Current Nanoscience - Volume 10, Issue 5, 2014

Recent years have witnessed various breakthroughs in the research of graphene-related materials since the emergence of a few promising techniques for large-scale production of mono- or multi-layer graphene films. With the help of various surface modification methods, the physicochemical properties of graphene are greatly improved and graphene shows superior sensitivity and selectivity for biological molecular analysis. This paper selectively reviews the application of graphene-based biosensors, especially for detecting nucleic acid, protein and biological small molecules. In addition, future perspectives of graphene-based biosensors are also prospected.

The global digital data has increased at an unprecedented rate during the last decade due to the digitization service of every industry as well as the rapid development of information technology. It is therefore timely to enhance the areal density of the mainstream storage devices in order to meet the current storage demand. In this paper, the development history of three major families of storage devices that consist of magnetic hard disk, magnetic tape, and optical disc has been reviewed associated with their respective strength and weakness when utilized for mass storage applications. Several emerging technologies that are likely to expand the areal density of the conventional recording forms beyond the physical limits are subsequently discussed in each case. The perspectives of these three devices used as next generation data storage memory are also compared with each other in terms of the areal density roadmap. According to the comparison, hard disk that is dominating the current mass storage market will still be the favorite candidate for next-generation storage device due to its ultra-high capacity and low cost, particularly with the help of several advanced technologies such as heat assisted magnetic recording and bit patterned media. In spite of much lower capacity than hard disk today, magnetic tape has exhibited an ample margin for booming the storage capacity, and its high stability and flexible removability render it a promising contender for data backup application. The prospect of optical disc seems to be somewhat pessimistic because of the rather slow progress on its capacity and the fairly high cost per GB. It is likely that optical disc will be superseded by the mass storage devices provided that no more innovative technologies than near-field recording and holographic storage emerge in the future. However, the potential merits of optical disc like long life time and portability may offer optical disc a new application that stores important data securely for long term such as official document and government legislation.

This paper describes the synthesis of gold nanorods, gold nanospheres and gold nanostars using modified versions of existing seed-mediated growth methods. The nanoparticles have been characterized on the basis of their morphology and optical properties using transmission electron microscopy (TEM) and spectrophotometry. Gold nanorods were synthesized using ascorbic acid as reducing agent, gold nanospheres were synthesized using mercaptosuccinic acid as stabilizing/ reducing agent and gold nanostars were synthesized using ascorbic acid as reducing agent and silver ion as anisotropic growth agent. Gold nanorods showed a sharp absorbance spectrum with peaks at 447 nm and 715 nm. Gold nanospheres were spherical, non porous with a diameter of 14-59 nm. The nanospheres were polycrystalline and showed variable branch length that was dependent on the relative proportions of ascorbic acid and gold salts. The spectra of gold nanostars revealed a broad absorbance pattern in the range of 660-775 nm and 930-1000 nm that may be attributed to plasmon resonance of nanostar core and plasmon resonance of nanostar branches, respectively.

We have developed silica stabilized ferrimagnetic magnetite nanocubes (MNCs) as effective heat mediators for magnetic hyperthermia. To do that, large hydrophobic magnetite nanoparticles, with a mean size of 79 and 124 nm were synthesized and transferred to water by silica surface modification. The heating ability of these water suspensions was studied by measuring the Specific Power Absorption (SPA) applying an AC magnetic field of amplitude H0 = 45 kA/m and frequency f = 360 kHz. High SPA values were obtained, ranging from 560 to 1160 W/g. The normalization of the SPA values by the inverse of the frequency and squared field amplitude was performed in order to compare our results with these described in literature. The SPA value for our samples, normalized in this way, yielded values of 0.7-1.5 nH m2/kg.

Photocatalysis of C.I. Acid Red 14 (AR14) by immobilized ZnO nanosheets on scallop shell was investigated. The mean crystallite size of the ZnO nanosheets on scallop shell sample was about 15 nm. Degradation efficiency of AR14 by immobilized ZnO is more efficient than suspension form in identical conditions. Effect of operational parameters including nanocatalyst dosage, pH and initial dye concentration on the UV/ZnO-scallop process was studied. Kinetic of the photocatalytic process was explained in terms of the Langmuir–Hinshelwood model. The values of the kinetic rate and the Langmuir adsorption constants were determined as 0.104 1/(mg/L) and 0.413 (mg/L)/min, respectively. The prepared photocatalyst demonstrated the proper photocatalytic activity even after five successive cycles.

An aqueous ferric nitrate nonahydrate (Fe(NO3)3.9H2O) and magnesium oxide (MgO) were mixed and deposited on silicon nanowires (SiNWs), the carbon nanotubes (CNTs) formed by the concentration of Fe3O4/MgO catalysts with the mole ratio set at 0.15:9.85 and 600°C had diameter between 15.23 to 90nm with high-density distribution of CNT while those with the mole ratio set at 0.45:9.55 and 730°C had diameter of 100 to 230nm. The UV/Vis/NIR and FT-IR spectroscopes clearly confirmed the presence of the silicon-CNTs hybrid structure. UV/Vis/NIR, FT-IR spectra and FESEM images confirmed the silicon-CNT structure exists with diameters ranging between 15-230nm. Thus, the study demonstrated cost effective method of silicon-CNT composite nanowire formation via Iron-oxide Catalyze synthesis.

Atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM) imaging of fibrillar J-aggregates of carbocyanine dye 3,3’-bis(2-sulfopropyl)-5,5’,6,6’-tetrachloro-1,1’- dioctylbenzimidacarbocyanine (C8S3) have been conducted on mica and glass substrates at a room temperature. High resolution AFM imaging reveals that thick fibrils consist of narrow subfibrils with the cross diameter in the nanometer range. A model of the "elementary fibril" with the cross-dimension of 3x4 nm2 was proposed as the aggregate of two J-ladders oriented face-to-face by their hydrophobic sides while the dye molecules are oriented normaly to the long fibril axis. The SNOM measurements have been conducted in the contact mode indicating the large mechanical strength on the fibrillar J-aggregate morphology

In this paper, polypyrrole was prepared using the vapor phase polymerization process on membrane filter. The resulting membrane filter is flexible with electrical conductivity of 6.7 S/cm. When used as a binder-free threedimensional porous electrode for supercapacitor, such membrane filter delivers high specific capacitances of 310 and 130 F/g at current densities of 1 and 5 A/g, respectively, with excellent cycling stability.

In this article, peristaltic flow of a Prandtl fluid model in an endoscope is analyzed in the presence of nanoparticles. Prandtl fluid model describe the shear thinning effects, another name for a shear thinning fluid is a pseudoplastic. This property is originated in certain complex solutions such as ketchup, fruit juice concentrates, shampoo, slurries, paint etc. The flow is modeled in both fixed and wave frame of reference. We have used homotopy perturbation method for the solutions of velocity profile, nanoparticles concentration and temperature profile. The results for velocity temperature, nanoparticles concentration, pressure rise, frictional forces, pressure gradient and stream lines are presented to interpret the behavior of various physical quantities of Prandtl fluid model along nanoparticles. The results for various wave forms are also presented and plotted.

Nano-Fe2O3 was prepared by the CO2-supercritical-process-assisted sol-gel method using Fe(NO3)3.9H2O as raw material and epoxypropane as the hydrolysis agent in non-aqueous solvent. The Fe2O3 gelatin and nano-Fe2O3 were determined by XRD, TEM, BET and IR. The effects of the concentration of the solution, the addition of epoxypropane, the supercritical process on the properties of gelatin were studied, and the effect of the heat treatment of gelatin on the morphology of nano-Fe2O3 was investigated in detail. The sol-gel reaction mechanism was fully discussed. The results indicate that it is helpful to achieve the gelatin with high surface area for the low solution concentration, the suitable addition of epoxypropane and good supercritical process; The epoxypropane undergoes SN2 nucleophilic substitution reaction through its protonation and ring opening reaction in the sol–gel synthesis, which facilitate the process of displacement of H2O ligand in the [Fe (H2O)6]3+ and polycondensation of -OH ligand. The substitution reaction takes place, and some new chemical bonds form in the supercritical fluid process. With the increase of heat treatment temperature of gelatin, the pore volume and specific surface area of the finished nano-Fe2O3 decrease greatly. Nano-Fe2O3 with high specific surface area and good pore structure could be obtained through the heat treatment of gelatin below 300°C.

α-glucosidase (AG) enzyme was immobilized onto amine functionalized multi-walled carbon nanotubes (MWCNTs-NH2) by treatment with cross linkers, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) via amide bonding. The immobilized AG was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). The performance of the electrode was evaluated by Spectrophotometric method and cyclic voltammetric (CV) method using p-nitrophenyl-α-D-glucopyranoside (PNPG) as a substrate. The immobilized AG enzyme retains about 84.16% activity of its initial response even after 30 days when stored at 4°C.

ZnO nanostructures, including ZnO nano quasi-spheres and nanoplates, were synthesized hydrothermally, from the reaction of zinc acetate, catalyzed by Preyssler type heteropolyacid (H14 [NaP5W30O110]), at 140°C in 48 and 72 hours, respectively. The ZnO nanostructures were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The diameter of nano quasi-spheres, was about 5-10 nm. The nano plates had hexagonal shape showing diameter of 40-60nm. Photocatalytic degradation of Methylene blue and Congo red was effectively performed, using the above prepared ZnO nanostructures, achieving almost 70% decolorization, in short time. First order reaction constants were evaluated as 0.0745 and 0.0746 for Methylene blue and Congo red degradation reactions, respectively, concluding first order kinetics via this protocol.

In this paper, for the first time the application of nanofluids is investigated from the point of view of thermoeconomics. For this purpose, the mixed convection flow of Al2O3-EG nanofluid in an isothermal vertical annulus is considered where three sets of models are used to calculate the viscosity and thermal conductivity of nanofluid. The main aim of this work is to estimate the operational costs ($) due to entropy generation using nanofluids in the annulus. The results show that using nanofluids is not cost-effective in short periods (i.e., 5–6 months) from the point of view of the second law of thermodynamics.In future works, besides the entropy generation, changes in the heat transfer rate that occurs using nanofluids, and their effects on the costs, can be considered.

In this paper, we have discussed the influence of induced magnetic field on a blood flow through an axissymmetric stenosed artery. The nature of blood is analyzed mathematically by treating it as Prandtl nanofluid. An analytical expression of velocity profile, nanoparticle volume fraction and temperature profile has been computed for mild stenosis by using the homotopy perturbation method. Physical features of resistance impedance, wall shear stress, wall shear stress at the stenosis throat, axial induced magnetic field and current density distribution have been discussed through graphs.

Let G be a molecular graph with bond set E(G) that admits a Kekulé structure. A global forcing set of G is any subset of E(G) such that no two Kekulé structures of G coincide on S. The number of bonds in a global forcing set of the smallest cardinality is called the global forcing number of G. The global forcing number gives some sort of identification of the minimal amount of information required to specify Kekule structures of a molecular graph. In this article, we give explicit formulae for global forcing numbers of handgun-shaped benzenoid systems. As a corollary, formulae for the global forcing numbers of parallelogram benzenoid systems can be obtained. [J. Sedlar, The global forcing number of the parallelogram polyhex, Discrete Appl. Math. 160 (2012) 2306-2313].