Sharif Digital Repository

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... 

ZnO nanopowder has been successfully synthesized by a microwave-assisted solution approach using Zn(CH3CO2)2.2H2O and NaOH. The results obtained from XRD, SEM and TEM show that the mean particle size is 30 nm. SEM and TEM micrographs of ZnO nanopowder also reveal that nanoparticles have spherical shape. A convenient one-pot multi-component reaction of aromatic aldehydes, enolizable ketones or β-keto esters and acetonitrile in the presence of acetyl chloride and 10 mol % ZnO nanoparticles for the synthesis of β-acetamido ketones/esters at room temperature is described. Catalytic activity of ZnO nanopowder for o-acylation of alcohol and phenol has also been investigated. On the other hand,... 

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... 

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... 

In this report, a combination of in-situ chemical synthesis and electrolysis methods was applied for the preparation of zinc oxide/graphene quasi core-shell nanoparticles. Pure zinc oxide was also prepared using the same method at different temperatures. The degree of 100 ◦C was selected for synthesizing of ZnO-GO quasi core-shell (zinc oxide as a core and few layer of graphene oxide as a shell). The particle size was 15±2 nm in all samples. In both processes, oxygen was the main reason for the connection between the core and the shell. Unlike chemical process that has all kind of functions in electrolysis process, one kind of function was produced and confirmed by FTIR. XRD patterns also... 

According to the growth in the world population and the decrease in fossil fuels resources and also according to the pollution caused by these unrenewable resources, using hydrogen as an alternative energy resource seems to be unavoidable. In the past decades, semi-conductor metal oxides were being used widely in the energy domain of study, due to their appropriate band gap in the ultra-violet and visible spectra. Among these metal oxides, ZnO has been under special attention because of its electron mobility and its reasonable production cost and also its friendliness to environment. But the high band gap of ZnO (3.2 eV) has impeded its use in visible light spectrum. In this project,... 

In this project, the photoelectrochemical properties of ZnO nanostructures modified by CdS and Graphene was studied. Firs, titanium foil was cut into rectangular shape with 1cm width and 3 cm length, cleaned by rinsing in acetone and ethanol and annealed at 4000C for an hour. As a result, a thin layer of titanium oxide was formed on Ti sheet. Then a layer of grapheme oxide was deposited on substrate using Electrophoretic deposition (EPD). After that, ZnO nanostructure was deposited on the TiO2 substrate using Electropulsation (EP) with 20 consecutive pulse followed by 3 minutes Electrodeposition (ED). Using SEM analysis, the morphology of ZnO was determined to be nanopetals in which the... 

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  

In this research, two type of graphene quantum dots (GQDs) have synthesized including, normal GQDs and nitrogen-doped GQDs (N-GQDs). Then, each of GQDs were deposited on the 1 dimensional zinc oxide (ZnO) nanostructures namely nanowires (NWs) and branched hierarchical (BH) systems. Then, photocatalytic activity of the samples were studied in photodegradation of methylene blue (MB) and methylene orange (MO) under visible light. First, ZnO nanowires (ZnO NWs) were fabricated by anodization of zinc sheet possessing wurtzite crystal structure with their average length and diameter measured in the range of 50-60 μm and 170-300 nm, respectively. Then, normal GQDs were synthesized by... 

Water Gas Shift (WGS) reaction is an old reaction in which syngas is used for producing Hydrogen. At the present time, the major application of this reaction is in fuel cells, since the necessary Hydrogen for these cells is provided by this reaction.
The present study investigate the influence of different preparation methods on properties of Cu-ZnO/Al2O3 catalyst for water gas shift (WGS) reaction, which is now known as the Commercial catalyst for low temperature WGS, and its influence on performance of Cu-ZnO/Al2O3 catalyst to derive an optimal Cu-ZnO/Al2O3 catalyst for water gas shift (WGS) reaction. Cu-ZnO/Al2O3 catalysts was synthesized by CP, DP, DP-Ultra, IWI , CP-Urea, and... 

Water-gas shift reaction (CO(g) + H2O(g) ↔ CO2(g) + H2(g)) is performed as the key step in the hydrogen and ammonia industrial plant. In this work, Fe/Cr/Cu high temperature water gas shift catalysts were synthesized by coprecipitation method, using sulfate precursors, in order to improve the catalytic performance and particular emphasis is placed on the catalytic activity affected by aging time, precipitating agent and ways of increasing the mechanical strength. Finally the prepared and industrial catalysts were compared when they were situated in the operating conditions (at 360oC and 2 bar) and were characterized by BET, XRD, TPR, TEM and crushing strength analysis. Catalysts being made... 

ZnO semiconductor has a wide band gap (3.3eV) and high electron mobility, making it a possible candidate for an effective structure-based Dye-sensitized solar cell (DSSC) semiconductor. Efficiency of DSSC based on ZnO is lower than TiO2 due to its low chemical satability. It is well known that the energy conversion efficiency of DSSC depends on the electron transport in the photoelectrode so in this investigation we fabricated high transport photoelectrode by doping Al in ZnO nanostructures. DSSC based on Al doped and undoped ZnO nanosheet synthesized by electrochemical deposition. Current density-voltage (J-V) characterizations indicate that Al-doping in ZnO crystal structure increases...