نانوساختارها
سال:1392 | دوره: | شماره: |تعداد مقالات:13

Titanium dioxide is one kind of important materials, which has been extensively investigated because of its unique electronic and optical properties. A large number of efforts have been made to synthesize TiO2 materials with different methods. In this review paper, we summarize the synthesis pathways, morphology, as well as crystallization of the nanostructured TiO2. In addition, we also mention several nanostructured TiO2 materials.

The effect of length variation on the magnetic properties of NiFe alloy nanowires electrodeposited into the alumina template was investigated. The diameter (45±2.5 nm) and length (~1.9, 7.12, 8.3, 9.5 and 13.3mm) of the nanowires were estimated from scanning electron microscopy images. Energy dispersive spectroscopy results showed Ni3Fe7 composition of the alloy nanowires. The magnetic properties of the samples were investigated by vibrating sample magnetometer. It showed that with increasing the length of the nanowires from 1.9±0.1mm to 13.3±0.66mm, coercivity reduced from 1050 Oe to 705 Oe and squareness reduced from 0.64 to 0.46. The results proved increasing the magnetostatic interaction between the nanowires with length. Progress toward the multi-domain behavior was predicted caused to drastically reduce in the coercivity.

Colloidal quantum dots offer broad tuning of semiconductor band structure via the quantum size effect. In this paper, we present a detailed investigation on the influence of the thickness of colloidal lead sulfide (PbS) nanocrystals (active layer) to the photovoltaic performance of colloidal quantum dot solar cells. The PbS nanocrystals (QDs) were synthesized in a non-coordinating solvent, 1-octadecene, using oleic acid (OA) as the ligand. It was found that the device with 50 nm of thickness of active layer showed a high Efficiency (h) of 0.667 under simulated Air Mass 1.5 Global (AM 1.5G) irradiation (100 mW/cm2) compared to the device with low thickness of active layer.

TiO2 nanorods can be used as dye-sensitized solar cells and as various sensors and photocatalysts. These nanorods are synthesized by a using thermal corrosion process in a NaOH solution at 200oC with TiO2 powder as a source material. In the present work, the synthesis of TiO2 nanorods in anatase, rutile and Ti8O15 phases and the synthesis of TiO2 nanorods by using the sol-gel method and alkaline corrosion to incorporate aluminum oxide dopant are reported. The morphologies and the crystalline structures of the TiO2 nanorods are characterized using field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), and X-ray diffraction (XRD) techniques.

Two Cu (II) complexes, [Cu (L1)2] (NO3) 2 (1) and [Cu (L2)2] (NO3)2 (2), which L1 and L2 Schiff base ligands are 2- (thiophene-2-yl) -1 H imidazo [4, 5-f] [1, 10] phenanthroline and 2- (furane-2-yl) -1 H imidazo [ 4, 5-f] [1, 10] phenenthroline, respectively, were synthesized and characterized by physico - chemical and spectroscopic methods. Corresponded CuO nanoparticles were prepared by calcination of the obtained complexes at 500oC. The structure of nano sized copper oxides were characterized by X- ray diffraction (XRD) and scanning electron microscopy (SEM). Electrocatalytic oxidation of acetylcholine (ACh) on copper oxide nanostructures were investigated. The results showed that acetylcholine (ACh) was oxidized irreversibly on copper oxide nanostructures with an excellent catalytic activity.

Highly crystalline Bi3+-doped cadmium oxide (CdO) sub-micron structures were synthesized by calcination the obtained precursor from a sol-gel reaction. The reaction was carried out with cadmium nitrate (Cd (NO3)2.4H2O), bismuth nitrate (Bi (NO3)3.5H2O) and ethylene glycol (C2H6O2) reactants without any additives at 80oC for 2h. Resulting gel was calcined at 900 oC with increasing temperature rate of 15oC per minute for 12 h in a furnace. As a result of heating, the organic section of gel was removed and Bi3+-doped cadmium oxide micro structure was produced. The obtained compound from the sol-gel technique possesses a cubic crystalline structure at micro scale. Powder x-ray diffraction (PXRD) study indicated that the obtained Bi3+-doped CdO has a cubic phase. Also, SEM images showed that the resulting material is composed of particles with the average diameter of 1 mm. Also, UV–vis and FT-IR spectroscopies were employed to characterize the Bi3+-doped CdO micro structures.

In this work, a novel method is described for the preconcentration of Pb2+, Cd2+and Zn2+ions in environmental samples using uniform silanized mesopor (LUS-1) functionalized by ethylenediamine groups as a new extractant. The determination of ions is done by inductively coupled plasma optical emission spectrometry (ICPOES). The extraction time and efficiency, pH and amount of adsorbent, minimum amount of stripping acid and break-through volume were investigated. The method’s enrichment factor is100 and detection limit is 0.45, 0.05 and 0.03 ng mL-1 for Pb2+, Cd2+and Zn2+ respectively. The maximum capacity of the one mg of functionalized LUS-1 was found to be 150.0 (±2.0) mg and 93.0 (±1.7) mg and 125.0 (±1.2) mg of Pb2+, Cd2+and Zn2+respectively. The method was applied successfully for the preconcentration and determination of trace amounts of Pb2+, Cd2+and Zn2+in water and food samples.

The direct synthesis of polyaniline-TiO2 nanocomposite coatings on aluminum alloy 3004 (AA3004) surface has been investigated by using the galvanostatic method. The synthesized coatings were characterized by FT-IR, SEM-EDX, SEM and AFM. Optical absorption spectroscopy reveals the formation of the emeraldine oxidation state form of polyaniline-TiO2 nanocomposite. The corrosion performances of polyaniline-TiO2 nanocomposite coatings were investigated in 3.5% NaCl solution by Tafel polarization and Electrochemical Impedance Spectroscopy (EIS) methods. The corrosion rate of polyaniline-TiO2 nanocomposite coating on AA3004 was found~260 times lower than bare AA3004 and corrosion potentials of these coatings have shifted to more positive potentials (105 mV). The results of this study clearly ascertain that the polyaniline-TiO2 nanocomposite coating has outstanding potential to protect the AA3004 against corrosion in a chloride environment.

In this work, hydrogel nanocomposites were synthesized by solution polymerization of acrylic acid (AA) and itaconic acid (IA) in the presence of cotton fabric. Ammonium persulfate (APS) was used as the polymerization initiator in the presence of a crosslinker, methylene bisacrylamide (MBA). Insertion of Ag followed by reduction of Ag+ cations results in a hydrogel nanocomposite. The structure and morphology of the resulting Ag nanoparticle-loaded grafted fabric was characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Xray diffraction (XRD). The influence of both APS and MBA concentration on the swelling capacity of nanocomposites was also studied.

The use of an inorganic phase in water-in-oil (w/o) microemulsion has recently received considerable attention for preparing metal oxide nanoparticles. This is a technique, which allows preparation of ultrafine metal oxide nanoparticles within the size range 40 to 80 nm. Preparation of nano chromium (III) oxide studied investigated in the inverse microemulsion system. Therefore the nucleation of metal particles proceeds in the water capsules of the microemulsion. the main advantage of this method iseasily controllable conditions with using low cost chromium source is merit to be considered for scaling up by industrial researchers. Besides we mainly focus on the catalytic property nano chromium (III) oxide. Oxidation of aromatic aldehyde/alcohol to the corresponding carboxylic acids can be performed highly efficiently in the presence of a catalytic amount of nano chromium (III) oxide in THF as solvent under mild conditions.

Higher solid contents (20% and 40%) nanocomposites of poly (styrene-co-butyl acrylate) including higher content of Cloisite 30B (7 wt% and 10 wt%) were prepared via miniemulsion polymerization. Stability of the final latexes proved outstanding combination of polymerization procedure and surfactants. Morphological studies revealed by TEM, SAX and XRD showed three structures of coreshell, armored and individual dispersion of clay layers within the polymer particles. The effect of Cloisite 30B content on the barrier properties presents excellent and wide use of these films for packaging and nanocoatings industries.

Germanium nanowires (GeNWs) were synthesized using chemical vapor deposition (CVD) based on vapor–liquid–solid (VLS) mechanism with Au nanoparticles as catalyst and germanium tetrachloride (GeCl4) as a precursor of germanium. Au catalysts were deposited on silicon wafer as a thin film, firstly by sputtering technique and secondly by submerging the silicon substrates in Au colloidal solution, which resulted in Au nanoparticles with different sizes. GeNWs were synthesized at 400 oC, which is a low temperature for electrical device fabrication. Effect of different parameters such as Au nanoparticles size, carrier gas (Ar) flow and mixture of H2 with the carrier gas on GeNWs diameter and shape was studied by SEM images. The chemical composition of the nanostructure was also examined by energy dispersive X-ray spectroscopy (EDS).

A new nano-sized cobalt (II) coordination polymer, (CoL1).0.5DMF. 1.5CH3OH (1); [H2L1=5- (4-Carboxy phenyl azo) salicyilic acid] has been synthesized by a sonochemical method. The thermal stability of compound1 was studied by thermo- gravimetric and differential thermal analyses. Nano-structure of this coordination polymer was characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction and scanning electron microscopy. Nanoparticles of Co3O4 were obtained by calcination of compound 1 at 550oC. The Co3O4 nano-particles were characterized by powder Xray diffraction and scanning electron microscopy.