Sharif Digital Repository

This work examines the dissolution kinetics of Sodium meta vanadate in water medium. The effects of temperature, solid/liquid ratio, agitation speed on the leaching kinetics were investigated. the dissolution kinetics was controlled by the internal diffusion at the surface of the Sodium metavanadate particles. The activation energy for the leaching was2/13 kJ/mol. In the current project, we report the preparation of VO_2 nanorods crystals using a ethylenediaminetetracetic acid assisted and Cetyl Trimethyl Ammonium Bromide hydrothermal synthesis route. NH_4 Cl and NaVO_3 solution were used as the starting materials and vanadiumoxide crystals were obtained following growth at 180 °C for 24... 

Synthesis, characterization and photocatalytic applications of core-shell like ZnO@CdS nanorods have been studied in this research. The synthesis of core-shell like ZnO@CdS nanorods was carried out in three different steps. At first, ZnO seed layer was formed on glass substrate via sol-gel process under optimum conditions using absolute ethanol solution containing zinc acetate and a stabilizer ( either Monoethanolamine (MEA) or diethanolamine (DEA)). When MEA used as stabilizer, the optimum concentration of sol was found 0.2 M, while increasing the sol concentration caused the seed layer to be grown in a string-like structure. The RMS surface roughness of seed layer prepared by 0.2 M sol... 

Recently, quasi 1D (Q1D) structures of materials such as nanowires, nanorods and nanobelts with high surface to volume ratio (A/V) and small grain size devoted an extensive part of researches. This is due to their unique properties and thus various applications in manufacturing of nanometric devices. Niobium pentoxide (Nb2O5) as semiconductor with wide bandgap has been applied in various fields including: electrochromic devices, gas sensors, anti-reflective coatings, capacitors, photocatalysts , field emission and recently; antibacterial systems. In this project , initially niobium thin films was deposited on Si(100) substrate using RF magnetron sputtering method and then niobium oxide... 

The broad range of applicability of nano devices particularly in electronics, optoelectronics, and micro/ nano-electro- mechanical systems has drawn the attentions of the industrial and scientific communities of various disciplines. This work is devoted to study the effect of surface and interface elasticity in the analysis of the mechanical behavior of ultra-thin objects in the presence of some statical or dynamical loadings. Based on the fact that the surface-volume ratio increases in nano-scale, description of the behavior of such a small structure via usual classical theories, which generally neglect the surface/interface effect, ceases to hold. In the present study, first, a... 

In this research we focus on fabrication and characterization of Dye and Cadmium based Quantum Dot Sensitized Solar Cells (QDSCs) based on TiO2 nanostructures. TiO2 nanorods were synthesized with a simple chemical method. TiO2 nanorods, TiO2 nanorod/TiO2 and ZnO nanoparticle composite structures were integrated as photoanode in dye sensitized solar cells (DSSCs). Incorporation of TiO2 nanoparticles into the bare nanorods increased the efficiency more than 45%. Monitoring electron transport properties of the cells, pointed out the crucial role of electronic structure of composite film components on the performance of cells. Suitable morphology of TiO2 nanorods, led us to use them, to make a... 

In the present work, one dimensional ZnO nanostructures were grown by seed-assisted hydrothermal method. Hydrothermal processing parameters were controlled to obtain ZnO nanorods with diameter lower than 120 nm. The products were characterized by FE-SEM, EDAX, XRD, PL, and ATR-FTIR analyses. ZnO nanoparticles were also synthesized via a simple solvothermal method and their photo peropeties were compared with onedimensional nanostructures. Thereafter dye-sensitized solar cells based on TiO2-ZnO double layer nanostructured film were fabricated. It was observed that DSSC efficiency increased with decreasing the thickness of the film. The highest efficiency of 2.41% was obtained  

Hydroxyapatite is the most substantial inorganic constituent of bone tissue which displays splendid biocompability and bioactivity. Nevertheless, its mechanical properties is not utmost appropriate for a bone substitutes. Therefore, it is used to improve the mechanical properties of polymer matrix composite scaffolds. In the present work polycaprolactone as a polymeric matrix was employed to fabricate hydroxyapatite-polycaprolactone biocomposite scaffolds via in situ route. Solvothermal method was employed to synthesize in situ hydroxyapatite in polymer matrix. Porous scaffolds were fabricated via freeze-drying/porogen leaching. Physical, mechanical (compressive module and compressive... 

This work describes the effect of hydroxyapatite with different morphology including nanorods and whisker on the properties of hydroxyapatite/polycaprolactone (HA/PCL) composite. Biodegradable polymer/Hydroxyapatite (HA) composites with the morphology of nanorods and whisker of (HA) as bone replacement scaffolds are synthesized by sol-gel and hydrothermal methods, respectively with a Ca/P ratio of 1.67 and 20:80 (HA/PCL).The crystallization behavior and porosity of HA/PCL composite are studied by scanning electron microscope and X-Ray diffraction. The response of bone marrow-derived human mesenchymal stem cells (hMSCs) in terms of cell proliferation and differentiation to the osteoblastic... 

Electrochemical sensing of glucose has received paramount attention in recent years, particularly, the non-enzymatic glucose sensing is one of the trends in the whole biosensing world. In this research, synthesis and evaluation of a hybrid structure of vertical oriented nickel nanorod-reduced graphene oxide sheets as a non-enzymatic glucose sensor were performed. The 3D array of nickel nanorods was synthesized by electrodeposition of nickel sulfate electrolyte in track-etched polycarbonate template with 100 nm pore size and 6-10 μm thickness. The electrodeposition performed in various conditions, and the best result was achieved by application of potential of 3 V for 60 minutes. The shiny... 

Because of the working conditions of semiconductors at ambient temperature and pressure, degradation of organic pollutants through semiconductors photocatalysis has attracted the interest of many researchers. Because of its large exciton binding energy,high chemical and physical stability,high electron and hole mobility, and low cost; zinc oxide, an n-type semiconductor with 3.2 eV direct band gap, is widely used in applications such as photocatalysts, solar cells, and light-emitting diodes. Among various morphologies of ZnO, 1D nanostructures such as nanowires and nanorods have recieved much attention due to their high surface to volume ratio. However, the application of ZnO as a... 

Amongst different methods for synthesis one-dimensional TiO2 nanostructures, hydrothermal process has various advantages such as use of water as growth media and can be defined as an environmentally friendly processing. Hydrothermal processing parameters including processing temperature and time, nature of titanium source and its primary particle size, concentration of titanium source, drying temperature, annealing temperature and re-hydrothermal process have significant influence on crystal structure and morphology of the final product. These parameters were investigated in the present study. Therefore, five different titanium sources including three TiO2 powders and two TiO2 sols as well... 

One-dimensional (1D) cadmium sulfide (CdS), nanostructures have significant potential applications in solar cells, photocatalysts and many electronic devices. There are many experimental approaches to synthesis 1D CdS nanostructures. Among them solvothermal method has many advantage such as controllable and inexpensive method. 1D CdS nanostructures with different properties in morphology, crystal structure, band gap energy and etc can be obtained by controlling solvothermal processing parameters. In the present work the effect of solvothermal processing parameters including reaction temperature (120ºC ,160ºC and 200ºC), process time (12h, 48h and 72h), sulfur source (S powder, Thiourea and... 

Recent studies have indicated that one-dimensional titanium dioxide (TiO2) shows excellent properties in comparison to other forms of TiO2 materials in photocatalysis, sensing, self-cleaning coating and photovoltaic applications. In this project TiO2 nanorods were grown in polycarbonate template, with pore diameter of 200 nm, by solelectrophoretic deposition method. Firstly, properties of TiO2 sol were investigated. The average particle size of TiO2 (measured by zeta sizer instrument) was 17 nm and the zeta potential was around 45 mV, which confirmed good stability of the sol against aging. Moreover, FTIR analysis showed that a full conversion of precursor (titanium isopropoxide) was... 

Today organometallic perovskites are very important in fabrication of solar cells. This materials have advantages like high mobility of charge carriers, changing in range of light aborption with changing in structures atoms, having longer charge carrier diffusion lengths than other materials, high stability and efficiency, Low-cost fabrication process, having capability of studying and processing in low temperatures and having flexibility because of Weak chemical bond in perovskite structure. Due to the low stability and rapid decomposition of this material with the presence of light and moisture, in this study has tried to use PbS quantum dots which is used in sensitive dye solar cells as... 

We demonstrated efficient direct electron transfer from the enzyme glucose oxidase to vertically aligned gold nanorods with a diameter of ~160 nm and a length of ~2 μm that are covalently linkage to a 3-dimensional network of reduced graphene oxide nanosheets. The assembly can be prepared by a 2-step electrochemical procedure. This hybrid structure holds the enzyme in a favorable position while retaining its functionality that ultimately provides enhanced performance for enzymatic sensing of glucose without utilizing mediators. The nanorod assembly was applied to the voltammetric detection of glucose. Figures of merit include an electrochemical sensitivity of 12 µA⋅mM-1⋅cm-2 (obtained from...