Electrochemical preparation and characterization of nickel and zinc-modified poly-2-aminothiazole films on mild steel surface and their corrosion inhibition performance

Poly-2-aminothiazole (pAT) was electrochemically synthesized on a mild steel (MS) specimen from 0.3 M aqueous ammonium oxalate solution containing 0.01 M 2-aminothiazole (2-AT) using cyclic voltammetry technique. The synthesized polymer film was then modified by electrodeposition of 100 μg cm⁻² Ni (MS/pAT–Ni) and Zn (MS/pAT–Zn) on top of the polymer surface. The surface morphologies of the polymer films were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elemental analysis of the surface films was performed by energy dispersive X-ray spectroscopy (EDX). The effectiveness of the coatings in preventing corrosion of MS in 3.5% NaCl solution was assessed using electrochemical techniques. It was found that the obtained coatings were adherent to the steel surface. The pAT film provided a good corrosion protection against the attack of corrosive environment. Moreover, the modification of pAT film by deposition of Ni and Zn on top of the polymer surface significantly enhances the corrosion protection performance of the polymer film by exhibiting an improved barrier effect against the attack of corrosive environment. The surface morphologies and protection ability of the layers were found to be dependent on the type of deposited metal.     

Electrochemical synthesis of poly-2-aminothiazole on mild steel and its corrosion inhibition performance

2-Aminothiazole (AT) was polymerized by electrochemical technique on a mild steel (MS) electrode from 0.01 M monomer containing 0.3 M ammonium oxalate solution. Cyclic voltammetry was used for the synthesis. Poly-2-aminothiazole (pAT) film with a light-brownish color was obtained on the MS surface. The effectiveness of polymer film in preventing corrosion of MS was tested in 0.5 M HCl solution. For corrosion tests, anodic polarization curves, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques were utilized. The results obtained indicated that, the polymer film adherent to the steel surface. The polymer film gives a good corrosion protection against the attack of corrosive environment.     

Corrosion inhibition of stainless steel by polyaniline,poly(2-chloroaniline), and poly(aniline-co-2-chloroaniline) in HCl

Polyaniline (PANi), poly(2-chloroaniline) (PClANi), and poly(aniline-co-2-chloroaniline) (co-PClANi) films were synthesized by electrochemical deposition on 304-stainless steel (SS) from an acetonitrile solution. The structural properties of these polymer films were characterized by spectroscopic (FTIR and UV–vis) and electrochemical (cyclic voltammetry) methods. Open circuit potential–time (E_ocp–time) curves, potentiodynamic polarization, and electrochemical impedance (EIS) measurements showed that these films have significant protective performance against corrosion of SS in 0.5 M HCl solution. It was found that co-PClANi film has acted as a passivator as well as barrier for cathodic reduction reaction in a similar manner as PANi film. However, PClANi film has behaved only as barrier for corrosion protection of SS in 0.5 M HCl.     

Protective properties of polyaniline and poly(aniline-co-o-anisidine) films electrosynthesized on brass

Polyaniline and poly(aniline-co-o-anisidine) films were deposited on brass (Cu40Zn). The synthesis processes of homo and copolymer film were carried out under cyclic voltammetric condition from 0.12 M aniline and 0.06 M aniline + 0.06 M o-anisidine containing 0.2 M sodium oxalate solutions. Homo and copolymer films were characterized by scanning electron microscopy (SEM). SEM images clearly show that one of the brass electrodes was covered with a black copolymer film of strongly adherent homogeneous characteristic while the other one with a porous dark green homo polymer one. The corrosion performances of coated and uncoated electrodes in 3.5% NaCl were evaluated with the help of AC impedance spectroscopy, anodic polarization plots and open circuit potential–time curves. The protective effect of homo and copolymer films formed on brass grew in parallel with extended exposure time. It was only observed with copolymer-coated electrode that changes in the charge transfer resistance of copolymer-coated electrode were related to strong adsorption of copolymer film on the brass surface which led to the formation of a protective oxide layer due to its catalytic behaviour.     

Electrochemical characterization of poly(eriochrome black T) modified glassy carbon electrode and its application to simultaneous determination of dopamine, ascorbic acid and uric acid

A polymerized film of eriochrome black T (EBT) was prepared on the surface of a glassy carbon (GC) electrode in alkaline solution by cyclic voltammetry (CV). The redox response of the poly(EBT) film at the GC electrode appeared in a couple of redox peak in 0.1 M hydrochloride and the pH dependent peak potential was −55.1 mV/pH which was close to the Nernst behavior. The poly(EBT) film-coated GC electrode exhibited excellent electrocatalytic activity towards the oxidations of dopamine (DA), ascorbic acid (AA) and uric acid (UA) in 0.05 mM phosphate buffer solution (pH 4.0) and lowered the overpotential for oxidation of DA. The polymer film modified GC electrode conspicuously enhanced the redox currents of DA, AA and UA, and could sensitively and separately determine DA at its low concentration (0.1 μM) in the presence of 4000 and 700 times higher concentrations of AA and UA, respectively. The separations of anodic peak potentials of DA-AA and UA-DA reached 210 mV and 170 mV, respectively, by cyclic voltammetry. Using differential pulse voltammetry, the calibration curves for DA, AA and UA were obtained over the range of 0.1-200 μM, 0.15-1 mM and 10-130 μM, respectively. With good selectivity and sensitivity, the present method provides a simple method for selective detection of DA, AA and UA in biological samples.     

Experimental investigations of semi-crystalline plasma polymerized polypyrrole for surface coating

Plasma polymerized thin film of conducting polypyrrole were deposited at room temperature by plasma enhanced chemical vapor deposition method using pyrrole monomer as precursor. The radio frequency (RF: 13.56 MHz, power supply: 30 W) was applied at constant argon gas pressure for the formation of plasma. The as grown thin films of polypyrrole have been characterized by ellipsometry, Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy, atomic force microscopy (AFM), X-ray diffractometry (XRD) and high-resolution transmission electron microscopy (HRTEM). UV–vis spectra showed the optical energy band gap of 2.3 eV. XRD pattern of plasma polymerized polypyrrole has revealed a clear peak at inter-planer separation of 0.687 nm. It was also noticed by HRTEM analysis that the distinguished reflection at d =  0.687 nm has a broadening effect that may be correlated with the crystallinity of the material.     

Studies based on the electrochemical response of 2-(2-nitrophenyl)-1H-benzimidazole at chemically modified electrodes with over-oxidized poly-1-naphthylamine

The development of a simple and efficient method to 2-(2-nitrophenyl)-1H-benzimidazole (NB) electrochemical determination using a polymer film coated chemically modified electrode is described. A glassy carbon (GC) electrode was modified employing an electro-polymerized film of 1-naphtylamine (1-NAP) followed by an over-oxidation treatment in 0.2 M sodium hydroxide solution (poly-1-NAPox electrode).The electrochemical behaviour of NB at the poly-1-NAPox electrode was investigated in a mixture of 10% ethanol + 90% buffer solution (pH 2) by cyclic voltammetry (CV) and square-wave voltammetry (SWV). The experimental results suggested that the poly-1-NAPox electrode had a good effect on NB electrochemical response because it avoided the electrode surface fouling as a consequence of the adsorption of NB reduction products, which was found when a bare GC electrode was employed as the working electrode. The NB cathodic current was dependent on the polymeric film over-oxidation degree (α).NB could be determined in the range from 2 × 10⁻⁶ to 5 × 10⁻⁵ M. The NB detection and quantification limits were 5 × 10⁻⁷ and 1.7 × 10⁻⁶ M, respectively. The percent relative standard deviation of the peak current to 10-replicated measurement using 1.2 × 10⁻⁵ M NB solution was 1.4%. The method showed to be rapid, simple and with a good sensitivity.     

Effect of nickel doping on structural,optical, electrical and ethanol sensing properties of spray deposited nanostructured ZnO thin films

Undoped and nickel (Ni)-doped ZnO thin films were spray deposited on glass substrates at 523 K using 0.1 M of zinc acetate dihydrate and 0.002–0.01 M of nickel acetate tetrahydrate precursor solutions and subsequently annealed at 723 K. The effect of Ni doping in the structural, morphological, optical and electrical properties of nanostructured ZnO thin film was investigated using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), UV–vis Spectrophotometer and an Electrometer respectively. XRD patterns confirmed the polycrystalline nature of ZnO thin film with hexagonal wurtzite crystal structure and highly oriented along (002) plane. The crystallite size was found to be increased in the range of 15–31 nm as dopant concentration increased. The SEM image revealed the uniformly distributed compact spherical grains and denser in the case of doped ZnO thin films. All the films were highly transparent with average transmittance of 76%. The measured optical band gap was found to be varied from 3.21 to 3.09 eV. The influence of Ni doping in the room temperature ethanol sensing characteristics has also been reported.     

Influence of sputtering pressure on surface structure and oxygen reduction reaction catalytic activity of thin platinum films

The work presents a study on the influence of the sputtering pressure on the surface structure and morphology of low Pt loaded electrodes and their electrochemical behaviour toward oxygen reduction reaction (orr) in sulphuric acid solution and polymer electrolyte membrane (Nafion 117). Pt was deposited as thin film upon hydrophobic carbon paper substrates at sputtering pressure varied in the range 2-13 Pa. The test samples are analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The catalytic activity is assessed by applying the methods of linear sweep voltammetry (LSV) on rotating disc electrode (RDE) and cyclic voltammetry (CV). The results obtained show strong influence of the sputtering pressure on the surface structure and crystal orientation which in turn, affects the orr efficiency. The best electrode performance in both electrolytes used is obtained for the Pt film deposited at pressure of 9 Pa. The results obtained in Nafion 117 show that catalyst utilisation in this electrode exceeds significantly the one for a commercial ELAT electrode at the same operation conditions. The research demonstrated that by simple variations in the sputter regime it is possible to optimise the catalysts morphology in order to increase the catalytic activity toward the electrochemical reaction of interest at the same time controlling precisely the required precious metal loading.     

Transparent and thermally stable improved poly (vinyl alcohol)/Cloisite Na/ZnO hybrid nanocomposite films: Fabrication,morphology and surface properties

A series of poly(vinyl alcohol)/Cloisite Na⁺-Tyrosine/Zinc oxide (PVA/Cloisite Na⁺-Tyr/ZnO) bionanocomposites were prepared by dispersing ZnO nanoparticles in solution containing mixture of the PVA and modified Cloisite Na⁺. Structure of nanocomposite coatings was investigated by X-ray diffraction and Fourier-transform infrared spectroscopy. The thermal stability and optical properties of bionanocomposite were characterized by thermogravimetric analysis and UV–vis spectroscopy, respectively. The introduction of ZnO nanoparticles into PVA/Cloisite Na⁺-Tyr mixed solutions significantly increased the thermal stability of the obtained films. The results revealed that the high UV-shielding efficiency of the composites: for a film containing 6.0 wt% of ZnO nanocrystals, over 92% of UV light at wavelengths of 368 nm was absorbed while the optical transparency in the visible region was slightly below that of a PVA/Cloisite Na⁺-Tyr film.     

Synthesis and characterization of poly(aniline) and poly(o-anisidine) films in sulphamic acid solution and their anticorrosion properties

Poly(o-anisidine) (POA) and polyaniline (PANI) coatings were synthesized on platinum (Pt) surface and stainless steel (SS) in monomer containing 0.50 M sulphamic acid (SA) solution by means of cyclic voltammetry (CV) technique. Meanwhile, poly(o-anisidine) film was also deposited with a different scan rate on SS electrode. The behaviour of PANI and POA films obtained on stainless steel examined by CV was different from the one obtained for PANI and POA on Pt electrode. The corrosion performances of PANI and POA coatings in 3.5% NaCl solution were investigated with anodic polarization technique and electrochemical impedance spectroscopy (EIS). EIS measurements verified the effect of monomers and that of scan rate on corrosion inhibition of coatings on SS electrode. The results showed that POA film synthesized at low scan rate exhibited an effective anticorrosive property on SS electrode. POA synthesized at low scan rate and PANI coatings provided a remarkable anodic protection to SS substrate for longer exposure time than the one observed for POA coating produced at high scan rate as well as that of bare SS electrode.     

Preparation and characterizations of highly transparent UV-curable ZnO-acrylic nanocomposites

A sol–gel chemical route was adopted to prepare the zinc oxide (ZnO) nanoparticles as small as 4 nm. UV-curable ZnO-acrylic nanocomposites were then prepared by employing 3-(trimethoxysilyl)propyl methacrylate (TPMA) as the surface modification agent of ZnO particles. UV–vis analysis revealed a high optical transparency (>95%) in visible light region for nanocomposite thin films with ZnO contents up to 20 wt.%. The addition of ZnO nanoparticles also enhanced the dielectric constants of nanocomposites and the dielectric constants greater than 4 in frequencies ranging from 1 to 600 MHz was obtained in the samples containing 10 wt.% of ZnO nanoparticles. A comparison of experimental results and theoretical calculation indicated that the interfacial polarizations in between ZnO nanoparticles and polymer matrix may play an important role in the enhancement of dielectric properties of nanocomposites.     

Poly(phenosafranin)-functionalized single-walled carbon nanotube as nanocomposite electrocatalysts: Fabrication and electrocatalysis for NADH oxidation

We report a new type of amperometric dihydronicotinamide adenine dinucleotide (NADH) biosensor based on a poly(phenosafranin) functionalized single-walled carbon nanotube (PPS-SWCNT) nanocomposite. This nanocomposite, which was fabricated on an edge-plane pyrolytic graphite (EPPG) electrode surface, was formed by electropolymerizing a phenosafranin (PS) monomer onto SWCNTs. The PPS-SWCNT composites were characterized by surface analysis using atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV–vis techniques and by electrochemical measurements using cyclic voltammetry (CV) and rotating disk electrode voltammetry (RDEV). Both the SEM and AFM studies revealed the successful immobilization of PPS on the SWCNT, whereas the UV–vis study suggested a strong charge–transfer interaction between them. The CV and RDEV results indicated that PPS-SWCNTs were able to mediate the oxidation of NADH effectively, with a remarkable decrease in overpotential by ca. 720 mV compared with the bare EPPG and with 10 times higher current than that at the PPS/EPPG electrode, (i.e., the catalytic reaction rate constant was estimated to be 3.36 × 10⁵ M⁻¹ s⁻¹). This nanocomposite electrode was found to possess excellent characteristics as an amperometric NADH sensor including a low detection potential (0.0 V vs. Ag|AgCl|KCl_(sat.)), rapid response (less than 2 s), low detection limit (10 nM), high sensitivity (576 μA cm⁻² mM⁻¹), high selectivity and reasonable stability. This new type of edge-plane-based electrochemical platform with a high surface area and catalytic activity offers great promise for creating a potentially alternative class of nanostructure electrodes for biosensing, biofuel cells and energy-conversion applications.     

Synthesis of CuGa2O4 nanoparticles by precursor and self-propagating combustion methods

Copper gallate spinels, CuGa₂O₄, have been synthesized by two wet chemical routes: precursor method and self-propagating combustion involving a glycine-nitrate system. All complex precursors have been characterized by chemical analysis, infrared spectroscopy (IR), ultraviolet visible spectroscopy (UV–vis), electron paramagnetic resonance spectroscopy (EPR), thermal analysis and scanning electron microscopy (SEM). The copper gallate spinel oxides have been further investigated by X-ray diffraction (XRD), SEM, IR, UV–vis, magnetic measurements and EPR. The crystallite size of the copper gallate was found about 280 Å.     

Polypyrrole as possible electrode materials for the aqueous-based rechargeable zinc batteries

Polypyrrole (PPy) thin film electrode was galvanostatically synthesized and characterized in 0.1 M HCl on graphite electrode as cathode materials for the aqueous-based rechargeable zinc batteries. The charge/discharge characteristics of PPy and zinc electrode in 0.1 M ammonium chloride and in the 0.1 M ammonium chloride with addition of 0.1 M sodium citrate were investigated. Electrochemical characteristic of possible Zn|PPy cell in chloride/citrate containing electrolyte was discussed and simulated.     

Effect of TiO2 supporting layer on Fe2O3 photoanode for efficient water splitting

For an electrochemical water splitting system, titanate nanotubular particles with a thickness of ∼700 nm produced by a hydrothermal process were repetitively coated on fluorine-doped tin oxide (FTO) glass via layer-by-layer self-assembly method. The obtained titanate/FTO films were dipped in aqueous Fe solution, followed by heat treatment for crystallization at 500 °C for 10 min in air. The UV–vis absorbance of the Fe-oxide/titanate/FTO film showed a red-shifted spectrum compared with the TiO₂/FTO coated film; this red shift was achieved by the formation of thin hematite-Fe₂O₃ and anatase-TiO₂ phases verified using X-ray diffraction and Raman results. The cyclic voltammetry results of the Fe₂O₃/TiO₂/FTO films showed distinct reversible cycle characteristics with large oxidation–reduction peaks with low onset voltage of I–V characteristics under UV–vis light illumination. The prepared Fe₂O₃/TiO₂/FTO film showed much higher photocurrent densities for more efficient water splitting under UV–vis light illumination than did the Fe₂O₃/FTO film. Its maximum photocurrent was almost 3.5 times higher than that obtained with Fe₂O₃/FTO film because of the easy electron collection in the current collector. The large current collection was due to the existence of a TiO₂ base layer beneath the Fe₂O₃ layer.     

The corrosion-inhibiting effect of polypyrrole films doped with p-toluene-sulfonate,benzene-sulfonate or dodecyl-sulfate anions,as coating on stainless steel in NaCl aqueous solutions

This article presents a study of the conditions for electro-synthesis of polypyrrole (PPy) films on stainless steel, in the presence of the anions p-toluene-sulfonate (pTS), benzene-sulfonate (BS) or dodecyl-sulfate (DS). Cyclic voltammetry (CV) was used in the synthesis of the polypyrrole films on the stainless steel (SS). These polymeric films were characterized by IR and UV–vis spectroscopy and their morphology and thickness were analyzed by scanning electron microscopy (SEM). Their performance as protective films against corrosive processes presented by the SS/PPy-pTS, SS/PPy-BS or SS/PPy-DS systems was evaluated in 0.1 M NaCl aqueous solution. The study of the corrosion processes of the stainless steel/polymer systems was conducted through measurements of open circuit potential (E_OCP), polarization curves (PC) and electrochemical impedance spectroscopy (EIS). The results showed that the protective capacity of these polymeric systems on stainless steel, mainly with regard to pitting, depends on the nature of the anion dopant used during electro-synthesis of the PPy film. The best performance was seen with the dopants pTS and BS.     

Visible light photocatalytic degradation of thiophene using Ag–TiO2/multi-walled carbon nanotubes nanocomposite

Ag–TiO₂ nanocatalyst, supported on multi-walled carbon nanotubes, was synthesized successfully via a modified sol–gel method, and the prepared photocatalyst was used to remediate aqueous thiophene environmentally by photocatalytic oxidation under visible light. The prepared Ag–TiO₂/multi-walled carbon nanotubes nanocomposite photocatalyst was characterized through X-ray diffraction, Brunauer–Emmett–Teller (BET), transmission electron microscopy, and UV–vis spectra (UV–vis). The results showed that both Ag and TiO₂ nanoparticles were well-dispersed over the MWCNTs and formed a uniform nanocomposite. Ag doping can eliminate the recombination of electron–hole pairs in the catalyst, and the presence of MWCNTs in the TiO₂ composite can change surface properties to achieve sensitivity to visible light. The optimum mass ratio of MWCNT:TiO₂:Ag was 0.02:1.0:0.05, which resulted in the photocatalyst's experimental performance in oxidizing about 100% of the thiophene in a 600 mg/L solution within 30 min and with 1.4 g L⁻¹ amount of catalyst used.     

Selective oxidation of serotonin and norepinephrine over eriochrome cyanine R film modified glassy carbon electrode

A novel ECR-modified electrode is fabricated by electrodeposition of Eriochrome Cyanine R (ECR) at a glassy carbon (GC) electrode by cyclic voltammetry (CV) in double-distilled water. The characterization of the ECR film modified electrode is carried out by atomic force microscopy (AFM), infrared spectra (IR), spectroelectrochemistry and cyclic voltammetry. The results show that a slightly heterogeneous film formed on the surface of the modified electrode, and the calculated surface concentration of ECR is 2 × 10⁻¹⁰ mol/cm⁻². The ECR film modified GC electrode shows excellent electrocatalytic activities toward the oxidation of serotonin (5-HT) and norepinephrine (NE). Furthermore, the modified electrode can separately detect 5-HT and NE, even in the presence of 200-fold concentration of ascorbic acid (AA) and 25-fold concentration of uric acid (UA). Using differential pulse voltammetry (DPV), the peak currents of 5-HT and NE recorded in pH 7 solution are linearly dependent on their concentrations in the range of 0.05-5 μM and 2-50 μM, respectively. The limits of detection are 0.05 and 1.5 μM for 5-HT and NE, respectively. The ECR film modified electrode can be stored stable for at least 1 week in 0.05 M PBS (pH 7) at 4 °C in a refrigerator. Owing to its excellent selectivity and sensitivity, the modified electrode could provide a promising tool for the simultaneous determination of 5-HT and NE in complex biosamples.     

Synthesis and characterization of cross-linked polymer from cardanol by solvent-free grinding polymerization

By grinding cardanol and anhydrous FeCl₃ powder using a glass pestle in a mortar at ambient and solvent-free condition, a novel cross-linked polymer from cardanol, a renewable resource, was synthesized in high yield up to 80% in 5 min. The products were characterized through UV–vis, FT-IR, and ¹H NMR; and the solvent-free grinding polymerization was consisted of Friedel–Crafts reaction, etherification reaction, and oxidative coupling reaction. The effect of these different techniques on spectral, thermal, optical, electrical, and morphological properties of polycardanol were investigated.