Sharif Digital Repository

The effect of thickness of TiO2 coating on synergistic photocatalytic activity of TiO2 (anatase)/α-Fe 2O3/glass thin films as photocatalysts for degradation of Escherichia coli bacteria in a low-concentration H2O2 solution and under visible light irradiation was investigated. Nanograined α-Fe2O3 films with optical band-gap of 2.06 eV were fabricated by post-annealing of thermal evaporated iron oxide thin films at 400 °C in air. Increase in thickness of the Fe2O3 thin film (here, up to 200 nm) resulted in a slight reduction of the optical band-gap energy and an increase in the photoinactivation of the bacteria. Sol-gel TiO2 coatings were deposited on the α-Fe2O 3 (200 nm)/glass films, and... 

The bioconversion of abundant and renewable cellulosic biomass into ethanol as an alternative to petroleum is gaining importance due to the realization of diminishing natural oil and gas resources. Agricultural and foresty plant residues are an abundant and renewable source of sugar substrates that could be fermented to ethanol. A thermochemical treatment of biomass in which both cellulose and hemicellulose are hydrolyzed to soluble sugar is necessary before yeast fermentation. After thermochemical treatment, cellulase enzymes must be introduced in the system to hydrolyze any remaining cellulose. The simultaneous saccharification and fermentation (SSF), is a method which converts... 

CuO nanoparticles with average diameter of about 20. nm were accumulated on surface of sol-gel silica thin films heat treated at 300 °C in air. Heat treatment of the CuO nanoparticles at 600 °C in a reducing environment resulted in effective reduction of the nanoparticles and penetration of them into the film. While the thin films heat treated at 300 °C exhibited a strong antibacterial activity against Escherichia coli bacteria, the reducing process decreased their antibacterial activity. However, by definition of normalized antibacterial activity (antibacterial activity/surface concentration of coppers) it was found that Cu nanoparticles were more toxic to the bacteria than the CuO... 

Titania thin film system containing noble metallic nanoparticles such as Au, Ag, and Cu have been prepared by utilizing radio frequency reactive magnetron cosputtering method. The structural and morphological properties of the thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). Surface chemical composition of the films was determined by X-ray photoelectron spectroscopy (XPS). Optical properties of the TiO 2 annealed films containing Au, Ag, and Cu metallic nanoparticles were investigated by UV-visible spectrophotometry showing surface plasmon resonance of the metals. The photocatalytic activity of all synthesized samples annealed at 600 °C in an Ar +... 

In this study TiO2 nanotubular fibers were prepared and subsequently loaded with CdS nanoparticles to obtain visible light activate nanofibers with modified structure. Preparation of TiO2 fibers was based on templating method and Liquid phase deposition technique (LPD) with cellulose fibers as templates. Using LPD, thickness of the TiO2 layer could be controlled precisely by adjusting the reaction conditions, therefore after removal of the template, the resulting material has a fibrous structure, mimicking the cellulose fibers shape. CdS nanoparticles were synthesized by thermochemical growth method and attached to TiO2 fibers through impregnation method. The pure composite nanofibers were... 

Nickel and nickel-manganese alloy modified graphite electrodes (G/Ni and G/NiMn) prepared by galvanostatic deposition were examined for their redox process and electrocatalytic activities towards the oxidation of methanol in alkaline solutions. The methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (EIS) were employed. In CV studies, in the presence of methanol NiMn alloy modified electrode shows a significantly higher response for methanol oxidation. The peak current of the oxidation of nickel hydroxide increase is followed by a decrease in the corresponding cathodic current in presence of methanol. The anodic peak currents show linear dependency upon the... 

TixSi1-xO2 compound thin-film systems were deposited by reactive RF magnetron co-sputtering technique. The effect of Ti concentration on the hydrophilicity of TixSi1-xO2 compound thin films was studied and it was shown that the films with Ti0.6Si0.4O2 composition possess the best hydrophilic property among all the grown samples. Surface ratio and average roughness of the thin films were measured by atomic force microscopy (AFM). Surface chemical states and stoichiometry of the films were determined by X-ray photoelectron spectroscopy (XPS). In addition, XPS revealed that the amount of Ti-O-Si bonds in nanometer depth from the surface of the Ti0.6Si0.4O2 films was the maximum, which resulted... 

We report experimental evidence of Cu surface segregation in Ni/Cu system, during deposition of Ni film onto Cu substrate at room temperature and during heat treatment in vacuum. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) by Tougaard's analysis results show that surface segregation defeats in competition with increase in Ni thickness and terminates when thickness of Ni increase to more than 4 nm. Surface energy and concentration were calculated using contact angle measurements and the results confirm that segregation reduces the surface energy. Surface segregation during heat treatment at 150-220 °C range as a function of time initially shows linear mass... 

Local annealing of amorphous NiTi thin films was performed by using an Nd:YAG 1064 nm wavelength pulsed laser beam. Raw samples produced by simultaneous sputter deposition from elemental Ni and Ti targets onto unheated Si (100) and Silica (111) substrates were used for annealing. Delicate treatment with 15.92 W/mm2 power density resulted in crystallization of small spots; while 16.52 and 17.51 W/mm2 power densities caused ablation of the amorphous layer. Optical microscopy, scanning electron microscopy, X-ray diffraction and atomic force microscopy were performed to characterize the microstructure and surface morphology of the amorphous/crystallized spot patterns  

In this study, the optimal sizing and performance analysis of a standalone integrated solar power system equipped with different storage scenarios to supply the power demand of a household is presented. One of the main purposes when applying solar energy resource is to face the increasing environmental pollutions resulting from fossil fuel based electricity sector. To this end, and to compare and examine two energy storage technologies (battery and hydrogen storage technology), three storage scenarios including battery only, hydrogen storage technology only and hybrid storage options are evaluated. An optimization framework based on Energy Hub concept is used to determine the optimum sizes... 

Micro and nanotechnology can potentially revolutionize drug delivery systems. Novel microfluidic systems have been employed for the cell culture applications and drug delivery by micro and nanocarriers. Cells in the microchannels are under static and dynamic flow perfusion of culture media that provides nutrition and removes waste from the cells. This exerts hydrostatic and hydrodynamic forces on the cells. These forces can considerably affect the functions of the living cells. In this paper, we simulated the flow of air, culture medium, and the particle transport and deposition in the microchannels under different angles of connection inlet. It was found that the shear stress induced by the... 

Hyperthermia generally means as increasing the temperature of particular region of body to rise 5 °C above the body's physiological temperature. Here, we investigate the thermal therapy of PEGylated cobalt ferrite nanoparticles prepared by hydrothermal approach on cancerous cell line in the alternative current magnetic field. To characterize of the magnetic nanoparticles (MNPs), scanning electron microscopy, dynamic light scattering, X-ray diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometer were used. X-ray diffraction analysis confirmed the spinel phase formation of the MNPs. Cytotoxicity of MNPs using MTT assay on L929 cell lines showed the PEGylated... 

In this work, V, Co-codoped TiO2(B) samples are synthesized through a hydrothermal method, and used as negative electrode materials for lithium ion batteries. The amount of dopants is varied in order to investigate their influence on electrochemical properties. The formation of V, Co-codoped TiO2(B) nanobelts with widths of 20 and 60 nm is demonstrated using X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma–optical emission spectrometry and field-emission scanning electron microscopy analyses. In addition, the electrochemical properties of the samples are tested by cyclic voltammetry, charging/discharging, and cyclic performance techniques. Compared to other... 

In this research pure HA and HA-ZrO2-TiO2 nanocomposite coatings (named HZT coatings) were successfully synthesized by merging two usual electroplating methods. In order to deposit pure HA coating a particular saline solution of Calcium and Phosphate was prepared with pH = 4.2, thermodynamically rich of hydroxyapatite. XRD and FTIR studies prove the synthesis of hydroxyapatite during electrodeposition process. To synthesize composite coatings with rational molar ratios of composite agents to matrix, two different concentrations of ZrO2-TiO2 suspensions were added to Ca-P solution at the pH = 4.2 and electrodeposition process done similar to pure HA sample. XRD, FTIR and FESEM (EDS) analyses... 

In drilling industry, barite particles settling and barite sag as a major problem can potentially impose significant operational issues. Static conditions, in which well undergoes an extended shut-in period, could occur during different drilling and completion operations such fishing operation, tripping, and logging. Despite its importance, such phenomenon is not well understood yet. To avoid issues related to barite settlement and barite sag, a good understanding of the impact of different drilling parameters on barite settlement and sag phenomenon is required. Recently, the mathematical formulation and modeling of settlement and sag processes have gained more attention. In order to better... 

The field emission properties of MoO2 nanostars grown on a silicon substrate and their emission performance in various vacuum gaps are reported in this article. A new structure of molybdenum oxides, named a nanostar, is grown by thermal vapor deposition with a length of ̃1 μm, a thickness of ̃50 nm, and its width in the range of 500-700 nm. The morphology, structure, composition, and chemical states of the prepared nanostars were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). According to XRD analysis, the grown nanostructures are composed of both crystalline Mo4O11 and... 

In this research, a parametric study is carried out on the effect of soil-structure interaction on the ductility and strength demand of buildings with embedded foundation. Both kinematic interaction (KI) and inertial interaction effects are considered. The sub-structure method is used in which the structure is modeled by a simplified single degree of freedom system with idealized bilinear behavior. Besides, the soil sub-structure is considered as a homogeneous half-space and is modeled by a discrete model based on the concept of cone models. The foundation is modeled as a rigid cylinder embedded in the soil with different embedment ratios. The soil-structure system is then analyzed subjected... 

Hydrogen storage capacities of raw, oxidized, purified and Fe-doped multi-walled carbon nanotubes (MWCNTs) were studied by electrochemical method. Based on transmission electron microscopy and Raman spectroscopic data, thermal oxidation removed defective graphite shells at the outer walls of MWCNTs. The analysis results indicated that the acid treatment dissolved most of the catalysts and opened some tips of the MWCNTs. Thermal gravimetric analysis and differential scanning calorimetry results illustrated that by oxidation and purification of MWCNTs, the weight loss peak shifts toward a higher temperature. N2 adsorption isotherms of the purified and oxidized MWCNTs showed an increase in N2... 

The visible light photocatalytic activity of α-Fe2O3 nanograin chains coated by anatase TiO2 nanolayer, as a photocatalyst thin film for inactivation of Escherichia coli bacteria, was investigated for the solutions containing 106 colony forming units per milliliter of the bacteria, without and with H2O2 (60 μM). Thin films of the α-Fe2O3 nanograins with the grain size of 40-280 nm were grown on glass substrates by post-annealing of the thermal evaporated Fe3O4 thin films at 400 °C in air. The TiO2 layer with thickness of about 20 nm was coated on the nanograins by dipping the Fe2O3 thin films in a prepared TiO2 sol and re-annealing them at 400 °C in air. The antibacterial activity of the... 

Nickel and nickel-copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) prepared by galvanostatic deposition were examined for their redox processes and electro-catalytic activities towards the oxidation of glucose in alkaline solutions. The methods of cyclic voltammetry (CV) and chronoamperometry (CA) were employed. The cyclic voltammogram of NiCu alloy demonstrates the formation of β/β crystallographic forms of the nickel oxyhydroxide under prolonged repetitive potential cycling in alkaline solution. It is also observed that the overpotential for O 2 evolution increases for NiCu alloy modified electrode. In CV studies, NiCu alloy modified electrode yields significantly higher...