Papers by Keyword: Cyclic Voltametry (CV)

Abstract: The aim of this work is to fabricate an ethylene gas sensor based on polyaniline (PANi). The conductive layer of emeraldine base PANi was prepared by electrochemical synthesis. The aqueous aniline solution in sulfuric acid was electrolyzed by repeating potential cycling between -0.4 and 1.0 V relative to the silver reference electrode and platinum counter electrode. The conductive layers of PANi were deposited on patterned interdigited gold substrate. The numbers of repeated potential cycles on the amount of deposited layers of PANi were investigated for ethylene gas detection. The morphology of PANi films was investigated by scanning electron microscope (SEM). The ethylene gas sensing of PANi-H2SO4 was evaluated based on the changes in conductivity of PANi-H2SO4. The results revealed that the magnitude sensing provided a good sensitivity against ethylene with concentration in the parts per million (ppm) ranges. The effect of amount of deposited layer of PANi on ethylene gas sensing will be presented.

Abstract: Precious metal nanoparticles (e.g. Au, Pd and Pt) on activated carbon cloths (ACCs) were simply prepared by impregnation of metal salts dissolving in ethanol solution. Pretreatment of the ACCs was firstly performed in hydrochloric acid solution and nitric acid as oxidizing agent was employed in order to introduce oxygen complex on the ACCs fiber surfaces. Uniformly dispersed metal nanoparticles with diameter of 5-20 nm on the ACC surfaces were simply achieved without using reducing agents. Morphology and composition of the metal adsorbed ACCs were examined by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), respectively. Electrolytic activity of metal/ACCs was investigated by using cyclic voltammetry (CV) to demonstrate the electron-transfer properties. Results demonstrate that metals adsorbed ACCs were easily prepared with simple procedures which will be more convenient for preparations and applications.

Abstract: In this paper both electrochemical and surface analysis technique, were performed in order to elaborate and investigate hybrid polymeric composite materials based on polypyrrole (PPy). SEM micrographs of PPy films obtained on zinc chromate electrode presented a cauliflower-like structure. The anticorrosive properties of composite coatings based on polypyrrole were improved using a pre-treatment with chromium salts on the zinc-coated steel surfaces.

Abstract: In this work, the monitoring of bacterial and chemical dissolution of massive bornite was performed using cyclic voltammetry (CV); the mineral surface was examined using scanning electron microscopy (SEM) and the elements were indentified by Energy Dispersive X-ray Analysis (EDXA). The electrolyte employed for the electrochemical tests was the medium used for bioleaching the electrodes (3.0 g•dm-3 (NH4)2•SO4, 0.5 g•dm-3K2HPO4, 0.5 g•dm-3 MgSO4•7H2O and 0.1 g•dm-3 Ca(NO3)2).The results showed differences in voltagramms carried out by Acidithiobacillus ferrooxidans and Acidithiobacillus caldus: In bioleached electrodes tested in the presence of Acidithiobacillus ferrooxidans, the anodic and cathodic current signals were larger than with Acidithiobacillus caldus The analysis of CV results allowed attributing the different peaks observed in both the direct and reverse potential scanning to the oxidation of bornite to a secondary copper mineral(chalcocite and covellite) and its reduction via different non stoichiometric copper sulphides intermediaries. Surface evidences were produced by SEM, and chemical elements evidences were also investigated by EDAX.

Abstract: In this work, we report the study of functionalized platinum (Pt) electrodes based on a polymeric membrane (PVC) including an ionophore (ethyln diamin tetracetic EDTA) sensitive for mercury ions Hg2+. The optimised working conditions of the sensors have been studied with regard to the sensitivity performances; in particular, the polarisation was adjusted to - 0.2V/SCE. Ion sensitivity of sensors have been tested for Hg(II) via Cd(II) in aqueous solution. A layer of EDTA deposited on platinum electrode has been characterised by impedance spectroscopy and cyclic voltammetry methods.

Abstract: Two arylenevinylenes compounds formed with thienyl or furyl units substituted by a cyano group at the ethylene linkage were studied by direct anodic oxidation in CH2Cl2/Bu4NBF4 0,2M medium on platinum electrode using cyclic voltammetry method. By applying a sequential linear potential scan rate of 100 mV.s-1 between 0-1,6 V versus Ag /Ag+ (0,1 M) / CH2Cl2, these two organic compounds could be polymerized. The electrosynthetized conducting polymers were also prepared by potentiostatic method then characterized by IR and UV spectroscopies and their conductivity was evaluated.

Abstract: The mainly process of electrochemical graining on 6063 aluminum alloy included graining at alternating current, anodizing and chemical coloring. The graining used NaBO2- H3BO3 system as film-forming solution, proper AC current density, treating time, temperature , adding agents and solution concentration were ascertained through operating orthogonal experiment, the grain of appropriate density and width could be obtained, the grained surface of aluminum alloy presented intergranular corrosion in the graining zone, the appearance was improved after anodizing, enough thick anodizing film could make intergranular corrosion eliminated. Cyclic voltammetry experiment was used to preliminarily explaine the grain process, the main cause of graining zone formation was hydrogen evolution.

Abstract: Boron-doped diamonds were deposited by microwave plasma chemical vapor deposition (MPCVD) method in order to investigate the influence of inlet boron concentration on the film properties. The substrate material of the specimens was pure titanium (99.9 %). Boron source was introduced into the vacuum chamber by bubbling of B2O3, acetone and methanol mixture. Samples were produced with different B2O3 concentrations in mixture (1000 ppm, 5000 ppm, and 10000 ppm). The surface morphology of the samples was observed by scanning electron microscope (SEM). X-ray diffraction was used to identify crystal structures of the films. Secondary ion mass spectroscopy was used to examine the qualitative boron contents in the films. For low B2O3 concentrations in liquid mixture (1000 ppm), the surface morphology of the film showed both micro crystalline diamond and nano crystalline diamond. For medium B2O3 concentrations in liquid mixture (5000 ppm), the surface morphology of the film was also consisted of micro crystalline diamond and nano crystalline diamond. However, the content of micro crystalline diamond decreased in comparison with low B2O3 concentration. For high B2O3 concentration in liquid mixture (10000 ppm), the surface morphology of the film was almost dominated by nano crystalline diamond. Therefore, the crystal size of boron doped diamond decreased with increasing boron concentration. From these results, it appears that boron will restrain the growth of diamond crystal during deposition.

Abstract: A novel technique has recently been presented for depositing metal layers onto a SAM. This is demonstrated here for Pd and Pt deposits on a mercaptopyridine (4-PyS) SAM. The SAMcovered Au(111) electrode is immersed into the metal-ion-containing solution without potential control. As a result, metal ions, e.g., Pd(II) (respectively Pt(II)) adsorb on the surface by forming a complex with the pyridine species. Subsequently, the electrode is transferred to a metal-ion-free solution, where the adsorbed metal ions are reduced electrochemically to its zero-valent state. Upon reduction, monoatomic high metal islands were observed in STM. Angle resolved XPS measurements show unequivocally that the reduced metal resides on top of the SAM.

Abstract: The goal of this paper is elaboration and characterization of chemical and electrochemical phosphate deposition on titanium. The behavior of the bioactive coating was evaluated using electrochemical methods (open circuit potential, cyclic voltametry) and spectroscopy (FTIR and atomic adsorbtion spectroscopy).