Transport phenomena of carbon nanotubes and bioconvection nanoparticles on stagnation point flow in presence of induced magnetic field

This article is a numerical study of stagnation point flow of carbon nanotubes over an elongating sheet in presence of induced magnetic field submerged in bioconvection nanoparticles. Two types of carbon nanotubes are considered i.e. single wall carbon nanotube and multi wall carbon nanotube mixed in based fluid taken to be water as well as kerosene-oil. The emphasis of present study is to examine effect of induced magnetic field on boundary layer flows along with influence of SWCNT and MWCNT. Physical problem is mathematically modeled and simplified by using appropriate similarity transformations. Shooting method with Runge-Kutta of order 5 is employed to compute numerical results for non-dimensional velocity, induced magnetic field and temperature. The effects of pertinent parameters are portrayed through graphs. Numerical values of skinfriction coefficient and Nusselt number are tabulated to study the behaviors at the stretching surface. It is depicted that induced magnetic field is an increasing function of solid nanoparticles volumetric fraction. Moreover, MWCNT contributes in rising induced magnetic field more as compared to SWCNT for both water and kerosene-oil based fluids.     

How the dispersion of magnesium oxide nanoparticles effects on the viscosity of water-ethylene glycol mixture: Experimental evaluation and correlation development

In this paper, the effect of dispersion of magnesium oxide nanoparticles on viscosity of a mixture of water and ethylene glycol (50–50% vol.) was examined experimentally. Experiments were performed for various nanofluid samples at different temperatures and shear rates. Measurements revealed that the nanofluid samples with volume fractions of less than 1.5% had Newtonian behavior, while the sample with volume fraction of 3% showed non-Newtonian behavior. Results showed that the viscosity of nanofluids enhanced with increasing nanoparticles volume fraction and decreasing temperature. Results of sensitivity analysis revealed that the viscosity sensitivity of nanofluid samples to temperature at higher volume fractions is more than that of at lower volume fractions. Finally, because of the inability of the existing model to predict the viscosity of MgO/EG-water nanofluid, an experimental correlation has been proposed for predicting the viscosity of the nanofluid.     

Three-dimensional flow of Powell–Eyring nanofluid with heat and mass flux boundary conditions

This article investigates the three-dimensional flow of Powell–Eyring nanofluid with thermophoresis and Brownian motion effects. The energy equation is considered in the presence of thermal radiation. The heat and mass flux conditions are taken into account. Mathematical formulation is carried out through the boundary layer approach. The governing partial differential equations are transformed into the nonlinear ordinary differential equations through suitable variables. The resulting nonlinear ordinary differential equations have been solved for the series solutions. Effects of emerging physical parameters on the temperature and nanoparticles concentration are plotted and discussed. Numerical values of local Nusselt and Sherwood numbers are computed and examined.     

Enhanced transport of zerovalent iron nanoparticles in saturated porous media by guar gum

In order to ensure adequate mobility of zerovalent iron nanoparticles in natural aquifers, the use of a stabilizing agent is necessary. Polymers adsorbed on the nanoparticle surface will give rise to electrosteric stabilization and will decrease attachment to the surface soil grains. Water saturated sand-packed columns were used in this study to investigate the transport of iron nanoparticle suspensions, bare or modified with the green polymer guar gum. The suspensions were prepared at 154 mg/L particle concentration and 0.5 g/L polymer concentration. Transport experiments were conducted by varying the ionic strength, ionic composition, and approach velocity of the fluid. Nanoparticle deposition rates, attachment efficiencies, and travel distances were subsequently calculated based on the classical particle filtration theory. It was found that bare iron nanoparticles are basically immobile in sandy porous media. In contrast, guar gum is able to ensure significant nanoparticle transport at the tested conditions, regardless of the chemistry of the solution. Attachment efficiency values for guar gum-coated nanoparticles under the various conditions tested were smaller than 0.066. Although the calculated travel distances may not prove satisfactory for field application, the investigation attested the promising role of guar gum to ensure mobility of iron nanoparticles in the subsurface environment.     

Effect of the shell on the transport properties of poly(glycerol) and Poly(ethylene imine) nanoparticles

Dendritic core–shell architectures containing poly (glycerol) and poly (ethylene imine) cores and poly(lactide) shell (PG-PLA and PEI-PLA respectively) were synthesized. Analogous of these core–shell architectures containing the same cores but poly (L-lactide) shell (PG-PLLA and PEI-PLLA, respectively) were also synthesized. In this work PG and PEI were used as macroinitiator for ring opening polymerization of the lactid and L-lactide monomers. Different molar ratios of monomer to end functional groups of PG ([LA]/[OH]) and PEI ([LA]/[NHn] (n = 1 or 2)) were used to prepare the core–shell architectures with different shell thickness. These core–shell architectures were able to encapsulate and transport the small guest molecules. Their transport capacity (TC) depended on the type and thickness of the shells. TC of core–shell architectures containing PLLA shell was higher than that for their analogs containing PLA shell. The diameter of core–shell architectures was between 20–80 nm. The rate of release of guest molecules from chloroform solution of nanocarriers to water phase was investigated and it depended on the type of the core, shell and solvent.     

Peristaltic blood flow with gold nanoparticles as a third grade nanofluid in catheter: Application of cancer therapy

Cancer is dangerous and deadly to most of its patients. Recent studies have shown that gold nanoparticles can cure and overcome it, because these particles have a high atomic number which produce the heat and leads to treatment of malignancy tumors. A motivation of this article is to study the effect of heat transfer with the blood flow (non-Newtonian model) containing gold nanoparticles in a gap between two coaxial tubes, the outer tube has a sinusoidal wave traveling down its wall and the inner tube is rigid. The governing equations of third-grade fluid along with total mass, thermal energy and nanoparticles are simplified by using the assumption of long wavelength. Exact solutions have been evaluated for temperature distribution and nanoparticles concentration, while approximate analytical solutions are found for the velocity distribution using the regular perturbation method with a small third grade parameter. Influence of the physical parameters such as third grade parameter, Brownian motion parameter and thermophoresis parameter on the velocity profile, temperature distribution and nanoparticles concentration are considered. The results pointed to that the gold nanoparticles are effective for drug carrying and drug delivery systems because they control the velocity through the Brownian motion parameter $N_b$ and thermophoresis parameter $N_t$. Gold nanoparticles also increases the temperature distribution, making it able to destroy cancer cells.     

Ultrasound-induced emulsification of subcritical carbon dioxide/water with and without surfactant as a strategy for enhanced mass transport

Pulsed ultrasound was used to disperse a biphasic mixture of CO₂/H₂O in a 1 dm³ high-pressure reactor at 30 °C/80 bar. A view cell positioned in-line with the sonic vessel allowed observation of a turbid emulsion which lasted approximately 30 min after ceasing sonication. Within the ultrasound reactor, simultaneous CO₂-continuous and H₂O-continuous environments were identified. The hydrolysis of benzoyl chloride was employed to show that at similar power intensities, comparable initial rates (1.6 ± 0.3 × 10^–3 s^–1 at 95 W cm^–2) were obtained with those reported for a 87 cm³ reactor (1.8 ± 0.2 × 10^–3 s^–1 at 105 W cm^–2), demonstrating the conservation of the physical effects of ultrasound in high-pressure systems (emulsification induced by the action of acoustic forces near an interface). A comparison of benzoyl chloride hydrolysis rates and benzaldehyde mass transport relative to the non-sonicated, ‘silent’ cases confirmed that the application of ultrasound achieved reaction rates which were over 200 times faster, by reducing the mass transport resistance between CO₂ and H₂O. The versatility of the system was further demonstrated by ultrasound-induced hydrolysis in the presence of the polysorbate surfactant, Tween, which formed a more uniform CO₂/H₂O emulsion that significantly increased benzoyl chloride hydrolysis rates. Finally, pulse rate was employed as a means of slowing down the rate of hydrolysis, further illustrating how ultrasound can be used as a valuable tool for controlling reactions in CO₂/H₂O solvent mixtures.     

Electronic properties of phenanthrimidazoles as hole transport materials in organic light emitting devices and in photoelectron transfer to ZnO nanoparticles

Phenanthrimidazoles as hole transport materials have been synthesized, characterized, and applied as nondoping emitters in organic light emitting devices. The synthesized molecules possess high fluorescent quantum yield and thermal properties and display film forming abilities. The highest occupied molecular orbital (HOMO) energies of these materials are shallower than the reported tris(8‐hydroxyquinoline)aluminum (Alq₃), which enables the hole transport ability of these phenanthrimidazoles. Taking advantage of the thermal stability and hole transporting ability, these compounds can be used as a functional layer between NPB [4,4‐bis(N‐(1‐naphthyl)‐N‐phenylamino)biphenyl] and Alq₃ layers and show that these phenanthrimidazoles can be alternatively used as novel hole transport materials and to improve the device performances. Geometrical, optical, electrical, and electroluminescent properties of these molecules have been probed. Further, natural bond orbital, nonlinear optical materials (NLO), molecular electrostatic potential, and HOMO–lowest unoccupied molecular orbital (LMO) energy analysis have been made by density functional theory (DFT) method to support the experimental results. Hyperpolarizability analysis reveals that the synthesized phenanthrimidazoles possess NLO behavior. The chemical potential, hardness, and electrophilicity index of phenanthrimidazoles have also been computed by DFT method. Photoinduced electron transfer explains the enhancement of fluorescence by nanoparticulate ZnO, and the apparent binding constant has been obtained. Adsorption of the fluorophore on ZnO nanoparticle lowers the HOMO and LUMO energy levels of the fluorophore. The strong adsorption of the phenanthrimidazoles on the surface of ZnO nanocrystals is likely due to the chemical affinity of the nitrogen atom of the organic molecule to Zn(II) on the surface of nanocrystal. Copyright © 2013 John Wiley & Sons, Ltd.     

Atomic mass,Bjorken variable,and scale dependence of quark transport coefficient in Drell-Yan process for proton incident on nucleus

By means of the nuclear parton distributions determined without the fixed-target Drell-Yan experimental data and the analytic expression of quenching weight based on the BDMPS formalism, next-to-leading order analyses were performed on the Drell-Yan differential cross section ratios from the Fermilab E906 and E866 collaborations. It was found that the results calculated only with the nuclear effects of the parton distribution were not in agreement with the E866 and E906 experimental data. The incoming parton energy loss effect cannot be ignored in the nuclear Drell-Yan reactions. The predicted results indicate that, with the quark transport coefficient as a constant, the suppression due to the target nuclear geometry effect is approximatelybegin{document}$ 16.85 $end{document}% for the quark transport coefficient. It was shown that we should consider the target nuclear geometry effect in studying the Drell-Yan reaction on nuclear targets. On the basis of the Bjorken variable and scale dependence of the quark transport coefficient, the atomic mass dependence was incorporated. The quark transport coefficient was determined as a function of the atomic mass, Bjorken variablebegin{document}$ x_2 $end{document}, and scale begin{document}$ Q^2 $end{document} by the global fit of the experimental data. The determined constant factor begin{document}$ hat{q}_0 $end{document} of the quark transport coefficient is begin{document}$ 0.062pm0.006 $end{document} GeVbegin{document}$ ^2 $end{document}/fm. It was found that the atomic mass dependence has a significant impact on the constant factor begin{document}$ hat{q}_0 $end{document} in the quark transport coefficient in cold nuclear matter.     

Deriving the mean primary-particle diameter and related quantities from the size distribution and the gravimetric mass of spark generated nanoparticles

Spark generated carbon and iridium nanoparticles were characterised by their electrical-mobility diameter D and by the mass of particulate matter collected in parallel on filter. The particles exhibited slightly skewed lognormal size distributions with mean mobility diameters between 18 and 74 nm. The masses calculated from the measured distributions under the assumption that the particles were spherical (diameter D) and of bulk mass density turned out to be much higher than the gravimetric mass, by factors between 8 and as high as 340. This very pronounced difference initiated a search for an improved relation between particle size and mass. Data analysis suggested that the mass increases linearly with increasing D. Hence the measured distributions were evaluated under the assumption that the spark generated matter was composed of spherical primary nanoparticles of mean diameter d, aggregated in the form of chains of joint length βD, with β>1. Using reasonable values of β between 2 and 4, the mean diameter of carbon primary particles turned out to be 10±1.8 nm, in excellent agreement with size data recently obtained by transmission electron microscopy (TEM). The primary iridium particles were found to be distinctly smaller, with diameters between 3.5±0.6 nm and 5.4±0.9 nm. The comparatively small uncertainty is due to the fact that the primary-particle diameter is proportional to the square root of β. The calculated volume specific surface areas range between 500 and 1700 m²/cm³. These numbers are close to the ‘active’ surface areas previously measured by the BET method. The good agreement with TEM and BET data suggests that the novel approach of nanoparticle characterisation is meaningful. Accordingly, the number concentrations of all individual primary particles rather than the concentrations measured by the mobility analyser should be␣considered the correct dose metric in studies on animal exposure to spark generated nanoparticles. The␣evaluated data imply that the numbers quoted in the literature must be enlarged by factors ranging between about 10 and a maximum as high as 80. An erratum to this article can be found at     

Electromagnetic energy flow near metal nanoparticles—II: Algorithms for the calculation of the light scattering of multi-spheres and photon energy transport via linear chains of Ag nanoparticles

We present a new algorithm to calculate the near-field distribution of scattered light of multiple nanospheres based on recursive order-of-scattering (OS) and the matrix inversion approaches, which avoids the divergent problem encountered in origin OS method at the resonance condition. Using this method, we investigate the light-transport properties of linear chains of Ag nanospheres. We found a maximum 3 dB damping length of 1.4 μm of the light propagation when the first sphere of the linear Ag spheres with the radius R=25 nm was illuminated. The optimal configurations that favor the photon energy transport are investigated as well.     

Numerical study of an electrostatic plasma sheath with non-thermal electrons and charged nanoparticles

Numerical solutions of the multi-fluid equations are used to investigate the effects of non-thermal electrons on the structure of an electrostatic plasma sheath in the presence of nano-sized dust grains. It is assumed that electrons obey the Cairns distribution [Cairns et al. Geophys. Res. Lett. 22, 2709 (1995)], with a parameter α that determines the effect of non-thermal electrons and shows the deviation from the Maxwellian distribution. The results revealed that sheath parameters are strongly modified in the presence of non-thermal electrons and with increasing α the sheath width increases. With the increase in α, the absolute dust charge increases while the dust density is reduced.     

Preparation and property of polyvinyl alcohol-based film embedded with gold nanoparticles

Gold nanoparticles were prepared by a simple heat-treated method using polyvinyl alcohol (PVA) as reducing and stabilizing agent in this article. UV/Vis spectroscopy was used to monitor the preparation. The formation of a sharp band at ~530 nm in the UV/Vis spectra and morphological characters revealed by transmission electron microscopy indicated the generation of Au nanoparticles. The PVA film embedded with Au nanoparticles was prepared by flow casting method and characterized by thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. The results showed that Au nanoparticles embedded in PVA film can improve the thermal stability of the film under investigation, leading to interesting technological applications.     

不同浓度Er掺杂Si纳米晶粒电子结构和光学性质的第一性原理研究

利用基于密度泛函理论的第一性原理,对不同浓度Er掺杂Si纳米晶粒的结构稳定性、电子和光学性质进行了研究.结果表明: Si纳米晶粒中Er掺杂浓度越低,结构越稳定;Er掺杂后的Si纳米晶粒引入了杂质能级,导致禁带宽度变窄;掺杂后的Si纳米晶粒在低能区出现了一个较强的吸收峰,随着浓度的降低,吸收峰峰值逐渐减小,甚至消失. 这为Si基发光材料的设计提供了理论依据. 关键词： Si纳米晶粒 掺杂 电子结构 光学性质     

Electronic transport of Lorentz plasma with collision and magnetic field effects

The electronic transverse transport of Lorentz plasma with collision and magnetic field effects is studied by solving the Boltzmann equation for different electron density distributions. For the Maxwellian distribution, it is shown that transport coefficients decrease as ? increases, ? is the ratio of an electron's magneto-cyclotron frequency to plasma collision frequency. It means that the electrons are possible to be highly collimated by a strong magnetic field. For the quasimonoenergetic distribution with different widths, it is found that the transport coefficients decrease greatly as εˉ decreases.In particular when the width approaches to zero the transverse transport coefficients are hardly affected by the magnetic field and the minimal one is obtained. Results imply that the strong magnetic field and quasi-monoenergetic distribution are both beneficial to reduce the electronic transverse transport. This study is also helpful to understand the relevant problems of plasma transport in the background of the inertial confinement fusion.     

Functionalization of gold and silver nanoparticles with diphenyl dichalcogenides probed by surface enhanced Raman scattering

This paper describes a surface‐enhanced Raman scattering (SERS) systematic investigation regarding the functionalization of gold (Au) and silver (Ag) nanoparticles with diphenyl dichalcogenides, i.e. diphenyl disulfide, diphenyl diselenide, and diphenyl ditelluride. Our results showed that, in all cases, functionalization took place with the cleavage of the chalcogen–chalcogen bond on the surface of the metal. According to our density functional theory calculations, the molecules assumed a tilted orientation with respect to the metal surface for both Au and Ag, in which the angle of the phenyl ring relative to the metallic surface decreased as the mass of the chalcogen atom increased. The detected differences in the ordinary Raman and SERS spectra were assigned to the distinct stretching frequencies of the carbon–chalcogen bond and its relative contribution to the ring vibrational modes. In addition, the SERS spectra showed that there was no significant interaction between the phenyl ring and the surface, in agreement with the tilted orientation observed from our density functional theory calculations. The results described herein indicate that diphenyl dichalcogenides can be successfully employed as starting materials for the functionalization of Au nanoparticles with organosulfur, organoselenium, and organotellurium compounds. On the other hand, diphenyl disulfide and diphenyl diselenide could be employed for the functionalization of Ag nanoparticles, while the partial oxidation of the organotellurium unit could be detected on the Ag surface. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation and characterization of waxy maize starch nanoparticles via hydrochloric acid vapor hydrolysis combined with ultrasonication treatment

The objective of this work was to develop a simple and efficient method to prepare waxy maize starch nanoparticles (SNPs) by hydrochloric acid (HCl) vapor hydrolysis combined with ultrasonication treatment. The size, morphology, thermal property, and crystal structure of the SNPs were systematically studied. HCl treatment introduces a smaller particle diameter of starch particles from 13.73 ± 0.93 μm to 1.52 ± 0.01–8.32 ± 0.63 μm. Further ultrasonication treatment formed SNPs that displayed desirable uniformity and near-perfect spherical and ellipsoidal shapes with a diameter of 150.65 ± 1.91–292.85 ± 0.07 nm. The highest yield of SNPs was 80.5%. Compared with the native starch, the gelatinization enthalpy changes of SNPs significantly decreased from 14.65 ± 1.58 J/g to 7.40 ± 1.27 J/g. Interestingly, the SNPs showed a wider melting temperature range of 22.77 ± 2.35 °C than native starch (10.94 ± 0.87 °C). The relative crystallinity of SNPs decreased to 29.65%, while long-time ultrasonication resulted in amorphization. HCl vapor hydrolysis combined with ultrasonication treatment can be an affordable and accessible method for the efficient large-scale production of SNPs. The SNPs developed by this method will have potential applications in the food, materials, and medicine industries.