سال:1394 | دوره: | شماره: |تعداد مقالات:14

One of the main issues of nanotechnology is producing materials with new properties. Nanotechnology, as a powerful tool, has the ability to create evolution in the agricultural system and food-medicinal industries across the world. Producing a high-performance material from reclaimed cellulose material will increase motivation to recycle these materials at all phases of paper production and remove them from the waste stream. Electrospinning typically produces nonwoven mats of nanofibers, which could provide nanoscale pores for industrial filters. Electrospinning (ES) technique is a method to produce nanofibers by applying an electric field on a fluid jet. Nanotechnology also play a role in recycling of agricultural crops residues and converting them into energy and industrial chemicals by using natural processes of biological, physical and chemical. For example, unfortunately, since cotton harvesting time up to producing textile more than 25% of the fibers are converted to wastes. By using an electro spinning method of cotton waste some products such as cotton balls, yarns and cotton batting are produced. In addition, you can use this method to produce nanocellulose fibers that constitute 90 percent of cotton yarn and also produce fibers less than 100 nanometers which are 1000 times smaller than the current produced fibers. The technique relies on electrical rather than mechanical forces to form nanofibers. Different applications of nanofibers can be used in fields such as nanomembrane filters, protective clothing, electronical and optical equipment, and biomedical applications reinforced composites.

Adsorption of NO2 molecule on pristine and N-doped TiO2 anatase nanoparticles have been studied using the density functional theory (DFT) technique. The structural properties (such as bond lengths and bond angles) and the electronic properties (such as density of states, band structures and atomic partial charges) have been computed for considered nanoparticles. The results show that, the adsorption of NO2 molecule on N-doped nanoparticles is more energetically favorable than the adsorption of NO2 molecule on the pure TiO2 nanoparticles. However, on the base of the obtained results, the N-doped TiO2 nanoparticles can be used in NO2 sensing and removing applications.

For analyzing of compositions molecular orbitals in this article in order to combination only- xylometazolin-C7 X2 (XY) and C60- xylometozolin-C65-X2 (FXY), first got energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) by using NBO analyze in Gaussian 03 software. Then, occupancy parameter, gap of energy, and DNmax were calculated by support of these energies. All calculations were implemented in gaseous phase by using of (DFT) method and basis series 6-31G**.

The Glucose Oxidase (Gox) electrochemical sensors were used to detect a little amount of glucose. In this paper, the pure platinum plate (length of 5 cm and a width of 3 mm), the Ag/AgCl electrode and platinum electrode (diameter of 1 mm) were applied as a working electrode (W.E), reference electrode and auxiliary electrode sequential. Factors measured, glucose concentration and pH is Phosphate-buffered saline (PBS) that design software QUALTEK-4 has been tested. The experiments performed tests of the software, with increasing concentration, the current output is increased. Optimal conditions were optioned in neutral pH and maximum glucose concentrations. After confirmation tests in optimum conditions the expected error rate of application lower than 10 %. It shows the true error rate test with high sensitivity and accuracy.

In This research, gold nanoparticles were synthesized and functionalized by the antibody of aflatoxins. The quenching of the fluorescence of excitation emission matrices (EEM) of two type of aflatoxins (B1, G1), provoked by the gold nanoparticles, was studied by principal component analysis (PCA) and multivariate curve resolution with alternating least squares (MCR-ALS). These aflatoxins show quenching in the presence of the gold-labeled antibodies. Solutions containing a constant concentration of aflatoxins and variable concentrations of gold-labeled antibodies have been prepared and the fluorescence spectra have been recorded by scanning excitation and emission wavelengths. Excitation and emission spectra and quenching profiles were extracted from EEM using MCR-ALS. Applying suitable constraints lead to satisfactory results for the determination of aflatoxins in all samples.

We report on the synthesis, morphology, chemically and structurally of La2O3-Co3O4-ZrO2 nanostructure. The La2O3-Co3O4-ZrO2 nanostructure was synthesized by a method based on the co-precipitation. Composite powders have been characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy) and BET (Brunauer-Emmett-Teller). X-ray diffraction showed the formation of nano crystalline, La2Zr2O7, ZrO2, La (OH) 3 and Co3O4 phases. Scanning electron microscopy revealed that nanostructure formed by increasing the calcinations temperatures. With BET and BJH (Barrett, Joyner and Halenda) method the pore size distribution was determined. The effects of chemical compositions and calcinations temperature on the surface topography and the crystallization of phases were studied. The lattice strain of nanocrystallite during thermal treatment was calculated.

Nanoparticles classified in 4 overall groups containing: Metallic nanoparticles, ceramic nanoparticles, polymeric nanoparticles and semiconductor nanoparticles. These nanoparticles are used in some biomedical applications such as carrying medicine and photographing agents. With attention to different criteria which are both qualitative and quantitative, selecting the most suitable nanoparticles is of great importance. In this research, we must verify the method of ranking and selecting the appropriate nanoparticles by using AHP method and the view of the experts of this industry. Results of this research show that with attention to all criteria for using in pharmacological and medical process, the most suitable nanoparticle is ranked in this position: semiconductor, metallic, polymeric and ceramic.

Expanded graphite nanosheets (EG-nanosheets) were used for adsorption of Malachite Green (MG) from aqueous solution. The influences of dye concentrations, absorbent dosage, pH values and the temperatures on the adsorption were investigated as well. The dye adsorption experiments were carried out by utilizing batch procedure. EG-nanosheets were initially characterized by scanning electron microscopy (SEM), fourier transform infrared (FT-IR) and X-ray diffraction (XRD). Adsorption efficiency increased with increment in initial pH, dye concentration and temperature, but decreased with increment in adsorbent dose. The rate parameters of adsorption were evaluated by First-order, pseudo-second-order, and intraparticle diffusion models. These data indicated an endothermic spontaneous adsorption process and kinetically followed the pseudo-second order model with activation energy of+17.44 kJmol-1. Langmuir, Freundlich and Temkin equations were used for analyzing of experimental isotherm data and found that the Langmuir isotherm model showed good fit to the equilibrium adsorption data. The maximum adsorption capacity of 158.9 mg g-1 of Malachite Green was achieved (dye initial concentration of 100 mg L-1). Thermodynamic parameters such as changes in the free energy of adsorption (DGo), enthalpy (DHo) and entropy (DSo) were calculated. The negative values of DGo indicate that the malachite green adsorption process is spontaneous in nature and the positive value of DHo shows the endothermic nature of the process. Adsorption onto EG has proved to be highly efficient technique for the handling of dye-contaminated waters.

Zinc oxide nano-particles with the average diameter of about 25 nm were modified with different mole ratios of trimetoxyvinyl silane (TMVS) and oleic acid, as coupling agents, in order to modify their surface properties and render them more hydrophobic. Then, dispersibility of the surface modified nano-particles was examined in some monomers with different levels of hydrophobicity, including methyl methacrylate (MMA), butylacrylate (BuA), and styrene with low, medium and high hydrophobicity, respectively. The modified ZnO nano-particles were characterized using elemental analysis (EA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM). Findings revealed that the surface modified ZnO nano-particles were more dispersible in the examined organic media indicating better compatibility. TMVS behaved more efficient than Oleic acid, as coupling agent, to make compatibility with MMA; Whereas, ZnO modified with oleic acid exerted more compatibility with styrene. The mixed coupling agent (50/50 Wt% TMVS/oleic acid) showed better compatibility with BuA.

An empirical electrical conductivity assessment of nanofluids comprising CuO nanoparticles water-based in different concentrations, particles size and various temperatures of nanofluids has been carried out in this paper. These experimentations have been done in deionized water with nanoparticles sizes such as 89, 95, 100 and 112 nm and concentrations of 0.12 g/l, 0.14 g/l, 0.16 g/l and 0.18 g/l so nanofluids obtain in temperatures such as 25oC, 35oC, 45oC and 50oC for investigation of their electrical conductivity. It is observed that, in water-based nanofluids, the electrical conductivity increases with increasing in both nanofluids temperatures and concentration respectively in the range 25-50oC and 0.12-0.18g/l. But in nanoparticles size rising in nanofluids we observe that electrical conductivity has a few increase when nanoparticles have 95nm diameters, so decrease for biggest nanoparticles such as 100 and 112nm. It seems that there is an optimum in electrical conductivity with resize of nanoparticles.

We report the growth by ion exchange synthesis of ZnS nanoparticles in MCM-41 matrices using Zn (CH3COO) 2 and Na2S starting sources. The final product (ZnS/MCM-41) was characterized by X-ray diffraction (XRD) pattern, transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared spectrometry (IR) and UV-vis spectroscopy. Its crystalline structure and morphology was studied by XRD and scanning electron microscopy. Exciton absorption peaks at higher energy than the fundamental absorption edge of bulk ZnS indicates quantum confinement effects in nanoparticles as a consequence of their small size.

In this research, some more applicable ferrofluids are produced and their mechanical specifications are measured, experimentally. Also, their treatments in the ventilated cavity geometry are assessed numerically. The magnetite nanoparticles are produced by a chemical combination of Fe2+and Fe3+with NH3. In order to solve the nanoparticles in the new mediums, a proper coating is added to them. Then they are solved in kerosene, brake oil, hydraulic oil and motor oil with different particle fractures. A pressure-based procedure to solve Navier-stokes equations with finite volume formulation is developed to simulate a magnetic fluid in ventilated cavity geometry. One of the usages of this geometry is found in magnetic separation. The ventilated cavity geometry includes a square medium with one velocity inlet and one velocity outlet. In addition, a magnetic field due to a DC current carrying wire is employed on the geometry. The magnetic field intensities, its positions and ferrofluids’ mediums are changed. Then, the flow characteristics for each case are obtained to find the optimum situation for magnetic separation. Finally, the optimum situations for magnetic separation and for local cooling are obtained and the best ferrofluid is suggested for each application.

An efficient synthesis route to 1, 4-dihydropyrimidine derivatives from reaction of divergent aldehydes with ethylacetoacetate and urea under solvent-free conditions by ZnO nanoparticles as a relative in expansive, eco-friendly, easy available, non-volatile, non-explosion, thermally robust, recyclable and easy to handle catalyst at 90oC with excellent yields is described. Unenhanced reaction times, simple reaction protocol and work-up, have been improved synthesis of these materials in the presence of this heterogeneous catalyst.

The quantum transport computations have been carried on four different width of zigzag graphene using a nonequilibrium Green’s function method combined with density functional theory. The computed properties are included transmittance spectrum, electrical current and quantum conductance at the 0.3V as bias voltage. The considered systems were composed from one-layer graphene sheets differing with each other in y-direction width. The number of unit cells for considered graphenes are one, three, five and seven in z-direction, whiles the scattering region and first super cells of semi-infinite right and left electrodes were formed from three unit cell in z-direction. At the first the considered structures have been optimized and next the NEGF calculations were carried out on the optimized structures. All of the computations have been done using OPENMX3.6 atomic scale simulation code. The results were presented and interpreted for the considered systems in terms of the z-direction width of studied graphenes.