Sharif Digital Repository

We have synthesized ZnxCd1-xS nanocrystals (NCs) using a microwave assisted method. Zn(Ac)2, CdSO4 and Na2S2O3 were used as the precursors and thioglycerol (TG) was used as the capping agent. Na2S 2O3 is a photo and heat sensitive material, which supplies S species needed for the reaction upon dissociation. In this facile method, microwave irradiation provides the activation energy for the dissociation of Na2S2O3 in and leads to the formation of ZnxCd1-xS NCs in 2 min. The question that to what extent Zn is incorporated into CdS structure was addressed using UV-Vis spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Our results showed that the real value of x in... 

Iranian olive leaf essential oil components were extracted by microwave-assisted hydrodistillation and analyzed using gas chromatography-mass spectrometry. Ninety-seven components were identified by direct similarity searches for olive leaf essential oil. Chemometrics was used to find more components with the help of multivariate curve resolution methods. Eigenvalues-based methods and Malinowski functions were used for chemical rank determination of GC-MS data. Multivariate curve resolution-alternative least squares as an iterative method was used for resolving the overlapped and embedded peaks. With the use of this method the number of 97 components was extended to 127 components. Major... 

In the present study, SiC samples with 3, 5, 7.5 and 10 wt% Al2O3–Y2O3 as additives were made by powder metallurgy method, then sintering was performed by microwave-assisted process. β–SiC samples sintering was performed for 100 min. The highest sintered relative density 91.06% was achieved at 10 wt% additives content. The maximum values of hardness and toughness were up to 23.3 GPa and 6.14 MPa.m− 1/2. α–SiC and α–SiC/β–SiC samples sintering was performed for 120 min. The maximum value of density and hardness were up to 96.38% T.D and 24.88 GPa in α–SiC with 7.5 wt% additives, whereas the highest toughness was achieved at 10 wt% additives content in β–SiC samples. The α–SiC samples... 

ZnFe2O4 nanoparticles have been successfully prepared through a controlled microwave-assisted co-precipitation. X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometer (VSM) were used for the structural, morphological and magnetic investigation of the product. SEM micrographs of ZnFe2O4 nanopowder also reveal that nanoparticles have spherical shape. Average particle size was obtained as 12 nm from XRD. Catalytic activity of ZnFe2O4 nanopowder for O-acylation of alcohol and phenol has been investigated. A trace amount of ZnFe2O4 has been effectively used as a nanocatalyst for the acylation of alcohol and... 

Through a fast, simple, low cost, surfactant-free and convenient microwave-assisted route, narcis-like ZnO nanostructures (10-15 nm size) with flower diameters in the range of 1-2.5 μm were synthesized. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and room temperature photoluminescence (PL) measurements were used to characterize the produced ZnO nanostructures. The principle raw materials - ammonium hydroxide (NH4OH) and zinc acetate dihydrate [Zn(CH3COO)2·2H2O] - were both inexpensive. The method was fast, simple and surfactant-free capable of producing larger quantities of zinc oxide... 

Flexibility and human-body compatibility have been emerged through the use of commercial fabrics (CFs) in designing wearable non-enzymatic glucose sensing platforms. In this work, electrodes fabricated through direct synthesis of ternary nickel–cobalt sulfide nanostructures (Ni-Co-S NSs) on the CFs (Ni-Co-S@CFs) using a fast and facile one-step microwave-assisted method for this purpose. Fabrication was followed by the structural and electrochemical characterization of the electrodes. The glucose-sensing ability of the prepared wearable electrodes was investigated via cyclic voltammetry (CV) and amperometry techniques in alkaline media. Two linear-responses in wide detection ranges of... 

In the present paper, new H2S gasochromic nanomaterial of mixed silver nickel ammonium phosphomolybdate synthesized by microwave assisted technique is reported. The microwave treatment was performed in the solid phase using urea and ammonium nitrate as the promoter and oxidizer agents. The designed process allows rapid synthesis of large amounts of this product in nanosized particulate morphology. Morphological and structural features of the prepared products were studied in detail. Chemical analyses indicated a stoichiometry of (NH4)0.5Ni0.75AgPMo12O40·4H2O revealing a Keggin-type framework with substitution of silver and nickel cations in its secondary structure. A home-made set-up was... 

Alumina-MWCNT composite was densified by microwave sintering. CNTs were coated with boehmite nanoparticles to enhance their distribution in composite samples. Calcination temperature of composite powder was determined by TGA analysis (5 °C/min). Samples containing 0 and 1vol%CNT were produced by cold isostatic pressing at 180 MPa. Microwave sintering (1520 °C for 45 min) was conducted under the flow of argon. Phase analysis of the calcined composite powder showed complete transformation of boehmite into gamma-alumina. The relative densities were 99.3% and 98.1% for monolithic alumina and composite, respectively. CNT addition improved the fracture toughness of alumina by ~37%. SEM images... 

ZnO nanopowder has been successfully synthesized by a microwave-assisted solution approach using Zn(CH3CO2)2·2H2O and NaOH. The results obtained from X-ray diffraction (XRD), scanning electron microscopy (SEM) and transition electron microscope (TEM) show that the mean particle size is 30 nm. SEM and TEM micrographs of ZnO nanopowder also reveal that nanoparticles have spherical shape. Catalytic activity of ZnO nanopowder for O-acylation of alcohol and phenol has been investigated. The results show that the reaction time by using ZnO nanopowder has been reduced by almost 24 times with higher yield than ZnO bulk. © 2007  

In this paper, the rapid synthesis of nanostructured NiTi–Ni3Ti intermetallic alloy from titanium and nickel powders through mechanical alloying followed by microwave-assisted sintering process was investigated. The sintered samples at different temperatures exhibited major phases of NiTi– B2 and Ni3Ti, and minor phases of NiTi–B19′ and Ti2Ni. The density, porosity and microhardness of the sample varied based on the sintering temperature, in which the highest density and microhardness (~750 H V) were obtained at sintering temperature of 1100 °C. Based on the results of this research, the microwave-assisted sintering can be applied to fabricate Ni–Ti alloys with improved mechanical properties... 

In this paper, the rapid synthesis of nanostructured NiTi–Ni3Ti intermetallic alloy from titanium and nickel powders through mechanical alloying followed by microwave-assisted sintering process was investigated. The sintered samples at different temperatures exhibited major phases of NiTi– B2 and Ni3Ti, and minor phases of NiTi–B19′ and Ti2Ni. The density, porosity and microhardness of the sample varied based on the sintering temperature, in which the highest density and microhardness (~750 H V) were obtained at sintering temperature of 1100 °C. Based on the results of this research, the microwave-assisted sintering can be applied to fabricate Ni–Ti alloys with improved mechanical properties... 

In this study, two different chemical solution methods were used to synthesize Zinc oxide nanostructures via a simple and fast microwave assisted method. Afterwards, the photocatalytic performances of the produced ZnO powders were investigated using methylene blue (MB) photodegradation with UV lamp irradiation. The obtained ZnO nanostructures showed spherical and flower-like morphologies. The average crystallite size of the flower-like and spherical nanostructures were determined to be about 55 nm and 28 nm, respectively. X-ray diffraction (XRD), scanning electronic microscopy (SEM), Brunauer-Emmett-Teller (BET), room temperature photoluminescence (RT-PL) and UV-vis analysis were used for... 

ZnO nano-architectures were produced with the aid of a fast, simple and low cost microwave-assisted synthesis method. Solid semispherical ZnO nanoparticles on the order of 600 nm in diameter along with rice-like ZnO nanorods 95 nm thick were produced from butanol, triethanolamine (TEA), and zinc acetate dihydrate. Solid spherical ZnO nano-architectures with an average diameter of 250 nm were produced from the same starting materials in addition to NaOH. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the ZnO nano-architectures as well as the precursor. This method is cheap, fast and simple; capable of producing large quantities... 

BiOBrxCl1-x (0xCl1-x. The UV-visible diffuse reflectance and photoluminescence (PL) spectroscopies revealed the indirect band gap of ∼2.82 eV for the bismuth oxybromochloride nanoflakes. Visible light-assisted photocatalytic studies showed that the degradation efficiency of the as-prepared BiOBrxCl1-x for (100 mL of 10 mg L-1)... 

Introduction - Recently, there have been growing attention on the modification and optimisation of new extraction and quantification methods, caused by the lack of environmentally friendly methodologies for the extraction of phytochemicals from complex matrices. In the case of pharmaceutical compounds, not only the extraction procedure but also the analysis method should be efficient, precise, fast and easy.Objectives - The essential pharmaceutical characteristics and trace concentration of withanolides led us to modify and optimise the previously reported extraction and quantification procedure for withaferin A (WA) as a candidate for withanolides.Matrial and methods - The WA from the... 

A high-throughput micro-solid-phase extraction device based on a 96-well plate was constructed and applied to the determination of pesticide residues in various apple samples. Butyl methacrylate and ethylene glycol dimethacrylate were copolymerized as a monolithic polymer and placed in the cylindrically shaped stainless-steel meshes of 96-micro-solid-phase extraction device and used as an extracting unit. Before the micro-solid-phase extraction, microwave-assisted extraction was employed to facilitate the transfer of the pesticide residues from the apple matrix to liquid media. Then, 1 mL of the aquatic samples was transferred into the 96-well plate and the 96-micro-solid-phase extraction... 

Highly porous nanocomposites of graphitic-carbon nitride and tin oxide (g-C3N4/SnO2) were prepared through simple pyrolysis of urea molecules under microwave irradiation. The initial amount of tin was varied in order to investigate the effect of SnO2 content on preparation and properties of the composites. The synthesized nanocomposites were well-characterized by XRD, FE-SEM, HR-TEM, BET, FTIR, XPS, DRS, and PL. A homogeneous distribution of SnO2 nanoparticles with the size of less than 10 nm on the porous C3N4 sheets could be obtained, suggesting that in-situ synthesis of SnO2 nanoparticles was responsible for the formation of g-C3N4. The process likely occurred by the aid of the large... 

An efficient route for the synthesis of 3-substituted coumarins via Knoevenagel condensation, using ZrOCl2.8H2O (10 mol %) as the. catalyst under microwave heating and solvent-free conditions, is described. This procedure offers several advantages, including the low loading of catalysts, high yields, clean reactions, short reaction times and the. use of various substrates, which make it a useful and attractive strategy for the. synthesis of 3-substituted coumarins. © Sharif University of Technology, June 2009