Synthesis and characterization of nickel sulfide nanoparticles via cyclic microwave radiation

In current study, nanoparticles of NiS were synthesized by applying microwave radiation. The effect of concentration of sulfur source, reaction time, and power of microwave irradiation on the treatment process was investigated. The morphology, structure, and composition of the as-synthesized nanostructures have been confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Optical properties of as-prepared sample were investigated by photoluminescence spectroscopy; the emission peak is at 555.04 nm and shows the blue shift.     

Formation of vesicular structures by a mono-tethered polyhedral oligomeric silsesquioxane amphiphilic diacid derivative in a solvent mixture

Polyhedral oligomeric silsesquioxane (POSS) molecules contain a silicon/oxygen nano-size cage substituted with organic groups. 2-(Propylcarbamoyl)terephthalic acid heptaisobutyl polyhedral oligomeric silsesquioxane (POSS DCA) is a novel mono-tethered POSS compound which is not commercially available yet and can be regarded as a single-tail surfactant. In contrast to theoretically possible micellization of amphiphilic POSS compounds very rare interest is paid by scientific community to this issue. POSS DCA vesiculation occurred at a very low concentration (0.09 mM) in a mixture of acetone, ethanol and 1-propanol according to the experiments. Critical packing parameter of POSS DCA is bigger than one and it must self-assemble into inverted-micelle morphology in a non-polar solvent. The vesicle formation for POSS DCA in a relatively polar solvent system was mainly attributed to formation of stable various-size intermolecular bridges of ethanol or 1-propanol. Also, π–π interaction between aromatic rings is another driving force. Vesicles can trap both hydrophilic and hydrophobic solvents and change composition of a solvent mixture. For the first time, we studied this property for POSS DCA vesicles in different concentrations by a gas chromatographic method. Significant increase in surface tension was attributed to the changes in solvent system composition due to vesicle formation and variation in vesicles morphology.     

Physical and mechanical properties of graphene oxide/polyethersulfone nanocomposites

The aim of this study was to investigate physical and mechanical properties of graphene oxide (GO)/polyethersulfone (PES) nanocomposite films. The films were produced by solution casting method. The mechanical properties of composite films were evaluated by tensile test. A significant enhancement in the mechanical properties of neat PES films was obtained incorporating a small amount of GO loading (0.05–1 wt.%). The highest tensile strength was observed at 1 wt.% of GO. Comparisons were made between experimental data and the Halpin–Tsai model predictions for the tensile strength and modulus of GO/PES composites. The effect of an orientation factor on model predictions was also acquired. The hydrophilicity of the nanocomposite was evaluated by assessing contact angle and enhanced wet ability of the films was obtained with increasing the amount of GO up to 1%. The morphology of the nanocomposites was investigated using scanning electron microscopy and transmission electron microscopy and the results revealed a good dispersion of GO in the PES matrix. The thermal behavior of the composite was also studied. Thermal stability of composites was increased by adding the GO. Copyright © 2013 John Wiley & Sons, Ltd.     

Antimicrobial Activity and Physical Characterization of Silver Nanoparticles Green Synthesized Using Nitrate Reductase from Fusarium oxysporum

Nanostructures from natural sources have received major attention due to wide array of biological activities and less toxicity for humans, animals, and the environment. In the present study, silver nanoparticles were successfully synthesized using a fungal nitrate reductase, and their biological activity was assessed against human pathogenic fungi and bacteria. The enzyme was isolated from Fusarium oxysporum IRAN 31C after culturing on malt extract-glucose-yeast extract-peptone (MGYP) medium. The enzyme was purified by a combination of ultrafiltration and ion exchange chromatography on DEAE Sephadex and its molecular weight was estimated by gel filtration on Sephacryl S-300. The purified enzyme had a maximum yield of 50.84 % with a final purification of 70 folds. With a molecular weight of 214 KDa, it is composed of three subunits of 125, 60, and 25 KDa. The purified enzyme was successfully used for synthesis of silver nanoparticles in a way dependent upon NADPH using gelatin as a capping agent. The synthesized silver nanoparticles were characterized by X-ray diffraction, dynamic light scattering spectroscopy, and transmission and scanning electron microscopy. These stable nonaggregating nanoparticles were spherical in shape with an average size of 50 nm and a zeta potential of ?34.3. Evaluation of the antimicrobial effects of synthesized nanoparticles by disk diffusion method showed strong growth inhibitory activity against all tested human pathogenic fungi and bacteria as evident from inhibition zones that ranged from 14 to 25 mm. Successful green synthesis of biologically active silver nanoparticles by a nitrate reductase from F. oxysporum in the present work not only reduces laborious downstream steps such as purification of nanoparticle from interfering cellular components, but also provides a constant source of safe biologically-active nanomaterials with potential application in agriculture and medicine.     

Cufe2O4 Nanoparticles: A Magnetically Retrievable Catalyst for Green Synthesis of Novel 2-(3-(Dicyanomethyl)-2-Oxoindolin-3-Ylthio)Acetic Acids

Abstract

A highly efficient and green method for the synthesis of new 2-(3-(dicyanomethyl)-2-oxoindolin-3-ylthio)acetic acids is described using magnetically recoverable and reusable CuFe₂O₄ nanoparticles. A wide variety of aryl isatylidene malononitrils underwent Micheal addition with thioacids to afford novel 2-(3-(dicyanomethyl)-2-oxoindolin-3-ylthio)acetic acids in good to excellent yields. The reaction protocol is operationally simple and mild. Moreover, water as solvent makes the reaction procedure eco-friendly and economically viable. All products were characterized by NMR and IR spectroscopies.     

Preparation,mechanical properties,and in vitro biocompatibility of novel nanocomposites based on polyhexamethylene carbonate fumarate and nanohydroxyapatite

In the current study a new biodegradable nanocomposite based on poly hexamethylene carbonate fumarate (PHMCF) and nano‐sized hydroxyapatite (nano‐HA) has been developed. A silane coupling agent γ‐methacryloxypropyltrimethoxy silane, was used to achieve a good interfacial adhesion between nano‐HA and PHMCF matrix. PHMCF with different nano‐HA contents were characterized using dynamical mechanical thermal analysis (DMTA) and hardness test. The effect of frequency on storage modulus, glass transition temperature (T_g) and the damping were investigated. In vitro cytotoxicity and proliferation were performed using G292 cell lines by MTT assay. The addition of nano‐HA resulted in an increment on the storage modulus and decrement on the damping. Along with improvement in mechanical properties of composites, the addition of nano‐HA resulted in enhanced cell proliferation. Following these results, the newly developed nano‐PHMCF composite scaffold may be considered for bone tissue engineering applications. Copyright © 2009 John Wiley & Sons, Ltd.     

On the buckling behavior of connected carbon nanotubes with parallel longitudinal axes

The application of hetero-junction carbon nanotubes (CNTs) is increasing continuously due to their outstanding properties in nano-mechanical systems. Several investigations have been conducted to study the behavior of CNTs. In this paper, straight hetero-junctions and their constituent CNTs (armchair and zigzag) were simulated by a commercial finite element package. Then, the buckling behavior of CNTs was evaluated by comparing the critical buckling load of each straight hetero-junction and its constituent CNTs. Both obtained, i.e. analytical calculations and computational, results were compared. The investigations showed that, first, the behavior of homogeneous CNTs under cantilevered boundary conditions follows the assumption of the classical Euler equation. Second, the analytical solutions are in good agreement with the finite element simulation results. In addition, it was shown that the first critical buckling load of hetero-junctions lies within the value of the fundamental homogeneous CNT range. It was also concluded that the buckling load of straight hetero-junctions and their fundamental CNTs increases by increasing the chiral number of both armchair and zigzag CNTs. The current study provides a better insight towards the prediction of straight hetero-junction CNTs behavior.     

Fatty acids profiling of avocado seed and pulp using gas chromatography–mass spectrometry combined with multivariate chemometric techniques

In the present study, the profiling of 17 fatty acids (FAs) in avocado seed and pulp was investigated. The fatty acids were extracted with vortex-assisted extraction, methyl esterified and finally preconcentrated by dispersive liquid–liquid microextraction. The preconcentrated fatty acid methyl esters (FAMEs) were analyzed using gas chromatography–mass spectrometry (GC–MS) to obtain qualitative and quantitative information. The GC–MS data were analyzed using multivariate curve resolution-alternating least squares (MCR-ALS) method to overcome general chromatographic problems such as overlapped peaks, background interference and peak shifts. The calibration data were prepared using pure analytical information obtained by MCR-ALS. The linear dynamic ranges and regression coefficients (R ²) for FAMEs were in the range of 0.19–65 mg L^?1 and 0.990–0.999, respectively. The relative standard deviation (RSD%) for determination of FAs in avocado seed and pulp was 0.17–8.84 and 0.64–17.93, respectively. The main FAs in the avocado pulp were: oleic acid (74.25 g Kg^?1), linoleic acid (26.87 g Kg^?1), palmitic acid (26.02 g Kg^?1), palmitoleic acid (1.22 g Kg^?1) and stearic acid (0.05 g Kg^?1). And, the main FAs in the avocado seed were: linoleic acid (1.09 g Kg^?1), palmitic acid (0.47 g Kg^?1), oleic acid (0.33 g Kg^?1), linolenic acid (0.12 g Kg^?1), and palmitoleic acid (0.04 g Kg^?1).     

A three‐component,one‐pot synthesis of oxazinoquinolin‐3‐one derivatives

Oxazino[5,6‐f]quinolin‐3‐one derivatives have been synthesized in a one‐pot, and efficient process by condensation of 6‐quinolinol, aromatic aldehydes and urea under microwave‐assisted and thermal solvent‐free conditions.