علی شکوهی راد

In this study, a specific sequence of oligonucleotides was attached to silver nanoparticles after thiolization in a saline medium. Investigation of this bond was performed using ultraviolet-visible spectroscopy (UV_Vis spectroscopy) by changing the silver nanoparticles' wavelength and thiol oligonucleotide attached to silver nanoparticles. Also, by bond transfer in polyacrylamide gel electrophoresis (PAGE) due to the increase in molecular weight after binding silver nanoparticles to a thiolated oligonucleotide, this bond's accuracy has been investigated. To find the bonds' electronic structure and stability, DFT studies have been performed using the Gaussian 09 program, aiming to see the optimal conditions for the binding of thiolated oligonucleotides to silver nanoparticles. In general, the binding of silver nanoparticles to thiolated oligonucleotides makes the specific adsorption of the sequence to the cell more targeted. Also, it increases the accuracy, precision, and specificity of adsorption. Calculations showed the absorption energy of -54.4 kJ / mol, the transfer of electric charge of 0.129 e after binding the thiolated oligonucleotide to silver nanoparticles, indicating a useful connection between them.

Separation and determination of trace amounts of cobalt ions in real samples due to their toxicity to humans is very important. In the present study, a nanocellulose was synthesized by the acid hydrolysis and then modified with 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol (5-Br-PADAP). The size of cellulose nanofibers was determined using transmission electron microscope (TEM). After modification of the nano-sorbent with the 5-Br-PADAP, the thermogravimetric analysis (TGA) of the modified nanocomposite was carried out, and the BET technique was used to determine the surface area of the nano-sorbent before and after modification. In the present work, the aim is to modify the surface of nanocellulose with ligand of 5-Br-PADAP to use them to extraction and pre-concentration of trace amounts of cobalt ions before determination it by flame atomic absorption spectroscopy in real samples.

Certain volume of cobalt ion into the test tube containing the modified nanosorbent was Poured and buffer solution with pH = 9 was added and place it in a shaker and finally centrifuged for 15 minutes and then discard the top solution and 1 mL HCl was added to recover cobalt ions and placed in a shaker for 10 minutes and then centrifuged, and the absorption of the supernatant was determined by FAAS. The results showed that the modified nanocellulose is very sensitive and selective towards the determination of cobalt ions which could be affected by several parameters such as pH, adsorbent amount, sample volume, extraction time, and type of eluetion.

The calibration curve is linear in the range of 10-500 ng/mL, and the detection limit and the relative standard deviation (RSD) are calculated to be 4.3 ng/mL and 1.8 %, respectively, that result in a high preconcentration and enrichment factor.

By using the flame atomic absorption spectrometry and applying the standard addition method, the proposed method was used to determination of the trace amounts of cobalt ions in the natural water samples such as seawater, river water, well water, lake water and tap water, with satisfactory results.

Due to the importance of removing heavy ions from water samples, in the present study, a magnetic nanocomposite based on Fe3O4 particles coated with polyaniline was developed and evaluated as a strong adsorbent to remove lead (II) ions from water and effluent samples. In order to characterize the nanocomposite, the transmission electron microscope was used to determine the exact size of the nanoparticles and the BET technique was used to determine the effective surface of adsorbent and also the CHNS and TGA analyses were used to confirm the coating of Fe3O4 magnetic nanoparticles with polyaniline and the survey of the thermal stability of nanocomposite, respectively. The flame atomic absorption spectroscopy was used to determine the values of lead ions in the solution. Characteristics affecting lead ion removal including pH, adsorbent value and contact time at different temperatures were optimized. Optimal values of pH and adsorption rate and contact time for 100 ml of solution with an initial concentration of 50 ppm were obtained in the pH of 9, 3 mg adsorbent, and contact time of 60 minutes, respectively. Equilibrium data from adsorption studies showed that the Langmuir isotherm showed better results than the Freundlich isotherm. Also, the maximum lead adsorption capacity (II) on Polyaniline/Fe3O4 nanocomposite was 114.9 mg of lead per gram of adsorbent.