Sharif Digital Repository

Superparamagnetic iron oxide nanoparticles (SPION) with proper surface coatings are increasingly being evaluated for clinical applications such as hyperthermia, drug delivery, magnetic resonance imaging, transfection, and cell/protein separation. Since the particles with various sizes exhibit different flow rates in the same environment (same capillary size), it is essential to use particles of a desirable size for targeted drug delivery and imaging. Particles of different sizes may be exposed to different viscosities and behave differently, particularly with regard to their velocities as they move through capillaries. In the present work, SPION with different size, purity, shape and... 

Poly (vinyl alcohol) (PVA) hydrogel is a biocompatible material, which has been widely applied in drug delivery applications. Microspheres, nanospheres, and other types of particle-based drug delivery vehicles have proven capacity for long-term release. There is growing interest to overcoming the inherent pharmacological limitations of hydrogels by formulating particulate systems into the hydrogel matrix to form new delivery platforms. We here describe a simple composite system based on poly (vinyl alcohol) (PVA) hydrogels containing entrapped drug-loaded poly (lactic acid) (PLA) microspheres for controlled delivery over extended period of time. Gamma-Irradiation and freeze-thawing was... 

Polyvinylalcohol/magnetite nanocomposite films were fabricated via solution casting. Magnetite (Fe3O4) nanoparticles were prepared by means of co-precipitation method and modified by citric acid. The nanoparticles and nanocomposites were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), vibrating sample magnetometer (VSM), fourier transform infrared spectroscopy (FTIR) and mechanical measurement. The results reveal that magnetite nanoparticles have a spherical shape with an average diameter of 19.7nm and are superparamagnetic at room temperature. The nanoparticles are observed to be uniformly dispersed in the polymer matrix due to a strong interaction between the... 

Polyvinylalcohol/MWCNT nanocomposite films were fabricated via solution casting method. Glycerol was added to the polymer matrix as plasticizer in order to improve the flexibility and toughness of resultant films. Surface modification of MWCNTs were carried out by subjecting to gamma irradiation of 60Co source to total doses of 50.0 and 75 kGy in pure ethanol and in a solution with equal volume fraction of water and ethanol. The produced nanocomposites in each case which contain different type of modified MWCNTs were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical and electrical measurements. The... 

This project aimed to fabricate the bone scaffolds with applying thermoplastic starch-based nano-biocomposites. The starting materials for this scaffold are as follows: thermoplastic starch, ethylene vinyl alcohol as the polymer matrix and nanoforsterite as the ceramic reinforcing phase. Furthermore, vitamin E was used as antioxidant for preserving starch against thermo-mechanical degradations. Likewise, 3D pore structure was developed using azo-dicarbonamide and water in injection moulding process. With blending thermoplastic starch and ethylene vinyl alcohol, some thermoplastic starch’s properties including degradation rate and water absorption were modified. In addition, having... 

This thesis is divided into two parts: In part I, which is theoretical part, we were looking for a computational method which is extensively comparable with experimental results to determine pKa of wide variety of organic compounds. The pKa is an important property in many sciences such as chemistry, biology, and material science, since inclination of a compound to donate or accept a proton is fundamental to understanding many chemical and biochemical processes. Experimentally determined pKa values are not always available from literature sources and often estimated values are employed in their place. It is useful, therefore, to have reliable and accurate means of calculating relative and/or... 

Poly vinyl alcohol/graphene oxide (GO) nanocomposites were made through solution casting method. The nanocomposite were characterized by XRD , FTIR , FESEM , DSC and mechanical measurements. Graphene oxide was irradiated by gamma ray at 35 KGy in a 50/50 water-ethanol solution and then added to PVA aqueous solution in various GO concentrations (0.3 , 0.7 , 1 wt%) and sonicated. The resulting suspensions were cast into petri dishes to make thin films. Also PVA/GO Hydrogels were prepared by gamma irradiation at 20 KGy. It was observed that GO uniformly dispersed within PVA indicating strong interaction through forming hydrogen bonds between hydroxyl groups of PVA and GO surface. Tensile... 

In this thesis, heterogenous catalysts based on magnetic nanoparticles were synthesized. In these catalysts, magnetic nanoparticles were coated with defferent fuctional groups to produce a catalyst with magnetic properties which is easily separated from the reaction medium. The structure of synthesized catalyst was characterized using techniques such as transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and CHNS elemental analysis. Easy preparation, low cost, biodegradability and high thermal stability are advantages of these catalysts. At the end, the catalytic properties of resulted catalysts were investigated in many... 

Graphene، a molecular single layer of graphite، has tremendous applications in materials science for the development of nanocomposites، tissue engineering and supercapacitors. Graphene application and its developing applications depend on its essential properties such as excellent mechanical and thermal properties. Accordingly، investigation on graphene has drawn significant attention to itself. Hence، exploitation of these important properties including the induction of graphene sheets in polymer matrix seems to be essential. In the present survey، salep، a biodegradable polysaccharide، has been used for either the reduction of graphene oxide or functionalization of graphene. Then، reduced... 

Double network (DN) hydrogels are a new interpenetrate polymer network (IPN) that are usually contain about 60-90 % water. Despite of this amount of water, they are though and strong. DN hydrogels comprise of two networks, the first one as the brittle gel, is generally high density crosslinked and the second one, the loose and stretchable network, is loosely crosslinked or even without crosslinking. Therefore, we used cationic polymer, chitosan, and anionic polymer, alginate, as the first networks, therefore, we used sodium phosphate for physical crosslinking of chitosan, and calcium chloride as the physical crosslinking agents for alginate network. Also, poly (vinyl alcohol) (PVA), as the... 

The nucleus pulposus, which is a part of intervertebral disc, is normally hydrated and gel-like to maintain normal biomechanical functions of the disc through intradiscal pressures. In a degenerated disc, however, water content of nucleus is significantly reduced, resulting in an abnormal stress state of the annulus. Surgical interventions cannot restore the biomedical function to vertebral segment. One approach to restore the normal biomechanics of an intervertebral disc is to replace the nucleus with a prosthetic material which leads to a restoration of the behavior of the disc. The mechanical behavior of poly(vinyl alcohol) and nanodiamond hydrogel may provide a material suitable for... 

The goal of this research project was to prepare gelatin/PVA porous scaffolds by chemical and gamma irradiation methods to be used for human dermal fibroblast cell culture. First, the polymers were dissolved in hot water and mixed properly to achieve a homogenous solution. The mixture was then frozen at -200C and immersed in ethanol/ glutaraldehyde solution at -200C for 48 hours in order to extract ice crystals and also form chemical crosslinks in gelatin by glutaraldehyde. After being rinsed with distilled water the samples were lyophilized. The effects of polymers solution concentration, gelatin/PVA ratio and glutaraldehyde /gelatin ratio were investigated on characteristics of the... 

In this project two manganese(III) complexes with 2-(2',4'-dihydroxyphenyl)-2-oxazoline ligand, [Mn(4-OHphox)3], [Mn(4-OHphox)2(CH3OH)2]ClO4 and a copper(II) complex with 2-(2'-hydroxy)-2-oxazoline ligand have been synthesized. The complexes and the ligands were characterized by elemental analysis (CHN), FT-IR and 1HNMR spectroscopies. Oxidation of sulfides catalyzed by these complexes using urea-hydrogen peroxide (UHP) as oxidant within short reaction times (5 min) was investigated. The results showed that catalytic efficiency of [Mn(4-OHphox)3] complex was better than other complexes. Optimization of the catalyst system presented a high selectivity of sulfoxide (90-100%) in a few time (5... 

Strain softening after the yield point is a prevalent phenomenon in the stress-strain response of cellular solids, consisting of porosities in micro/macro-meter scale, as well as polymers, consisting of free volumes in sub-nanometer molecular scale. Although the underlying micromechanisms for softening in cellular solids are already known, the molecular origin for softening in polymers is still unknown. In this thesis, the micromechanisms of the softening in both materials are investigated. Then, a hypothesis is raised and evaluated to connect the nano-mechanics of softening in polymers to the micro-mechanics of softening in cellular solids. Experiments of compression test, positron-based... 

Today, tissue engineering research is expanding to a large extent, so tissue engineering has the ability to build artificial organs and tissues. In this project, we have used two polymers of polyethylene glycol and polyvinyl chloride, which are used for network irradiation. After irradiation, these polymers were made by drying the freewheeling porous scaffolds and the effect of different parameters on the structure of these scaffolds was investigated. To investigate the effect of different factors on gelation, swelling, tensile test, degradability and finally the conditions of fibroplast cell growth on scaffolds were investigated. The results of the gel test showed that the gel was higher... 

Fed-batch fermentation is a valuable and cost-effective method for bio-based production of various products such as ethanol, which has various applications in various industries.In recent years, bioethanol production has been given special attention in many countries. For this reason, the mathematical modeling of production of these products is very important for their optimal and cost-effective production. Given the transient and dynamic nature of fermentation and its specific complexity, mathematical modeling of fed-batch bioreactors is difficult and complicated. In this research, an unstructured model was used to predict the production of ethanol from blackstrap sugar cane molasses based... 

This research project contains two parts that investigating new approaches for becoming closer to green chemistry principals is clear in it. In the first part we tried to synthesis dithiocarbamate salts using aromatic amins and than Michael addition of them to prepare bifunctional dithiocarbamats. But we found ?-thiols as final product. In the second part of this project, we investigated the regioselective epoxide ring opening with aromatic amines by using boric acid and glycerol in water as a green media. Corresponding ?-amino alcohols were obtained with excellent yields and considerable regioselectivity. High yields of the products, mild reaction conditions, using green catalyst and water... 

In this work, Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method was applied to investigate the decomposition routs of -halo alcohols on Ni(111) and Cu(111) crystallographic planes and Ni2Cu1(111) and Ni1Cu2(111) alloys. UBI-QEP calculates energetics, H and E, along reactions routes using heats of atomic adsorption as empirical inputs and in this way avoids needs to be very specific about every system. The results of analysis of -halo-propanols on Ni and Cu surfaces are in good agreement with experimental findings; namely in the formation of carbon-monoxide, ethylene, water and hydrogen over Ni and propene and water over Cu. Predicted activity of -halo-propanols,... 

The enzyme L-asparaginase (L-asparagine amidohydroxylase , EC 3.5.1.1) is utilizable in the treatment of acute childhood lymphoblastic leukaemia. L-asparaginase catalyses the hydrolysis of the amino acid L- asparagines to L-aspartic acid and ammonia. Unlike normal cells,malignant cells which can only slowly synthesize L-asparagine , are killed by lacking exogenous supply. In contrast, normal cells are protected from Asn-starvation due to their ability to produce this amino acid.
In this study , L- asparaginase from E.coli, was immobilized onto a polymeric compound, poly(vinyl alcohol)(PVA) with cross-linking agent glutaraldehyde and calcium alginate beads .. Herein ,with the use of the... 

Aerobic oxidation plays important role in industrial processes and pollutant remediation. The catalysts accelerating oxidation reaction rate are included thermal (typical) catalysts such as Pt or Au on oxide supports and photocatalysts such as TiO2 or ZnO. Although well-studied Au/TiO2 system have been under deep
investigations but Au/ZnO system have less investigated because Au/ZnO has low activity relative to Au/ZnO. Gold nanoparticles supported on ZnO nanostructures were prepared through a simple chemical-thermal method and characterized by SEM, TEM, XRD, BET and photo luminescence (PL) spectroscopy. Effect of
annealing temperature on catalytic activity of these Au/ZnO...