Sharif Digital Repository

Superparamagnetic ZnFe2O4/reduced graphene oxide (rGO) composites containing ZnFe2O4 nanoparticles (with ∼5-20 nm sizes) attached onto rGO sheets (with ∼1 μm lateral dimensions) were synthesized by hydrothermal reaction method. By increasing the graphene content of the composite from 0 to 40 wt%, the size as well as the number of the ZnFe2O4 nanoparticles decreased and the saturated magnetization of the composites reduced from 10.2 to 1.8 emu/g, resulting in lower responses to external magnetic fields. Concerning this, the time needed for 90% separation of ZnFe2O4/rGO (40 wt%) composite from its solution (2 mg/mL in ethanol) was found 60 min in the presence of an external magnetic field (∼1... 

Tungsten oxide thin films (deposited by thermal evaporation or sol gel method) were used for photocatalytic reduction of graphene oxide (GO) platelets (synthesized through a chemical exfoliation method) on surface of the films under UV or visible light of the environment, in the absence of any aqueous ambient at room temperature. Atomic force microscopy (AFM) technique was employed to characterize surface morphology of the GO sheets and the tungsten oxide films. Moreover, using X-ray photoelectron spectroscopy (XPS), chemical state of the tungsten oxide films and the photocatalytic reduction of the GO platelets were quantitatively investigated. The better performance of the sol-gel tungsten... 

Graphene is usually synthesized through deoxygenation of graphene oxide (GO) by hydrazine as the most common and one of the strongest reducing agents. But, due to the high toxicity of hydrazine, it is not a promising reductant in large-scale production of graphene. Here, for the first time, we used melatonin (MLT), as a powerful antioxidant and a biocompatible competitor of hydrazine in reduction of GO suspension. X-ray photoelectron spectroscopy (XPS), current-voltage and optical characteristics of the sheets indicated that the deoxygenation efficiency of the GO suspensions by MLT and under heating in an alkaline condition for 3 h was comparable with the efficiency obtained by hydrazine in... 

An easy method for preparing CuO nanoparticles incorporated in a mesoporous structure was presented based on the thermal decomposition of a copper complex. The novel copper coordination compound of [Cu(anic)2]·0.75H2O (anic= 2-aminonicotinate) with the microflake morphology was synthesized through the reaction of 2-aminonicotinic acid (Hanic) and copper(II) nitrate. Using elemental analysis and Fourier transform infrared (FTIR) spectroscopy, the chemical composition of CuC12H11.5N4O4.75 was proposed. Calcination process at 550 °C for 4 h transformed the microflakes into CuO nanoparticles incorporated in a mesoporous structure. The FTIR peaks assigned to 2-aminonicotinate were completely... 

Various morphologies of monoclinic CuO powders were synthesized by hydrothermal treatment of copper nitrate, copper acetate or copper sulfate. The synthesized samples were characterized by scanning electron microscopy, X-ray diffractometry, the Fourier transform infrared spectroscopy, and diffuse reflectance spectrophotometry. Antibacterial activity of the samples was studied against Escherichia coli bacteria in dark and under visible light irradiation. Although the different precursors yielded the same band gap energies (≈1.6 eV) for the synthesized CuO samples, they resulted in various morphologies (hierarchy of stabilized micro/nanostructures), specific surface areas, concentrations of... 

Hollow microblocks of [Zn(anic)2], as a novel coordination compound, were synthesized using 2-aminonicotinic acid (Hanic) and zinc (II) nitrate tetrahydrate. The chemical composition of the zinc complex, ZnC12H10N4O4, was determined by Fourier transform infrared (FTIR) spectroscopy and elemental analysis. The synthesized zinc complex was used as a precursor to produce ZnO nanostructures by calcination at 550 °C for 4 h. Morphological studies by scanning electron microscopy and transmission electron microscopy revealed the formation of porous microbricks of ZnO nanoparticles. N2 adsorption-desorption analysis showed that the... 

Graphene oxide (GO) sheets with a low concentration (∼1 wt%) were deposited on surface of hydrothermally synthesized ZnO nanorod films. The deposited films were heat treated at 450 °C in order to achieve suitable GO/ZnO hybrid thin films for photocatalytic purposes. The photocatalytic activity of the nanocomposite films was investigated based on degradation of methylene blue (MB) dye which is a typical pollutant model. The GO/ZnO hybrid thin films could degrade higher MB (∼90%) than the bare ZnO nanorods (which showed only ∼75% degradation) after 450 min UV irradiation. A further significant improvement (resulting in a nearly complete degradation of MB) was achieved by exposing the GO/ZnO... 

Nanoscale graphene oxide (NGO) sheets were synthesized and used as carbocatalysts for effective oxidation of benzylic alcohols and aromatic aldehydes. For oxidation of alcohols in the presence of H2O2 at 80 °C, the NGOs (20% mass fraction) as carbocatalysts showed selectivity toward aldehyde. The rate and yield of this reaction strongly depended on the nature of substituents on the alcohol. For 4-nitrobenzyl alcohol, <10% of it was converted into the corresponding carboxylic acid after 24 h. By contrast, 4-methoxybenzyl alcohol and diphenylmethanol were completely converted into the corresponding carboxylic acid and ketone after only 9 and 3 h, respectively. The conversion rates for... 

The reverse osmosis (RO) desalination capability of hydrogenated and hydroxylated graphene nanomesh membranes (GNMs) inspired by the morphology of carbon nitride (C2N) has been studied by using molecular dynamics simulation. As an advantage, water permeance of the GNMs is found to be several orders of magnitude higher than that of the available RO filters and comparable with highly strained C2N (S-C2N) as follows: 6,6-H,OH > 12-H > S-C2N > 5,5-H,OH > 10-H. The reverse order is found for salt rejection, regardless of S-C2N. The hydrophilic character of the incorporated -OH functional group is believed to be responsible for linking the water molecules in feed and permeate sides via the... 

Single-layer MoS2-MoO3-x heterojunction nanosheets with visible-light-sensitive band gap energy and average lateral dimensions of ~70 nm were synthesized by using a two-step combined exfoliation method. The exfoliation was initiated from pristine MoS2, while some sulfur sites in expanded MoS2 sheets during exfoliating were substituted by ambient non-thermal oxygen, resulting in formation of α-MoO3-x crystalline domains. The morphological features, crystalline structure, phase formation, number of layers, and optical properties of the MoS2-MoO3-x nanosheets were determined by atomic force microscopy; X-ray diffraction; field emission electron microscopy; transmission electron microscopy; and... 

Thin films of (WO3)1 - x-(Fe2O 3)x composition were deposited by thermal evaporation on glass substrates and then all samples were annealed at 400 °C in air. Optical properties such as transmittance, reflectance, and optical bandgap energy of the "as deposited" and the annealed films were studied using ultraviolet-visible spectrophotometry. It was shown that the annealing process did not substantially change the optical transmittance and reflectance of all the films except the films having x = 0.75. By increasing Fe2O 3 content in the films from x = 0 to x = 0.75, optical bandgap energy decreased from 3.4 to about 1.3 eV and from 3.1 to 2.1 eV for the "as deposited" and the annealed samples,... 

In this investigation, we have studied the elemental diffusion coefficients of the Cu/Ta and Ta/Si interfaces in the Cu/Ta/Si(1 1 1) structure. The diffusion parameters for Cu diffusion into the Ta barrier layer, Ta diffusion into the Si substrate and diffusion of Si atoms into the Ta layer have been calculated using conversion of RBS data to concentration-depth profile curves and the solution of Fick's equation based on a constant diffusing amount boundary conditions. Furthermore, by calculating grain boundary diffusion coefficients, we have estimated grain boundary slabs of the Ta layer at different temperatures. It was shown that, the width of grain boundary slabs in the Ta layer at 700°C... 

In this investigation, we have studied the effect of negative bias voltage on the properties of a sputtered Ta layer deposited at high Ar pressure (13.3 Pa) which is used as a diffusion barrier in a Cu/Ta/Si structure focusing on its silicidation process. According to Rutherford backscattering spectrometry, the Cu(85 nm)/Ta(100 nm, unbiased)/Si(111) structure was found to be stable up to 300°C in a N2 environment for 30 min. At a temperature of 450°C, TaSi2 was formed at the Ta/Si(111) interface, and the Ta diffusion barrier completely failed. By applying various negative bias voltages ranging from 0 to -150 V, an optimum bias voltage of Vb = -50 V for the sputtered Ta layer was found from... 

Vertically aligned ZnO nanowires (NWs) hybridized with reduced graphene oxide sheets (rGO) were applied in efficient visible light photoinactivation of bacteria. To incorporate graphene oxide (GO) sheets within the NWs two different methods of drop-casting and electrophoretic deposition (EPD) were utilized. The EPD method yielded effective penetration of the positively charged GO sheets into the NWs to form a spider net-like structure, whereas the drop-casting method resulted in only a surface coverage of the GO sheets on top of the NWs. The electrical connection between the EPD-incorporated sheets and the NWs was checked by monitoring the electron transfer from UV-assisted photoexcited ZnO... 

Thin films of (WO3)1-x-(Fe2O 3)x composition were deposited by thermal evaporation on glass substrates and then all samples were annealed at 200-500 °C in air. Optical properties such as transmittance, reflectance, optical bangap energy, and the optical constants of the "as deposited" and the annealed films were studied using ultraviolet-visible spectrophotometry. It was shown that the annealing process changes the film optical properties which were related to Fe2O3 concentration. Moreover, using X-ray photoelectron spectroscopy, we have indicated that WO3 is stoichiometric, while iron oxide was in both FeO and Fe2O3 compositions so that the FeO composition converted to Fe2O3 after the... 

The Cd (3 wt%)-doped ZnTe nanoparticles with average size of 5 nm and band gap energy of 3.15 eV were synthesized by sol-gel method. The optical properties (such as band gap energy) and the size distribution of the nanoparticles have been investigated by using UV-Vis spectroscopy and transmission electron microscopy, respectively. Then, thermoluminescence property of the nanoparticles exposed to various doses of gamma radiation of Cs137 has been studied. The thermoluminescence glow peak of the nanoparticles showed a displacement from 290 to 230°C by increasing the dose of gamma radiation from 7.5 to 67.5 mSv. The thermoluminescence intensity of the synthesized Cd-doped ZnTe nanoparticles... 

Antibacterial activity of tungsten oxide nanorods/microrods were studied against Escherichia coli bacteria under visible light irradiation and in dark. A two-step annealing process at temperatures up to 390 °C and 400-800 °C was applied to synthesize the tungsten oxide nanorods/microrods on tungsten foils using KOH as a catalyst. Annealing the foils at 400 °C in the presence of catalyst resulted in formation of tungsten oxide nanorods (with diameters of 50-90 nm and crystalline phase of WO3) on surface of tungsten foils. By increasing the annealing temperature up to 800 °C, tungsten oxide microrods with K2W6O19 crystalline phase were formed on the foils. The WO3 nanorods showed a strong... 

The graphene-based materials with unique, versatile, and tunable properties have brought new opportunities for the leading edge of advanced nanobiotechnology. In this regard, the use of graphene in gene delivery applications is still at early stages. In this study, we successfully designed a new complex of carboxylated-graphene (G-COOH) with ethidium bromide (EtBr) and used it as a nanovector for efficient gene delivery into the AGS cells. G-COOH, with carboxyl functions on its surface, in the presence of EtBr, formaldehyde, and cyclohexylisocyanide were participated in Ugi four component reaction to fabricate a stable amphiphilic graphene-EtBr (AG-EtBr) composite. The coupling reaction was... 

Graphene-based materials are revealing the leading edge of advanced technology for their exceptional physical and chemical properties. Chemical manipulation on graphene surface to tailor its unique properties and modify atomic structures is being actively pursued. Therefore, the discovery of robust and general protocols to anchor active functionality on graphene basal plane is still of great interest. Multicomponent reactions promise an enormous level of interest due to addressing both diversity and complexity in combinatorial synthesis, in which more than two starting compounds react to form a product derived from entire inputs. In this article, we present the first covalent... 

Spontaneous generation of nanobubbles (NBs) was developed by using a controllable platform of superfast microvortices, based on turbulent jet flows in the presence of graphene oxide (GO) sheets. Very high energy dissipation rates through discharging warm water into cold N2 aqueous solutions resulted in creation of micro/submicro-vortices. Shear stresses in these domains generated gas local supersaturations, leading to the formation of high concentration (∼109 mL−1) of stable NBs. Introducing GO sheets into the microvortex system resulted in effective manipulation of NBs by providing energetically favorable sites for prompt heterogeneous nucleation as well as stronger shear rate fluctuations....