ali shokuhi rad

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.

The lignocellulosic wastes produced in food industries are suitable raw materials for the production of biological products. In this study, the solid state fermentation of Aspergillus flavus on lignocellulosic wastes was evaluated for microbial protein production. The fraction of the full factorial method was applied for experiment design and process optimization. The results analysis was performed through signal to noise statistical index using the Taguchi approach via Qualitek-4 software. Glycine, ammonium sulfate and iron sulfate concentration as well as temperature were considered as effective parameters. The maximum biomass concentration of 45.7 g/kg containing 55.75% (w/w) pure protein was obtained at optimal conditions including 0.5, 0.02, and 2 g/kg of ammonium sulfate, iron sulfate and glycine, respectively, at 25 °C. Ammonium sulfate (33.78% (w/w) contribution) and culture temperature (31.98% contribution) were evaluated as the most effective factors on biomass and microbial protein production. The highest interaction occurred between ammonium sulfate and glycine with an interaction severity index of 50.03%. The low deviation of 3.94% was determined between optimum theoretical biomass concentration (43.9 g/kg) and the experimentally measured one (45.7 g/kg). Due to the high protein content of 55.75% (w/w), Aspergillus flavus was introduced as a suitable strain for industrial protein production.

In order to produce biodiesel from waste cooking oil and optimize its yield, a two-stage process of esterification/ transesterification has been used in this study. First, we used the acidic catalysts H2SO4 in order to diminish the content of free fatty acid (FFA) in oil that caused reducing the oil acidity from 6.1% to 0.57% through esterification. Then, the biodiesel was produced by transesterification of resulted oil using heterogeneous CaO nanoparticles as catalyst. At each stage, the best possible conditions have been determined by applying Taguchi methodology for each major variable, including time, temperature, alcohol/oil molar ratio, and the amount of catalyst. The optimum conditions for esterification are achieved at 80°C temperature, 120 minutes time, 6:1 molar ratio of alcohol/oil, and H2SO4 content of 1% (w/w oil). The optimum condition for transesterification were found in 100 °C temperature, 90 minutes time, 8:1 molar ratio of alcohol/oil, and 3% (w/w oil) of CaO nanoparticles as catalyst. After applying full optimization of these two stages, the yield of the produced biodiesel has achieved 96.4%.

Zeolites are widely used in wastewater and contaminated water refinement due to their great adsorption properties. However, Clinoptilolite (as one type of Zeolites) has a relatively low adsorption capacity at least for arsenic ions. Therefore, in order to increase the adsorption capacity, natural Clinoptilolite was modified with sulfuric acid and various tests were then conducted to determine the best conditions for obtaining the maximum capacity of adsorption. The results showed that parameters such as arsenic initial concentration, adsorbent's particles size, adsorbent dosage and solution pH affect the adsorption capacity. Arsenic maximum adsorption was obtained at pH 8. Furthermore, the maximum adsorption capacity was found to be in an adsorbent modified with 1 M acid. The contact time or the time of balance between the adsorbent and analyte was determined to be 240 min and the optimal amount of Zeolite to obtain was determined to be 480 g/L. The rate of arsenic removal under the optimal conditions is 27.69%. The modified Clinoptilolite capacity for arsenic adsorption increased with reducing the adsorbent particles size to 0.5 mm. Besides, among the three examined isotherms including the Langmuir, Freundlich and Dubinin-Radushkevich isotherms, the Langmuir and Freundlich models well described arsenic adsorption. Considering the more favorable adsorption efficiency of Clinoptilolite modified with sulfuric acid compared to natural Clinoptilolite, the modified one can be proposed as an appropriate and inexpensive adsorbent for arsenic removal in waste water refinement.

In the present study we search potential of Pt-decorated graphene (PtG) as a new nanostructure adsorbent for nitrous oxide (N2O) using density functional theory (DFT). After fully relaxation of different possible orientations of N2O-PtG complex, we distinguished two optimized configurations for this system; 1- terminal N-side of gas is oriented towards Pt so that the molecule axis is perpendicular to the surface (P1), and 2- O-side of the molecule is closing to Pt while the axis of molecule has an angular configuration to the surface (P2). Our results showed high adsorption of N2O on PtG, however there is a significant difference between the value of adsorption for P1 compared to that for P2 (-113.6 (-88.7 BSSE) vs. -41.2 (-32.0 BSSE) kJ mol-1). Results of the charge analyses reveled interesting net charge transfer; the direction of charge is from N2O to PtG for P1 configuration and the reverse is found for P2.