry techniques has been used to study the underpotential deposition (UPD) of copper on polycrystalline gold (pc Au) electrodes. The experiments were conducted in an electrolyte composed of CuSO4 (5 mM) and H2SO4 (0.5 M). The results revealed that the concentration of copper (II) ions and the applied voltage exerted a synergistic effect on the position, shape, and range of spanning of the curves describing the redox potential and current density. The charge transfer resistance (Rct) corresponding to the UPD of Cu decreased monotonically with a decrease in the applied voltage, and the phase angle shifted toward high-frequency regions with a negative shift in the potential. The process of UPD of Cu on pc Au can be divided into three stages: Langmuir-type adsorption, growth of Cu monolayers on pc Au following the process of two-dimensional instantaneous nucleation, and the continuous two-dimensional nucleation of grains on the Cu layer. UPD on single crystal substrates and the single-layer and multi-layer structures associated with UPD have been extensively studied worldwide. However, the UPD of polycrystalline electrodes with various crystal faces, grain boundaries, and defects is complex, and the associated mechanism has rarely been studied. In recent years, the process of UPD has been widely used in various fields, such as fields associated with electrochemical sensing, fabrication of fuel cells, electrochemical CO2 reduction, and fabrication of solar cells.

Electric double layer contribution to sum frequency generation signal from Au electrode.

Understanding the electric double layer (EDL) of the metal electrode-electrolyte interface is essential to electrochemistry and relevant disciplines. In this study, potential-dependent electrode Sum Frequency Generation (SFG) intensities of polycrystalline gold electrodes in HClO4 and H2SO4 electrolytes were thoroughly analyzed. The potential of zero charges (PZC) of the electrodes was -0.06 and 0.38V in HClO4 and H2SO4, respectively, determined from differential capacity curves. Without specific adsorption, the total SFG intensity was dominated by the contribution from the Au surface and increased similar to that of the visible (VIS) wavelength scanning, which pushed the SFG process closer to the double resonant condition in HClO4. However, the EDL contributed about 30% SFG signal with specific adsorption in H2SO4. Below PZC, the total SFG intensity was dominated by the Au surface contribution and increased with potential at a similar slope in these two electrolytes. Around PZC, as the EDL structure became less ordered and the electric field changed direction, there would be no EDL SFG contribution. Above PZC, the total SFG intensity increased much more rapidly with potential in H2SO4 than in HClO4, which suggested that the EDL SFG contribution kept increasing with more specific adsorbed surface ions from H2SO4.

Electrochemistry and Mass Transport of Ytterbium(III) in Bis(trifluoromethylsulfonyl)imide-Based Room-Temperature Ionic Liquids: Effects of Temperature, Viscosity, and Electrode Materials

Cyclic staircase voltammetry, rotating disk electrode voltammetry, controlled potential coulometry, and electrochemical impedance spectroscopy were used to probe the electrochemistry and mass transport of Yb3+ in the six room temperature ionic liquids based on the bis(trifluoromethylsulfonyl)imide (Tf2N−) anion with, 1-(1-butyl)−3-methylimidazolium (BuMeIm+), 1-(1-butyl)−1-methylpyrrolidinium (BuMePyro+), 1-(1-butyl)pyridinium (BuPy+), 1-butyltrimethylammonium (BuMe3N+), 1-ethyl-3-methylimidazolium (EtMeIm+), and tri(1-butyl)methylammonium (Bu3MeN+) cations. These investigations were carried out at glassy carbon as well as polycrystalline gold, platinum, and tungsten electrodes. The heterogeneous electron transfer rate of the quasireversible Yb3+/2+ redox couple was found to depend strongly on the electrode materials with the fastest rate observed at gold and the slowest rate found at tungsten, but was independent of the physicochemical properties of the various ionic liquids, in particular, the absolute viscosity. However, the mass transport of Yb3+ was dependent on the viscosity, and the temperature dependence of the diffusion coefficients was well represented by a Vogel-Tammann-Fulcher type expression for glass-forming ionic liquids. Analysis of the diffusion coefficient data with the Stokes-Einstein equation indicated that the solvodynamic radius of the diffusing Yb3+ was constant and independent of the structure and properties of the ionic liquid cations. The solvodynamic radius of Yb3+ was estimated from the “stick model” for the Stokes-Einstein equation. Application of the Random Closest Packing (RCP) model for spheres in consideration of the solvodynamic radius of the diffusing Yb3+ and the ionic radii of Yb3+ and Tf2N−, indicated that the former must diffuse in association with ∼5–6 of the anions.

Sulfur adlayer on gold surface for attaining H2O2 reduction in alkaline medium: Catalysis, kinetics, and sensing activities

The sensitive detection of hydrogen peroxide (HP) on Au surface is quite challenging owing to the potential dependent decomposition of HP. The current study investigated the development of chemisorbed sulfur adlayer onto the surface of the polycrystalline gold electrode to attain electroreduction of hydrogen peroxide in an alkaline medium using cyclic voltammetry (CV), chronoamperometry, and square wave voltammetry (SWV) measurement techniques. The sulfur adsorbed layer significantly reduces the decomposition of hydrogen peroxide onto the Au (pc) electrode surface allowing the hydrogen peroxide reduction process to proceed. The kinetic diagnosis suggests that the reduction is mass transfer controlled process where electron transfer is the rate determining step in the concerned reduction reaction. The presented electrochemical sensor exhibited high sensitivity and a quick amperometric response to HP in the concentration range of 10–2000 μM, with a detection limit of 6.0 μM.

Spectroelectrochemical Studies of CTAB Adsorbed on Gold Surfaces in Perchloric Acid.

The behaviour of CTAB adsorbed on polycrystalline gold electrodes has been studied using a combination of spectroelectrochemical methods. The results indicate that the formation of the layer is the consequence of the precipitation of the CTAB micelles on the electrode surface as bromide ions, which stabilize the micelles, are replaced by perchlorate anions. This process leads to the formation of CTA+ layers in which perchlorate ions are intercalated, in which the adlayer suffers a continuous rearrangement that leads to the formation of micro-dominions of different types of hydrogen-bonded water populations throughout the adlayer. After prolonged cycling, a stable situation is reached. Under these conditions, water molecules permeate through the adlayer toward the electrode surface at potentials positive of the potential of zero charge, due to the repulsion between the CTA+ layer and the positive charge of the electrode.

Electrochemical properties of Au Nanoparticles

TiO2 NPs powder (titanium oxide nanoparticles powder) is synthesized via anodization in 0.7 M HClO4 is annealed in N2 at 450°C for 3 hrs to obtain the TiO2 NPs -N2 powder as catalyst support to which Au is loaded via photodeposition technique using tetrachloroauric acid (HAuCl4) and isopropanol as a sacrificial donor. The physicochemical characterizations of TiO2 NPs arrays powder were performed by transmission electron microscopy (TEM). The TEM image suggested that Au nanoparticles were circular and there was a tendency of agglomerations. The electro-catalytic activity of Au NPs/TiO2-NTs-N2 catalysts in ferrocyanide system , KOH ,and H2SO4 electro-oxidation was examined by cyclic voltammetry (CV) and contrasted with a financially accessible polycrystalline gold electrode. Au-TiO2 NPs-N2 powder electrode catalyst displays a strikingly high electrocatalytic activity in KOH and H2SO4 solutions. The results indicate Au NPs/TiO2-NTs-N2 catalysts as a promising support material improve the excellent electro-catalytic activity for acidic and basic oxidation.

Gold nanoparticles loaded on TiO2 nanoparticles doped with N2 as an efficient electrocatalyst for glucose oxidation: preparation, characterization, and electrocatalytic properties

A powder of titanium oxide nanoparticles (TiO2 NPs) was synthesized in this study by anodizing in 0.7 M HClO4 and then annealing in N2 at 450 °C for 3 h to produce TiO2 NPs-N2 powder as a catalyst. These TiO2 NPs-N2 nanoparticles were then encrusted with Au nanoparticles utilizing the photodeposition procedure with tetrachloroauric acid (HAuCl4) and isopropanol as sacrificial donors. With a surface area of 121 m2g−1, the Au NPs/TiO2 NPs-N2 powder catalyst has a high surface area, according to the Barrett–Joyner–Halenda technique. According to X-ray diffraction (XRD) analysis, TiO2 NPs-N2 contained uniformly integrated Au nanoparticles with an average crystallite size of about 26.8 nm. The XRD patterns showed that the prepared Au NPs/TiO2 NPs-N2 were crystallites and nano-sized. The transmission electron microscopy image revealed the spherical shape of the nanoparticles and their tendency for agglomeration. Utilizing the cyclic voltammetry, the electrochemical properties of the catalyst TiO2 NPs powders in a basic glucose solution were investigated. The electrocatalytic activity and stability of the loaded Au NPs/TiO2 NPs-N2 powder on the working electrode for the electrocatalytic oxidation of glucose were astonishingly high. The Au NPs/TiO2 NPs-N2 catalyst demonstrated electrocatalytic characteristics that were superior to a commercially available polycrystalline gold electrode in the application involving glucose alkaline fuel cells.

Development of [I(ads)|Au(pc)] electrode to attain electrocatalytic oxidation of paracetamol: An efficient platform for quantitative analysis

Electrochemical oxidation of paracetamol (PCT) has exclusively been investigated using polycrystalline gold electrode modified with iodine adlayer [I(ads)|Au(pc)] in alkaline medium. Irreversible adsorption of PCT makes Au(pc) surface unfeasible for studying PCT oxidation reaction. This limitation of Au(pc) surface could be eliminated simply by iodide (I-) adsorption. It was noticed that the spontaneous I- adsorption blocks PCT adsorption sites on Au(pc) surface, which additionally improves PCT oxidation reaction by increasing electron transfer rate. Iodine adlayer (I-adlayer) formulated electrode facilitated PCT electro-oxidation via an alternative diffusion-controlled pathway with an anodic electron transfer coefficient (β) of 0.47 and heterogeneous rate constant (ko) of 0.0911 cm s−1 where an electron transfer step determines the reaction rate. The sensing experiments revealed that the [I(ads)|Au(pc)] electrode attained linear dynamic range from 4.5 to 1600 μM of PCT. The obtained sensitivity and limit of detection (LOD) of the [I(ads)|Au(pc)] electrode surface was determined to be 8.37( ± 1.6)× 10−4 mA cm−2 μM−1 and 0.65 ± 0.02 μM, respectively. The formulated [I(ads)|Au(pc)] catalyst was applied to quantify the relative PCT percentage in commercial tablets using batch injection analysis supported by chronoamperometry. Obtained relative percentage closely matched with the corresponding analysis performed with Raman spectroscopy. Therefore, developed I-adlayer coated Au(pc) electrode is analytically robust and validated for routine analysis of PCT concentration in relevant pharmaceutical applications.

The application of cyclic voltammetry and digital simulation for the examination of hydroquinone oxidation at a polycrystalline gold electrode in HClO4

The application of cyclic voltammetry and digital simulation for the examination of hydroquinone oxidation at a polycrystalline gold electrode in HClO4

Self-Assembled Monolayer of Monomercaptoundecahydro-closo-dodecaborate on a Polycrystalline Gold Surface.

In this work, we present an electrochemical study of the boron cage monomercaptoundecahydro-closo-dodecaborate [B12H11SH]2− in solution and in a self-assembled monolayer over a polycrystalline gold electrode. Cyclic voltammetry of the anion [B12H11SH]2− in solution showed a shift in the peak potentials related to the redox processes of gold hydroxides, which evidences the interaction between the boron cage and the gold surface. For an Au electrode modified with the anion [B12H11SH]2−, cyclic voltammetry response of the probe Fe(CN)63−/Fe(CN)64− showed a ΔEp value typical for a surface modification. Electrochemical impedance spectroscopy presented Rtc and Cdl values related to the formation of a self-assembled monolayer (SAM). A comparison of electrochemical responses of a modified electrode with thioglycolic acid (TGA) reveals that the boron cage [B12H11SH]2− diminishes the actives sites over the Au surface due to the steric effects. Differential capacitance measurements for bare gold electrode and those modified with [B12H11SH]2− and (TGA), indicate that bulky thiols enhance charge accumulation at the electrode–solution interface. In addition to electrochemical experiments, DFT calculations and surface plasmon resonance measurements (SPR) were carried out to obtain quantum chemical descriptors and to evaluate the molecular length and the dielectric constant of the Boron cage. From SPR experiments, the adsorption kinetics of [B12H11SH]2− were studied. The data fit for a Langmuir kinetic equation, typical for the formation of a monolayer.

Influence of experimental conditions on the electrochemical window. Case study on bis(trifluoromethylsulfonyl)imide-based ionic liquids

Ionic liquids (ILs) are often selected as electrolytes in various devices, such as batteries, capacitors and sensors, because of their chemical stability, non-flammability, low volatility, high electrical conductivity, low melting point, high thermal stability, and wide electrochemical window (EW). The width of the EW of an IL depends on the cation type, the water content, the electrode material, and the chosen specific current density used to measure it. In this work, the EWs of four ILs containing the common and stable bis(trifluoromethylsulfonyl)imide anion and triethylsulfonium, 1-(2-hydroxyethyl)-3-methylimidazolium, 1-methyl-1-propylpiperidinium and 1-butyl-1-methylpiperidinium cations were investigated by linear sweep voltammetry in order to analyze their electrochemical stability toward reduction and oxidation at polycrystalline platinum, gold and glassy carbon disc electrodes under anhydrous conditions. Specific current densities of 0.1 mA·cm−2 or 1 mA·cm−2 or the linear fitting method were used for the systematic comparison of the EWs obtained from each dataset. The results indicate the dependence of the EW width of each IL on the electrode material and, more importantly, on the chosen specific current density. In this paper, we present new insight into some of the difficulties encountered during determination of the EW for ILs.

Spotlight on the Effect of Electrolyte Composition on the Potential of Maximum Entropy: Supporting Electrolytes Are Not Always Inert.

The influence of electrolyte pH, the presence of alkali metal cations (Na+, K+), and the presence of O2 on the interfacial water structure of polycrystalline gold electrodes has been experimentally studied in detail. The potential of maximum entropy (PME) was determined by the laser‐induced current transient (LICT) technique. Our results demonstrate that increasing the electrolyte pH and introducing O2 shift the PME to more positive potentials. Interestingly, the PME exhibits a higher sensitivity to the pH change in the presence of K+ than Na+. Altering the pH of the K2SO4 solution from 4 to 6 can cause a drastic shift in the PME. These findings reveal that, for example, K2SO4 and Na2SO4 cannot be considered as equal supporting electrolytes: it is not a viable assumption. This can likely be extrapolated to other common “inert” supporting electrolytes. Beyond this, knowledge about the near‐ideal electrolyte composition can be used to optimize electrochemical devices such as electrolyzers, fuel cells, batteries, and supercapacitors.

A Novel Amperometric Genosensor for Rapid Detection of Canine Parvovirus in Feces.

A highly sensitive novel amperometric genosensor has been developed for rapid detection of canine parvovirus (CPV) DNA in fecal swabs of naturally infected dogs. The genosensor is based on a single stranded 5°-thiolated (SH) DNA probe complementary to VP1/VP2 gene of canine parvo vaccine strain, immobilized covalently on a polycrystalline gold (Au) electrode. The genosensor has been characterized by scanning electron microscopy (SEM), Fourier Transform Infra-Red Spectroscopy (FTIR), cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectra (EIS). The ssDNA-SH/Au electrode was hybridized with single stranded target DNA (ss T-DNA) in the sample. This hybridization was detected by reduction in current, generated by interaction of methylene blue (MB) with free guanine of ssDNA. The current response of genosensor was determined by CV, DPV and EIS. The sensor detected single stranded genomic DNA (ss g-DNA) isolated from vaccine strain of CPV in the range, 1.0-12.0 ng/μl at 25 °C for 10 min. Subsequently, the genobiosensor was applied for detection of CPV viral DNA in fecal swabs of naturally infected dogs. The limit of detection (LOD) of the sensor was 1.0 ng/μl of fecal viral DNA. To the best of our knowledge, this is the first report on development and application of amperometric biosensor for rapid, sensitive, specific point of care detection of viral DNA of CPV in feces.

The electrosorption of 3-bromo-2-nitrothiophene on gold as studied with surface-enhanced Raman spectroscopy

The electrosorption of 3-bromo-2-nitrothiophene on a polycrystalline gold electrode has been studied with surface-enhanced Raman spectroscopy SERS. Results imply a tilted orientation of the 3-bromo-2-nitrothiophene molecule with a sulfur atom of the thiophene ring and oxygen atoms of the nitro group interacting directly with the gold surface. The UV-Vis spectrum of the 3-bromo-2-nitrothiophene is recorded and its results indicated that the SERS spectra were measured under off-resonance conditions. Cyclic voltammetry measurements of the 3-bromo-2-nitrothiophene were made and the oxidation and reduction potentials of the 3-bromo-2-nitrothiophene at the gold electrode have been reported. The experimental infrared and Raman data are supported by density functional theory (DFT) calculations of 3-bromo-2-nitrothiophene using the B3LYP level of theory and 6-31G (d) basis set. The vibrational frequencies of the molecule were computed using the optimized geometry obtained from the DFT calculations. The calculated spectra are very close to the recorded infrared and Raman of the solid 3-bromo-2-nitrothiophene. No imaginary frequencies are observed in the calculated spectra. Also, DFT calculations are performed to predict and investigate the adsorption behavior of 3-bromo-2-nitrothiophene on the Au surface. In this DFT calculations, the adsorbed 3-bromo-2-nitrothiophene on the gold electrode surfaces was modeled as the metal−molecule complex. Synopsis: Electrosorption of 3-bromo-2-nitrothiophene on a polycrystalline gold electrode was discussed. The adsorption orientation and adsorption sites of the 3-bromo-2-nitrothiophene molecule at the gold surface were reported. Electrochemical investigations show a reversible redox behavior in the anodic and cathodic scan direction. The computed frequencies of the 3-bromo-2-nitrothiophene molecule support the results obtained from the recorded IR and Raman spectra.

Capacitive Hysteresis Effects in Ionic Liquids: 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate on Polycrystalline Gold Electrode

Ionic liquids (ILs) add complexity to electrochemical interfaces that cannot be adequately treated with traditional double layer models. We present a series of carefully controlled capacitance measurements to optimize the collection of reproducible and uniform capacitance-potential datasets. We quantitatively evaluate analysis methods on the experimentally observed capacitance of l-ethyl-3-methylimidazolium trifluoromethauesulfonate [Emim][TFO] IL at the gold-IL interface. The major outcomes of our work are to identify how experimental data collection methods affect capacitive hysteresis, and to suggest a systematic approach to collect reproducible capacitance data for IL systems. We evaluate different potential scan directions, examine varying potential sweep rates, and capacitance collection methods. We find that faster scan rates can mitigate the capacitive hysteresis between the anodic and cathodic scans for a particular collection technique. However, faster scan rates also result in more variation between the collection techniques. We also find that decreasing the effective potential sweep rate reduces hysteresis between different collection techniques when other factors are held constant. It is crucial for researchers to consistently report the direction of the potential sweep and the effective rate of potential sweep. Our data suggest that using slower effective potential perturbation rates would reduce discrepancies in capacitance data collected from different laboratories under different experimental conditions.