Sharif Digital Repository

In this research, fabrication of a mediator free nano-biosensor for the detection of cyanide has been studied. This biosensor utilizes 75 nm diameter (nano) ZnO particles synthesized with sol- gel method for modification and immobilization of Horseradish peroxidase (HRP). Cyanide plays inhibitory role in decomposition of H2O2 while HRP plays catalyst role in this reaction. Cyanide inhibits enzyme activity thorough binding with enzyme active sites and result in decreasing electrical current in electrochemical decomposition of H2O2. Amperometery response of biosensor shows linear relation between inhibition percent and cyanide concentration in range of 3µM - 24µM with detection limit of 0.62µM... 

Photocatalytic degradation is one of the developing modern and effective methods for decontamination of hazardous pollutants of chemical industrial wastewater. This method has several advantages including the possibility of using free and sustainable energy of sun. However, it is still needed to active photocatalysts under solar light and also the enhancement and optimization of operating parameters, and consequently, these topics are selected as goals of the present thesis. Accordingly in this research, first, to obtain a photocatalyst that is highly efficient (especially under visible and solar light), multi-doping and polyethylene glycol (PEG) were used and for the first time,... 

Monopropellant thrusters are one of the most common types of propulsion systems that are used extensively in space applications. Especially thrusters with a capacity of less than 50N, they are used on space satellites and are developing rapidly. Problems such as contamination, toxicity of the propellant, difficulty in storing and custody, as well as price, led to the removal of the hydrazine from the focus of attention and focus on green propulsion. One of these, is the green propellant of hydrogen peroxide, which is decomposed in the proper catalytic vicinity, and the only chemical decomposition products are oxygen and water vapour. The present study aims to design and construct mono... 

Oxidative desulfurization (ODS) is one of the desulfurization processes that posseses several important advantages such as mild operating conditions. In the present work, oxidative desulfurization of kerosene with a total sulfur content of 2335 ppm and gas oil with a total sulfur content of 7990 ppm were carefully investigated. By evaluation of different oxidation systems, the hydrogen peroxide-formic acid system was selected for the oxidation of sulfur-containing compounds of the light fuel oils. The effects of main operating parameters of the oxidation system including temperature, hydrogen peroxide to sulfur molar ratio (O/S), and formic acid to sulfur molar ratio (Acid/S) on the... 

Silver and gold are precious, expensive metals and are used in various applications, such as jewellery and ornamentals, electronics and optics. In the present study, soda-lime glass surfaces firstly were activated with acidic stannous chloride solution. Then, silver and gold were coated on these surfaces via simultaneous spraying of two solution: A silver- or gold-complex bearing solution and a reducing agent (Dextrose for Ag and H2O2 for Au) bearing solution. For silver coating, the effect of various parameters such as time, reducing agent concentration, number of passes, presence and concentration of Urotrpin and Decamethylcyclopentasiloxane (DMCPS) as microstructural modifiers and... 

In the first part, the preparation of metallic, bi-metallic (alloy or mixtures) and metallic oxide nanoparticles on the substrate of carbon nanostructures (carbon nanotube and graphene based nanosheets) has been performed using chemical and electrochemical procedures. Then, the prepared nanostructures were characterized by electron microscopy, spectroscopy and electrochemical techniques. Finally, the nanofilms have been evaluated for sensing applications as a modifier on the electrode surface for accurate determination of trace amounts of some important pharmaceutical and biological compounds. In the first work, multi-walled carbon nanotubes decorated with Fe3O4 nanoparticles... 

In this study, we investigate the effect of adding potassium persulfate (PDS) (K2S2O8) and hydrogen peroxide (H2O2) to E.coli (as a model microorganism) photocatalytic removal system in the presence of the TiO2-P25 as photocatalyst and UV irradiation. In this regard, the PDS and H2O2 oxidants were added separately in the different levels of pH and photocatalyst loading under UV irradiation. The experimental points were determined based on the central composite design (CCD) and in order to study the main and the interactive effects of the photocatalyst concentration (mg/L), oxidant concentration (mg/L) and the pH on the final concentration of E.coli (cfu/mL), a response surface model (RSM)... 

Hydrogen peroxide (H2O2) is of great importance in numerous fields such as pharmaceuticals, mining, textile, environmental and food industry. Therefore, the development of low cost, on-site, and uncomplicated H2O2 sensors are of high interest. To date, colloidal quantum dots (QDs) have been used to detect H2O2 based on the quenching of fluorescence intensity in a single wavelength. However, intensity of fluorescent signal could be easily disturbed by various factors. To overcome these undesirable effects, here, a ratiometric sensor has been developed by adding a second fluorophore (as reference) to QDs. For this purpose TGA-capped CdTe QDs were prepared. To detect H2O2, the ratiometric... 

In this study, transition metal sulfide, with a high accessible surface and abundant electroactive centers, was used as an electrocatalyst to fabrication an electrochemical sensor of hydrazine and hydrogen peroxide. the direct growth of thin film of nanocomposite can be considered as an efficient method to modify the electrode surface, and the application of these modified electrodes as electrochemical sensors. the cobalt iron sulfide (CoFeS) nanosheets were directly grown on Cu2O nanospheres in order to design hierarchical nanocomposite by using efficient, inexpensive and fast method. Here, Cu2O nanospheres not only served as substrate, but also steer the CoFeS to attach on nanospheres...