سال:1391 | دوره: | شماره: |تعداد مقالات:10

In this work the conduction of ion-water solution through two discrete bundles of armchair carbon and silicon carbide nanotubes, as useful membranes for water desalination, is studied. In order that studies on different types of nanotubes be comparable, the chiral vectors of C and Si-C nanotubes are selected as (7, 7) and (5, 5), respectively, so that a similar volume of fluid is investigated flowing through two similar dimension membranes. Different hydrostatic pressures are applied and the flow rates of water and ions are calculated through molecular dynamics simulations. Consequently, according to conductance of water per each nanotube, per nanosecond, it is perceived that at lower pressures (below 150 MPa) the Si-C nanotubes seem to be more applicable, while higher hydrostatic pressures make carbon nanotube membranes more suitable for water desalination.

In this paper, we report on the synthesis of Cu nanoparticles through a single-precursor route by controlling the growth temperature. Selective adsorption of oleylamine on various crystal planes may play an important role in the growth process. The understanding of this self-assembling process will help us develop reliable and reproducible methods to synthesis other three dimensional nanostructured architectures and increase the knowledge of self-assembly. The catalytic activities of these nanoparticles of different sizes have been tested on the yield of production of biphenyl from the iodobenzene in reaction. The as synthesized products were characterized by powder X-Ray diffraction (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX) analysis and UV-vis spectra.

In this paper, the electrochemical hydrogen storage in nanocomposite materials was studied. Multi-Walled Carbon Nanotubes (MWCNTs) electrode was prepared by mixing with special composite. The optimum ratio of MWCNTs was estimated 30-70% (w/w) in the composite material. MWCNTs were synthesized by Chemical vapor deposition (CVD). The nanocomposite was homogenized by microwave. Cyclic voltammetry (CV) was applied to study the behavior of electrode. Ni nanoparticles were electrodeposited on working electrodes via dual-pulse method. Voltammograms indicated that, Ni nanoparticles have electrocatalytic effect on hydrogen storage capacity.

A novel zinc oxide-agar nanocomposite was successfully synthesized using zinc chloride as a precursor. The nanocomposite was prepared using a domestic microwave oven. The prepared nanocomposites have been characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and UV-visible spectroscopy. The crystalline properties of the synthesized materials were investigated by XRD and Raman spectroscopy. The UV-visible spectra shows a characteristic the absorption peak at 356 nm. The morphological observation of the SEM results reveals that the ZnO nanostructures are between 50 to 100 nm in size, and are embedded in the agar matrix.

Tellurium nanostructures have been prepared by physical vapor deposition method in a tube furnace. The experiments were carried out under argon gas flow at a pressure of 1 mbar. Tellurium powder was evaporated by heating at 350oC and 430oC and was condensed on substrates at 110–250oC, in the downstream of argon gas flow. The products were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). FESEM revealed that most of the products have one dimensional structure. X-Ray diffraction (XRD) patterns show that the products are crystalline with hexagonal structures.

This paper addresses the annealing temperature effect on nanostructure and phase transition of copper oxide thin films, deposited by PVD method on glass substrate (at 110 nm thickness) and post annealed at different temperatures (200-400oC) with a flow of 1 cm3s-1 Oxygen. The X-ray diffraction (XRD) was employed for crystallographic and phase analyses, while atomic force microscopy (AFM) was used for morphology investigation. The results showed (CuO2) cuprite phase for samples annealed at 200 and 250oC and (CuO) tenorite phase for samples annealed at 350 and 400oC, while sample annealed at 300oC had a complex phases (CuO2 and CuO). The size of the grains increased, but roughness increased and then decreased by increasing of annealing temperature. Furthermore, calculated activation energy from grain diameter (at arrhenius plot) was 0.54 eV.

In the present study, natural convective heat transfer in a partitioned square cavity utilizing nanofluids is studied. The vertical left and right walls are considered as the hot and cold walls, respectively and the partitions assumed to be adiabatic. The nanofluid used in this study is Al2O3 with the volume fraction of 20%. It is assumed that nanofluid is a single phase fluid. FLUENT 6.3.26 is used to simulate the problem. The influence of different parameters such as Rayleigh number (Ra=105 and 107), height of partition (h=0.1, 0.3, 0.5H) at a fixed distance from the walls (d=0.3H) are studied. According to the results, Rayleigh number and height of the partition are important factors that extremely affect the streamlines and isotherms. At Ra=107, the flow is confined in the distance between walls and partitions. Furthermore, at high partitions, the isotherms are horizontal between two partitions. For a fixed amount of the partition height, Nusselt number increases as the Rayleigh number rises. On the other hand, for a fixed Rayleigh, with the increasing partition height, Nusselt number decreases along the hot wall.

Ion channels are naturally occurring pores through the proteins that regulate the passage of ions and thus maintain the concentration of ions inside and outside the cell. The ion channels control many physiological functions and they can show selectivity for a specific ion. Ion channels are mostly observed in nerve cells and muscle cells. The influx of ions into cells can be regulated by a gate, like voltage controlled gate. Here we have investigated the ion transport through an ion channel by Poisson-Nernst-Plank model. In this model, proteins are approximated as cylindrical tubes embedded in a lipid membrane. Different ion channels with different channel radii are taken into consideration. The electrostatic potential, ion concentrations, ion flux and ion current are found. Simulation of ion channel is of vital importance in preparing biosensor where the molecular switching mechanism of ion-channel can regulate the flow of a particular ion in an analyte, if detected. The ion channels show voltage-current relationship similar to that of diodes and transistors. A major challenge in nanomedicine is the quick detection of antigens causing a disease and thus the finding of a novel commercial technique (better than ELISA) is essential. Towards this aim, a nanobiosensor can be devised where an ion-channel may serve as its primary component.

The Silver nanoparticles are well-known for their antimicrobial, anti-inflammatory wound healing abilities. We synthesized Silver nanoparticles using chemical reduction method and the formation of the silver nanoparticles was characterized by UV-Vis absorption spectroscopy, FT-IR and SEM techniques. The minimum inhibitory concentration of the synthesized nanoparticles was determined for both gram negative and gram positive bacteria. Then these nanoparticles were coated over an absorbable surgical gut suture, after the immobilization of them in Sodium alginate, by slurry dipping technique. The controlled release of the nanoparticles checked in vitro in Simulated Body Fluid. Antimicrobial activity also evaluated by Disc diffusion method on the culture plates of E. coli and S. aureus. The successful release of silver nanoparticles under physiological PH depicts the applicability of this novel suture in surgery for the prevention of surgical wound infection and to enhance wound healing.

A noninteracting quantum-dot arrays side coupled to a quantum wire is studied. Transport through the quantum wire is investigated by using a noninteracting Anderson tunneling Hamiltonian. The conductance at zero temperature develops an oscillating band with resonances and antiresonances due to constructive and destructive interference in the ballistic channel, respectively. Moreover, we have found the number of antiresonant exactly depends on the number of quantum dot in every array and increasing array make antiresonants wide increase.