Sharif Digital Repository

In present research work, methods of preparing ion exchange membranes, especially anion exchange membranes, were studied and chemical modification of polysulfone was chosen as a safe and economical method for preparing anion exchange membranes. The chloromethylated polysulfone was characterized by HNMR spectroscopy and functionalization degree was determined according to peak area integration. Membranes were produced by mixing and amination of the chloromethylated and normal polysulfone (40-100% wt). Morphology and chemical structure of membranes were investigated by SEM images and FTIR spectroscopy.The ionic conductivity, ion exchange capacity and water content of samples were measured. The... 

Electrocatalytic oxidation of L-ascorbic acid (L-AA) on silver electrode in alkaline solutions was studied employing cyclic voltammetry, chronoamperometry and impedance spectroscopy techniques. In comparison to Pt, the onset potential for L-AA electro-oxidation process on Ag, in a solution containg 0.02 M L-AA and 0.5 M NaOH, was 0.1 V more negative. Also, L-AA oxidation current increased more than 900% at -0.26 V/SCE. According to voltammety and impedance spectropy findings, although hydroxide anion presence was vital for L-AA oxidation to occur, at potentials more positive than -0.2 V/SCE, hydroxide ion tends to inhibit the oxidation process. Studies on the L-AA oxidation process on Ag in... 

During all operations in oil and gas reservoirs, it is possible to cause formation damage. These damages can greatly reduce the rate of production. One of the major damages that can seriously affect the performance of a reservoir is the damage caused by drilling fluid. The main purpose of this thesis is to study the main mechanisms of formation damage caused by water-based drilling fluid using a glass micromodel for the first time. An accurate understanding of the mechanisms of formation damage can provide a good understanding of the selection of the type and concentration of materials used, as well as appropriate methods to control and eliminate damages. for controlling the drilling fluid... 

Nowadays, there is no doubt about the importance of investigation of physicochemical properties of nucleosides in order to determine the structure of these biopolymers. Nucleotides have a variety of roles in cellular metabolism. They are the constituents of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), the molecular repositories of genetic information. The metal ions play a significant role in several biological processes. Synthesis, replication, and cleavage of DNA and RNA as well as their structure integrity are affected by the presence of these ionized metals in the cell nucleus. To understand the role of cations in the biophysics of DNA, it is necessary first to... 

In just a decade, perovskite solar cells have emerged as the next generation of photovoltaic technologies due to their high efficiency, low manufacturing cost, and easy fabrication methods compared to silicon solar cells. To date, highly efficient perovskite cells (with an efficiency of approximately 25.5%) have been fabricated on small substrates by a spin-coating process. In the spin coating process, perovskite precursor is spread on the substrate through shear force. However, the reproducibility of the cells coated with this method varies between research laboratories. Furthermore, since the solution is wasted during the deposition of the perovskite precursor on large substrates, a... 

In the present work, a series of nanohybrids based on ZIF-8 as a physicochemical stable metal-organic framework (MOF) and different amounts of Chitosan (CS) (0.5–15 wt%) were synthesized and used as adsorbents for anionic (Congo Red, CR) and cationic (malachite green, MG) dyes from contaminated water in single and binary dye solutions. The single adsorbents and their nanohybrids were characterized by FESEM, FTIR, XRD, TGA, BET, and zeta potential measurements. The experimental adsorption results displayed that the synthesized nanohybrids presented higher adsorption capacity for anionic dyes compared to cationic dyes in both single and binary dye solutions. It was deduced that the... 

In this treatise, the effect of type of macrocycle ring on the final structure of the complexes which made from them was investigated. For this purpose, by changing the 15-membered benzylic macrocycle with two pyridine pendant arms (2p), which was studied in our previous experiments (the effect of the position of the nitrogen atom of the pyridine ring in the side arm and the type of metal ion in the geometry of its complexes), two new macrocycles by adding a naphthalene rings instead of benzylic ringsin in 2p and increasing the ring size from 15 to 17 members, Lpy-naph and Lpy-benz were symthesized respectively. The molecular formula and structure of Lpy-naph and Lpy-benz were confirmed by...