Sharif Digital Repository

Folic acid is a pterin derivative containing a glutamyl moiety and essential for biological reactions. Pterins are a class of heterocyclic compounds with unique structures and biological functions. Tetrahydrobiopterine has been known to be essential for catalytic hydroxylation of aromatic amino acids by metal ions-containing aromatic amino acid hydroxylases. Metal ions at the active site of these enzymes have been inferred to be closely associated with the pterin cofactors in the catalytic reactions.Information on pterin-metal interaction may give clues to the role of metal ions in enzymatic reactions. With these points in mind, studies have been conducted to verify the formation of ternary... 

The complexation between folic acid and the complexes of Cu(L)2 (L = Glycine, Alanine, Valine) were investigated using UV.Vis spectroscopy. The values of the equilibrium constant K and molar absorption coefficient Ɛ of the complexes were estimated in the aquation environment at various temperatures. The temperature dependence of the K can be used for the determination of the thermodynamic reaction quantities (∆G, ∆H, ∆S) for linear regression fits to the Van’t Hoff equation. The kinetic studies reveals that the stoichiometry of reaction were 1:1 for these systems. All reaction were endothermic and the values of the ∆H are positive. In all cases entropy increased and the values of the ∆S... 

In recent years, metallic nanoparticles, specially gold and silver nanoparticles, have received great attention for biological and metal ions analysis, due to the surface plasmon resonance phenomena. Gold nanoparticles (AuNPs) have recently gained much interest in colorimetric probe based on aggregation or anti-aggregation of AuNPs, due to their simplicity and having high order of magnitude extinction coefficients, in addition to the dependence of surface plasmon resonance wavelength and intensity on the interparticles distances. In the first part of this thesis, a highly sensitive colorimetric method for detection of copper ions based on anti-aggregation of citrate capped AuNPs was... 

In this thesis, a novel graphene oxide (GO)/sodium alginate (SA)/polyacrylamide (PAM) ternary nanocomposite hydrogel with excellent mechanical performance has been fabricated through freeradical polymerization of acrylamide (AAm) and SA in the presence of GO in an aqueous system followed with ionically crosslinking of calcium ions. Physical and chemical characteristics of the composite were investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. The swelling behaviors of the composite hydrogels were investigated under varying conditions of time and pH. The optimized swelling capacity in standard conditions was found to be 1711% per gram of the hydrogel. The... 

Today, the use of graphene quantum dots has been very much considered due to easy synthesis methods, strong fluorescence emission, and many sources of synthesis. In this study, the effect of changing capping agent of graphene quantum dots toward iron (Ⅲ), copper (Ⅱ) and mercury (Ⅱ) ions was studied. The linear range of response of the graphene quantum dots synthesized with ethylenediamine for mercury (Ⅱ) and iron (Ⅲ) ions was 10-70 µM, and this sensor also responded to Cu (Ⅱ) ions. Urea synthesized graphene quantum dots also responded to all three ions. The linear range of the response for mercury (Ⅱ) , iron (Ⅲ) and copper (Ⅱ) ions was 5-25, 10-70 and 120-120 μM respectively. The linear... 

The use of fluorophores in metallic and non-metallic analysis, have received great attention for chemical sensing due to the high sensitivity and selectivity. Fluorophores through participating in emission mechanisms, interact with analyte and the emission intensity changes, which leads to determination of analyte concentration. These mechanisms are included fluorescence resonance energy transfer and fluorescence emission quenching. In the first part of this thesis, a highly sensitive probe for detection of copper ions was developed based on fluorescence resonance energy transfer due to the plasmonic peak of citrate capped gold nanoparticles and emission peak of FITC. Quenched emission of... 

In this study, a polyoxotungestate containing copper was impregnated as catalyst on a magnetic metal-organic framework (Fe3O4/MIL-101(Cr)). Initially, the desired polyoxotungestate was synthesized using sodium tungestate and sodium metasilicate salts and then copper(ІІ) ion was fixed on it. Subsequently, the MIL-101(Cr) metal-organic framework was prepared by solvothermal method; using chromium nitrate salt and 1,4-benzen dicarboxylic acid at 220 ◦C and was magnetized by co-precipitation method. Finally, the corresponding polyoxotungestate was stirred at ambient temperature for 24 h with MIL-101(Cr) and then the brown precipitate was separated using a magnet. Different techniques such as IR,... 

Wastewater, especially with heavy metal contamination, is a global environmental concern. Numerous techniques have been tested for online controlling and monitoring the concentration of heavy metal ions; yet, there are many challenges in performing these techniques. Biosensor is cheap, easily available, simple, fast, selective, sensitive, and repeatable so it is an excellent alternative for the detection and quantification of hazardous particles in the wastewater. In this study, a Nano biosensor with high detection of copper ions has been fabricated. PEDOT:PSS as a highly conductive polymer is coupled with gold nanoparticles to modify the surface of graphite electrode and results in higher...