Sharif Digital Repository

Dye Sensitized Solar cell (DSC) is the third class of solar cell, which consists of a nanocrystalline, mesoporous of semiconductor(The best one is Tio2), covered with a monolayer of dye molecules, platinum coated on FTO as a counter electrode and a redox electrolyte. This Photovoltaic cell which is promising low-cost materials, works on electron separation of dye molecule, and electron injection to semiconductor’s conduction photo- electrode structure and its porosity is affected the DSC’s performance. Recently, use of electrophoretic deposition (EPD) for TiO2 electrode (which best found for photo-electrode in DSC) fabrication has gained increased interests. In this method charged particles... 

This research is focused on fabrication of TiO2 layers by electrophoretic deposition (EPD) for application as photoanode in Dye Sensitized Solar Cell (DSC). DSCs are third generation of solar cells, also known as the Grätzel cell, after its inventor Michael Grätzel. A DSC is composed of a porous layer of wide band gap semiconductor such as TiO2 and ZnO, covered with a molecular dye that absorbs sunlight, and a counter electrode contacted by a liquid redox electrolyte. Dye Sensitized semiconductor (photoanode) has important role in conversion of photon to electricity. To achieve higher efficiency, preparation of photoanode with high surface area resulted to enough dye adsorption is necessary.... 

In this thesis, we study optomechanics of subwavelength nanoparticles based on the Green's function formulation. First, we investigate the optical force exerted upon Rayleigh particles in the free space using the dipole approximation method. Then, we present a new method based on the Taylor expansion of the polarization field to calculate the optical forces beyond the Rayleigh regime. Subsequently, we study the optical force exerted upon Rayleigh particles in non-free spaces, and model the backaction effect using the scattering Green's function. We show that the backaction effect can modify the polarizability of the particle and thereby can affect the gradient force, radiation pressure, and... 

In this study, polyethylene films made of LDPE / LLPE / reinforced with mechanical barrier of clay and reactant of iron nanoparticles were made in their optimal combination and necessary improvements were made on them. Investigations show that, independent of volume fraction, the addition of spherical nanoparticles does not have much effect on reducing the polymer matrix’s permeability. In nanocomposites containing cylindrical particles, for considerable reduction of the permeability, over 20 volume percent of nanoparticles it is required, while in platelet nanoparticles, less than 10% vol is sufficient. In clays with modifier concentration above the cation exchange capacity, there is less... 

In this work, a new catalyst based on gold nanoparticles immobilized on magnetic GO (graphene oxide) has been introduced. A new ligand based on pyridine has been used to the functionalization of GO to design robust heterogeneous catalyst for reduction in a short time using a low amount of the catalyst. The prepared catalyst was employed in the synthesis of aromatic amines using various types of nitroarnes in water. This catalyst is readily prepared from available starting materials and also is a reusable catalyst having very good stability to air and moisture. The proposed procedure applied here can conduct the reactions under milder reactions. Finally, due to total removal of the... 

The first report of anti-aggregation-based sensor arrays is presented. The strategy is based on the competitive interaction of citrate-capped gold nanoparticles (AuNPs) and heavy metal ions (i.e., Hg(II), Ag(I), Fe(III), and Pb (II)) with three aggregation reagents (i.e., cysteine, melamine, and arginine). In the presence of aggregation reagent,the color and UV–vis spectra of AuNPs are changed indicating the aggregation ofAuNPs. Addition of the aggregation reagents which are firstly treated with the ions, causes AuNPs turn from the aggregation to the dispersion state. The anti-aggregation capability of ions towards various aggregation reagents is different because of distinct stability... 

Detection of pentaerythritol tetranitrate (PETN) as an explosive has been of great interest because of public safety and military concerns. Here, we have presented a simple, selective and sensitive colorimetric method for direct detection of PETN. The gold nanoparticles (AuNPs) were first exposed to arginine which has primary amines in its structure. Primary amines from arginine as electron donors could strongly interact with electron deficient –NO2 group of PETN. Also, hydrogen bonding could happen between the –NO2 group of PETN and –NH2 group of arginine molecules. Therefore, selective aggregation of AuNPs happened because of the donor-acceptor and hydrogen bonding interactions. Due to the... 

The exitance of a certain amount of halide ions including Chloride (Cl-), Bromide (Br-) and Iodide (I-) in human body is crucial for ensuring health. However, exposure to high levels of these ions can cause diseases, such as goiter and neurological disfunction. As a result, the development of a simple and efficient analytical method for determining the aforesaid halide ions is so important. Triangular silver nanoparticles (TSNPs) display wide color variations due to their tunable plasmonic properties dependent on the aspect ratio of the nanoparticles. Hence, designing a colorimetric sensor array using the optical properties of TSNPs for determination and discrimination of halide ions is of... 

There is great attention in developing rapid and straightforward methods for the identification of various pesticides that are usually used simultaneously in agricultural products. It is due to the extensive use of a diverse class of pesticides in agricultural products and their high toxicity which causes serious diseases in the human body. In the current study, a non-enzymatic sensor array has been developed for the identification and discrimination of five different pesticides belong to diverse classes including organophosphate, carbamate, and bipyridylium. For this aim, gold nanoparticles with two different capping agents consisting of citrate and borohydride were used as sensing... 

The occurrence of the COVID-19 pandemic and the subsequent rising demand for purchasing alcohol-based sanitizers led to a remarkable prosperity in supplying these hygiene products. Hence, the development of a straightforward and efficient analytical strategy for discrimination of antiseptic alcohols including methanol, ethanol and isopropanol is of great importance. By exploiting the alcohol-sensitive membranes of probiotic bacteria, this research aims to develop a colorimetric sensor array for discriminating methanol, ethanol and isopropanol. In this design, the aggregation of citrate-capped gold nanoparticles (Au NPs) on the thiol-modified surface of two probiotic bacteria, including... 

In this thesis, pure –known as T- and chromium doped titanium dioxide nanoparticles –known as -CTx- with different dopant atomic ratio (0.1 to 5 %at.) were synthesized using a facile, fast and efficient method. FESEM and XRD studies showed no morphologic and structural change via Cr doping of nanoparticles (size in the range of 20-30 nm). However, according to DRS analysis, Cr intrusion in TiO2 crystal structure, drastically reduced band gap energy of pure TiO2 from 3.14 eV to 1.81 eV for CT3 powder and improved absorption range of UV-Vis spectrum. Mott-Schottky plots indicated that, Cr doping, caused reduction in donor density of TiO2 and an upward shift in the conduction band edge.... 

well known metal-free nanostructure carbon-based catalyst, mesoporous graphitic carbon nitride, with diverse morphologies were synthesized by using ethylendiamine/carbontetrachloride as a precursor, SBA-15 and SBA-15 nanorod as hard templates. We have investigated morphology effect on the catalytic performance. The catalysts were characterized by means of low angle and wide angle XRD, BET, FT-IR, CHNOS, FE-SEM analysis. Because of high surface area, pore volume and high nitrogen content, which acts as lewis basic site, for the first time, carbon nitride is chosen for selective catalytic oxidation of hydrogen sulfide to sulfure. Reaction was taken place in a fixed-bed reactor and at... 

The purpose of this study is to assess the inhibitory effects of an appropriate nanoparticles loaded with gallic acid on the fibrillation of alpha-synuclein. Alpha-synuclein is a major component of protein plaques in synucleinopathies, particularly Parkinson’s disease. Gallic acid (GA, 3,4,5-trihydroxy benzoic acid) is a well–known small molecule which can inhibit the formation of α-synuclein fibrils. For the process of fibrillation, purified protein was incubated at 37◦C and pH 7.2. Fibrillation was analyzed by the standard fibril methods.after that investigated fabricating of gallic acid trapped in the chitosan nanoparticles and gallic acid loaded in chitosan –coated mesoporous silica... 

Due to population growth, the demand for water supply has increased. This need has drawn attention to the use of consumed and treatable water resources. Organic pollutants are a key source of water pollution. On the other hand, petrochemical oil pollution and frequent oil accidents during oil production or maritime transport have become one of the environmental problems.There are different methods for water and oil separation and water purification that in the present project, selective separation can be achieved by using hydrophobic materials and surface roughness and creating surfaces with two properties: superhydrophobic and ultra-oil friendly. This method is also very effective, cheap... 

Population growth and community development has a large role in the demand for fresh water for a variety of uses. In recent decades, over-harvesting and abusing of water resources has led to water crisis. On the other hand, the increase in various pollutants, in addition to environmental hazards, is a threat to groundwater pollution and the existence of valuable fresh water. Due to the potential hazards of emerging pollutants, new treatment technologies such as advanced oxidation and photocatalytic methods are being developed. One of the contaminants resistant to traditional treatment methods is textile contaminants. In this research, by designing and constructing a photocatalytic reactor,... 

A system of electrospun scaffold containing drug-loaded chitosan nanoparticles was introduced for using in spinal cord tissue engineering. In spinal cord injury treatment, the formation of glial scar after injury which contains proteoglycans and activate glial cells should be avoided. In this study, the release of Dexamethasone sodium phosphate (DEXP) as a steroid anti-inflammatory agent from electrospun nanofiber composite containing chitosan nanoparticles was investigated. DEXP is believed to act through its glucocorticoid receptors found in most neurons and glial cells. These receptors’ pathways are involved in the inhibition of astrocyte proliferation and microglial activation.... 

In this project, a novel system of bioactive electrospun scaffold for bladder tissue engineering , has been investigated to control in vitro cell differentiation, and utilize in in vivo vascularization and tissue formation. This method doesn’t have custom bioactive scaffolds problems such as, protein instability, technical complexity and, difficulties in accurate kinetics prediction. First of all, protein loaded chitosan nanoparticles based on ionic gelation interaction between chitosan and Sodium tripolyphosphate were prepared. Maximum protein loading efficiency (80% for BSA & 99% for TGF-beta1) in chitosan nanoparticles was obtained at mean diameter of 51nm. Moreover polycaprolactone... 

Three sizes of silica nanoparticles (160±7, 450±10 and 600±25) were sythetized via template-removing method. The synthetized nanoparticles were functionalized with N-(2-aminoethyl)-3-aminopropyl trimethoxy-silane (EDS) to provide a positive charge on the surface of nanoparticles. BET analysis showed that the average pore diameter, surface area and pore volume of nanoparticles were 2.3 nm, 769 m2.g-1 and 0.44 cm3.g-1, respectively. showed that the Amine-functionalized silica nanoparticles were used to enhance the application of alginate polymer for 3D encapsulation of mammalian cells. Incorporating of silica nanoparticles can be suitable for the bead integrity and attachement of mammalian... 

In this thesis, manganese oxide nanoparticles with about 5 nm size were synthesized via solvothermal to maximize surface and active sites for proton relaxation. The synthesized nanoparticles were coated with gentisic acid to acquire suitable colloidal stability and biocompatibility. The nanoparticles showed low cytotoxicity in MTT assay. Electrosteric mechanisim was employed for colloidal stability. This mechanisim doesn’t need high surface charge and thick coat which are vital for particles functionality. Then by cell culture eliminating and adding protamine sulfade, nanoparticles uptake were increased tremendously. In this thesis for first time Prussian blue was utilized for staining... 

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...