Linear Sweep Stripping Voltammetry Research Articles

Enhancement of the Negative Capacitance Associated with the Dissolution of Silver by Salt Concentrations by Means of Anodic Stripping Voltammetry

The amount of anodically dissolved charge of silver by linear sweep stripping voltammetry has been observed to be smaller than that of the potentiostatically deposited charge. The imbalance in the charge is opposite to the participation in the double-layer capacitance. This can be explained in terms of the negative capacitive current, which is caused by dipoles of generated redox charge (Ag+) with counterions (NO3−). Lower concentrations of counterions may suppress the capacitance to retain the equality of the charge. This prediction is examined in this work by the oxidation of silver film at various concentrations of NO3− by anodic stripping voltammetry. The capacitance decreased with a decrease in the salt concentrations less than 0.05 mol dm−3. Low concentrations of salts prevent loss of the anodic charge in electroanalysis. This dependence was related with the lifespan of generated silver nitrate dipoles and is described theoretically.

Electrochemical determination of the levels of lead and cadmium in soil samples from Niger and Ogun States, Nigeria: remediation potential with chitosan phosphate and implications for human health and disease

Lead and cadmium poisoning is common in some parts of Nigeria as a result of artisanal mining of gold. The poisoning has led to the deaths of hundreds of women and children below the age of five years. In this study, the concentrations of lead and cadmium in eight soil samples collected from selected artisanal gold mining locations in Niger State and battery dismantling site in Ogun State were electrochemically determined. Linear sweep stripping voltammetry technique was used with glassy carbon as working electrode, Ag/AgCl as reference and platinum as auxiliary electrode. The cathodic peak current for the reduction of lead was observed at − 490 mV while that of cadmium was observed at − 675 mV. The concentrations of lead in the soil samples ranged between 19 and 417 mg/kg while that of cadmium was in the range 20–182 mg/kg. The ability of chitosan phosphate to adsorb lead and cadmium in the polluted soil samples was investigated as a step towards carrying out remediation of the polluted environment. Chitosan phosphate was derived from chitosan which was prepared by the deacetylation of chitin obtained from crab. The chitosan phosphate was found to remove the lead and cadmium from all the soil samples studied.

Development of an Electrochemical Method Employing Carbon Screen-Printed Electrodes (C-SPEs) for Detection and Study of MDMA Redox Process

According to ONU reports, the use of abusive drugs has increased, requiring sensitive techniques for the detection of these substances [1]. This interconnection brings a scenario in which chemical detection of narcotics by conventional, low-cost methods is necessary for drug control. Thus, instrumental analytical techniques appear as indispensable tools for analysis of unknown substances in the forensic field because of their ability to bring low detection limits and selectivity. Thus, the carbon Screen-Printed electrode was elected to develop an electroanalytical method and to study the electrochemical behavior of MDMA for its drug detection potential, low cost, and easy applicability. So, our objective was to develop an electrochemical method with Carbon Screen-Printed electrodes for MDMA detection and study of its redox processes.Palmsens ® Screen-Printed electrodes were utilized in this work. The behavior de the redox processes of MDMA were carried out with a 1.3×10-3 mol L-1 solution in 0.1 mol L-1 phosphate buffer (PBS) at 2.0, 4.0, 6.0, 8.0, 9.0, and 10.0 pH, since MDMA structure can be protonated at the amino group and turns easier the π orbitals delocalization [2]. The MDMA quantification method development utilized PBS 0.1 M at pH 9.0. The absence of cathodic peaks narrowed the sweeps just as anodic. Thus, Cyclic Voltammetry (CV), Linear Sweep Stripping Voltammetry (LSSV), Differential Pulse Voltammetry (DPSV), and Square Wave Stripping Voltammetry (SWSV) were employed. Adulterants such as caffeine (0.31 mmol L-1), lidocaine (0.25 mmol L-1), acetaminophen (0.66 mmol L-1), AAS (0.28 mmol L-1) and phenacetin (0.56 mmol L-1) were utilized to observe possible interference in the MDMA detection.The scan rate study indicated that the anodic peak currents are directly proportional the square root of the scan speed in the range from 5 to 100 mV s-1, indicating that the electron transfer reaction of the MDMA on the electrode is diffusion controlled, as predicted by Randles-Sevcik equation. Using carbon SPE, the influence on the change of electrolyte pH through CV was evaluated. Its It was observed that the best currents are obtained at pH 9.0 with supporting electrolyte in 0.1 mol L-1 concentration. For the development of the analytical method, the investigation of the redox processes of MDMA were obtained with LSSV, SWSV and DPSV. The LSSV modality presented the best peak resolution (1.92 ×10-4 AV-1) when compared to SWSV (9.26 × 10-5 AV-1) and DPSV (1.7 × 10-5 AV-1) ). Using LSSV, the equilibrium time parameter was optimized (2.5 to 80 s), such as MDMA preconcentration potential (-1 to 1 V), electrodeposition time (20 to 600 s), and scan speed (5 to 100 mV.s-1) in the potential range from 0.2 to 1.2 V. The best oxidation currents of MDMA were observed at 10 s equilibrium time, -0.5 V preconcentration potential, and electrodeposition time of 20s, using ν = 20 mV.s-1. The merit figures for the developed method were evaluated through analytical curves. PBS solutions at pH 9.0 were prepared with MDMA concentrations ranging from 8.0×10-5 to 1.3×10-3 mol L-1. The analytical curve showed a linear range in this concentration range with detection limit of 7.3×10-5 mol L-1, amperometric sensitivity of 1.43×10-2 A.mol-1.L and linear correlation coefficient of 0.998. Just lidocaine and phenacetin showed electroactivity in this method, but did not demonstrate interference at MDMA response. The results indicated that the analytical method proposed using linear sweep stripping voltammetry showed good analytical performance indicating that the proposed electrode are able to the detection and determination of MDMA in ecstasy samples. Acknowledgements FAPESP (process n°2019/04439-3, and 2016/23825-3) and CAPES (Pro-Forenses 25/2014).

Bovine Serum Albumin Enhances Silver Nanoparticle Dissolution Kinetics in a Size- and Concentration-Dependent Manner.

The dissolution of silver nanoparticles (AgNPs) to release Ag(I)(aq) is an important mechanism in potentiating AgNP cytotoxicity and imparting their antibacterial properties. However, AgNPs can undergo other simultaneous biophysicochemical transformations, such as protein adsorption, which can mediate AgNP dissolution behaviors. We report the comprehensive analysis of AgNP dissolution and protein adsorption behaviors with monolayer surface coverage of AgNPs by bovine serum albumin (BSA). AgNP dissolution rate constants, kdissolution, were quantified over several particle sizes (10, 20, and 40 nm) and BSA concentrations (0-2 nM) using linear sweep stripping voltammetry. Across all particle sizes, the dissolution rate constant increased with increasing BSA concentrations. However, protein-enhanced dissolution behaviors were most pronounced for 10 nm AgNPs, which exhibited 3.6-fold and 7.7-fold relative enhancement when compared to 20 and 40 nm AgNPs, respectively. Changes to AgNP surface properties upon interaction with BSA were monitored using dynamic light scattering and zeta potential measurements, while BSA-AgNP complex formation was evaluated using UV-vis spectroscopy and circular dichroism spectroscopy. A subtle increase in the BSA-AgNP association constant was observed with an increase in the AgNP size. Together, these results suggest that the AgNP size dependence of BSA-enhanced dissolution of AgNPs is possibly mediated through both displacement of Ag(I)(aq)-loaded BSA by excess protein in the bulk solution and minimized accessibility of the AgNP surface because of BSA adsorption.

In Situ Quantification of Silver Nanoparticle Dissolution Kinetics in Simulated Sweat Using Linear Sweep Stripping Voltammetry.

Linear sweep stripping voltammetry (LSSV) is demonstrated as a sensitive, rapid, and cost-efficient analytical technique for the quantification of silver nanoparticle (AgNP) dissolution rates in simulated sweat. LSSV does not require the extensive sample preparation (e.g., ultrafiltration or centrifugation) needed by more commonly employed techniques, such as atomic spectroscopy. The limit of detection (LOD) of Ag(I)(aq) was 14 ± 6 μg L-1, and measured dissolution rate constants, kdissolution, varied from 0.0168-0.1524 h-1, depending on solution conditions. These values are comparable and agree well with those determined by others in the literature using atomic spectroscopy. Importantly, LSSV had the necessary sensitivity to distinguish the effects of SSW solution conditions on AgNP dissolution rates. Specifically, enhanced dissolution rates were observed with decreased pH and with increased NaCl concentration. The colloidal stability of AgNPs in SSW solutions was also characterized using dynamic light scattering (DLS), ζ potential, and quantitative UV-vis spectroscopy measurements. An increase in AgNP aggregation rate was observed with increased NaCl concentration in SSW, suggesting that the enhancement in AgNP dissolution is driven by the large Cl/Ag ratio, even as the AgNPs undergo significant aggregation.

Highly sensitivity electrochemical sensor based on ErGO/MWCNTs nanohybrid for 2,4-dinitroanisole electroanalysis

An electroreduction process was used to prepare electrochemically reduced graphene oxide/multi-wall carbon nanotubes for detecting 2,4-dinitroanisole (DNAN) by linear sweep stripping voltammetry (LSSV). DNAN is a less delicate explosive organic compound, it is modified by bacterial action when mixed with soil, in human body its converted to 2, 4-dinitrophenol. Reduced graphene oxide/multi-walled carbon nanotubes (ErGO/MWCNTs) nanohybrid was modified onto a glass carbon electrode (GCE) to detect DNAN. The synergistic effect makes the composite to have better electrochemical catalytic activity for DNAN. The composite materials showed the feature of high specific surface area, high conductivity and good electrocatalytic activity enhanced the electrocatalysis for DNAN. Under the optimized conditions, the reduction peak current of ErGO/MWNTs/GCE has a good linear relationship with the corresponding concentration of DNAN in the range of 0.1–5 μM and 5–30 μM. The limit of detection (LOD) is 0.084 μM (S/N = 3). The ErGO/MWCNTs sensor showed high catalytic activity, good selectivity, repeatability and stability towards DNAN.

Size-Dependent Electrophoretic Deposition of Catalytic Gold Nanoparticles.

Here we describe size-dependent electrophoretic deposition (EPD) of citrate-stabilized Au nanoparticles (NPs) onto indium-tin-oxide-coated glass (glass/ITO) electrodes as studied by linear sweep stripping voltammetry (LSSV) and scanning electron microscopy (SEM). LSSV allows both the determination of the Au NP coverage and NP size from the peak area and the peak potential, respectively. Two-electrode EPD in aqueous solutions of Au NPs plus H2O2 reveal that a minimum potential of 1.5 V is needed for significant deposition of 4 nm diameter Au NPs as opposed to 2.0 V for 33 nm diameter Au NPs. EPD at 0.4 V in a solution of Au NPs prepared with a short 5 min reaction time led to the successful capture of 1-2 nm diameter Au NPs with appreciable coverage. In all cases, deposition did not occur in the absence of H2O2. Three-electrode experiments with a real reference electrode revealed the same size selective deposition with potential and that the amount of Au deposited depends on the deposition time and H2O2 concentration. The deposition occurs indirectly by oxidation of H2O2, which liberates protons and neutralizes the citrate stabilizer, leading to precipitation of the Au NPs onto the glass/ITO electrode. Studies on pH stability show that larger Au NPs aggregate at lower pH compared to smaller Au NPs. More importantly, though, 4 nm diameter Au NPs are much more catalytic for H2O2 oxidation, which is the main reason for the size selective deposition.

Electrocatalytic Reduction of Selenate on Gold Electrodes Alongside Copper Deposition

Reduction of aqueous selenate (SeO4 2-) to lower oxidation states of selenium is regarded as a very difficult reaction and thus far, only very few methods have yielded positive results [1-6]. One such previous study asserts that gold electrodes can catalyze reduction of commercial selenate at potentials below 0.6 V vs SHE [1], forming an elemental selenium deposit that can be anodically stripped above 0.9 V vs SHE, (see peaks A and B, black curve in Fig. 1 recorded in 1 mM Na2SeO4 in 0.1 M HClO4). However, commercially supplied selenate usually contains some selenite (SeO3 2-), a far more electroactive selenium oxyanion believed to yield elemental selenium and/or selenides as the product(s) of reduction. In fact, as shown by experiments performed in our laboratories, such voltammetric features vanished upon removal of selenite from the selenate solutions by adsorption on TiO2(see red curve in Fig. 1). This contribution will present strong evidence that the reduction of selenate under the same conditions can proceed on a layer of underpotentially deposited copper on Au, yielding a corresponding layer of CuxSe. To be discussed are various aspects of the formation mechanism of this CuxSe using potentiostatic deposition and linear sweep stripping voltammetry (LSSV) experiments. During LSSV experiments, Cu can be anodically stripped, leaving behind a layer of adsorbed elemental Se (peak C, Fig. 2). At higher potentials, this layer is oxidized to selenite (peak B, Fig. 2) [7-9]. Repetitive formation and oxidation of the CuxSe product on gold electrodes via an AC deposition / stripping waveform may allow for continuous turnover of selenate into selenite.

Electrocatalytic Reduction of Selenate on Gold Electrodes in the Presence of Copper (II)

Reduction of aqueous selenate (SeO4 2-) to lower oxidation states of selenium is typically a very slow reaction, but important to the detection and removal of soluble selenium from wastewater. Electrocatalytic reduction of selenate has not been exhaustively explored; only a few electrocatalytic methods for reducing selenate have been reported to date [1-6]. Commercially available selenate is often contaminated with selenite (SeO3 2-), a species that can be readily reduced to yield elemental selenium or selenides. No selenate reduction studies to date acknowledge the presence of this impurity. Furthermore, not all these studies unambiguously show that selenate itself is reduced, as opposed to these traces of selenite. Previous literature claims that gold electrodes are capable of reducing selenate at electrode potentials below 0.6 V vs SHE [1], forming a selenium deposit that strips anodically above 0.9 V vs SHE. Cyclic voltammetry experiments in this work reproduced the reported redox features, shown in Fig. 1 as peak A and B, respectively. However, when selenite was removed from selenate solutions with a titania adsorbent, no redox activity is seen on gold electrodes. It can be concluded that the previous report [1] was in fact measuring currents associated with trace selenite reduction. Selenate undergoes specific adsorption on gold and no other reaction. Peak C in Fig. 1 can be attributed to specific adsorption of selenate. Figure 1: Cyclic voltammetry at 0.2 V/s on Au wire electrode with 1mM of selenate in 0.1 M HClO4. Two purities of selenate were used. The first was selenate decahydrate purchased from Alfa Aesar at a purity of 99.9%, used as received. The other sample of selenate was the same, but was exposed to a titania adsorbent in order to remove traces of selenite. A cyclic voltammogram is also shown after selenite addition. We have found that the chemical inertness of selenate can be overcome by addition of copper (II) salts. Copper (II) can be reduced to an adlayer of underpotential deposited copper on gold electrodes between 0.64 and 0.24 V SHE. Once formed, we have found that this adlayer induces slow reduction of selenate, yielding a thin copper selenide film. The mechanism for CuxSe formation was investigated using potentiostatic deposition, followed by linear sweep stripping voltammetry. This technique allows determination of Cu and Se stripping charges separately, observed in Fig. 2 as peak D and E, respectively. At lower electrode potentials (< 0.24 V vs SHE), where copper (II) is reduced to bulk copper metal, selenate both accelerates Cu deposition and is reduced. Selenium co-deposits with bulk copper formed in selenate / copper (II) solutions. In this regime, selenate reduction is much faster than reduction by UPD copper. Figure 2: Linear sweep stripping voltammograms at 0.1 V/s after potential holds at 0.325 V on a Au electrode. Solution was 0.1 M HClO4 with 5 mM Cu(ClO4)2 and 1 mM Na2SeO4(titania purified). Potential hold duration for each curve is indicated in the legend.

Liquid / Liquid Interface-Based Electrochemical Sensing of Ractopamine and Salbutamol

An electrochemical sensor based on ion transfer across micro- and nano-liquid / liquid interfaces has been developed for the detection of protonated drugs, ractopamine (RacH+) and salbutamol (SalH+) via cyclic voltammetry (CV) and linear sweep stripping voltammetry (LSSV). These voltammetric methods enabled the detection and characterisation of the ionised drugs despite that they transferred at high applied potentials. The drugs’ thermodynamic and analytical parameters were determined. The limit of detection in the sub-μM range is suitable for applications to detection in real samples. Electrochemistry at the liquid / liquid interfaces was shown to be a viable technique for drug sensing.

Influence of the electrografting method on the performances of a flow electrochemical sensor using modified electrodes for trace analysis of copper (II)

The performances of carboxylate- and cyclam-modified graphite felt electrodes prepared by different electrografting methods for trace analysis of copper (II) were compared to determine the influence of the immobilization process of the linkers on the sensor properties. The derivatization performed by cathodic reduction of diazonium salts and by anodic oxidation of amines in organic and aqueous media was first evaluated by cyclic voltammetry and X-ray photoelectron spectroscopy analyses, showing a higher surface coverage for the reduction process. Cyclam was subsequently attached on the COOH-modified graphite felts by a coupling reaction. The modified electrodes were then employed in a flow analytical system for trace analysis of copper (II) ions. The influence of the surface coverage and the nature of the linker on the electrochemical signal obtained by linear sweep stripping voltammetry analysis after a preconcentration step performed at open circuit was highlighted. The selectivity estimated in the presence of lead used as a common ion interferent was higher when a selective receptor was used and depends on the nature of the linker.

Electrochemical detection of ractopamine at arrays of micro-liquid | liquid interfaces

The behaviour of protonated ractopamine (RacH+) at an array of micro-interfaces between two immiscible electrolyte solutions (micro-ITIES) was investigated via cyclic voltammetry (CV) and linear sweep stripping voltammetry (LSSV). The micro-ITIES array was formed at silicon membranes containing 30 pores of radius 11.09±0.12µm and pore centre-to-centre separation of 18.4±2.1 times the pore radius. CV shows that RacH+ transferred across the water |1,6-dichlorohexane µITIES array at a very positive applied potential, close to the upper limit of the potential window. Nevertheless, CV was used in the estimation of some of the drug’s thermodynamic parameters, such as the formal transfer potential and the Gibbs transfer energy. LSSV was implemented by pre-concentration of the drug, into the organic phase, followed by voltammetric detection, based on the back-transfer of RacH+ from the organic to aqueous phase. Under optimised pre-concentration and detection conditions, a limit of detection of 0.1µM was achieved. In addition, the impact of substances such as sugar, ascorbic acid, metal ions, amino acid and urea on RacH+ detection was assessed. The detection of RacH+ in artificial serum indicated that the presence of serum protein interferes in the detection signal, so that sample deproteinisation is required for feasible bioanalytical applications.

Simultaneous Determination of Iron and Copper in Ethanol Fuel Using Nafion/Carbon Nanotubes Electrode

AbstractThis work presents the analytical method development for iron and copper determination in ethanol fuel. This method was developed using stripping voltammetry with a glassy carbon electrode modified with Nafion/Carbon‐nanotubes. With linear sweep stripping voltammetry was achieved a limit of detection of 7.1×10−7 mol L−1 for Fe3+ and 5.1×10−8 mol L−1 for Cu2+. The amperometric sensitivities were 2.0×106 µA mol−1 L for Fe3+ and 2.8×107 µA mol−1 L for Cu2+. The recovery study showed that the method has good accuracy and repeatability, with recovery of 108 and 103 % for Fe3+ and Cu2+ respectively.

Application of artificial neural networks to the determination of pesticides by linear sweep stripping voltammetry

Abstract In this work, artificial neural network (ANN), a powerful chemometrics approach for linear and non-linear calibration models, was applied to detect three pesticides in mixtures by linear sweep stripping voltammetry (LSSV) despite their overlapped voltammograms. Electrochemical parameters for the voltammetry, such as scan rate, deposit time and deposit potential, were evaluated and optimized from the signal response data using ANN model by minimizing the relative prediction error (RPE). The proposed method was successfully applied to the detection of pesticides in synthetic samples and several commercial fruit samples.

Silver and silver–copper electrodeposition from a pyridinium-based ionic liquid

Silver(I) was extracted from aqueous solutions in the absence and presence of copper(II) with the ionic liquid (IL) 3-butylpyridinium bis(trifluoromethanesulfonyl)imide, [3-BuPyr][NTf2]. After extraction, silver and silver–copper were electrodeposited on glassy carbon at room temperature from the ionic liquid phase. The mechanism of silver electrodeposition has been studied using electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry (CA). At suitably overpotentials silver electrocrystallization proceeds via a diffusion controlled mechanism and was analyzed using the Scharifker and Hills model for potentiostatic growth. The growth-nucleation mechanism of silver from the extracted phase is more progressive in character at low overpotentials, while at elevated overpotentials an instantaneous nucleation behavior was determined. In contrast, the silver nucleation closely followed the response predicted for instantaneous nucleation in neat [3-BuPyr][NTf2]. The electrochemical co-deposit of Ag–Cu was studied by linear sweep stripping voltammetry (LSSV). The resultant electrodeposits were characterized by scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis.

Determination of the Antiretroviral Drug Zidovudine in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

This paper describes a stripping method for the determination of zidovudine at the submicromolar concentration levels. This method is based on the controlled adsorptive accumulation of zidovudine at the thin-film mercury electrode, followed by a linear-sweep stripping voltammetry measurement of the surface species. Optimal experimental conditions include a NaOH solution of 2.0 × 10–3 mol●L–1 (sup-porting electrolyte), an accumulation potential of –0.30 V and a scan rate of 100 mV?s–1. The response of zidovudine is linear over the concentration range 0.01 - 0.08 ppm. After an accumulation time of 5 minutes, the detection limit was found to be 0.67 ppb (2.5 × 10–9 mol●L–1). More convenient methods to measure zidovudine concentration in the presence of the didanosine, acyclovir, nevirapine, lamivudine, and efavirenz, were also investigated. The presence of zidovudine together with ATP or ssDNA demonstrates the utility of this method.

Improvement in performance of a flow electrochemical sensor by using carbamoyl-arms polyazamacrocycle for the preconcentration of lead ions onto the electrode

A flow electrochemical sensor for trace analysis of lead, using TETRAM-modified graphite felt electrode is reported here. TETRAM ligands are covalently immobilized on the graphite felt by chemical reactions on amino acid linkers, previously attached to the electrode by an electrochemical process. The detection is performed in two steps: the preconcentration of Pb 2+ ions by complexation with immobilized TETRAM and the analysis by linear sweep stripping voltammetry. A calibration curve typical of at least two equilibrium processes is obtained. A limit of detection of 2.5 × 10 −8 mol L −1 is reached for a total analysis time of 35 min. Interestingly, the flow sensor shows a good selectivity toward lead in presence of Cu 2+, Cd 2+, Ni 2+, Zn 2+ and Co 2+ ions. This new sensor exhibits improved sensitivity and selectivity compared to the previously reported sensor using cyclam-modified electrode. It is stable after three uses, using strong acidic medium for the regeneration step.

Flow electroanalytical system based on cyclam-modified graphite felt electrodes for lead detection

A flow sensor for trace analysis of lead, using cyclam-modified graphite felt as working electrode is reported here. The detection is performed in two steps: the preconcentration of Pb 2+ ions by complexation with immobilized cyclam and the analysis by linear sweep stripping voltammetry. Cyclam ligands are covalently immobilized onto the graphite felt by chemical reactions on amino acid linkers, previously attached to the electrode by an electrochemical process. A surface concentration of about 12% is estimated by cyclic voltammetry analyses, using redox probes. The factors, affecting the performances of the flow sensor are reported, such as the flow rate and the volume of the analyzed solution used during the preconcentration step. A calibration curve typical of an equilibrium process is obtained for lead ions with a limit of detection able to reach 2.5 × 10 −8 mol L −1, showing the ability of the cyclam-modified electrode to complex Pb 2+ ions. The flow sensor shows a good selectivity toward lead in the presence of Cu 2+ and Zn 2+ ions.

Stripping voltammetry of Pb and Cu using a microcantilever electrode

Microfabricated silicon microcantilevers coated with gold on one side have been used as working electrode in a three-electrode electrochemical arrangement. In addition to electrochemical current, cantilever bending has been used as a signal for monitoring electrode reactions on the cantilever surface. The microcantilever bending was measured by an optical beam deflection method as the surface potential was scanned and electrochemical reactions occurred on the surface. The microcantilever bending due to differential surface stress was used to sense Pb and Cu using cyclic voltammetry (CV) and linear sweep stripping voltammetry (LSSV).

Aluminum UPD and Alloy Formation on (111)-Textured Au in AlCl3-EMIC

The kinetics of Al-Au surface alloy formation was examined during Al underpotential deposition (upd) onto (111)-textured Au from Lewis acidic aluminum chloride - 1-ethyl-3-methylimidazolium chloride (AlCl3-EMImCl) using linear sweep stripping voltammetry following potentiostatic deposition. The upd of Al on Au is a two-step process, the first step may be the reductive decomposition of AlCl4- that is known to be adsorbed on the Au surface. Following completion of the Al monolayer, two alloys are formed. The first is only present at short times and is restricted to the near surface while the second is the more stable of the two and extends into the Au substrate. The upd of Al causes a negative (compressive) change in the surface stress; however the stress change becomes tensile in the region of alloy formation. The magnitude of the tensile stress change observed experimentally is close to that calculated from the elastic strain associated with the change in molar volume and from the reaction kinetics obtained from stripping voltammetry.