Journal of Nano Structures
Volume:3 Issue: 4, Autumn 2013

In this investigation, Nano silica chloride (nano SiO2Cl) has been found to be efficient, chemoselective and recyclable catalyst for facile and simple synthesis of germinal diacetates from aromatic and heteroaromatic aldehydes in shorter reaction durations. The products were obtained in high to excellent yields. This work consistently has the advantages of excellent yields, short reaction time, mild condition and work-up procedures. This method might be useful in the future for the preparation of similar derivatives.

Sulfonic acid functionalized SBA-15 as a nanoporous acid catalyst was used in the synthesis of 2-Aryl benzoxazoles 4 by the condensation of 2-aminophenol 1 and benzoyl chlorides 2 under microwave irradiation in solvent free reaction conditions. The advantages of this methodology are good product yields (60-98%), being environmentally benign, short reaction times and easy work up.

In this study, Cu50-Ni50 alloy were synthesized by mechanical alloying. The alloy was then reinforced by dispersion of multiwalled carbon nanotubes using a planetary high energy ball mill. X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer were used to evaluate the effects of CNT addition on the characteristics of the nanocomposites. XRD results of Cu-Ni sample showed that, the homogeneous Cu50-Ni50 alloy with a mean crystallite size of 25 nm was formed after 10 h of milling. It was found that presence of CNTs and the stage of CNT addition can alter the phase composition, morphology and magnetic properties of the nanocomposites. Also, CNTs prevent the complete dissolution of nickel in copper and change the chemical composition of the alloy. SEM micrographs revealed that the addition of CNTs caused a significant reduction of powder particle size. More ever, the distribution of CNTs in the matrix decreases the saturation magnetization and increases the coercivity of the nanocomposites.

The performance of nanoscale Field Effect Diodes as a function of the spacer length between two gates is investigated. Our numerical results show that the Ion/Ioff ratio which is a significant parameter in digital application can be varied from 101 to 104 for S-FED as the spacer length between two gates increases whereas this ratio is approximately constant for M-FED. The high-frequency performance of FEDs is investigated and the cut-off frequency of the intrinsic transistor without parasitic capacitance is calculated. The figures of merit including intrinsic gate delay time and energy-delay product have been studied for the field effect diodes which are interesting candidates for future logic applications.

In this paper, for the first time we have studied theoretically the effect of exchange-correlation holes around electrons in GaAlAs/GaAs/GaAlAs nanostructure on the temperaturedependent dynamic dielectric function of two-dimensional electron gas by employing random phase, STLS and Hubbard approximations. Also, we have investigated another interesting system which is coupled quantum wells structure. To make a good comparison and show the effect of local field, the numerical results have been compared with those obtained within RPA which considers long-range interactions and ignores exchange-correlation effects completely. We found that taking into account the exchange-correlation effects changes considerably the values of dynamic dielectric function at low electron densities at finite temperatures.

The aim of this research is preparation of SnO2 nanowires by means of Thermal chemical reaction vapor transport deposition (TCRVTD) method from SnO powders. The morphology, chemical composition and microstructure properties of the nanowires are characterized using field emission scanning electron microscope (FE-SEM), EDS, and XRD. The XRD diffraction patterns reveal that the SnO2 nanowires have been grown in the form of tetragonal crystal structures with the lattice parameter of a=b=0.440 nm, and c=0.370 nm. The SEM images reveal that SnO2 nanowires have successfully been grown on the Si substrate. The EDS patterns show that only elements of Sn, O and Au are detected. Prior to the VLS process the substrate is coated by a thin layer of Au. The diameter of nanowires is measured to be something between 20-100 nm.

Cupric oxide nanostructures were synthesized via a simple reaction between copper nitrate and sodium hydroxide using a sonochemical-assisted method. The synthesized CuO was then characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, ultraviolet-visible and photoluminescence spectroscopy. Our studies show that the CuO nanostructure can be used as a humidity sensor with a short response time (about 6 sec) and a long recovery time (up to 650 sec). Variation of relative sensor impedance (defined as sensing) at relative humidity of 90% was measured to be about 80, which indicates a high sensing of our designed sensor.

Introduction of the metallic nanoparticles (NPs) in the bulk glass received a large interest due to their versatile applications. The effect of silver NPs on optical properties of the Eu3+-doped zinc tellurite glasses is presented for the first time. Glass samples are prepared by melt-quenching technique. The surface plasmon absorption bands of silver NPs are recorded in the visible region. The enhancements in the order of 2.2-2.4 times are observed in the luminescence of the Eu3+ ions by introduction of silver NPs up to 1 mol% and are attributed to contribution of the NPs with average size of about 8 nm. In addition, energy transfer from surface of the metal to the rare earth ion is discussed as the second channel for the enhancement. This report highlights the excellent performance of tellurite glasses for applications such as LEDs, color displays and nanophotonics.

A cylindrical direct current magnetron sputtering coater with two targets for deposition of multilayer thin films and cermet solar selective surfaces has been constructed. The substrate holder was able to rotate around the target for obtaining the uniform layer and separated multilayer phases. The Al/ Cu multilayer film was deposited on the glass substrate at the following conditions: Working gas = Pure argon, Working pressure = 1 Pa, Cathode current = 8 A and cathode voltage = -600 V. Microstructure of the film was investigated by X-Ray Diffraction and the scanning electron microscopy analyses. The elements profile was determined by glow discharge–optical emission spectroscopy analysis. During deposition, both targets with magnetron configuration were sputtered simultaneously by argon ions. A Plasma column on the targets surface was generated by a 290 G permanent magnet unit. Two DC power supply units with three phases input and maximum output of 12 A/1000V were used to deposit the multilayer thin films. A control phase system was used to adjust output voltage.

In this paper, we present a simple method for preparation of graphene-ZnO nanocomposites (G-ZnO). The method is based on thermal treatment of the graphene oxide (GO)/ZnO paste which reduces the graphene oxide into the graphene and leads to the formation of the G-ZnO nanocomposite. The structure, morphology and optical properties of synthesized nanocomposites are characterized with XRD, FESEM, FTIR and Raman spectroscopies. Here CdS quantum dots are deposited on G-ZnO nanocomposite structure and is integrated as a photoanode in CdS quantum dot sensitized solar cells (QDSSCs). Photovoltaic properties of CdS QDSSC based on bare ZnO nanoparticles and G-ZnO nanocomposite photoanodes are studied here. The cell with GZnO/ CdS photoanode shows two times higher photoelectric conversion efficiency than that of the pure ZnO photoanode (0.94 vs. 0.45).

Nano-silica supported titanium tetrachloride (TiCl4.SiO2) was prepared and used as an acid catalyst for the 14-aryl or alkyl-14Hdibenzo[a,,j]xanthenesreaction under solvent-free conditions. Compared to the classical 14-aryl or alkyl-14Hdibenzo[a,j]xanthenesreaction conditions, this method consistently has the advantage of excellent yields, mild reaction conditions, ease of workup, survival of different functional groups and short reaction times.

This paper is concerned with the surface and small scale effects on transverse vibration of a viscoelastic single-layered graphene sheet (SLGS) subjected to an in-plane magnetic field. The SLGS is surrounded by an elastic medium which is simulated as Visco- Pasternak foundation. In order to investigate the small scale effects, the nonlocal elasticity theory is employed due to its simplicity and accuracy. The effect of structural damping of SLGS is taken into account based on Kelvin’s model on elastic materials. An analytical method is used to obtain the natural frequency of the system. A detailed parametric study is conducted to elucidate the effects of the surface layers, nonlocal parameter, magnetic field, Visco-Pasternak elastic medium, viscoelastic structural damping coefficient and aspect ratio of graphene sheet. The findings indicate that enhancing the magnetic field and the density of surface layers leads to an increase in the natural frequency of SLGS.

In this work, BSEA-SBA-15 was prepared for the first time, which was prepared by covalently anchoring Schiffbase compound (N,N´-bis(salicylidene)ethylenediamine (BSEA) on SBA-15 by hydrothermal method. The structure and physicochemical properties were determined by elemental analysis, XRD, nitrogen adsorption– desorption, thermogravimetric analysis and FTIR spectroscopy, SEM, BET surface area and BJH pore size. The average pore diameter after the modification is 69Å. It is expected that BSEA-SBA-15 can be used as an effective adsorbent for the removal of metal ions due to having porous structure and active functional groups.

In this article, the bending and free vibration analysis of functionally graded (FG) nanocomposites Timoshenko beam model reinforced by single-walled boron nitride nanotube (SWBNNT) using micromechanical approach embedded in an elastic medium is studied. The modified coupled stress (MCST) and nonlocal elasticity theories are developed to take into account the size-dependent effect. The mechanical properties of FG boron nitride nanotube-reinforced composites are assumed to be graded in the thickness direction and estimated through the micro-mechanical approach. The governing equations of motion are obtained using Hamilton’s principle based on Timoshenko beam theory. The Navier''s type solution is implemented to solve the equations that satisfy the simply supported boundary conditions. Furthermore, the influences of the slenderness ratio, length of nanocomposite beam, material length scale parameter, nonlocal parameter, power law index, axial wave number, and Winkler and Pasternak coefficients on the natural frequency of nanocomposite beam are investigated. Also, the effect of material length scale parameter on the dimensionless deflection of FG nanocomposite beam is studied.