hossain ali rafiee-pour

This paper reports the green preparation of silver oxide and nickel oxide nanoparticles. The malva sylvestris extract was used as the green reductant and capping agent. The prepared nanoparticles were characterized using XRD, SEM, FT-IR, and EDX analysis. The XRD analysis discloses that the prepared silver oxide nanoparticles comprise both Ag2O and Ag metal phases. In addition, it was found that the prepared nickel oxide nanoparticles have an amorphous structure. The FT-IR results show the presence of metal-oxide bonds at the wavenumber range 750-600 cm-1. Also, the green synthesis of the metal oxide nanoparticles was confirmed by the existence of the organic functional groups on the surface of the prepared samples. The SEM images show the spherical nanoparticles in the size range below 50 nm for both prepared nanoparticles. These results reveal the superior ability of the malva sylvestris extract to prepare the fine metal oxide nanoparticles. In this research, synthesized Ag2O nanoparticles (Ag2O NPs) and NiO nanoparticles (NiO NPs) were used as modifiers for carbon paste electrode (CPE) and their effect on the electrochemical determination of Quercetin (QCT) was investigated by using differential pulse voltammetry (DPV).

Widespread use of ionizing radiation in medicine, industry, agriculture, education and research, the increasing production of nuclear waste and nuclear incidents, has exposed humans and organisms to this radiation. Despite the benefits of ionizing radiation, these beams can cause serious damage to living systems. Hence, the need for radiation protection actions requires accurate, fast, inexpensive, and comprehensive detection and dosimetry systems. In this regard, in this paper, an electrochemical sensor based on the carboxylated multi walled carbon nanotubes-silver nano particles (MWCNTs-COOH/AgNPs) nanocomposite modified glassy carbon electrode is designed for superoxide anion detection and measurement. Also, the possibility of ionizing radiation sources detection, by measurement of superoxide which is produced during the radiolysis of aqueous environment under these radiations, is discussed. For this purpose; firstly, the surface of glassy carbon electrode modified with MWCNTs-COOH and AgNPs respectively. Ultraviolet-visible spectroscopy (UV-Vis), fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) images used to characterize the MWCNTs-COOH, AgNPs and study of the glassy carbon electrode modification with MWCNTs-COOH/AgNPs nanocomposite. Then the reduction process of superoxide produced from a solution of dimethyl sulfoxide containing potassium superoxide, on the surface of modified glassy carbon electrode studied, using cyclic voltammetry method. Also, by performing chronoamperometric studies, two linear response limits for superoxide for low concentrations (1.5 to 43 mM) and high concentrations (136 to 323 mM) and detection limit of 0.39 mM was obtained. At the end, the MWCNTs-COOH/AgNPs nanocomposite modified glassy carbon electrode was used for the detection of ionizing radiation emitted from cesium-137 and cobalt-60. The difference between electrochemical responses of the electrode, in the aqueous medium before and after the sources irradiation, attributed to the presence of superoxide and confirmed the successful performance of the sensor.

The waste produced by households, industry and factories to use as wash water and cooling systems and equipment, is caused environmental complications. Waste created a suitable environment for the growth of odor and pathogenic bacteria. This study aimed to isolate microorganisms in the wastewater and use them for the reduction of BOD (biochemical oxygen demand) and COD (chemical oxygen demand).The samples were collected aseptically from different parts of wastewater of herbal distillation industry. The bacterial strains were isolated from the samples in LB media. The isolates were distinguished based on the morphology and biochemical characteristics. Among the total 69 isolates, four isolates were selected to measure the ability to reduce BOD and COD and added to the waste water. Reduction of BOD was measured using BOD meter. Also, COD was determined by titration method. The isolates were identified by biochemical tests. The amount of BOD and COD reduction after adding selected strains to wastewater was 47.43 - 71.82% and 44.79 - 56.5% respectively. Also, the consortium of bacterial strains showed better ability to reduce BOD and COD (38.32-57.29%and 76.6-83.21% respectively). The results determined that wastewater contains bacterial strains which have shown significant reduction in BOD and COD and organic matter decomposition in wastewater and reuse it in agricultural and industrial sectors. Therefore, we can use these bacteria for wastewater treatment.

Over the past years, DNA biosensors have been developed to analyze DNA interaction and damage that have important applications in biotechnological researches. The immobilization of DNA onto a substrate is one key step for construction of DNA electrochemical biosensors. In this report, a direct approach has been described for immobilization of single strand DNA onto carboxylic acid-functionalized carbon nanotubes modified glassy carbon electrode. To do this, we first modified the glassy carbon electrode surface with MWCNT-COOH. The immersion of MWCNT-COOH/GCE in ss-DNA probe solution, with different pH and ionic strength, was followed by suitable interaction between amine group of ss-DNA bases and carboxylic groups of MWCNT-COOH. This interaction leads to successful ss-DNA immobilization on MWCNT-COOH that was confirmed by cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy. Immobilization of ss-DNA on the modified electrode increased the charge transfer resistant but decreased the peak current of redox probe ([Fe(CN)6]3-/4-). The result of cyclic voltammograms implicates that enhancements in the DNA immobilization are possible by adroit choice of low pH and high ionic strength. The standard free-energy of adsorption (ΔG°ads) was calculated from electrochemical impedance spectroscopy data (-47.75 kJ mol-1) and was confirmed covalent bond formation. atomic force microscopy topographic images demonstrate increased surface roughness after ss-DNA immobilization. Results offer a simple, rapid and low-cost of DNA immobilization strategy can be opportunities to design of novel nucleic acid biosensors.

Cysteine self assembled monolayer-modified gold (Cys/Au) electrode is used to immobilize superoxide dismutase (SOD) and establish a direct electron transfer between enzyme and electrode surface. However, due to the redox activity of copper ion on Cys monolayer, there would be an ambiguity in electrochemical studies of immobilized SOD on Cys/Au electrode. We designed a series of experiments to clarify the role of Cys in this process. Comparison between voltammograms of different electrodes revealed that the current intensity was increasing by the order of Cu+2/Cys/Au>SOD/Cys/Au>Cys/Au, while their electrochemical working windows were overlapping. Furthermore, for these electrodes the electron transfer rate constant were 0.77, 0.73, and 0.29 s-1 and the surface concentration of electroactive species were 1.05×10-10, 1.51×10-11, 1.50×10-11 mol cm-2, respectively. When phosphate buffer solution (PBS) was prepared by ultrapure phosphate salts (copper ion free) no redox response was observed while, by deliberately addition of Cu2+ the Cys/Au electrode showed a redox response. EDTA as chelating agent could pick up Cu2+ from PBS and consequently no electrochemical response was observed for Cys/Au electrode. Comparing these results indicated that the source of the inherent electrochemical activity of Cys/Au electrode is Cu+2. Finally, the Cys/Au electrode was also examined as a sensing system for determination of O2 •−.

Nowadays scientific and cultural references are needed not only among the students and researchers but also for all rank of societies. To increase the knowledge of people, it is necessary to access freely to required references in every time and places. This general requirement caused the establishment of world digital library (WDL) with multilingual translation in a cyberspace; WDL is going to create an internet-based, easily-accessible collection of the world’s cultural, historical and geological riches which include promoting knowledge of societies and cultural diversity on the web. In this article we introduce this library and some of its treasures.

A thin layer of poly methylen green (PMG) was covered on glassy carbon (GC) electrode surface by electrochemical polymerization method. In the next step by dropping a suspension of carboxylic acid functionalized carbon nano-tubes on the PMG/GC electrode a layer of CNTs was coated on the electrode. Thereafter, to immobilize the enzyme on electrode surface, three layers of PMG, alcohol dehydrogenase and PMG were added to the modified electrode, respectively. The Fourier transform infrared, scanning electron microscopy and cyclic voltammetry measurements clearly confirmed the successful immobilization of enzyme on the GC electrode.