فهرست مطالب

  • Volume:15 Issue:2, 2019
  • تاریخ انتشار: 1398/02/11
  • تعداد عناوین: 6
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  • A. A. Dudhane, S. R. Waghmode *, L. B. Dama, V. P. Mhaindarkar, A. Sonawane, S. Katariya Pages 75-82
    The use of plant extracts for nanoparticles synthesis are green, economical and cost effective approach.  The present study reports the bio-synthesis of gold nanoparticles (Au NPs) using leaf extract of Terminalia arjuna. After exposing the gold ions to aqueous solution of leaf extract, rapid reduction of gold ions into gold nanoparticles is observed within few minutes. The characterization of biosynthesized Au NPs were carried out by ultraviolet-visible spectroscopy (UV-Vis), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) techniques. UV-visible spectrum of the aqueous medium containing gold nanoparticles showed a peak of 530 nm. TEM analysis was performed to examine the size and shape of the biosynthesized gold nanoparticles. TEM analysis indicated that gold nanoparticles were well dispersed and ranged between 15 to 30 nm in size. Antibacterial activity of the biosynthesized Au NPs was studied against common human pathogens such as Staphylococcus aureus (NCIM 5021), Pseudomonas aeruginosa (NCIM 5029), and Salmonella typhimurium (NCIM 2501) by agar well diffusion method. This method exploits the economical and greener approach for the synthesis of metallic nanoparticles.
    Keywords: Terminalia arjuna, Au NPs, TEM, Antibacterial activity, Green synthesis.‎
  • T. Gangaiah *, N. Saidulu, A. Venkata Lakshmi Pages 83-98
    The present article describes the effects of thermal radiation and heat source/sink parameters on the mixed convective magnetohydrodynamic flow of a Casson nanofluid with zero normal flux of nanoparticles over an exponentially stretching sheet along with convective boundary condition. The governing nonlinear system of partial differential equations along with boundary conditions for this fluid flow converted to a system of nonlinear ordinary differential equations by using appropriate similarity transformations. The converted system of equations were solved numerically by using Runge-Kutta fourth order method with shooting technique. The influence of various non-dimensional governing parameters on velocity, temperature and nanoparticle volume fraction profiles have been discussed and presented graphically. Furthermore, the impacts of these parameters on skin friction coefficient and local Nusselt number are exhibited graphically and analized. It found that the velocity profiles and skin friction coefficient increases with an increase in the mixed convection parameter whereas, an opposite trend observed with Casson fluid parameter and magnetic field parameter. The thermal boundary layer thickness enhanced with an increase in Biot number, magnetic field parameter, radiation parameter and heat source/sink parameter. Also, the local Nusselt number decreases with an increase in radiation parameter and heat source/sink parameter.
    Keywords: Thermal Radiation, Heat source, sink, Mixed Convection, Casson nanofluid, Exponential stretching.‎
  • L. Omalanga *, S. Iyuke, B. Nkazi, P. Biyela Pages 99-115
    In this research, the classical phase inversion method was used to produce the polysulfone (PSF) membrane by using three different solvents: N, N-dimethylformamide (DMF), chloroform (CHCL3) and tetrahydrofuran (THF). Furthermore, different concentrations of functionalized multi – walled carbon nanotubes (MWCNTs) were added to PSF membranes by the classical phase inversion method. MWCNTs were synthesized using chemical vapour deposition (C.V.D) then functionalized by acid treatment. The morphology and the structure of the membrane and MWCNTs were characterized by using the scanning electron microscope (SEM) and transmission electron microscope (TEM). The characterization of the functionalization of the MWCNTs was performed by using the Raman spectroscopy. It was found that the chemical, physical and mechanical properties of the polymeric membrane improve with the content in functionalized MWCNTs concentration in the polymeric membrane matrix. The membrane with the MWCNTS concentration of 0.4% w/w showed the highest flux of 117 L/m^2.h and solute rejection. The selectivity and permeate flux of the polymeric membrane were increased with functionalized MWCNTs content for the membranes produced with the three different solvents.
    Keywords: Multi - walled carbon nanotubes, Organic solvents, Polysulfone membrane, Contact angle. ‎
  • N. Paseban, P. Ghadam *, P. S. Pourhosseini Pages 117-126
    Particles with the size of 1-100 nm are known as nanoparticles (NPs). The widespread use of silver NPs (AgNPs) makes it familiar in different industries. They have unique properties as a result of their high surface to volume ratio, although aggregation of NPs interferes with their functions. This phenomenon has several side effects on the environment, the amount of which may depend on the stability of AgNPs. Stability of colloids depends on various agents, such as capping agents and environmental conditions, including pH and ionic strength. In this study, the effects of a variety of electrolytes, such as NaCl (10mM), NaNO3 (10 and 100mM), andCa (NO3)2 (10mM)at different values of pH were investigated on the aggregation of AgNPs synthesized using an aqueous extract of dried Juglans regia green husk. In NaNO3 10mM pH 9, NPs were more stable than in other media. Therefore, the special optical and electronic properties of AgNPs in such a medium as well as in water were investigated. The UV-visible extinction spectra of AgNPs in both water and NaNO3 (10 mM, pH 9.0) showed a surface plasmon resonance (SPR) at 445 nm as well as a broad peak at shorter wavelengths (255 nm). The fluorescence emission spectra of AgNPs at different excitation wavelengths in the range of 245-290 nm revealed emission peaks that were red-shifted in the range of 487-580 nm by the increase in the excitation wavelength. This behavior is attributed to the existence of a variety of emission centers with different energy levels.
    Keywords: Aggregation, AgNPs, Fluorescence, Juglans regia green husk.‎
  • G. Utkan *, T. Ozturk, O. Duygulu, E. Tahtasakal, A. A. Denizci Pages 127-136
    Here, we report that the reduced graphene oxide nanosheets were successfully synthesized using the ‎Lactobacillus plantarum biomass in a simple, environmentally friendly and scalable manner. We ‎produced graphene oxide by oxidization and exfoliation of graphite flakes with modified Hummer's ‎method and then reduced to reduced graphene oxide by using Lactobacillus plantarum biomass as a ‎reducing agent. Samples were characterized using Fourier transform infrared spectroscopy, X-ray ‎photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, ‎microconfocal raman spectroscopy and thermogravimetric analysis. After the reduction, we observed ‎that a considerable decrease in the oxygen containing functional groups of graphene oxide and an ‎increase in C/O ratio from 1.7 to 3.3 in which confirms sp2 graphitic carbons increase. Mainly, we ‎observed a significant decrease in epoxy and alkoxy functionalities. Furthermore, we determined an ‎exfoliation of graphene oxide to one or several (2-5) layers after the complete reduction. In addition to ‎reducing potential, Lactobacillus plantarum biomass also plays an important role as stabilizing agent; ‎here the reduced graphene oxide showed a good stability in water. The green synthesis reported in this ‎work is concerned with the production of high purity water-dispersible reduced graphene oxide using ‎Lactobacillus plantarum CCM 1904.‎
    Keywords: Graphene, microbial reduction, 2D material, Lactobacillus.‎
  • F. Mohamadpour * Pages 137-144
    This procedure has developed the use of TiO2 nanoparticles as an environmentally friendly and highly efficient heterogenous nanocatalyst for the eco-safe, facile and one-pot three-component Biginelli synthesis of biologically active corresponding 3,4-dihydropyrimidin-2-(1H)-one/thione derivatives under solvent-free conditions. This eco-friendly protocol provides high to excellent yields, short reaction times, clean reaction, simplicity and easy work up and mild conditions compared to the traditional method of synthesis. Furthermore, environment-friendly, readily available, low-cost and non-toxic nanocatalyst made this protocol economic and sustainable.
    Keywords: TiO2 Nanoparticles, 4-Dihydropyrimidin-2-(1H)-one, thione derivatives, High atom-economy, ‎Environment-friendly procedure, Solvent-free conditions.‎