Scientia Iranica
Volume:27 Issue: 6, Nov-Dec 2020

Various plant extracts have been currently used for the bioproduction of nanoparticles that find enormous applications. Rauvolfia tetraphylla flower extracts were employed to obtain silver nanoparticles (Ag NPs) by bioproduction. The biologically produced nanoparticles were characterized by XRD, FTIR, UV-Vis, BET, SEM, EDAX and TEM analysis. The phytochemical screening of the Rauvolfia tetraphylla flower extracts indicated presence of nine different constituents. The bioreduction of Ag NPs by phytochemicals was revealed by FTIR analysis. The elemental composition of Ag NPs was reported by EDAX spectral analysis. The Ag NPs exhibited anti-bacterial activity against Pseudomonas aeruginosa, Staphylococus aureus, Klebsiella aerogenes and Escherichia coli, anti-fungal activity against Penicillium citrinum and Aspergillus flavus and anti-mitotic activity. The response of amines through formic acid within the sight of an Ag NPs catalyst in dissolvable free condition provides high yielded convention for the N-formylation to shape the comparing formamide derivatives. N-fromylation includes incite recyclability, clean strategy and naturally neighbourly under milder response conditions and straightforward work-up to brilliant yield of the coveted items.

Over the past decade preparation, characterization and modeling of nanofluids plentifully deliberated to improve the heat transfer effects. Hence to gratify the advancements this paper focuses on heat transfer effects of three distinct hybrid nanoparticles and with a base fluid (water). So this work numerically investigated the influence over a permeable flat surface with aligned magnetic field in the presence of suction or injection or impermeable together with the Marangoni convection of different hybrid nanofluids. The present results are validated with previous experimental and numerical results. The effect of solid volume fraction of hybrid nanoparticles, angle of inclination, magnetic parameter and wall mass transfer parameter are deliberated and offered through graphs together with the surface velocity and rate of heat transfer is presented in tabular form. It is found that the rate of heat transfer is increased with an increment of wall mass transfer parameter and an opposite effect of the rising of magnetic parameter. Among the three hybrid nanofluids water hybrid nanofluid has higher surface velocity, water hybrid nanofluid has higher temperature profile and water hybrid nanofluid has higher heat transfer rate.

This article addresses salient features of gyrotactic microorganism and activation energy in flow of nanofluid by rotating disk. An exponential space dependent heat source (ESHS) process is implemented to examine the thermal transport characteristics. Additionally nanoparticles mass flux condition is considered. The solutions are numerically computed. Impacts of various physical variables appearing in the solutions of non-linear systems are carefully analyzed. The current work identifies that temperature distribution of nanoliquid enhances for higher values of thermophoresis and Brownian motion variables. Moreover activation energy and temperature difference parameters diminish the nanoparticles concentration. Comparative study is provided in order to validate our outcomes.

Simultaneous impacts of non-linear radiation and magnetohydrodynamics in Marangoni convection nanoliquid are addressed Novel aspects of activation energy and space dependent heat source are addressed. Nanoliquid attributes Brownain movement and thermophoresis diffusion. NDSolve base shooting technique is employed for the numerical simulation. Aspects of various embedded variables are focused on velocity, heat and mass transport distributions via graphical interpretations. Moreover temperature gradient at the surface is estimated and analyzed. Our study identified that exponential based space heat source (ESHS) parameter significantly enhanced the thermal field. Activation energy and temperature difference parameters decrease the nanoparticles concentration. Moreover temperature gradient enhances for higher Marangoni ratio parameter, Hartmann number, dimensionless activation energy and thermophoresis parameter.

This study presents a new prediction model for estimating the size of AgNPs prepared by green synthesis via gene expression programming (GEP). Firstly, 30 different experiments were used to construct the GEP models. Plant extract, reaction temperature, concentration of AgNO3 and stirring time parameters were considered as input and the size of AgNPs parameter selected as output variables. By consideration of correlation coefficient (R2), mean absolute error (MAE), root relative square error (RRSE) as criteria, the performance of proposed models by GEP were compared each other. Finally, the best model (i.e., GEP-1) with R2=0.9961, MAE=0.2545 and RRSE=0.0668 proposed as a new model with simplified mathematical expressions to estimate the size of AgNPs. The results of sensitivity analysis showed that the amount of plant extract, the concentration of AgNO3, stirring time and reaction temperature are the most effective parameters on the size of AgNPs, respectively. Proposed model via gene expression is satisfactory and can be extended for a wide range of applications. Moreover, the proposed model provides the possibility of preparation of the minimum materials consumption for preparation of the lowest size of AgNPs by consideration of practical or economical constraints.

The physiological significance of determining glutathione (GSH) and its oxide form is obvious from their applications in clinical practices such as diagnostic experiments for diabetes, Parkinson’s disease, and cancers. Such an important detemination still needs the development of certain experimental procedures that are easy, fast, and cheap enough to implement. These procedural advantages can be provided through electrochemical methods. Therefore, in this study, at the surface of a glassy carbon electrode (GCE), a composite of functionalized multi-walled carbon nanotubes (MWCNTs) and formazon was used as a mediator to determine GSH electrochemically. The results indicated that this modified GCE is electrocatalytically very active for glutathione oxidation. Several techniques including cyclic voltammetry (CV), scanning electron microscopy (SEM), and differential pulse voltammetry (DPV) were used to characterize the electrode. Also, such kinetic parameters as the charge transfer rate constant and the transfer coefficient were calculated. In optimized conditions, there was a linear relationship between the DPV peak current of GSH oxidation and GSH concentration in the ranges of 1.0-100.0 and 100.0-800.0 µM at pH 7.0. As for the detection limit, it was found to be 0.73 µM.

This study is involved for an MHD rotating nanofluid flow over a stretching surface. The base fluid via water and kerosene liquids are employed with Barium Ferrite BaO.6〖Fe〗_2 O_(3 ) nanosize particles in our investigation and normally say to ferrofluid. Governing equations involving partial derivatives of the problem are established and converted into dimensionless forms of ordinary derivatives by means of suitable and compatible similarity transformations. Transformed system of equations is tackled by a reliable numerical scheme as midpoint integration pattern together with an extrapolation scheme of Richardson. This numerical pattern is launched in maple software. Variations in flow, velocity and temperature due to involving parameters are recorded via graphs and tables. Our targeted quantities like local tangential stress and heat transfer rate at the wall are calculated for nanofluid. Heat transfer rate at surface level z=0 rises with rise in solid nanoparticle φ but it falls with a rise in magnetic factor M, spin factor λ, and Eckert number Ec. The higher heat transfer rate is recorded in case of kerosene grounded Ferro fluid. Base fluid owns a vital role for determinations. We prefer water as a base fluid for significant outcomes.

Here consideration is given to the peristalsis of magneto- nanoparticles suspended in water. Explicitly water nanofluid is utilized for two-dimensional flow in a symmetric channel with complaint walls. Uniform magnetic field is applied. Temperature equation is arranged for viscous dissipation. Second order velocity and thermal slip conditions are utilized. Small Grashof number leads to perturbation solution. Examination of entropy generation is also carried out in this study. Maxwell and Hamilton-Crosser models are used. Analysis is based on the comparative study of these two models representing the cylindrical and spherical shaped particles. Graphs for velocity, temperature, entropy generation and Bejan numbers are plotted under the influence of sundry variables. Streamlines are also plotted for the sake of trapping phenomenon.

Color-transition features of polydiacetylene (PDA) have gained attention in recent years owing to its potential use in a wide range of sensors. This paper investigates electrospinning of PDA and polyvinylpyrolidone (PVP) to develop thermochromic nanofibrous composites. Polymer mixtures at different mass ratios and concentrations were electrospun and characterized afterwards. SEM results showed successful electrospinning of continuous and bead-free nanofibers with different diameters depending on the mass ratio of PVP to PDA. The obtained fibrous mats were then photo-polymerized under UV irradiation, which led to generation of a blue color showing the self-assembly of diacetylene monomers. The colorimetric transition of the fibers was also investigated and a color change from blue to red occurred by heating the fibers up to 80°C because of the conformational alterations in the PDA molecules. FTIR and DSC analysis validated these findings as well. As a result, the fabricated nanofibrous composites are potentially appropriate candidates for sensing applications.

This work gives an account of unsteady and steady radiating magnetohydrodynamics (MHD) nanofluid flow over a slippery stretching sheet embedded in a porous medium. A widely used similarity variables of such flows reduces a governing partial differential equations (PDEs) into a new set of partial differential equations (PDEs) in which a dependent variable is a function of two independent variables rather than three. At the same time, third order PDEs are converted into a second order PDEs by defining a new variable wherever it is deemed necessary. For the time integration, we perform first order explicit Euler method and spatial derivatives are approximated by the finite difference formulas in the context of node-centered finite volume method. It is revealed that for the unsteady flow the temperature of the nanofluid is higher near the surface without thermophoresis parameter Nt and reduced significantly when Nt is present. We also show that the concentration boundary layer thickness decreases with an increase of Darcy number Da.