Sharif Digital Repository

Polyaniline/graphene oxide (PANI/GO) co-doped with Zn2+ and Fe3+ was synthesized via a simple and low cost one-step chronoamperometry method on stainless steel (SS) as the substrate. The Fe3+-Zn2+-PANI/GO nanocomposite is characterized using X-ray diffraction as well as Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. Also, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy are used to study the electrochemical performance of the as-prepared electrode materials. Significantly, the Fe3+-Zn2+-PANI/GO nanocomposite exhibits a specific... 

Nanostructured hollow polyaniline (PANI) capsules are good candidates for encapsulation of corrosion inhibitors and pH-responsive release when incorporated into organic coatings. In previous studies, the corrosion protection performance of PANI capsules, containing organic inhibitor 2-Mercaptobenzothiazole (MBT), was demonstrated. The present work studies the influence of capsule concentrations (i.e., 0.3, 1, and 2 wt%) on the corrosion protection properties of the coating system. Anti-corrosion properties of different coatings were compared by means of Electrochemical Impedance Spectroscopy (EIS) and Scanning Vibrating Electrode Technique (SVET). MBT loaded PANI capsules in epoxy ester... 

In this work, we study the role of nanotextured ZnFe2O4/Fe2O3composite thin films fabricated by ultrasonic spray pyrolysis (USP) on the photoelectrochemical water oxidation reactions. The ZnFe2O4/Fe2O3 composites with different molar ratios are deposited on three-dimensional nanospikes (NSP) substrate, and the results are compared with those for planar devices. It is observed that optical absorption and charge separation due to larger surface area is significantly enhanced in nanotextured photoactive ZnFe2O4/Fe2O3 films. After characterization of ZnFe2O4/Fe2O3 composite films with different molar ratios (ZF1, ZF2, and ZF3), we find that the nanotextured ZF1 composite with a molar ratio of... 

A new ternary nanocomposite based on graphene oxide (GO), polypyrrole (PPy) and vanadium pentoxide (V2O5) is obtained via one-step electrochemical deposition process. Electrochemical deposition of V2O5, PPy and GO on a stainless steel (SS) substrate is conducted from an aqueous solution containing vanadyl acetate, pyrrole and GO to get V2O5/PPy/GO nanocomposite. Characterization of the electrode material is carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The electrochemical performance of the as-prepared nanocomposite is evaluated by... 

A simple and low-cost electrochemical deposition method is used to prepare reduced graphene oxide/polypyrrole/Cu2O-Cu(OH)2 (RGO/PPy/Cu2O-Cu(OH)2) ternary nanocomposites as the electrode material for supercapacitor application. First, graphene oxide-polypyrrole (GO/PPy) nanocomposite is electrochemically synthesized on Ni foam by electro-oxidation of pyrrole monomer in an aqueous solution containing GO and Tiron. Subsequently, the GO/PPy film is converted to the corresponding reduced form (RGO/PPy) by an effective and eco-friendly electrochemical reduction method. Then, a thin layer of Cu2O-Cu(OH)2 is formed on RGO/PPy film by chronoamperometry. The RGO/PPy/Cu2O-Cu(OH)2 nanocomposite is... 

Abstract: Here, the synthesis of TiO2 rutile nanorod arrays (TiO2 NRs) decorated with bimetallic gold–palladium cocatalyst nanoparticles (AuPd NPs) is described. The modified photoelectrode was characterized by field-emission scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, UV–vis spectroscopy, and electrochemical impedance spectroscopy (EIS). AuPd–TiO2 NRs (AuPd–TiO2) demonstrate high photocatalytic activity for photoelectrochemical (PEC) water splitting. The tailored structure of AuPd–TiO2 depicts a boosted photocurrent of 3.36 mA cm−2 under AM 1.5 illumination... 

In this work, nanostructured composites of Cr2O3-graphene oxide (Cr2O3/GO) with conducting polymers; polyaniline (PANI) and polypyrrole (PPy) with the shape of cauliflower were synthesized via s simple and low cost one-step chronoamperometry method. The structures and morphologies of the resulting ternary nanocomposites were characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The electrochemical capacitive properties of the prepared nanocomposites were evaluated by using cycle voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The... 

A new Zinc phosphating bath, which produces coatings at relatively lower temperatures within a reasonable time by using of chemical accelerators has been devised. Improvement of the bath performance by the addition of divalent cations like calcium, nickel has been studied. Bath formulation and operating conditions have been optimized by coating weight determinations. Stable samples of phosphating formulations with and without calcium and nickel salts were prepared and the structure and morphology of the phosphate coatings were determined by using X-ray diffraction (XRD) techniques, scanning electron microscopy. ASTMB117 salt spray test and electrochemical impedance spectroscopy (EIS) were... 

The effect of the bath chemistry and operating conditions on the chemical composition, microstructure and properties of NiWmdashB alloys deposited from tartrate baths on working electrode was studied for the first time by the pulsed current method. The investigations included the measurement of the current efficiencies and determination of the tungsten content in the electrodeposits. UV spectrometry was used for characterisation of complex formation. The grain size of deposits was determined by XRD. Also, the morphology of the deposits was studied by SEM. Amorphous NimdashWB alloys were successfully obtained by electrodeposition from the tartrate bath. The corrosion behaviour of NiWmdashB... 

TiO2 deposited on a membrane of Ag fibers was prepared as a photoelectrochemical cell electrode. Ag fibers were made by reduction of Ag complexes on cellulose fibers, followed by burning out the template. TiO 2 photocatalyst layers were grown on the fibers by electrophoretic deposition of TiO2 nanoparticles. Ag fibers could be uniformly deposited. Photocatalytic tests by dye decomposition and electrochemical impedance spectroscopy (EIS) under UV illumination demonstrate that Ag fibers act as a good substrate that provides both high surface area and good separation of photogenerated electron-hole pairs and causes the enhancement of photocatalytic activity in comparison with a thin film of... 

The mechanism and kinetics of the hydrogen evolution reaction (HER) on tin electrode in 0.1 M H2SO4 solution were studied using the methods of steady-state polarization and electrochemical impedance spectroscopy. The simulation of the data obtained from these two methods, using nonlinear fitting procedure allowed us to determine the rate constants of Volmer, Heyrovsky and Tafel steps associated with the mentioned reaction. The kinetic results indicate that HER mechanism at low negative potentials is a serial combination of Volmer step and parallel Tafel and Heyrovsky steps. At high negative potentials where the hydrogen coverage reaches its limiting value, a Tafel line with the slope of -... 

Electrocatalytic activity of electrodeposited nanocrystalline CoNiFe alloy in hydrogen evolution reaction (HER) was studied in 1 M NaOH solution. The steady-state polarization measurement and electrochemical impedance spectroscopy were used to determine the Tafel slope, the exchange current density and the activation energy. The simulation of the data obtained from these two methods, using a nonlinear fitting procedure, allowed us to determine the surface coverage and the rate constants associated with the mentioned reaction. The ac-impedance spectra measured at various overpotentials in the HER region exhibited three semicircles in the complex plane plots. The high-frequency semicircle was... 

Aluminum electrocrystallization is studied by means of electrochemical impedance spectroscopy (EIS). A model based on random birth and deterministic growth of monolayers is proposed, in which the edges are assumed to follow a propagation law. The high frequency impedance data show charge transfer reaction of AlCl4- reduction while the low frequency features signifies the growth mode of deposits. The inductive response observed in the course of polycrystalline deposition reflects the activation of electrode area while a capacitive loop appears in regular growth. Parameters of impedance model in this system can be calculated from the fitting of experimental data to the Faradaic impedance... 

Two-dimensional MXenes are the newly emerging family of nanomaterials with competitive performance for nano-device development. Surface functional groups and abundant binding sites make these materials ideal candidates for sensor applications. Herein, we report the successful fabrication of a MXene-based nano-bio device for capturing, sensing, and filtering the Escherichia coli (E. coli) bacteria. Mannose carbohydrate, which binds strongly to E.coli's fimH protein via glucan multivalent interactions, is used as the bio-receptor element. MXene's structure was engineered to guarantee efficient E. coli capturing without mannose detachment. Electrochemical impedance spectroscopy (EIS) and cyclic... 

In this work, a nanocomposite containing manganese dioxide (MnO2) modified reduced graphene oxide (rGO) supported bimetallic palladium-nickel (Pd-Ni) catalyst is prepared by electrodeposition method. The nanocomposite modifier film is prepared by forming a thin layer of graphene oxide (GO) via drop-casting of GO nanosheet dispersion on glassy carbon electrode (GCE), followed by electrochemical reduction of the film to provide rGO/GCE. Then, a two-step potential procedure is applied to deposit MnO2 nanoparticles on rGO/GCE. At the optimum deposition conditions, MnO2 nanoparticles with a thickness of 30-50 nm homogeneously covered the rGO surface (MnO2/rGO/GCE). Finally, the bimetallic Pd-Ni... 

Since Gram-negative bacteria have a predominant role in nosocomial infections, there are high demands to develop a fast and sensitive method for diagnosis of bacteria in clinical samples. To address this challenge, we designed a novel electrochemical biosensor based on aptamers immobilized in engineered zeolitic imidazolate Framework-8 (ZIFs-8) via EDC-NHS chemistry. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were conducted to monitor the electrochemical characterization. With respect to unique π-πinteractions between aptamer and graphene oxide (GO), the differential pulse voltammetry technique was applied with ferrocene-graphene oxide (Fc-GO) as an... 

In the field of energy storage by high-rate supercapacitors, there has been an upper limit for the total interfacial capacitance of carbon-based materials. This upper limit originates from both quantum and electric double-layer capacitances. Surpassing this limit has been the focus of intense research in this field. Here, we precisely investigate the effect of chemical functional groups and physical confinement on the electrochemical performance of graphene nanoribbons. We present the results of a quasi-one-dimensional single-layer graphene nanoribbon (120 nm in width and -100 μm in length) microelectrode fabricated by mechanical exfoliation of graphite, followed by electron beam lithography... 

Herein, we present a novel, simple, and ultrasensitive electrochemical DNA (E-DNA) sensor based on hollow carbon spheres (HCS) decorated with polyaniline (PANI). A thiolated 21-mer oligonucleotide, characteristic of HBV DNA, is immobilized via electrodeposited gold nanoparticles on HCS-PANI. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) are used to characterize the electrochemical properties of the prepared nanocomposite. Scanning electron microscopy is employed to investigate the morphological texture of the fabricated modifier. An enhanced intrinsic signal of PANI is probed to evaluate the biosensing ability of the prepared... 

Carbon nanocapsules doped separately with epoxy and polyamine were used to fabricate an epoxy nanocomposite coating. Carbon nanospheres with dual-encapsulated epoxy/polyamine were dispersed uniformly in the epoxy resin at concentrations of 2, 5, and 10 wt %. The mechanical properties of the nanocomposites were studied by tensile testing and scratch hardness measurements. Furthermore, nanocomposites were applied on mild steel substrates, and their corrosion protection and barrier performance were evaluated using electrochemical impedance spectroscopy (EIS). Adhesion loss measurements of coatings after 240 h exposure to 3.5 wt % NaCl solution were performed by pull-off adhesion testing. Also,... 

In the present study, a rational two-step strategy is employed for the green, fast, very simple, and highly controllable synthesis of the bimetallic nickel-cobalt-based metal-organic frameworks (MOFs) on glassy carbon substrates by in situ transformation of nickel-cobalt-layered double hydroxide nanosheet (NiCo-LDHs NSs) intermediates into nickel-cobalt-benzene tricarboxylic acid MOFs (E-NiCo-BTC MOFs). The structural characteristics of the electrode materials in each step were investigated via Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, elemental mapping, field emission scanning electron microscopy, and transmittance electron microscopy....