Sharif Digital Repository

The catalytic activity of Pt/Ni/TiO 2 nanotubes electrode toward glucose has been studied. Fabrication of Pt/Ni nanostructures was done in a single-bath solution through electrochemical pulse method by changing the deposition potential between -0.3 and -4 V vs. SCE, respectively. The resulting modified electrode represented high conductivity due to the effective presence of metallic components and uniform surface area caused by dispersion of Pt and Ni nanostructures. The scanning electron microscopy images also confirmed that a large amount of metals colonies were well-dispersed at the edge of the TiO 2 nanotubes. In addition, the Pt/Ni TiO 2 nanotubes modified electrode exhibited an... 

An electro-catalysis non-enzymatic electrode is proposed based on alloyed Pt/Ni nanowire arrays (NWAs) for the detection of glucose. The Pt/Ni NWAs were prepared by pulse electrodeposition of Pt and Ni within a nano-pore polycarbonate (PC) membrane followed by a chemical etching of the membrane. The electrode structure is characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The resulting Pt/Ni NWAs electrode shows high electrocatalytic activities towards the oxidation of glucose in alkaline solution. Consequently, a sensitive amperometric detection of glucose is achieved under 0.45 V vs. SCE with a low detection limit of 1.5 μM within a wide linear... 

A simple modified TiO2 nanotubes electrode was fabricated by electrodeposition of Pd, Pt and Au nanoparticles. The TiO2 nanotubes electrode was prepared using the anodizing method, followed by modifying Pd nanoparticles onto the tubes surface, offering a uniform conductive surface for electrodeposition of Pt and Au. The performance of the modified electrode was characterized by cyclic voltammetry and differential pulse voltammetry methods. The Au/Pt/Pd/TiO2 NTs modified electrode represented a high sensitivity towards individual detection of dopamine as well as simultaneous detection of dopamine and uric acid using 0.1 M phosphate buffer solution (pH 7.00) as the base solution. In both case,... 

Hydrolysis of titanium isopropoxide alcoholic solution has been used to prepare the crystallized TiO2 nanoparticles at low temperature. Concentration ratio was used to control the pathway of sol-gel process and change the physical characteristics of TiO2 nanopowders. The crystallinity, morphology and size of aged TiO2 nanopowders were studied by X-ray diffraction and Scanning Electron Microscopy (SEM). FTIR and, Thermo-Gravimetric (TG) analysis were used to identify the functional groups and thermal behavior of prepared samples. Experimental results have shown that high crystalline TiO2 nanomaterial with anatase polymorph can be obtained at room temperature. It has been found that the... 

Kinetics of oxidation of MgO-C refractory bricks containing 14.3% graphite, 80.9% magnesia, and 4.8% phenolic resin is investigated comprehensively. Effect of temperature and grain size distribution on the rate of oxidation of graphite is evaluated by application of a mathematical model developed on the basis of shrinking core/progressive conversion regime to the gas-solid processes involved. Incorporation of the experimental data into the mathematical model indicates that a mixed controlling mechanism governs the oxidation rate. Three activation energies were recognized: (a) 68 kJ/mol for chemical adsorption of gas on the surface of the graphite flakes, (b) 22 kJ/mol for pore diffusion of... 

We have investigated hydrogen sensing properties of electrodeposited Pd clusters on macroporous silicon substrates. Porous layer was prepared by electrochemical etching of p-type silicon (100) wafer in organic electrolyte DMF (dimethylformamide) diluted by HF (%95 Vol. %). The deposition of Pd was carried out by linear voltammetry (LV) technique. This technique was taken for reduction of palladium ions in the potential range from 0.4 V to -1 V vs. SCE, at the scan rate of 20 mV s-1. Some samples were annealed at 300°C for an hour in air to study the effect of heat treatment on their gas sensitivity. Surface structural and chemical properties of the samples were characterised using Scanning... 

A nanowire arrays system consisting of an ordered configuration of Pt, Ni and Co was constructed in single-bath solution through pulse electrodeposition. This structure was evaluated as a potential amperometric non-enzymatic sensor to detect glucose in alkaline solution. We observed a strong and fast amperometric response at low applied potential of 0.4 V vs. SCE over linear ranges of 0-0.2 mM and 0.2-8 mM glucose with sensitivities of 1125 and 333 μA mM-1 cm-2, respectively. We also observed a low detection limit for glucose of 1 μM. Correlation of the electronic and geometric modifications with the electrochemical performance characteristics enhanced catalytic activity of the electrode by... 

Progressive conversion/shrinking core (PC-SC) models of constant-size cylinders were exploited to interpret the decarburization reactions of MgO-C-Si bricks heated up under blown air. Chemical adsorption/solid (or pore) diffusion mechanisms governed the reaction rate. With 5% silicon, chemical adsorption vanished at 1000 and 1100°C. The oxidation rate lowered then with temperature. This was due apparently to the blocking of the pore-end gorges by the voluminous compounds (like Forstrite). Arrhenius plots of the specific rates yielded the activation energies of the prevailing steps. Without Si antioxidant, three steps were appreciated having activation energies of 51.65 (for chemical... 

Kinetics of air oxidation of MgO-C-Al refractory at 600°-1300°C were investigated using the software based on the modifled shrinking core model (KDA). Commercial bricks containing 88.5% MgO, 10% residual carbon, and 1.5% aluminum anti-oxidant were oxidized isothermally with air. Combination of experimental data with model calculations indicated gas diffusion through solid material and pores as a major controlling step. Previously observed chemisorption process was eliminated from the rate-controlling mechanism with addition of aluminum antioxidant. Comprehensive rate equations were devised for MgO-C-Al and MgO-C oxidation reactions. Overall activation energies of Q id (internal diffusion) =... 

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 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... 

In this study a novel Pt/Ni nanostructure consisting of nano-bushes and nanocubes was fabricated onto TiO 2 nanotubes. The scanning electron microscopy images showed that a large amount of well-dispersed nano-architectures had uniformly covered all over the surface which made an electrode with high surface area. It was obviously seen that the nanocube structures mainly consists of Ni had been grown on top of each other while the Pt colonies represented bush-like structures. As a non-enzymatic glucose biosensor, the Pt/Ni TiO 2 nanotubes modified electrode exhibited an excellent performance. The proposed biosensor had two linear ranges for detection of glucose from 0 to 0.12 mM (correlation... 

Electrodeposition of the Co-Ni/Cu multilayer films was carried out in sulfate solution. Cyclic voltammetry and current transient techniques were utilized to characterize the multilayer system and to obtain the nucleation and growth mechanism. The cyclic voltammograms clearly showed that electrodeposition of cobalt-nickel alloy layer was controlled by a kinetic process, where copper ions were reduced under diffusion-controlled mechanism. In addition, the current transients revealed that nucleation mechanism was instantaneous with a typical three-dimensional growth process. The microstructure of the Co-Ni/Cu films was also changed with overpotential. In this system, the growth of multilayer...