Sharif Digital Repository

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... 

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... 

The World Health Organization's annual statistics show that 83% of wounds are caused by bacterial infections. Diabetic ulcers affect approximately 28 million people worldwide. The use of antibacterial dressings can help control infections. Recent studies have found that electrical stimulation can accelerate wound healing. However, there is still a need for interventions that speed up epithelial tissue formation. New dressings with zinc and silver particles that have electrical activity are being developed, but research on these methods is limited. Zinc oxide nanoparticles have been used as antibacterial agents due to their unique surface properties. This research aims to use these... 

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... 

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... 

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... 

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... 

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... 

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.... 

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... 

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... 

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...