Poly-3,4-ethylenedioxythiophene Film Research Articles

PCN-222 MOF decorated conductive PEDOT films for sensitive electrochemical determination of chloramphenicol

PCN-222, a kind of zirconium-based porphyrinic metal-organic frameworks, was decorated on poly 3,4-ethylenedioxythiophene (PEDOT) films modified ITO electrode to fabricate a sensitive chloramphenicol (CAP) sensor. The designed PCN-222-CHIT/PEDOT/ITO sensor combined the CAP adsorption of PCN-222 and the good conductivity of PEDOT films. Cyclic voltammetry and differential pulse voltammetry techniques was examined to investigate the electrochemical performances of this sensor. Under the optimized experimental condition, the proposed sensor exhibited an ultralow detection limit of 0.0018 μM (S/N = 3). Good anti-interference ability and reproducibility were also displayed. Furthermore, the designed sensor realized the accurate detection of CAP in the real sample. • PCN-222-CHIT/PEDOT/ITO displayed the synergistic effect between the CAP adsorption of PCN-222 and the conductive PEDOT films. • The sensing performance of PCN-222-CHIT/PEDOT/ITO sensor was optimized systematacially. • An ultralow detection limit of PCN-222-CHIT/PEDOT/ITO sensor was obtained.

Oxidative MLD of Conductive PEDOT Thin Films with EDOT and ReCl5 as Precursors.

Because of its high conductivity and intrinsic stability, poly(3,4-ethylenedioxythiophene (PEDOT) has gained great attention both in academic research and industry over the years. In this study, we used the oxidative molecular layer deposition (oMLD) technique to deposit PEDOT from 3,4-ethylenedioxythiophene (EDOT) and a new inorganic oxidizing agent, rhenium pentachloride (ReCl5). We extensively characterized the properties of the films by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Raman, and conductivity measurements. The oMLD of polymers is based on the sequential adsorption of the monomer and its oxidation-induced polymerization. However, oMLD has been scarcely used because of the challenge of finding a suitable combination of volatile, reactive, and stable organic monomers applicable at high temperatures. ReCl5 showed promising properties in oMLD because it has high thermal stability and high oxidizing ability for EDOT. PEDOT films were deposited at temperatures of 125–200 °C. EDS and XPS measurements showed that the as-deposited films contained residues of rhenium and chlorine, which could be removed by rinsing the films with deionized water. The polymer films were transparent in the visible region and showed relatively high electrical conductivities within the 2–2000 S cm–1 range.

Structure, optical and sensory properties of poly-3,4-ethylenedioxythiophene films doped with graphene oxide

The conditions of electrochemical deposition of the poly-3,4-ethylenedioxythiophene (PEDOT) thin films and the PEDOT films doped with graphene oxide (GO) on the surface of a transparent SnO2 electrode have been established. As it has been shown by the transmission electron microscopy (TEM) the synthesized polymer films have the globular structure with uniform distribution of aggregates with the measuring of 80–90 nm. It has been found that the doping of PEDOT with GO nanoparticles led to the increase of globule sizes to 200–250 nm and composite structure formation with graphene oxide. The PEDOT doping with GO caused changes in the optical spectra of the polymer film and significantly increased (by 10 times) the sensory sensitivity of the obtained films to nitrogen (IV) oxide.

Electrochemical Characteristics of Azo Dyes Doped Poly(3,4-Ethylenedioxythiophene)

In the present study, the electrosynthesis and the electrochemical characterization of azo dyes doped poly(3,4-ethylenedioxythiophene (PEDOT) were described. PEDOT film was electrochemically deposited onto indium doped tin oxide (ITO) coated/glass electrode, following azo dyes adsorption. The electropolymerized-PEDOT films on ITO glass were doped with various azo dyes; 4-Phenylazo-2-phenyliminomethyl-phenol (PAPM), 4-Phenylazo-2-(p-tolyimino-methyl)-phenol (PATM) and 4-[(2-Hydroxy-5-phenylazo-benzylidene)-amino]-benzenesulfonic acid (HPAB). The structures of azo dyes-doped PEDOT were characterized via cycle voltammograms and electrochemical impedance spectroscopy (EIS). Diverse doping counterions have a significant influence on the electrochemical behaviour of electropolymerized-PEDOT film. The electropolymerized-PEDOT doped by HPAB (PEDOT-HPAB) film possesses higher electrochemical activity than other azo dye-doped PEDOT composites. The main characteristics of PEDOT-azo dyes films contain uniformity, durability, and adherent on ITO electrodes, which are better when it is compared to PEDOT film.

Electrochemical PEDOT Sensor for Antioxidantsin Beverages and Milks

Introduction The conducting polymer PEDOT (poly(3,4-ethylenedioxythiophene)) as an electrochemical sensor element possesses redox-mediating properties that allow excellent separation of signals due to antioxidants present in beverages such as teas and coffee [1]. This includes the phenolic acids present in white wines, with specific features noted for nanostructured microelectrodes [2]. Excellent separation of signals due to ascorbic acid and sulfites, alongside the response due to the oxidation of polyphenols in beverages, has been achieved using the redox-mediating properties of PEDOT [3]. Method PEDOT films were grown by cycling to +1.2 V (Ag/AgCl) on 3 mm dia. glassy carbon electrodes and 10 µm dia. gold microelectrodes in 0.1 M EDOT/ 0.1 M LiClO4 in propylene carbonate at 100 mV s-1. The electrodes were then transferred to undiluted milks (c. pH 6.5), or to an aqueous 0.1 M sodium phosphate buffer (PBS) at pH 6.6 containing uric acid and ascorbic acid standards, prior to testing by cyclic voltammetry (CV). A background PEDOT curve was taken in the PBS solution and subtracted from the voltammograms obtained for the milk samples. Results and Conclusions The PEDOT sensor showed an excellent response for the oxidation of uric acid, with an anodic peak seen at 350 mV (Ag/AgCl), taken at pH 6.6, with both uric acid standards and undiluted milks [4]. A small peak due to ascorbic acid was at times located close to 0 mV, enabling the simultaneous detection of the two antioxidants. Very good linear relationships were obtained between peak current intensities and concentrations in the range of 6-100 μM for uric acid and 30-500 μM for ascorbic acid. The newly developed sensor was then successfully applied to 36 commercial milk samples for a fast voltammetric determination of uric acid and ascorbic acid concentration. An independent HPLC analysis was also performed immediately after running the same milk samples, with a pre-treatment step to remove fats and proteins from the milk. The average difference between the results for uric acid from the two methods was 7%, demonstrating an acceptable degree of agreement between the two measurement methods. At the same time the results were obtained much more rapidly with the electrochemical method than in the lengthy HPLC procedure.The polyphenols present in teas, chocolate and flavoured milks present additional analytical challenges, due to strong adsorption effects. PEDOT-modified electrodes have been successfully developed to quantify flavonoids present in chocolate-flavoured milks, and hydroxycinnamic acids present in coffee-flavoured milks. Strong adsorption effects were seen with regular and flavoured milks at PEDOT microelectrodes. Rather than a diffusion-controlled plateau current, peaks with current densities up to 1000 times greater than observed at the corresponding macroelectrodes were observed, consistent with an extremely high surface area and fractal-type growth of PEDOT at microelectrodes [2].

Relationship between Charge Transfer Diffusion Coefficients and Doping Level for electro generated thin PEDOT films on ITO

Thin films of poly-3,4-ethylene dioxythiophene (PEDOT) were electrodeposited on transparent electrodes of indium tin oxide (ITO) using potentiostatic regime. These films had thicknesses ranging from 15 nm to 60 nm and were studied using UV-vis absorption and chronoamperometric techniques in monomer-free tetrabutylammonium perchlorate/acetonitrile solutions. The charge transfer diffusion coefficient (D) of the films were calculated using Cottrell model for a wide range of potential steps from −1.60 to 1.60 V vs. Ag°/AgNO3. For p-doped films, the highest diffusion coefficients were obtained when a potential of 0.70 V was applied. Moreover, a direct relationship between film thickness and their diffusion coefficients was found for thin PEDOT films showing D values up to 1.4 × 10−9 cm2 s−1 for 60 nm thickness films. These values are remarkably higher than the D of 1.8 × 10−11 cm2 s−1 obtained for spin-coated PEDOT: PSS films of similar thickness.

Methanol electro-oxidation by nanostructured Pt/Cu bimetallic on poly 3,4 ethylenedioxythiophene (PEDOT)

Herein, we report the preparation, characterisation and electrocatalysis of Pt/Cu bimetallic nanostructure formed on Poly 3,4 ethylenedioxythiophene (PEDOT) modified glassy carbon electrode, Pt-Cu-PEDOT/GC. A three-step procedure was adopted for the fabrication of the catalyst. Initially the glassy carbon electrode (GC) was modified by a uniform coating of PEDOT by potential cycling. Copper NPs were then deposited on the PEDOT film by deposition from a 2 mM solution of CuSO4 in 0.1 M NaClO4 at a constant potential of −0.477 V vs. SCE. Pt/Cu-PEDOT/GC catalyst was prepared by substitution of copper by galvanic displacement with various concentrations of H2PtCl6. The electrode thus prepared displayed very good electrocatalytic effect for methanol oxidation characterized by cyclic voltammetry. It was found that the catalyst prepared with 2 mM H2PtCl6 exhibited the highest catalytic activity, with If/Ib values of 1.80 and 1.38 for methanol concentrations of 1 M and 5 M, respectively. At a relatively low Pt loading of 5.48 × 10−6/cm2, the Pt/Cu-PEDOT/GC should be a cost-effective alternative anode catalyst for DMFC.

Polymer Sensitive Elements for Gas Sensors of Ammonia

The influence of ammonia on the optical absorption spectra of thin films of polyaniline (PANI), poly-3,4-ethylenedioxythiophene (PEDOT), mixtures thereof, and the bilayer film structures based on PANI and PEDOT obtained by electrochemical method were studied. The kinetics of changes in the optical absorption of these structures under the action of ammonia was explored in the spectral range of 350 ... 900 nm. We proved that the thin-film structure of PANI / PEDOT significantly extends the spectral range of sensitivity to ammonia of individual PANI n PEDOT films by superposition of high gas sensitivity of PANI and PEDOT films in the range of wavelength of 500 ... 700 nm and 350... 550 nm respectively. It was shown that the area under the spectra of change of the optical absorption of thin-film structure of PANI / PEDOT is in 1.45 times larger than the area of the same for individual components of the layers, which is the key to increasing the sensitivity of the gas sensors. The results can be used to optimize ammonia gas sensors for monitoring biotechnological processes in food industry and the environment.

Synthesis and Characterization of Poly-3,4-ethylenedioxythiophene/2,5-Dimercapto-1,3,4-thiadiazole (PEDOT-DMcT) Hybrids

Organosulfur Compounds (OSCs) represent an attractive alternative as organic cathode materials for electrochemical energy storage (EES) applications. They intrinsically have high gravimetric capacity (although low volumetric) and are typically inexpensive, since they are composed of abundant elements (i.e. C, N, O, and S). However, OSCs, specifically thiolate-containing OSCs generally suffer from slow charge transfer kinetics. To mitigate the charge transfer limitations, conducting polymers (CPs) such as poly-3,4-ethylenedioxythiophene (PEDOT) have been employed as electrocatalysts. In this manuscript, we have covalently modified a PEDOT film with an OSC (i.e. 2,5-dimercapto-1,3,4-thiadiazole di-lithium salt (Li2DMcT)). We have developed a synthetic strategy that employs, for the first time, a post-polymerization modification reaction as a tractable and viable technique to modify organic materials for EES electrodes. Electrochemical characterization, via cyclic voltammetry showed the expected pseudocapacitive response of PEDOT with the superimposed faradaic processes of the covalently bound DMcT. Moreover, spectroscopic characterization using Raman spectroscopy provided mechanistic insights into the electrochemical reactions. Furthermore, we electropolymerized films onto coin-cell electrodes and tested them in half-cell configurations and found that the capacity retention of the films was significantly enhanced, when compared with the PEDOT/DMcT composites (mixed but not covalently bound).

Characterization of PEDOT Films for Electrochromic Applications

Poly 3,4-ethylenedioxythiophene (PEDOT) films were formed on Indium Tin Oxide (ITO)-coated glass by electrodeposition. Cyclic voltammetry, AFM and UV-Vis spectroscopy were employed to investigate the properties of the PEDOT films. Two different types of PEDOT films, i.e., (i) smooth and homogenous surface with pinnacle-like structure and (ii) rough and nonhomogenous with grain-like structure) were produced in two ways. These included varying deposition times and by applying different deposition potentials. The surface roughness of the PEDOT films increased with increasing deposition time and applied potential used. The smooth film prepared at +1.1 V for 15 s has good electrochromicc and optical properties. However, its stability over repetitive usage is inadequate and needs further improvement.

Synthesis and electrochemical properties of composite films based on poly-3,4-ethylenedioxythiophene with inclusions of silver particles

The electrochemical behavior of PEDOT/Ag composite films obtained by chemical deposition of ultrafine Ag particles into the poly-3,4-ethylenedioxythiophene (PEDOT) matrix was studied. The film morphology was characterized by transmission electron microscopy (TEM). The changes in the mass of the films during the chemical deposition of silver into the polymer structure were evaluated microgravimetrically. The mass of the included metallic silver particles depends on the synthesis time and the initial concentration of silver ions in solution. The cyclic voltammograms (CVs) of PEDOT/Ag films in sodium nitrate solutions and sodium nitrate solutions with additions of chloride ions were studied. The cyclic voltammograms of PEDOT/Ag films in chloride-containing solutions showed the peaks of the oxidation of silver and reduction of the oxidation product, which were absent on the CVs of the starting PEDOT film.

A liquid-junction-free reference electrode based on a PEDOT solid-contact and ionogel capping membrane

Liquid-junction-free reference electrodes have been prepared on screen printed substrates using poly-3,4-ethylenedioxythiophene (PEDOT) as solid-contact and novel ionogels as capping membrane. The chemico-physical properties of the PEDOT layer were tuned by changing the electropolymerization media and the electrodeposition technique. Electrodepositing PEDOT films potentiostatically or potentiodynamically were found to have a significant impact on the stability of the electrodes during the conditioning step. Optimization of the capping membrane formulation, e.g., acrylate monomers, ionic liquid, cross-linkers and photo-initiators, produced electrodes with properties almost equivalent with a commercial reference electrode. Thus, calibration plots of Na+ ion-selective electrodes against the optimized solid-contact ionogel reference electrodes (SCI-REs) or against a double-liquid junction Ag/AgCl electrode did not present any significant difference. Such SCI-REs may provide an effective route to the generation of future low-cost components for potentiometric sensing strips.

PEDOT-supported Pd nanoparticles as a catalyst for hydrazine oxidation

Composite poly-3,4-ethylenedioxythiophene (PEDOT)/palladium (Pd) films were obtained by chemical deposition of dispersed palladium nanoparticles into PEDOT conducting polymer matrix. The amounts of palladium particles incorporated into PEDOT films were estimated by electrochemical quartz crystal microbalance measurements. It was shown that palladium loading depends on the time a PEDOT film is exposed in the solution, containing Pd(II)-ions, on the concentration of Pd(II) ions and the film thickness. X-ray photoelectron spectroscopy data have confirmed the presence of metallic palladium in the polymer. The morphology of pristine and composite films as well as the size of Pd nanoparticles and their distribution were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From SEM images, it was found that Pd particles decorated PEDOT globular structures as quasi-spherical particles, and their mean size was dependent on synthesis conditions. The nanoparticles were non-uniformly dispersed on the polymer surface. The comparison of TEM images of composite PEDOT/Pd films obtained for different times of metal loading was made. The remarkable effect of loading time on the size of particles has been established: the mean size of dominating palladium particles was close to 6–10 nm for 30 s of metal deposition, and it was getting larger with the increase of deposition time (close to 15–30 nm for 120 s). It is most likely that with prolongation of synthesis time, the deposition of palladium predominantly proceeds on the already deposited palladium clusters, resulting in the extension growth of their size. Catalytic properties of PEDOT/Pd composite films were studied in respect to hydrazine oxidation by cyclic voltammetry and voltammetry on rotating disk electrode. The obtained data allow to conclude that the process of hydrazine oxidation on PEDOT/Pd composites takes place predominantly on palladium particles, located on the surface or in the near-surface layers of the polymer. The diffusion nature of the limiting current of hydrazine oxidation on composite PEDOT/Pd film in phosphate buffer solution рН = 6.86 was confirmed, and hydrazine diffusion coefficient was calculated. The increase of the limiting currents of hydrazine oxidation with the increase of Pd deposition time was observed, resulting from the increase of the active surface area of palladium particles, acting as microelectrodes. The electroanalytical applications of these nanocomposite materials for the determination of hydrazine were demonstrated.

Electrochromic enhancement of latent fingerprints by poly(3,4-ethylenedioxythiophene)

Spatially selective electrodeposition of poly-3,4-ethylenedioxythiophene (PEDOT) thin films on metallic surfaces is shown to be an effective means of visualizing latent fingerprints. The technique exploits the fingerprint deposit as an insulating mask, such that electrochemical processes (here, polymer deposition) may only take place on deposit-free areas of the surface between the ridges of the fingerprint deposit; the end result is a negative image of the fingermark. Use of a surfactant (sodium dodecylsulphate, SDS) to solubilise the EDOT monomer allows the use of an aqueous electrolyte. Electrochemical (coulometric) data provide a total assay of deposited material, yielding spatially averaged film thicknesses, which are commensurate with substantive filling of the trenches between fingerprint deposit ridges, but not overfilling to the extent that the ridge detail is covered. This is confirmed by optical microscopy and AFM images, which show continuous polymer deposition within the trenches and good definition at the ridge edges. Stainless steel substrates treated in this manner and transferred to background electrolyte (aqueous sulphuric acid) showed enhanced fingerprints when the contrast between the polymer background and fingerprint deposit was optimised using the electrochromic properties of the PEDOT films. The facility of the method to reveal fingerprints of various ages and subjected to plausible environmental histories was demonstrated. Comparison of this enhancement methodology with commonly used fingerprint enhancement methods (dusting with powder, application of wet powder suspensions and cyanoacrylate fuming) showed promising performance in selected scenarios of practical interest.

Electroless deposition of gold into poly-3,4-ethylenedioxythiophene films and their characterization performed in chloride-containing solutions

Au-containing polymer films were obtained by electroless deposition of gold from diluted solutions of HAuCl4 into preliminarily reduced poly-3,4-ethylenedioxythiophene (PEDOT) films. Structural peculiarities of such pristine and composite films were characterized by scanning and transmission electron microscopy methods. It was established that the gold clusters forming under such deposition appear on the outer surface of polymer films and their pores. The clusters’ sizes ranged between 30 and 100 nm depending on the time of exposition of a PEDOT film in solutions of Au(III) ions and the concentration of these ions. It was also observed that in contrast to pristine PEDOT films, cyclic voltammograms (CVs) of composite films in the presence of chloride ions show additional redox peaks resulting from oxidation of gold with formation of an insoluble product and followed by the product reduction under reversal of the potential scan direction. As a result of parallel electrochemical quartz crystal microbalance (EQCM) and CV measurements, it was also established that the number of chloride ions per one transferring electron in the gold oxidation process is near to unity. To elucidate the oxidation degree of gold in the presence of chloride ions, a special procedure of changing the electrode potential was used. It consisted of clamping the high anodic potential in the region of gold oxidation (0.97 V, Ag/AgCl) and subsequent gradual decrease of the electrode potential with a constant scan rate. Under these conditions, it was possible to completely oxidize all the gold particles containing in a composite film and find out the maximum amount of electricity consumed for the product particles’ reduction. A comparison between such data and the results obtained in EQCM determinations of the gold content in the same film led to the conclusion that the oxidation state of gold in the complexes formed is Au(III). The effects of chloride ion concentration and scan rate of the electrode potential on current responses of PEDOT–Au films were investigated. Some primary conclusions on the kinetics of the studied processes are made.

Enzymeless creatinine estimation using poly(3,4-ethylenedioxythiophene) -β-cyclodextrin

A novel enzymeless biosensor has been constructed for the quantitative estimation of creatinine using β-cyclodextrin (βCD) incorporated poly-3,4-ethylenedioxythiophene (PEDOT) modified glassy carbon electrode (GCE). The PEDOT film with and without βCD was deposited on a GCE by electropolymerization of EDOT from an aqueous solution containing lithium perchlorate and βCD. Polymer films were characterized by UV–visible spectroscopy, cyclic voltammetry and scanning electron microscopy (SEM). The selective interactions of the βCD-incorporated PEDOT film with creatinine in neutral Tris buffer solutions were elucidated using electrochemical impedance analysis. Complex formation between βCD and creatinine was inferred from regular shifts in the electrode potential versus creatinine concentration. In the potentiometric evaluation, the biosensor electrode exhibited a fast response time (60 s), linear shift in the potential over a concentration range of 10 −4–10 −1 M with a lower detection limit of 5 × 10 −5 M and good stability, retaining nearly 95% of the initial response after 1 month of shelf life. The results of the studies on the interferences from glucose, ascorbic acid, uric acid, urea and ammonium ions are also presented.

Hydrogen peroxide electroreduction on composite PEDOT films with included gold nanoparticles

Composite PEDOT/Au films were obtained by chemical deposition of dispersed gold nanoparticles into PEDOT (poly-3,4-ethylenedioxythiophene) conducting polymer matrix. Morphology of the obtained gold-containing films was studied by SEM and TEM methods. To study the kinetics of the hydrogen peroxide electroreduction that proceeds on glassy carbon electrodes modified with such films, we used phosphate buffer solutions containing addenda of hydrogen peroxide species. It was observed that the electroreduction process takes place on both the gold clusters’ surface and the film surface free of metal inclusions. The rate of the process is higher in the first case and rises with increasing the gold content in modifying films, but in the limit of large gold contents it is limited only by diffusion of hydrogen peroxide species in the bathing solution. A simple theory of such parallel electroreduction is proposed, which appears to allow for quantitative treatment of the obtained results.

Synthesis and structure of poly-3,4-ethylenedioxythiophene film with the inclusions of palladium nanoparticles

By chemical deposition of ultrafine particles of metallic palladium on the polymer matrix of poly-3,4-ethylenedioxythiophene (PEDOT) composite PEDOT/Pd films were obtained. The conditions of synthesis of the composite films in dependence on the duration of exposure of the reduced form of PEDOT film in a solution of palladium chloride, its concentration and the film thickness were studied. By the methods of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) it was shown that in the process of the synthesis of the composite films the nanosized palladium particles of predominantly quasispherical shape precipitated on the globular structure of the polymer. The size of the palladium nanoparticles in the composite PEDOT film and the nature of their distribution over the film bulk were revealed. An increase in the duration of deposition of the palladium nanoparticles on the film was shown to lead to an increase in their size and in the density of particles in the film.

Plastic dye-sensitized photo-supercapacitor using electrophoretic deposition and compression methods

A plastic photo-rechargeable capacitor is studied using a three-electrode configuration, separating a flexible dye-sensitized solar cell (DSSC) and a supercapacitor by sharing a common Pt electrode. The thick and uniform TiO 2 film is formed by using commercially available TiO 2 nanocrystals, which are treated in an isopropyl alcohol without surfactant by the electrophoretic deposition (EPD) to deposit the mesoporous TiO 2 photoanode film with good adherence onto the plastic substrate. Afterward, a static mechanical compression technique as the post-treatment is employed to the electrophoretic deposited film in order to enhance the particles connection. In addition, a supercapacitor using PEDOT (poly(3,4-ethylenedioxythiophene)), which is potentiostatically electropolymerized to form a thick film, is fabricated to store the energy. The flexible DSSC part is fabricated with a TiO 2 film of 10.9 μm thickness and it can provide photoelectric conversion efficiency up to 4.37% under 1 sun illumination. The photocapacitor is made with such a flexible DSSC and a supercapacitor with ca. 0.5 mm thick PEDOT film, which provides a specific capacitance of 0.52 F cm −2.

Gold electroless deposition into poly-3,4-ethylenedioxythiophene films

By electroless deposition of gold into poly-3,4-ethylenedioxythiophene (PEDOT) films, the composite films (PEDOT-Au) are synthesized. Their electrochemical properties are studied by cyclic voltammetric (CVA) method. It is shown that in contrast to the original PEDOT film, the CVA curves of composite PEDOT-Au films measured in the presence of chloride ions reveal additional redox peaks associated with the presence of gold particles. The loading of metal gold particles by its chemical deposition into the polymer film is quantitatively assessed using quartz crystal microbalance method. The film mass is shown to depend on the time of gold loading and its original concentration in solution. The gold particles are shown to be oxidized by a reaction of the first order with respect to chloride ions. Based on the results of voltammetric and microbalance methods, the formation of a poorly soluble gold oxidation product Au(I)Cl in chloride-containing solutions was inferred.