Applied Nanoscience (v.4, #5)

In the present paper, we have examined the peristaltic flow of Williamson nanofluid in a curved channel comprising compliant walls. The governing equations of a Williamson fluid model with nanoparticles for curved channel are derived, including the effects of curvature and heat dissipation. The highly nonlinear, partial differential equations are simplified by using the wave frame transformation, long wave length and low Reynolds number assumptions. The reduced, nonlinear, coupled differential equations are solved analytically with the help of the homotopy perturbation method. The physical features of pertinent parameters have been discussed by plotting the graphs of velocity, temperature, concentration profile and stream functions.
Keywords: Peristaltic flow; Williamson fluid; Nanoparticles; Curved channel; Compliant walls; Homotopy perturbation method

The present study involves the development of nanobiosensor to determine toxicological behavior of Mitoxantrone (MTX). Mitoxantrone intercalates with DNA and produces MTX–DNA adduct, resulting in blockade of protein synthesis and excessive production of free radicals in the myocardium eventually leads to cardiac toxicity. Potentiometry was applied to develop an electroanalytical procedure for the determination of MTX and its interaction with DNA immobilized on the electrode surface modified with Silicon dioxide (SiO2) nanoparticles. The nanobiosensor immersed in MTX solution to monitor MTX–DNA interaction with respect to time and alters the resistance of the nanobiosensor. It was observed that MTX–DNA interaction is fast initially and as time elapses, the change in interaction gets slow due to formation of MTX–DNA adduct. Determination limit of the nanobiosensor is 100–10 ng/ml. This study suggests that the nanobiosensor allows real-time monitoring of the drug–DNA interaction changes by measuring the potential at sensor interface which can prove to be an important tool in drug discovery pipelines and molecular toxicology.
Keywords: Nanobiosensor; DNA; Mitoxantrone (MTX); MTX–DNA interaction; Silicon dioxide (SiO2)

Structural, optical and ferroelectric properties of V doped ZnO by Rahul Joshi; Parmod Kumar; Anurag Gaur; K. Asokan (531-536).
Present work reports the structural, optical and ferroelectric properties of vanadium doped ZnO samples synthesized via solid state reaction method. X-ray diffraction (XRD) study confirms the presence of hexagonal wurtzite phase and the slight changes in lattice parameters is observed after V doping in host ZnO and impurity oxide of ZnV2O6. Presence of E1 and E2 modes in Raman spectroscopy of V doped ZnO indicates the stability of the wurtzite structure of ZnO, which is consistent with the XRD results. UV–Vis spectroscopy results show decrease in band gap of ZnO from 3.35 to 3.24 eV for 1 % V doped sample, whereas it increases with the V doping and increase in the impurity of ZnV2O6. Furthermore, it is observed that the ferroelectric polarisation of ZnO improves by V doping. Above results show that one need to consider the presence of ZnO in composite form of oxides of Zn and V and not as a pure V doped ZnO system.
Keywords: Zinc oxide; Raman spectroscopy; Ferroelectricity and hysteresis curve

It has been recently shown, that manufacturing of pn junctions by dopant diffusion or ion implantation in heterostructures and optimization of annealing time leads to increasing of their sharpness and homogeneity of dopant distribution in enriched area. In this paper, we consider influence of defects of doped structure (mismatch dislocations and similar), which became as drain of atoms of dopant, on dopant distribution in diffusive-junction rectifier.
Keywords: Diffusion-heterojunction rectifier; Modeling of dopant diffusion; Accounting drain of dopant; Optimization of annealing of dopant

Incorporation of multi-walled carbon nanotubes in microspheres used as anion exchange resin via suspension polymerization by Mahmoud Fathy; Th. Abdel Moghny; Ahmed E. Awadallah; Abdel-Hameed A.-A. El-Bellihi (543-549).
Amination of vinylbenzyl chloride-divinylbenzene (VBC-DVB) copolymers is an effective method for preparation of anion-exchange resins. Conventionally, the starting polymer is produced by chloromethylation of a styrene–divinylbenzene copolymer that utilizes chloromethyl methyl ether, a known carcinogen. An alterative approach is to copolymerize vinylbenzyl chloride with divinylbenzene to generate the necessary VBC-DVB. This method provides precise control over the density of the ion-exchange groups. The regiochemistry of the vinylbenzyl chloride methods was realized using solvent-ion exchange groups. These resulting anion-exchange polymers were characterized by a variety of techniques such as analytical titrations, transform infrared spectroscopy and thermal gravimetric analysis. Testing of these copolymers for breakthrough was performed. The results indicate that these anion exchangers have a meaningful increase in thermal stability over commercial anionic exchange beads. Resins containing MWCNTs achieved anion exchange capacity value of 323.6 meq/100 g over than that of copolymer resins and that useful in water desalination or treatment.
Keywords: Grafting; CNTs; Oxidized; Carbon nanotubes; Suspension polymerization; Resin

One-step pyrolysis was applied to synthesize mesoporous charred carbon from used cigarette filters. Proximate analysis suggested that cigarette filters are decent carbon precursors due to their moderate carbon (around 11 %) and low ash (around 0.1 %) contents. To investigate the effects of pyrolysis parameters on porous surface area, a full factorial design of experiment including heating rate, soaking time and pyrolysis temperature was used with each factor at three levels. The analysis of variance revealed that the temperature and heating rate had the most significant effects on total surface area of the synthesized carbon. Response surface model (RSM) was applied to best fit a surface through the experimental data. It was seen that the quadratic RSM model with a reasonable R2 value of 63 % was the best developed model. The maximum BET surface area (597 m2/g) was reached at a pyrolysis temperature of 900 °C when the precursor was heated at 5 °C/min and hold at this temperature for 3 h. The produced N2 adsorption–desorption isotherm showed a certain degree of mesoporosity in the charred carbon with an average pore size of 3.32 nm calculated by Barrett–Joyner–Halenda method. Scanning electron microscopy also showed the presence of macroporosity on the charred carbon surface. Fourier transform infrared spectroscopy revealed the presence of acidic surface functional groups such as carboxyl and phenol which were accordingly confirmed by Boehm titration. In addition, Boehm titration showed that the produced carbon’s surface was more acidic than basic in nature.
Keywords: Pyrolysis; Mesoporous charred carbon; Response surface method

Recently, biosynthesis of nanoparticles has attracted scientists’ attention because of the necessity to develop new clean, cost-effective and efficient synthesis techniques. In particular, metal oxide nanoparticles are receiving increasing attention in a large variety of applications. However, up to now, the reports on the biopreparation and characterization of nanocrystalline copper oxide are relatively few compared to some other metal oxides. In this paper, we report for the first time the use of brown alga (Bifurcaria bifurcata) in the biosynthesis of copper oxide nanoparticles of dimensions 5–45 nm. The synthesized nanomaterial is characterized by UV–visible absorption spectroscopy and Fourier transform infrared spectrum analysis. X-ray diffraction confirms the formation and the crystalline nature of copper oxide nanomaterial. Further, these nanoparticles were found to exhibit high antibacterial activity against two different strains of bacteria Enterobacter aerogenes (Gram negative) and Staphylococcus aureus (Gram positive).
Keywords: Green synthesis; Copper oxide nanoparticles; Brown alga; Antimicrobial activity

Interfacing carbon nanotubes (CNT) with plants: enhancement of growth, water and ionic nutrient uptake in maize (Zea mays) and implications for nanoagriculture by D. K. Tiwari; N. Dasgupta-Schubert; L. M. Villaseñor Cendejas; J. Villegas; L. Carreto Montoya; S. E. Borjas García (577-591).
The application of nano-biotechnology to crop-science/agriculture (‘nanoagriculture’) is a recent development. While carbon nanotubes (CNTs) have been shown to dramatically improve germination of some comestible plants, deficiencies in consistency of behavior and reproducibility arise, partially from the variability of the CNTs used. In this work, factory-synthesized multi-walled-CNTs (MWCNTs) of quality-controlled specifications were seen to enhance the germinative growth of maize seedlings at low concentrations but depress it at higher concentrations. Growth enhancement principally arose through improved water delivery by the MWCNT. Polarized EDXRF spectrometry showed that MWCNTs affect mineral nutrient supply to the seedling through the action of the mutually opposing forces of inflow with water and retention in the medium by the ion-CNT transient-dipole interaction. The effect varied with ion type and MWCNT concentration. The differences of the Fe tissue concentrations when relatively high equimolar Fe2+ or Fe3+ was introduced, implied that the ion-CNT interaction might induce redox changes to the ion. The tissue Ca2+ concentration manifested as the antipode of the Fe2+ concentration indicating a possible cationic exchange in the cell wall matrix. SEM images showed that MWCNTs perforated the black-layer seed-coat that could explain the enhanced water delivery. The absence of perforations with the introduction of FeCl2/FeCl3 reinforces the idea of the modification of MWCNT functionality by the ion-CNT interaction. Overall, in normal media, low dose MWCNTs were seen to be beneficial, improving water absorption, plant biomass and the concentrations of the essential Ca, Fe nutrients, opening a potential for possible future commercial agricultural applications.
Keywords: MWCNT; Maize; Germination; Ion; Nano-biotechnology; Nanoagriculture

The structure, binding energy, magnetic moments, and electronic structure of Fe m Ir n (2 ≤ m + n ≤ 4) nano clusters are investigated using first principles density functional theory techniques. Fully unconstrained structural relaxations are undertaken by considering all possible non-equivalent cluster structures. The optimized clusters are all compact, indicating a clear tendency to maximize the number of nearest neighbor Fe–Ir pairs. The binding energy shows an increment with cluster size. All the clusters preserve ferromagnetic order after optimization and the average magnetic moment shows a general increment with Fe concentration. An enhancement of the local Fe moments in Ir-rich environment is observed, while that of Ir is minimal. The highest occupied molecular orbital–lowest unoccupied molecular orbital energy gaps show a general reduction with alloying, indicating more metallicity for the doped clusters than the pure ones.
Keywords: Fe m Ir n (2 ≤ m + n ≤ 4) nano clusters; Binding energy; Bond length; Magnetic moments; HOMO–LUMO; Ab initio calculations

Strengthening of semicoke based carbon composites through multi-wall carbon nanotubes by Rajeev Kumar; Sanjay R. Dhakate; R. B. Mathur (601-611).
The present investigation explored the possibility of developing carbon composites using semicoke as matrix precursor and multi-walled carbon nanotubes (MWCNTs) as reinforcement. The different weight fraction of MWCNTs was incorporated in semicoke-based composites, and these composites were heat treated at 1,000, 1,400 and 2,500 °C. The MWCNTs carbon composite was characterized for electrical, thermal and mechanical properties. It was observed that the bulk density of composites with 1 wt% of MWCNTs was 1.92 g/cc, whereas without nanotubes it was 1.87 g/cc. The bending strength of carbonized composites was increased by 78 % and that of graphitized ones by 69 % at 1 wt% of MWCNTs. This value of bending strength was three times higher than that of conventional graphite. The electrical and thermal conductivity increased by 12 and 33 %, respectively. The Raman spectroscopic studies showed that intensity ratio of D and G band (ID)/(IG) ratio minimum deflects the lower level of defects and higher degree of graphitization in carbon composites at 1 wt% of MWCNTs. This demonstrates that in case of MWCNTs, semicoke-based carbon composites with 1 wt% of MWCNTs were sufficient for strengthening carbon composites, if MWCNTs were well dispersed in semicoke.
Keywords: Coal tar pitch; Semi coke; MWCNTs; Electrical; Thermal and mechanical properties; Composite

The study of nanoparticles concentration for the Jeffrey fluid model is considered with the process of peristaltic waves in a three-dimensional rectangular channel. The main theme of the present study is to study the effect of lateral walls on nanoparticle phenomenon in peristalsis with non-Newtonian fluid model in a duct of rectangular cross-section. The flow is considered in a wave frame under the assumptions of long wavelength and low Reynolds number. The resulting three-dimensional nonlinear and coupled partial differential equations are then solved using homotopy perturbation technique. The physical features of lateral walls, mean volume flow rate, Jeffrey fluid parameter, the Brownian motion parameter, the thermophoresis parameter, local temperature Grashof number and local nanoparticle Grashof number are discussed simultaneously through presenting graphical discussion. Three-dimensional phenomenon is also investigated through graphs to see the variation of velocity profile with space coordinates. Trapping scheme is also manipulated with the help of streamlines for various pertinent parameters.
Keywords: Peristaltic flow; Jeffrey fluid; Nanoparticles; Rectangular duct; Homotopy perturbation method (HPM)

Numerical solution of non-Newtonian nanofluid flow over a stretching sheet by S. Nadeem; Rizwan Ul Haq; Z. H. Khan (625-631).
The steady flow of a Jeffrey fluid model in the presence of nano particles is studied. Similarity transformation is used to convert the governing partial differential equations to a set of coupled nonlinear ordinary differential equations which are solved numerically. Behavior of emerging parameters is presented graphically and discussed for velocity, temperature and nanoparticles fraction. Variation of the reduced Nusselt and Sherwood number against physical parameters is presented graphically. It was found that reduced Nusselt number is decreasing function and reduced Sherwood number is increasing function of Brownian parameter $$ N_{ ext{b}} $$ N b and thermophoresis parameter $$ N_{ ext{t}}$$ N t .
Keywords: Jeffrey fluid model; Nanofluid flow; Stretching sheet; Brownian motion; Thermophoresis; Numerical solution

Homogeneous flow model is used to study the flow and heat transfer of carbon nanotubes (CNTs) along a flat plate subjected to Navier slip and uniform heat flux boundary conditions. This is the first paper on the flow and heat transfer of CNTs along a flat plate. Two types of CNTs, namely, single- and multi-wall CNTs are used with water, kerosene or engine oil as base fluids. The empirical correlations are used for the thermophysical properties of CNTs in terms of the solid volume fraction of CNTs. For the effective thermal conductivity of CNTs, Xue (Phys B Condens Matter 368:302–307, 2005) model has been used and the results are compared with the existing theoretical models. The governing partial differential equations and boundary conditions are converted into a set of nonlinear ordinary differential equations using suitable similarity transformations. These equations are solved numerically using a very efficient finite difference method with shooting scheme. The effects of the governing parameters on the dimensionless velocity, temperature, skin friction, and Nusselt numbers are investigated and presented in graphical and tabular forms. The numerical results of skin friction and Nusselt numbers are compared with the available data for special cases and are found in good agreement.
Keywords: Carbon nanotubes; Flat plate; Navier slip boundary; Shooting method; Nanofluids; Effective thermal conductivity

Physical properties of α-Fe2O3 nanoparticles fabricated by modified hydrolysis technique by Muhammad Waseem; Sajida Munsif; Umer Rashid; Imad-ud-Din (643-648).
We have tested modified hydrolysis method for the preparation of α-Fe2O3 nanoparticles. The particles after synthesis were applied for a series of physicochemical techniques. Iron chloride was used as a precursor material. The particle size distribution was determined using zeta sizer and scanning electron microscopy. The surface area and the morphology of the particles vary by changing the concentration of the precursor material. The size of nanoparticles varies from 10 to 90 nm. The particles having size of 23 ± 1 nm were separated out from the solution and their size remains almost the same even after one month. Energy dispersive X-ray analysis (EDX) of Fe2O3 nanoparticles confirms the purity of the desired material. The weight loss of the particles with respect to the temperature was studied by thermogravimetric and differential thermogravimetric (TG/DTG) analysis. X-ray diffraction (XRD) has been employed to study the crystallinity of the particles.
Keywords: Characterization; DLS studies; Hydrolysis method; Iron oxide nanoparticles