JOURNAL OF NANOSTRUCTURES
Year:2012 | Volume:2 | Issue:2|Papers Count:27

By means of first principles calculations we show that both rutile and anatase phases of bulk TiO2 doped by S, Se or Pb can display substantial decreasing in the band gap (up to 50%), while doping by Zr does not sizably affect the band-gap value. Moreover, the absorption edge is shifted (up to 1 eV) to the lower energy range in the case of TiO2 doped by S or Pb that opens a way to enhancing of absorption of sun’s radiation. We also discuss how our findings can improve efficiency of photovoltaic cells and photocatalytic cells for hydrogen generation.

Two new nano-sized lead(II) and mercury(II) coordination polymers, [Pb(2-bpdh)(NO3)2(H2O)]n(1); (2-bpdh=2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene)} and [Hg(4-bpdb)(SCN)2]n (2); (4-bpdb= 1,4-bis(4-pyridyl)-3,4-diaza-1,3-butadiene) were synthesized by a sonochemical method. The structure of 1 may be considered coordination polymer of lead(II) and Single crystal X–ray analysis of compound 2reveals that consists of one-dimensional zigzag chains formed by bridging SCN and 4-bpdb ligand. The new nano-structures of coordination polymers were characterized by scanning electron microscopy, powder X-ray diffraction, elemental analyses and IR spectroscopy. The size of the samples was about 70 nm and 60 nm for compound 1 and 2, respectively.

The austenitic stainless steel (SS) has been used as a material for building ultra high vacuum (UHV) chamber. Recently significant efforts have been concerned a comparing the standard cleaned for ultra high vacuum, passivity stainless. In this work Austenitic nanocomposites were synthesize by sol- gel method. The morphologies and topographies of the samples have been studied with using Scanning Electron Microscopy (SEM) and X-Ray diffraction (XRD) Techniques. The principal aim is the Nanostructural evolution of these samples. The obtained results indicate that adding 10.8 gr Ni particles into SS matrix, modified SS device mechanical structures.

Nowdays, iron nanoparticles due to their unique characteristics are used in all of sciences and technology. These nano particles due to their electrical, magnetic, optical and catalytic properties and having high area and activity that is promped by their small size and most importantly many scientists from the entire world are interested in their low cost production. In this project we used method of reduction in the liquid phase for synthesis of iron nano particles. Unlike synthesis so far has been done and they used different kinds of surfactants and capping or they used starch for stabilization, we used chelating agent diethylene triamine penta acetic acid (DTPA) for increasing the stability of iron nano particles for the first time in the world. Ammonium iron(II) sulfate were used for make iron nano particle and Sodium borohydride was used for reduction. This method not only was simple and cheap but also didn’t need special instruments. Also determining of structure, size, particles distribution and surface morphology of this nano particles we used the analysis of FT-IR, XRD and SEM that all of them showed the synthesis of zero valent iron nanoparticles, metallic iron, has been done correctly. The average of synthesis of zero valent iron nano particles is 18 nm and crystal structure of nano particles was designed by using vertical nano lab software. Finally, we studied opration Removal of Radioactive Uranium From groundwater by using iron nanoparticle.

Ag\Al2O3 nanocomposite were synthesized by solution combustion Technique using ammonium carbonate as a new fuel under simultaneous combustion of alumina and silver particles condition. Samples prepared with different amount of silver, were characterized by XRD, BET, SEM and optical Absorption measurements. XRD analysis was used to determine the change in phase and size of the synthesized nanoparticle with adding silver. BET analysis showed that added silver reduced specific surface but which is still suitable for catalytic application. BJH analysis showed that pores in Ag/Al2O3 nano composite are mesoporous and in Al2O3 nano particles is microporous. TEM and SEM showed that silver was distributed completely homogenously in pores of Alumina, and didn’t change in surface of Alumina. Optical transmission showed the different existence of different Ag species.

Nanofluids are kinds of fluids engineered by dispersing nanoparticles in base fluids, a new challenge for thermal sciences provided by nanotechnology. Due to their excellent characteristics, nanofluids find wide applications in enhancing heat transfer. This paper presents synthesis and characterization of TiO2-CNTs nanocomposites by sonochemical method and investigation of some properties of TiO2-CNTs nanocomposite suspended in 50:50 (by weight) propylene glycol and water mixture as a new nanofluid.

The magnetoresistance of a one-dimensional electron gas in a metallic ferromagnetic nanowire containing two atomic-size domain walls has been investigated in the presence of spin-orbit interaction. The magnetoresistance is calculated in the ballistic regime, within the Landauer-Büttiker formalism. It has been demonstrated that the conductance of a magnetic nanowire with double domain walls can be controlled through the domain walls separation. Also, we have represented another alternative way that enables us to handle easily the magnetoresistance of such a system as well as its conductance by utilizing the Rashba-type spin-orbit interaction induced by the external gates.

The stabilized zirconia with different Cu contents synthesized via sol-gel method. The samples were prepared by hydrolysis and condensation of orgnomatelic sol. After that the result gels were dried at 800C and then calcined at various temperatures. Tِhe differential thermal analysis (DTA), X-ray diffraction (XRD), field emission scanning electronic microscopy (FESEM) and transmission electronic microscopy (TEM) were used to determine the characteristics of nanoparticles. Unlike the stable pure ZrO2 that has monoclinic structure at room temperature, the synthesized pure ZrO2 and ZrO2-CuO powders have been cubic and tetragonal structure at room temperature after calcinations. Moreover, it is obtained those changes in the crystallite size affect the stabilization of tetragonal or cubic structure at room temperature, and increase in content of dopant favored decrease of the crystallite size and metastabilization of both tetragonal and cubic polymorphs.

In this article, simple, convenient synthesis of 2-aryl-1- arylmethyl-1H-1,3-benzimidazole (1,2-disubstituted benzimidazoles) via condensation of 1,2-phenylenediamine and aromatic aldehydes using SBA-Pr-SO3H as a nanoporous solid acid catalyst in green protocol was reported.

A general synthetic route to the synthesis of imidazoles has been developed using nano SbCl5/SiO2 under solvent-free conditions. The multi-component reactions of aldehydes, benzil and ammonium acetate were carried out to afford some trisubstituted imidazole derivatives. This method provides several advantages like simple work-up, environmentally benign, and shorter reaction times along with high yields. The mentioned nano catalyst was investigated by SEM, TEM and XRD. Meanwhile, structures of trisubstituted imidazoles were elucidated by FT-IR, 1H NMR and 13C NMR spectra.

In this reaserch, photocatalyst titanium dioxide was doped with silver and modified by polyethylene glycol by sol gel method and the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The purpose of the present study was to evaluate the photocatalytic bactericidal effects of prepared nanocomposite on human pathogenic bacteria under visible light irradiation whereas; many studies have been published on the use of titanium dioxide as a photocatalyst, which decomposes various organic compounds. We observed that TiO2 reveals the bactericidal property against the Staphylococcus aureus, Shigella dysanteriae, Salmonella enterica subsp. enterica serovar Paratyphi bacteria and pathogenic fungi Candidia albicans which is increased by the essence of silver and visible light.

A simple method for fabrication of highly ordered gold nanorod film is introduced in this article. The procedure is based on thermal evaporation of gold into a porous anodic alumina film (PAA). The PPA film was fabricated by combining the hard and mild anodization. This combination effectively decreases the processing time of fabrication of highly ordered porous anodic alumina film with controlled pore diameter and length. It was found that gold nanorods configuration affected by the porous anodic alumina film structure such as pore diameter and length. Furthermore the evaporation process change the rods diameter along the nanopores via the decreasing the pore mouth during the gold deposition.

Nano-SnCl4.Si02 as a reusable and efficient catalyst was prepared from reaction of SnCl4 with nano silica gel at room  temperature. The structure of nano-SnCl4.Si02 evaluated by ATR, and XRD. The SEM and TEM photograph of this catalyst improve the size of its particles in nanometer. 1- amidoalkyl-2-naphthols were prepared via multi-component reaction of 2-naphthol, aldehydes, and amides in the presence of nano-SnCl4. SiO2 under solvent free condition at 90oC. Short reaction times, high yields, scale up and easy work-up are the advantages of this protocol.

Poly(vinylidene fluoride) (PVDF) fibers with two molecular weights were prepared via electrospinning process. In this process, the concentration of spinning depended drastically on the gelation process. Also, it was experimentally smaller than obtained concentration in the solution entanglement number approach (SENA). Proof of this incompatibility was explained by the properties of PVDF and its solutions with DMF (i.e. PVDF crystallization, microgel formation and spinodal decomposition). These factors caused to early stabilize liquid jet. Also, early gelation inhibited from the fiber formation by blockage of syringe needle with Mw= 180,000 g/mol and early spinodal decomposition helps to fiber formation by isolated droplets of polymer-rich phase with Mw=275,000 g/mol. Finally, a mechanism was proposed for the electrospinning of these solutions.