Search for: zinc-oxide
0.008 seconds
Total 182 records

    Detecting Intermediate Particles in the Growth of Colloidal Zinc Oxid Nanoparticles in Different Chemical Routes Using MCR-ALS

    , M.Sc. Thesis Sharif University of Technology Kafrashi, Fatemeh (Author) ; Jalali Heravi, Mahdi (Supervisor) ; Hormozinezhad, Mohammad Reza (Supervisor)
    Zinc oxide(ZnO) nanoparticles have been used in a wide-ranging of applications such as transparent UV protection, medical treatments, light emitting diodes, sensors and photovoltaic cells. Many applications of ZnO nanoparticles could be improved by changing the particle size, shape and morphology. In order to take advantage of the unique size dependent properties observed for ZnO anoparticles, knowledge of how particle growth can be controlled is required. As an alternative to transmittance electron microscopy (TEM), which is already used in the study of size and monodispersity of ZnO nanoparticles during synthesis, we proposed a simple spectrophotometric method coupled with chemometric... 

    Synthesis and Characterization of a Novel Hydrogel Wound Dressing based on Silk Fibroin and Zinc Oxide Nanoparticles

    , M.Sc. Thesis Sharif University of Technology Tayefeh Kazemi, Minoo (Author) ; Nemati, Ali (Supervisor) ; Shokrgozar, Mohammad Ali (Supervisor) ; Farokhi, Mehdi (Co-Supervisor)
    Recently, some wound dressings have been designed that are expected to enhance the wound healing process and prevent blood bleeding and infection. Polymeric dressings have attracted attention due to their biocompatibility, biodegradability, lack of toxicity, and non-allergenic nature. There is widespread interest in using silk fibroin (SF) for this purpose because of its unique properties. Given these points, we have designed an injectable antioxidant hydrogel wound dressing based on SF and Polydopamine(PDA) modified ZnO nanoparticles. First, ZnO nanoparticles were doped with Cu and then modified with PDA (ZnCuO@PDA). XRD, FTIR, SEM, and TEM characterizations were carried out to confirm the... 

    Nanopowder synthesis of zinc oxide via solochemical processing

    , Article Materials and Design ; Volume 28, Issue 2 , 2007 , Pages 515-519 ; 02613069 (ISSN) Vaezi, M. R ; Sadrnezhaad, S. K ; Sharif University of Technology
    Elsevier Ltd  2007
    Zinc oxide is used in functional devices, catalysts, pigments, optical materials and many other important applications. ZnO nanopowders can be produced mechanochemically or solochemically. The synthesis of ZnO nanopowder has been carried out via solochemical processing from an aqueous solution of a zinc containing complex in this research. This is the newest economic method for synthesis of ZnO nanopowder. The results obtained from XRD and TEM show that the nanoparticles are single crystals and the mean particle size is 45.3 nm. TEM micrographs of ZnO nanopowder reveal that the particles have elongated particulate shape with a narrow size distribution. Solochemical processing can thus be an... 

    ZnO Coating, Containing SiO2 Nano Particles, Prepared by Sol-gel Process and Investigation of Surface Properties

    , M.Sc. Thesis Sharif University of Technology Rostami, Rahman (Author) ; Ghorbani, Mohammad (Supervisor) ; Askari, Masoud (Co-Advisor)
    Zinc oxide thin films due to special specification and properties have variable application in different industries. Recently because of wide application of zinc oxide doped SiO2 in optoelectronics and sensors, lots of investigation have been focus on it. Meanwhile due to the SiO2 hydrophilic properties, doping of ZnO with SiO2 can improve self-cleaning properties zinc oxide membrane.It this project zinc oxide and ZnO doped SiO2 thin films with different composition were made by sol-gel and dip-coating process used for coating of mentioned sol over the quartz surface(15*25 mm). At first point different sol with different components was mixed with each other to make composite films but due to... 

    Synthesis of ZnO and ZnO-TiO2 Nanocoatings by Sol-Gel Methode and Study in Their Antibacterial and Photocatalyst Properties

    , M.Sc. Thesis Sharif University of Technology Nournia, Shayan (Author) ; Dolati, Abolghasem (Supervisor)
    The goal of this study is synthesis of nanocoating on basis of ZnO by Sol-Gel method and evaluation of their antibacterial and photocatalyst properties changes by different values of TiO2. For this purpose in both method of synthesis contents of TiO2 hase been changed from 0-25 molar percent. Dip coat method has been used for coating from sol with 1.4 mm/s withdrawal speed and 2 minute immersion time. After each step of coating samples has been dried at 150oC for 10 minute and for increasing thickness this process has been repeated 4 times. In first method zinc acetate dihydrate in 0.1 M final concentration and titanium tetraisopropoxide are sol precursors at in situ way of synthesis. In... 

    Synthesis of Highly Substituted Pyrrole and A-pyrone Derivatives using ZnO Nano Catalyst

    , M.Sc. Thesis Sharif University of Technology Motamen, Sara (Author) ; Matloubi Moghaddam, Firouz (Supervisor)
    Herein, we report an efficient one-pot four-component reaction of commercially available 1,3-dicarbonyl compounds, aromatic aldehydes, amines, and nitromethane in the presence of ZnO nanoparticles, which leads to highly substituted pyrroles in moderate to good yields. A mild and efficient tandem process for the synthesis of highly substituted α-pyrones starting from 2-arylacetic acid of high com-mercial availability has been developed. The synthesis is based on the Knoevenagel condensation of 1,3-cyclohexadiones to various β-keto-Esters, followed by lactonization in the presence of 20 mol% ZnO as a nanocatalyst. Moderate to high yields, easily available and less expensive starting materials... 

    , M.Sc. Thesis Sharif University of Technology Yosefi, Mahdie (Author) ; Moshfegh, Alireza (Supervisor)
    ZnO is a wide and direct band gap (3.37 eV) semiconducting material with a large exciton binding energy (60 meV). It has been extensively studied in the last few years owing to its potential applications in various fields such as surface acoustic wave devices (SAW), transparent electrode, solar cell windows, photovoltaic devices, gas sensors and photoelectrochemical cells. Recently, much attention has been paid to rare-earth (RE) doped ZnO for possible applications in visible emitting phosphors in displays, high power lasers, and other optoelectronic devices. In this thesis, initially ZnO thin films were deposited on glass and ITO substrates using sol-gel dip-coating method. Optical and... 

    Three-dimensional hybrid graphene/nickel electrodes on zinc oxide nanorod arrays as non-enzymatic glucose biosensors

    , Article Sensors and Actuators, B: Chemical ; Volume 251 , 2017 , Pages 462-471 ; 09254005 (ISSN) Mazaheri, M ; Aashuri, H ; Simchi, A ; Sharif University of Technology
    Elsevier B.V  2017
    We present a novel hybrid electrode based on reduced graphene oxide/nickel/zinc oxide heterostructures. The sensor was fabricated by template-free hydrothermal growth of ZnO nanorod arrays on conductive glass substrates (FTO) followed by conformal electrodeposition of nickel nanoparticles with an average size of 18 nm. Then, in-situ reduction and electrophoretic deposition of graphene oxide (GO) nanosheets on the structured ZnO/Ni electrode was performed. The prepared three-dimensional nanostructure exhibited fast electrocatalytic response (<3 s) towards glucose oxidation due to the large surface area and high electro-activity. The prepared biosensor possessed a wide linear range over... 

    Rapid and efficient one-pot synthesis of 1,4-dihydropyridine and polyhydroquinoline derivatives through the hantzsch four component condensation by zinc oxide

    , Article Journal of the Iranian Chemical Society ; Volume 6, Issue 2 , 2009 , Pages 317-324 ; 1735207X (ISSN) Matloubi Moghaddam, F ; Saeidian, H ; Mirjafary, Z ; Sadeghi, A ; Sharif University of Technology
    A one-pot four-component reaction of aldehydes, ethyl acetoacetate/5,5-dimethyl-1,3-cyclohexanedione, ethyl acetoacetate and ammonium acetate in the presence of 10 mol% of ZnO as a heterogeneous catalyst for the synthesis of corresponding 1,4-dihydropyridine and polyhydroquinoline derivatives via the Hantzsch condensation is described. The present methodology offers several advantages such as simple procedure, excellent yields, and short reaction time  

    Production of zinc oxide nanoparticles by liquid phase processing: An investigation on optical properties

    , Article 2nd International Conference on Diffusion in Solids and Liquids, DSL-2006, Aveiro, 26 July 2006 through 28 July 2006 ; Volume 553 , 2007 , Pages 252-256 ; 02555476 (ISSN); 0878494383 (ISBN); 9780878494385 (ISBN) Vafaee, M ; Youzbashizade, H ; Sharif University of Technology
    Trans Tech Publications Ltd  2007
    In the recent years, many researchers have been interested in nanoparticles because of their unique properties. In this study, a method for producing ZnO nanoparticle colloids is proposed. The colloids were characterized by spectroscopic analyzer. By absorption spectrum study, we found out that colloids were consisted of nanoparticles with less than 10 nanometer size. The quantum confinement effect in these spectrums was recognized through blue shift of onset absorption wavelengths. These wavelengths shift from 370 nm to 340 nm by decreasing the particles size. Transmittion electron micrographs showed formation of zinc oxide nanoparticles  

    Studies on recycling of zinc-containing waste

    , Article REWAS'04 - Global Symposium on Recycling, Waste Treatment and Clean Technology, Madrid, 26 September 2004 through 29 September 2004 ; 2005 , Pages 2797-2799 ; 8495520060 (ISBN) Taghavi, S. M ; Halali, M ; Sharif University of Technology
    In this report, the possibility of recovering zinc oxide from zinc containing wastes, also the effect of temperature, time and depth of bed on recycling has been studied. Zinc oxide with a purity of 93.5% was obtained  

    Fabrication and Characterization of Electron Transport and Buffer Layer Thin Films, Employing Sputtering Method, for All-Oxide Solar Cells

    , M.Sc. Thesis Sharif University of Technology Farahani, Elham (Author) ; Iraji zad, Azam (Supervisor) ; Mohammadpour, Raheleh (Co-Advisor)
    In this study, transparent conductive thin film of Aluminum doped ZnO (ZnO:Al) have been fabricated thorough RF sputtering. The main goal of fabrication of these layers is achieving thin films with minimum resistivity and maximum optical transparency in visible range of spectrum employing as transparent electrodes and buffer layer at the entirely oxidized solar cells. To achieve the suitable structure, various parameters including pressure, power and the thickness of the deposition and annealing on morphologies of thin film has been investigated. According to these results, thin film of ZnO:Al has the transparency of 80% in the visible light range . Doping of ZnO with Aluminum caused... 

    Utilizing Metal Oxide as Hole/Electron Injection layer in Hybrid Light Emitting Diode

    , Ph.D. Dissertation Sharif University of Technology Alehdaghi, Hassan (Author) ; Taghavinia, Nima (Supervisor) ; Irajizad, Azam (Supervisor) ; Marandi, Maziar (Supervisor)
    Organic light emitting diodes (OLEDs) are one of the main subjects of research in the organic electronic advanced technology. There are many advantages for OLEDs like self-emitting, high efficiency, wide vision angle, high contrast, and rapid response time. The main challenge in this area is the long-time stability of performance in air ambiance. Although the encapsulation process could overcome the instability problem, it increases the final cost. In this project, metal oxides have been utilized for the injection of electrons and holes in hybrid light emitting diodes (HyLEDs). In the first stage, inverted structure of HyLEDs with ZnO and MgxZn1-xO layers was fabricated and characterized.... 

    Kinetics of TSCD zinc oxide nano-layer growth by modified diffuse-interface model

    , Article Ceramics International ; Volume 33, Issue 8 , December , 2007 , Pages 1409-1417 ; 02728842 (ISSN) Sadrnezhaad, S. K ; Vaezi, M. R ; Sharif University of Technology
    Deposition of zinc oxide films from aqueous solutions containing complex Zn2+ ions on soda-lime substrates were studied by two-stage chemical deposition (TSCD) process. It was shown that the film thickness can be controlled by the number of dipping stages. Nano-layers were produced with less than nine times dipping stages. Greater dipping numbers resulted in film thickness exceeding 100 nm. The growth rate obeyed double-stage zeroth order with respect to the concentration and first order with respect to the temperature. This rate was proportional to the difference between the temperature of the hot water and the substrate. Overall activation energy of 17.20 ± 0.42 kJ mol-1 and frequency... 

    Highly textured ZnO thin films: An economical fabrication, doping by Mn2+ and Sn2+ and approachment for optical devices

    , Article Materials and Design ; Volume 28, Issue 3 , 2007 , Pages 1065-1070 ; 02613069 (ISSN) Vaezi, M. R ; Sadrnezhaad, S. K ; Sharif University of Technology
    Elsevier Ltd  2007
    Fabrication of high quality zinc oxide thin films and analysis on its physical, chemical properties have applications in opto-electronic devices, UV laser, microelectronics and micro-machining schemes. Highly textured ZnO thin film with a preferred (0 0 2) orientation was prepared by two-stage chemical deposition (TSCD) using an aqueous solution containing zinc complex on a soda-lime glass substrate. From the results obtained, it can be shown that the preferred orientations of the film microcrystal changes with the doping process. The film was characterized by X-ray diffraction (XRD), SEM, EDAX, optical technique, Fourier transform infrared spectroscopy (FTIR) in order to qualify its... 

    Preparation and Characterization of One-dimensional Copper Oxide Nanostructures for Field Ionization Gas Sensors

    , M.Sc. Thesis Sharif University of Technology Hassan, Ahmadvand (Author) ; Iraji Zad, Azam (Supervisor)
    The purpose of this project is to construct a gas sensor based on one-dimensional nanostructured electrodes of copper oxide. By creating of these nanostructures, can be reduced breakdown voltage of gases, including flammable, to a few hundred volts. The CuO nanowires were grown by thermal oxidation on copper substrate to form self-assembled. In this method, by heating the copper foil,Cu2O also was formed on substrate. Effects of surface tension of substrate and oxidation temperature on surface density and structure of the nanowires were studied. SEM images taken from the samples showed that the surface tensions increases the density of nanowires and increasing the oxidation temperature leads... 

    Synthesis and Characterization of Electrospun N/S Doped ZnO and Investigation of their Applications in Dye Degradation

    , M.Sc. Thesis Sharif University of Technology Shirvani Shiri, Tayyebe (Author) ; Poujavadi, Ali (Supervisor)
    In this research, the synthesis of the electrospum nano fiber doped zinc oxide and its photocatalyst usage was investigated. The band gap of the zinc oxide in the area of UV leads to deactivation of this material at the visible light. With due the attention to sunny weather in Iran and the fact that about 50 percentage of sunlight is visible light, producing and usage of catalyst materials actived at visible light is economical. Doping is one of the ways of activating ZnO at visible light, so in this research thiourea is used as the source of ZnO doping. The results of the expriments done at visible light and also spectrums of DRS, XPS and XRD prove that the doping is happened. Also, in this... 

    Applacation of Zinc Oxide Nanoparticles in Lichen Removal from the Historical Stone Surfaces

    , M.Sc. Thesis Sharif University of Technology Nodeh, Razieh (Author) ; Khorashe, Farhad (Supervisor) ; Sohrabi, Mohammad (Co-Advisor) ; Baghalha, Morteza (Co-Advisor)
    There are many archeological sites, historic building monuments and inscriptions in Iran and other countries in the world which have been damaged by environmental as well as biological causes. Lichens are one of the biological causes which, through their growth, bring about change and damage to the stones. Different methods, each of which has both advantages and disadvantages, have been used in order to deal with the problem. Since there are many historic buildings in our country which have been damaged by different biological causes including the lichens, doing a research on the topic seems to be quite significant and necessary. The Persepolis is among one of the most important historic... 

    Synthesis, Characterization and Photocatalytic Application of ZnO/g- C3N4 Composite Nanorods Fabricated by Combined Sol Gel-Hydrothermal Methods

    , M.Sc. Thesis Sharif University of Technology Soltani, Mojtaba (Author) ; Moshfegh, Alireza (Supervisor)
    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... 

    Synthesis of Nanoparticles and Application of the Prepared Catalyst for Some Organic Reactions, Efficient Synthesis of New Thiophene Derivatives and Asymmetric Synthesis of Sulfonic Acid Derivatives

    , Ph.D. Dissertation Sharif University of Technology Saeidian, Hamdollah (Author) ; Matloubi Moghaddam, Firouz (Supervisor)
    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,...