سال:1395 | دوره: | شماره: |تعداد مقالات:10

Silver nanoparticles (AgNPs) are amongst the most investigated materials in nanotechnology in view of their unique physio-chemical features and and applications in restorative science. Their progressive usage in different fields of science and some predominant restrictions with conventional methods for their synthesis have demanded analysts to discover green courses for their creation. Biological methods are the preferred to combat with the issues concerned with the nanoparticle synthesis. Within this decade, thousands of plants have been screened to analyze the final impact on characterization and morphology of AgNPs compared to general modes of their synthesis. Phytosynthetic method is an eco-friendly route that can lead to an advanced production of silver nanoparticles with controlled morphology. We herein reviewed the present aspects of phytosynthesis of AgNPs and their importance in modern science. Moreover, overviews of proposed mechanisms in this technology have also been included, which ultimately provide some insights of their safe use and demand for further research.

Carbon nanotubes (CNTs) are a novel material that exhibits good adsorption behavior toward various toxic pollutants in aqueous solution. These adsorbents have a fast adsorption rate and high adsorption efficiency, efficient to remove various pollutants and they are easy to recover and reuse. These features highlight the suitability of CNTs for the treatment of water polluted with heavy metal ions and dyes. This review outlines the preparation of CNTs as well as different methods of surface modification of these materials by non-covalent and covalent functionalization strategies. Additionally, an overview of recent developments and applications of CNTs for heavy metal ions and dyes pollutant removal is discussed in detail. Based on current research and existing materials, some new and futuristic approaches in this fascinating area are also discussed. The main objective of this review is to provide up-to-date information about the most important features of CNTs and to show their advantages as adsorbents in the treatment of polluted aqueous solutions.

Molecular sieves MCM-41 were synthesized from rice husk ash (RHA) as alternative sources of silica. e material was synthesized by a room temperature method from a gel with the molar composition SiO2: 1.6 EA: 0.215HDTMABr: 325H2O with pH correction. The cetyltrimethylammonium bromide (CTMABr) was used as a structure template. Nanocomposite containing 5.0 and 10.0 wt.% of Cu was synthesized under solid state reaction. the calcinations of samples were done at two different temperatures, 400 and 600°C. The morphology and the physicochemical properties of the prepared samples were investigated by X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). TEM images indicated that nanoparticles size of CuO is ~3 nm.

New two nano- sized Schiff base complexes [M (L)], where L=2, 2' - ((1E, 1E') - (1, 2 phenylen bis (azanylylidene)) bis (methanylylidene)) bis (4-bromo phenolato) and M=Cu or Zn, (a, b complexes) were synthesized by ultrasonic irradiation. These complexes were characterized by elemental analysis, molar conductivity, FT-IR, fluorescence emission, 1H NMR, field emission scanning electron spectroscopy (FESEM) and UV-Vis spectroscopy. The UV-Vis spectroscopic data and fluorescence emission bands of these nano-sized Schiff base complexes show a shift in comparison with the bulk sample analogue, due to the reduction in particle size to nano scale. In vitro antimicrobial activities of the title compounds against some Gram-positive (Staphylococcus aureus, Micrococcus luteus, Bacillus cereus, Eterococcus faecalis) and Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Klebsiella sp, Pscudomonas sp) and fungus strain (Candida albicans) were investigated and compared with each other. It was found that Cu (II) complex showed higher antibacterial activity than the Zn (II) complex.

In present study, it has been reported the biological synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract prepared using hot percolation treatment of wheat varieties (PBW343, Triticum durum and Aegilops tauschii) for the reduction of silver ions to silver nanoparticles. Bioreduction of Ag+ to Ag0 was observed when an aqueous extract of wheat leaves augmented with silver nitrate (AgNO3) was incubated for 2 hours at 100o C. The formation of silver nanoparticles was con rmed by surface plasmon resonance as determined by UV-Vis spectra at 430 nm. Silver nanoparticles of size ranging from 5-14 nm of spherical shape were characterized using transmission electron microscopy (TEM). These nanoparticles were found to possess potential antibacterial activity against (Escherichia coli, Staphylococcus aureus, Klebsiella) using disc diffusion method and macro dilution (tube) broth method. This environmental friendly method provides a simple, easy, fast and cost effective method for nanoparticles synthesis and can be used in several areas of medicines and industries.

In this study, Graphene Oxide- Gold nanoparticles (GO-AuNPs) nanocomposite as novel adsorbent was synthesized by direct reaction between GO and chloroauric acid for removal of amoxicillin from aqueous solution.Nanocomposite (GO-AuNPs) was characteristic by FT-IR spectroscopy. The changes of parameters such as contact time, pH of solution, initial amoxicillin concentration and temperature were measured and investigated by several adsorption experiments various factors affecting the uptake behavior. The adsorption kinetics well described by a pseudo-secondorder rate model.

In this work, the synthesis of porous structure of cadmium oxide with multilayered sheet-like morphology in nano-meter size using adipic acid as soft template by solvothermal/thermal decomposition process is reported.Chemical analyses exhibited that the formation of porous sheet-like structure is originated from bidentate coordination mode of adipate units to Cd-center. It was found that the change of reaction conditions can vary final morphology of product due to the different coordination modes of adipate units. The structural and morphological characterizations of product were discussed in detail. Brunauer-Emmett-Teller (BET) analysis indicated a specific surface area of 52.08 m2g-1with pore size distribution centered at 11.7 nm for prepared CdO sheet-like nanostructure. The capability of the as prepared product for adsorption of dye pollutants from aqueous solution was also studied. The results showed a maximum adsorption capacity (qmax) of 500 mg g-1 for adsorption of Congo Red (CR) dye in water revealing a superior ability of this product for adsorption of dye pollutants.

In this project, a nano catalyst (TiO2) and ozone combined with each other and they were used for the removal of 4-nitrophenol (4NP) in industerial wastewater. The effect of some operational parameters such as initial pH (3-9), the concentration of pollutant (20-80 mg/L), and amount of TiO2 were investigated. In O3/TiO2 process, the anion radical formed before the production of hydroxyl radical. These results were different from the Ozonation process alone, in which high pH had a positive effect on the degradation of 4NP, because hydroxyl radicals was formed.In ozonation and O3/TiO2 processes, about 89 and 97% of 4NP were degraded respectively, at optimum pH and 60 min of reaction. In catalytic ozonation the degradation rate of 4NP was higher at weak acidic pH conditions (pH=5). The removal of chemical oxygen demand (COD) was increased from 49% (only ozonation) to 74% (O3/TiO2) at 90 min of reaction. The kinetic of degradation was pseudo-first-order and degradation and mineralization of 4NP were estimated by HPLC and COD tests, respectively.

Composite solid propellants were prepared with and without nano-alloys (Ti-Co, Ti-Ni, Ti-Zn), where nano-alloys used as catalyst. These Nano-alloys are prepared by Hydrazine reduction method. Catalytic properties of these nanomaterials were measured on Ammonium perchorate / Hydroxyterminatedpolybutadiene propellant by Thermogravimetery analysis and Differential thermal analysis. Both experimental results show enhance in the thermal decomposition of propellants in presence of nano-alloys. In this Differential thermal analysis method experiments had done in 3 heating rate b1=5, b 2=10, b 3=15 degree on minute. Independent to model free, calculation of activation energy of high temperature decomposition step was done by using following Kissinger equation. Burning rate of propellants is also calculated.

An efficient, simple and convenient route is described for the synthesis of bis coumarin (3, 3' - (arylmethylene) bis (4-hydroxy-2 H -chromen-2-one)) by using recyclable catalyst TiO2@KSF. In this procedure, we synthesize abis coumarin derivative via the three multi-component reactions (3MCRs) of two equivalent 4-hydroxycoumarin with one equivalent of various aromatic aldehydes in the presence of 20 mg nano TiO2@KSF as homogeneous catalyst under solvent-free conditions at 100oC for the convinced reaction times (8–5 min). e advantages of this protocol towards the synthesis of bis coumarin derivatives are: a) use of solvent-free conditions, b) inexpensive catalyst, c) using commercially available precursors, d) reusability of TiO2@KSF up to four cycles without much loss in reactivity, e) simple work-up, f) high yields of pure products, g) short reaction times. The structure of all biscoumarin derivatives were confirmed by M.p., TLC, FT-IR, 1H NMR spectra and were compared with reliable references.