Sharif Digital Repository

The objective of the work ahead is presentation of a new carbon paste electrode (CPE) modified by TiO2 nanoparticles (TiO2NPs) and 1,2-bis-[o-aminophenyl thio] ethane (APTE) ligand as a selective cation receptor for determination of the Cd (II) ions using differential pulse anodic stripping voltammetry (DPASV). The electrode shows an excellent tendency to Cd (II) ions in presence of some interfering species. Under the optimum conditions, a linear calibration curve was obtained in the concentration range of 2.9 nM to 4.6 μM with a correlation coefficient of 0.9969 in the anodic potential of 0.54 (V vs. Ag/AgCl). The metal detection limit was 2.0 nM after 10 min preconcentration (S/N = 3). The... 

The effect of pulse reverse current (PRC) method on Ni-Mo coatings electroplated from chloride solution was investigated by various plating parameters such as plating duration, the anodic duty cycle, the anodic current density and the cathodic current density. By increasing the anodic duty cycle and anodic current density, the Mo content of coatings reached 68wt.% and 78wt.%, respectively at cathodic current densities of 500 and 300mAcm-2. The Mo content of coatings increases by the preferential dissolution of Ni on the anodic pulse and also by the replenishment of Mo complexes in the diffusion layer near the substrate surface during the anodic pulse. In comparison with the direct current... 

Titanium anodes coated with noble metal oxides are widely used in chlorate industry. In fact, these anodes are dimensionally stable. In this article, the electrochemical characteristics of the ternary oxide coating created by sol-gel on titanium, which consisted of Ti, Ru and Ir, were investigated in the number of different layers. The electrochemical properties of anodes, morphology of samples, and phase analysis were investigated respectively by cyclic voltammetry and polarization measurements, Field Emission Scanning Electron Microscope (FESEM) and XRD. The result indicated that the application of the more layer number increases the rate of chlorine evolution. Also, The morphology of the... 

The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran's sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. One failed valve body was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The valve body alloy was A216-WCC cast carbon steel. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results... 

The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran's sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. One failed valve body was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The valve body alloy was A216-WCC cast carbon steel. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results... 

WO3 thin film photoanodes containing different concentrations of Ag nanoparticles were synthesized by solegel method. Based on UV-visible spectra, presence of a surface plasmon resonance peak at 470 nm of wavelength indicated formation of silver nanoparticles in the WO3 films. According to atomic force microscopy (AFM) analysis, the highest value for surface roughness and the effective surface ratio was observed for the sample containing 2 mol% of Ag. X-ray diffraction (XRD) patterns revealed that WO 3 nanocrystalline structure was formed in the monoclinic phase with the average size of about 18.2 nm while Ag nanocrystals were determined in cubic phase. X-ray photoelectron spectroscopy (XPS)... 

In this study, we explore resonance-enhanced optical absorption in Ta 3N5 photoanodes for water splitting. By using a reflecting Pt back-contact and appropriate Ta3N5 film thickness, the resonance frequency can be tuned to energies just above the bandgap, where the optical absorption is normally weak. The resonance results in a significant improvement in the photoanode's incident photon-to-current efficiency. The Ta3N5 films are made by high-temperature nitridation of Ta2O5. The nitridation time is found to be critical, as extended nitridation result in the formation of nitrogen vacancies through thermal reduction. These insights give important clues for the development of efficient... 

Electrodes made of group VIII and IB metals were examined for their redox process and electrocatalytic activities towards the oxidation of ethylene glycol in alkaline solutions. The method of cyclic voltammetery (CV) and Open circuit potentials measurement (OCP) was employed. It is found that considerable electrooxidation current are observed for silver and copper but lower anodic overpotential for oxidation is obtained for gold and platinum. Oxide layer produced on the surface of all electrodes in alkaline solution under anodic scan participates in ethylene glycol electrooxidation. Oxidation current observed in the reverse scans for platinum and gold are higher than those observed in... 

Here we analyze the effect of two relevant aspects related to cell preparation on quantum dot sensitized solar cells (QDSCs) performance: the architecture of the TiO 2 nanostructured electrode and the growth method of quantum dots (QD). Particular attention is given to the effect on the photovoltage, V oc, since this parameter conveys the main current limitation of QDSCs. We have analyzed electrodes directly sensitized with CdSe QDs grown by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR). We have carried out a systematic study comprising structural, optical, photophysical and photoelectrochemical characterization in order to correlate the material... 

Microbial fuel cells (MFCs) represent a new method for simultaneous wastewater treatment and biological electricity generation. In this study, petrochemical wastewater with 8000 mg/l of chemical oxygen demand was examined in a membrane-less single chamber MFC. Effects of wastewater concentration as substrate for microbial oxidation, and anode material (stainless steel or carbon brush) were investigated as designing parameters  

A mixture of multi-walled carbon nanotube/graphite paste electrode modified with a salophen complex of cobalt was prepared and was applied for the study of the electrochemical behavior of 6-mercaptopurine (MP) using cyclic and differential pulse voltammetry (DPV). An excellent electrocatalytic activity toward the oxidation of MP was achieved, which led to a considerable lowering in the anodic overpotential and remarkable increase in the response sensitivity in comparison with unmodified electrode. Utilizing DPV method, a linear dynamic range of 1-100 μM with detection limit of 0.1 μM was obtained in phosphate buffer of pH 3.0. The electrochemical detection system was very stable, and the... 

TiO 2 nanorods, TiO 2 nanorod/TiO 2 nanoparticle and TiO 2 nanorod/ZnO nanoparticle composite structures were integrated as photoanodes in backside illuminated dye-sensitized solar cells (DSSCs). Incorporation of TiO 2 nanoparticles into the bare nanorods increased the dye loading and improved the short-circuit current density (J sc) from 2.22 mA/cm 2 to 3.57 mA/cm 2. ZnO nanoparticles electrochemically grown into the TiO 2 nanorod layer could increase the surface area. Nevertheless, this considerably reduced the J sc to 0.57 mA/cm 2 and consequently cell efficiency. Electrochemical impedance spectroscopy (EIS) results showed that ZnO incorporated samples have better effective diffusion... 

In this study, tensile strength of gypsum-based composite with aluminum fibers up to 15 vol.% was studied. To increase the interfacial bond strength between fibers and matrix, aluminum fibers were anodized under different conditions. Single fiber pull-out tests were carried out to investigate the bond strength. The interface was examined by scanning electron microscope. The ability of the composites to withstand longitudinal tensile load was also studied by tensile tests of dog bone-shaped, randomly oriented fiber-reinforced gypsum. By the introduction of aluminum fibers in gypsum as a randomly oriented composite, considerable increment in the strength is achieved and the toughness of the... 

In order to improve titanium corrosion behavior, we can increase the thickness of oxide layer on titanium surface during anodizing process and by electrochemistry. In this research, self-color anodizing of Ti in sulfuric acid was done, and anodizing layers were created in different colors. The highest value of chromaticity was 37.8 for the anodized sample in 10 V, and the lowest value was 8.6 at 15 V. The oxide layer thickness was calculated by optical method (light refraction). The anodic film thickness increased by increasing the anodizing voltage. The highest thickness of anodic film was 190 nm in sulfuric acid solution for the anodized sample in 80 V. Corrosion resistance of anodized Ti... 

Catalytic activity of carbon/Pt nanoparticles modified TiO 2 nanotubes electrode was studied by using dopamine contained solutions. The TiO 2 nanotubes electrode was prepared using anodizing method in aqueous solution. The electrochemical pulse method was then applied for electrodeposition of Pt nanoparticles onto the TiO 2 nanotubes. Further modification was achieved by decomposition of polyethylene glycol in a tube furnace to have a carbon/Pt nanoparticles modified TiO 2 nanotubes electrode. The final modified electrode could successfully detect the electro-oxidation of dopamine in a ImM contained solution using cyclic voltametry method. Also, a high sensitivity towards the oxidation of... 

The main goals in zinc electrowinning process are decreasing of power consumption and increasing of current efficiency. The purpose of this research was to investigate effect of different alloy compositions used in production of lead-based anodes on the zinc electrowinning process. The anode compositions prepared and examined in this study were binary alloys Pb - (0.5 and 2 %) Ag and quaternary alloys Pb - 0.5 % Ag - 1 % Ca - 2 % Sn, Pb - 0.5 % Ag - 1 % Ca - 1 % Sn - 1 % Sb and Pb - 0.5 % Ag - 1 % Ca - 1 % Sn - 1 % Bi. The electrowinning experiments were conducted using a laboratory-scale apparatus, at a plating time of 4 hours, a current density of 500 to 1000 A/m2, industrial zinc sulfate... 

A promising electrochemical sensor was developed based on a layer by layer process by electro-polymerization of pyrrole in the presence of new coccine (NC) as dopant anion on the surface of the multi-walled carbon nanotubes (MWCNTs) pre-coated glassy carbon electrode (GCE). The modified electrode was used as a new and sensitive electrochemical sensor for voltammetric determination of sumatriptan (SUM). The electrochemical behavior of SUM was investigated on the surface of the modified electrode using linear sweep voltammetry (LSV). The results showed a remarkable increase (∼12 times) in the anodic peak current of SUM in comparison to the bare GCE. The effect of experimental variables such... 

The present work describes sensing application of modified TiO 2 nanotubes having carbon-Pt nanoparticles for simultaneous detection of dopamine and uric acid. The TiO 2 nanotubes electrode was prepared using anodizing method, followed by electrodeposition of Pt nanoparticles onto the tubes. Carbon was deposited by decomposition of polyethylene glycol in a tube furnace to improve the conductivity. The C-Pt-TiO 2 nanotubes modified electrode was characterized by cyclic voltam-metry and differential pulse voltammetry methods. The modified electrode displayed high sensitivity towards the oxidation of dopamine and uric acid in a phosphate buffer solution (pH 7.00). The electro-oxidation currents... 

Enzymatic decolorization of reactive blue 221 (RB221) using laccase was investigated in a dual-chamber microbial fuel cell (MFC). Suspended laccase was used in the cathode chamber in the absence of any mediators in order to decolorize RB221 and also improve oxygen reduction reaction in the cathode. Molasses was utilized as low cost and high strength energy source in the anode chamber. The capability of MFC for simultaneous molasses and dye removal was investigated. A decolorization efficiency of 87% was achieved in the cathode chamber and 84% COD removal for molasses was observed in the anode chamber. Laccase could catalyze the removal of RB221 and had positive effect on MFC performance as... 

Nanoparticulated TiO 2 fibers as one-dimensional long structures were introduced into TiO 2 P25 nanoparticle films using coelectrophoretic deposition. This prevented the usual crack formation occurring in wet coatings, and resulted in less porosity and higher roughness factor of the films that provided more favorable conditions for electron transport. The films used as the photoanode of a dye solar cell (DSC) produced 65% higher photovoltaic efficiency. TiO 2 fibers can be excellent binders in single-step, organic-free electrophoretic deposition of TiO 2 for DSC photoanode