Sharif Digital Repository

Due production and use of large amount of chemical and emissions of pollutants in air, detection and control of these compounds are necessary. One of the common methods to detect these pollutants in the ambient is using metal oxide semiconductor sensors. However, these types of sensors suffer from low selectivity toward a certain compound in the mixture of different gas components. In this study, the object was to investigate the effect of different amount of CNTs on performance of tin oxide to improve their selectivity for detection of 50 ppm of hydrogen sulfide at low temperature. To perform the study, nanoparticles of pure tin oxide and SnO2 base hybrids containing 0.25wt%, 0.5wt%, 2.5wt%... 

Free-standing TiO2 nanotube array (TNA) films were fabricated via two-step anodization of titanium sheet. The electrolyte consisted of DI water and ethylene glycol (99.9%, Merck) solution with volume ratio of 10:90, containing 0.5 M NH4F. Then, a few drops of 1M H3PO4 aquaes solution have been added to adjust pH at 5.7. The anodization process was performed at optimized applied voltage of 60 V for 200 min. Indeed it does in two-step for 50 and 150 min, and samples were sonicated of 40s between two steps. Then, to crystallize the grown structures, they were annealed in air at 500˚C for 80 minutes. Surface of TNA was modified by sequential-chemical bath deposition (S-CBD) method to fabricate... 

In the first part of this research, we have developed a simple and effective ratiometric fluorescence sensor for selective detection of dopamine (DA) in alkaline media by simply mixing thioglycolic acid (TGA) functionalized orange fluorescent cadmium telluride (CdTe) quantum dots (QDs) with amino-functionalized blue fluorescent carbon nanodots (CDs). Under a single excitation wavelength of 365 nm, the sensor exhibits dual-emissions centered at 445 and 603 nm. The fluorescence of CdTe QDs is selectively quenched by DA, whereas the fluorescence of CDs is insensitive to the analyte. In the presence of different amounts of DA, the variations in the dual emission intensity ratios exhibit a... 

In general, release of hazardous gas in chemical process plants could be due to two reasons. First is failures due to degradation of components that have inventory of hazardous gas in standard process conditions, and the second is deviation of system from standard process conditions because of different failure modes of related components, e.g. controller equipments. The purpose of this study is, calculating the probability of H2S releasing in GS(03) plant of Arak Heavy Water factory, using PSA methods and its risk assessment. At First, fifteen groups of initiating events were identified with Hazop study for desired system. Then, for calculating the frequency of each event, the combination... 

H2S is a toxic and corrosive gas which is detrimental for both human’s health and some of important industries such as oil and gas. Based on different experimental research among various systems, resistive sensors fabricated from SnO2-CuO nanostructures have promising performance toward detection of this gas. High sensitivity and selectivity, response time of order of seconds, recovery times of order of tens of seconds and determining concentration of H2S gas below ppm level are advantages of this system. Unfortunately due to lack of a theoretical model, current experimental researches are excessively based on “trial and error” methodology. In this research some of the basic questions which... 

Petroleum contains a large variety of metal compounds with vanadium and nickel being the major metals. Some 6–34% of the total vanadium content is made up out of metallo-oxo-porphyrins, also referred to as petroporphyrins. Metalloporphyrins have long excited interest as oxidation and epoxidation catalysts. In the other hand the selective oxidation of sulfides to sulfoxides is of interest because of the importance of sulfoxides as synthetic intermediates in organic synthesis. A range of sulfides can be selectively oxidized to the corresponding sulfoxides in good yields using catalytic quantities of vanadyl complexes. Vanadium oxo tetraphenylporphyrin VO(TPP) catalyst is successfully applied... 

Due to the potential risk of sulfur compounds in fossil fuels and according to today’s regulations, sulfur content should be kept as low as possible, e.g., below 5 ppm. Mercaptans are one of the sulfur components in natural gas. Scope of this research defined as catalytic removal of ethyl mercaptan from the gas stream. For this purpose, two microreactor systems placed in series. In the first microreactor, catalytic decomposition of ethyl mercaptan has been investigated. In the first step of this survey, a microreactor with 24 microchannels with a newly designed distributor has been developed with a computational fluid dynamic technique. in comparison to the conventional triangular... 

Tin sulfide with an energy gap of about 1.1 ev is a semiconductor suitable for applications such as solar cells, lithium-ion batteries, photocatalysts and other semiconductor-based devices. There are several methods for synthesizing this semiconductor at the nanometer scale, among which the solvothermal method is an efficient, controllable and inexpensive method. By precisely controlling the parameters of this process, two-dimensional tin sulfide nanosheets with high purity and desirable morphology can be produced. In this research, tin sulfide has been synthesized by solvothermal / hydrothermal chemical method and its metallurgical properties have been studied. Effect of solvothermal... 

In this study polyoxotungstate-based inorganic-organic hybrid [C272H162N80Cu16.5W36O129Na9] .80.5H2O was synthesized in situ. This inorganic-organic hybrid resulted from the reaction between copper salt and sodium tungstate with the benzimidazole ligand. Combining inorganic-organic hybrid with polyoxotungstate improved the ability of this catalytic system in oxidation and cycloaddition reactions. The resulting product was identified by IR, X-ray diffraction (XRD), elemental analysis (CHNS), inductively coupled plasma (ICP-OES), field emission scanning electron microscope (FE-SEM) and EDX were technique. The catalyst was used in optimal conditions in sulfide oxidation and azide-alkyne... 

Today, due to the decreasing of fossil fuel reserves and the need to use clean fuels, hydrogen is a suitable alternative, and hydrogen production has received considerable attention. One of the best methods of hydrogen production is water splitting. Overall water splitting can be divided into two half reactions including the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which selecting the appropriate electrocatalyst for these half reactions plays an important role. The four-electron transfer process in OER leads to slow kinetics of the reaction and a large overpotential. The noble metal-based oxides, including IrO2 and RuO2, are known as outstanding OER... 

The global energy outlook has been altered as a result of mounting concerns regarding fossil fuels. Electrocatalysts have become a favorable alternative for renewable energy production processes, particularly in the fields of hydrogen evolution reactions (HER) and oxygen evolution (OER). This study focuses on the production and enhancement of nanocatalysts, specifically materials based on ZIF-67, for the purpose of water splitting. The initial phase included the synthesis of the ZIF-67 structure through the simple room-temperature coprecipitation process, utilizing cerium as a dual-metal component. The molarity of the cerium was optimized in the ZIF-67 framework to achieve the most desirable...