Current Nanoscience - Volume 10, Issue 3, 2014

The nanotechnology and the use of nanoparticles are increasing each day. The number of experiments with nanoparticles is enormous and is corroborating the use in humans. However some points must be more defined before a final approval. In this study we analyzed nanoparticles of EDTMP under different conditions in rats and observed some characteristics that should be taken into account. Nanoparticles were injected either intraocular or in a jugular vein, and the data were compared. The behaviors of the samples were very different, which may have led to erroneous interpretation of nanoparticle data in previous studies by many authors. In all cases, the results of the biodistribution were quite different, which may lead to different conclusions. Analyzing the data, we conclude that the biodistribution test should be standardized, and the way that it is conducted may change the final results drastically.

We review a compact, semi-empirical model of Carbon Nanotube Field Effect Transistors (CNTFETs), already proposed by us, in which we have introduced several issues to allow an easy implementation in the most common circuit simulators. The CNTFET equivalent circuit is similar to a common MOSFET one, where the quantum capacitances have been computed from the charge in the channel. A procedure, based on a best-fitting between the measured and simulated values of output device characteristics, is reviewed in order to extract the optimal values of the CNTFET equivalent circuit elements. Finally we have implemented our model both in SPICE, using ABM library, and in Verilog-A in order to demonstrate the model flexibility and in order to compare them. Typical analogue circuits and logic blocks have been simulated and results have been presented to validate the implementation of our CNTFET model both in Verilog-A and in SPICE.

Fully integrated CMOS single pole double through (SPDT) Transmit/Receive (T/R) switch is an essential component of every compact transceiver for enabling sharing of a single antenna between its transmitter and receiver. The switch is expected to encompass very low insertion loss, relatively higher isolation with high power handling capability. But there is inevitable trade-off among the parameters of the switch which makes the design even more challenging at 2.4 GHz ISM band. This paper presents a bibliographical survey of the work published on improved performance of different switch topologies for 2.4 GHz ISM band transceiver applications. Different techniques reported in literatures for further improvements in the characteristics of CMOS switches are also highlighted. This review will serve as a comparative study and reference for the researchers in designing T/R switches for future 2.4 GHz ISM band applications.

The applications of nanoparticles have been tremendously increased in the field of targeted drug release, gene silencing, therapeutics, industrial and environmental catalysis, water purification and optoelectronics. These are because of their versatile sizes and shapes, large specific surface area with convenient surface properties, high chemical reactivity, physical affinity and optical, electrical and magnetic properties. However, the synthesis of nanoparticles with controlled nano/microstructures and desired surface properties has been remaining a challenging task. Various approaches have been proposed for the commercial production of nanostructured particles from solid bulk materials. Chemical methods for the synthesis of controlled structure nanoparticles from rare-earth solid compounds have showed limited success in terms of yield, purity and cost. Recently, surfactant assisted high energy ball milling has been exploited for the synthesis of various nanomaterials, nanograins and nanocomposites from solid state. Self-assembled structures of surfactants act as cationic, anionic or charge neutral lubricants to control the nano/microenviroment of the nanostructured materials, producing nanoparticles with improved dispersion. In high-energy ball milling, plastic deformation, cold-welding and fracture predominantly contribute to bring a change in size, shape and nano/microenvironment of nanoparticles. In this review, we have systematically presented the basic concept and applications of surfactant assisted mechanical milling for the synthesis of various nanomaterial, nanocomposite and nanoparticles.

The goal of this work was to evaluate the microstructure and dynamics of water nanodroplets in isopropyl myristate (IPM)/dioctyl sodium sulfosuccinate (DOSS)/water nanoemulsions (NE) utilized as reactors for nanoparticle synthesis. The characterization of the microstructure and dynamics of selected NE’s was performed using rheology, dynamic light scattering (DLS), and sub-ambient differential scanning calorimetry (SA-DSC). The results obtained from rheological evaluation demonstrated that all the selected IPM/DOSS/water systems exhibited Newtonian behavior. The DLS measurements showed that depending on composition, the water nanodroplets had diameters in the range of 6 to 16 nm. The nanoemulsions did not show droplet aggregation or coalescence over a one-month period of observation, as indicated by the multi-angle DLS study. SA-DSC experiments delineated the states of water within the ternary mixtures. A concentration-related variation in the internal microstructure was identified when water-freezing temperatures were plotted as a function of water content. The ternary mixtures reported in this research were utilized to synthesize silver sulfadiazine and calcium alginate nanoparticles. Insights obtained from this study are being assimilated to design efficient and effective reactors capable of use in nanoparticle synthesis.

In this work we evaluated the suitability of three synthetic membranes for the in vitro assessment of drug release from semisolid dosage forms containing polymeric nanocapsules. The use of cellulose acetate (0.45 µm pore size), polycarbonate (0.05 µm pore size) and dialysis cellulose (12 kDa cut off) membranes was investigated. For this purpose, drug release studies from hydrogels containing clobetasol propionate-loaded lipid-core nanocapsules were carried out. A higher amount of clobetasol propionate reached the release medium using cellulose acetate and polycarbonate membranes, compared to the use of dialysis cellulose membrane. Photon correlation spectroscopy analyses showed an overlap between the particle size distributions of the receptor media from the release studies using cellulose acetate and polycarbonate membranes and the original lipid-core nanocapsules suspension diluted in the receptor medium. The presence of nanoparticles was further confirmed by transmission electron microscopy. On the other hand, particle size distribution observed in the receptor medium of release studies using dialysis cellulose membrane did not show particles at nanoscale. The overall results suggest that the dialysis cellulose membrane ensures that only released drug will reach the receptor compartment, and that it should be the first choice for in vitro drug release studies from semisolid dosage forms containing drug-loaded nanocapsules.

The present study is focused on the applications of biosynthesized silver nanoparticles in various fields. Silver nanoparticles are synthesized in vitro using marine bacteria Shewanella algae bangaramma in the laboratory. The silver nanoparticles are characterized by using UV–Vis spectrum, TEM, FTIR, EDAX, XRD and AFM analysis. The synthesized silver nanoparticles are spherical, crystalline and 5-30 nm in diameter. They were found to have both larvicidal and bactericidal activities. There is no mortality in the control. The maximum LC 50 and LC 90 values with 95% confidential limit (4.529 mg/ml (2.478 - 5.911), 9.580 mg/ml (7.528-14.541) were observed with III- instar larvae of Lepidiota mansueta (Burmeister). In exposed groups the mortality of the larvae was significantly increased in all concentrations (p < 0.0001). The order of bactericidal activity against marine fouling bacteria is found to be Pseudomonas sp. < Vibrio cholerae < Roseobacter sp. < Alteromonas sp. To date, this is the first report on the marine bacteria mediated synthesis of silver nanoparticles in culture medium which has effective larvicidal and antifouling activities.

Recently, magnetic nanoparticles have been introduced as a novel antimicrobial material. Listeria monocytogenes are the causative agent of listeriosis and stands among the major public health issues. This bacterium can attach to the host cell membrane and trigger molecular responses leading to phagocytosis of the bacterial cell. In the present study, the effect of iron oxide nanoparticles (IONs) on the invasion power of L. monocytogenes was investigated. IONs were synthesized by coprecipitation method and coated with 3-aminopropyltriethoxysilane (APTES). Listeria monocytogenes cells were exposed to the prepared particles and interactions between IONs and bacterial cells were visualized by scanning electron microscopy. Invasion power of listerial cells for penetration HepG-2 cells monolayer was also examined in various concentrations of IONs. IONs have reduced invasion power of L. monocytogenes in a concentration-dependent manner. Almost 4-fold reduction in the invasion power of L. monocytogenes was observed at 20 µg ml-1 IONs concentration.

Flower-shaped Ag-ZnO microplates were directly synthesized from an aqueous solution of zinc nitrate and silver nitrate in the presence of CTAB at 120°C. The as-synthesized products were investigated in terms of their morphological, structural, photocatalytic properties. Methylene blue (MB) and gaseous iso-propanol (IPA) are employed to evaluate the photocatalytic activity of the Ag-doped ZnO microplates. The photocurrent response experiments are also carried out. The as-formed composite shows higher efficiency of photocatalytic degradation on MB and IPA. Moreover, it also exhibits obvious photocurrent under light irradiation.

A faster and precise field programmable gate array (FPGA) based current dq proportional and integral (PI) controller is developed to reach the optimal efficiency and steadiness of the motor drive. Current dq PI controller is generally implemented in digital signal processor (DSP) based computer. However, DSP based solution reaches its physical limits, which are usually few microseconds. Conversely, FPGA indeed enhances the performance of current controllers. FPGA implementation of the overall controlling algorithm will certainly trim down the execution time significantly to guarantee the steadiness of the motor. In this research, an FPGA based current dq PI controller is developed. The controller operates at 30MHz clock speed and results show that the overall execution time is only 68 ns that is the lowest computational cycle for the era.

In this paper, silicon nanowire (SiNW) arrays with the different structural parameters were prepared by the electroless metal assisted chemical etching method through changing the AgNO3 concentration in the etching solution and etching time. For the concentration of AgNO3 of 0.04M and the etching time of 8 min, the SiNW arrays with minimum reflectance were obtained. The average reflectivity of the SiNW arrays could be as low as 2.0% for the wavelength in the range of 300-1100nm. The measurements of reflectivity and morphology of SiNW arrays indicated that the reflectivity of SiNW arrays were not only sensitive to the length of the nanowires, but also dependent on the diameter, distribution period and the filling ratio of diameter to distribution period of the nanowires. When the filling ratio is around 0.45, the distribution period of the SiNW arrays is 110 ± 10nm, diameter is smaller and length is longer, the reflectivity will be lower.

This paper discusses numerically the unsteady flow and heat transfer of a viscous fluid driven by an impulsively started infinite flat plate in a nanofluid. The governing partial differential equations are transformed into a system of ordinary differential equations, which is then solved numerically by a shooting method. Results are presented graphically and the effects of the Brownian motion parameter Nb and the thermophoresis parameter Nt on the dimensionless heat transfer rate are discussed. It is found that the heat transfer rate is a decreasing function of both Nb and Nt.

Strontium titanate (SrTiO3) nanocrystals have been synthesized, for the first time, through a facile method using SrC2O4·H2O-TiO2 precursor. DTA-TG techniques were used to follow the titanate formation process. XRD and FT-IR measurements were used to characterize the intermediate decomposition products as well as the titanate formation. XRD showed single-phase, crystalline, cubic perovskite with a lattice constant of 3.9017 Å. TEM image exhibited agglomerated cubic particles with size of about 70 nm. BET measurements, used to characterize the surface properties, revealed a surface area of 9.5 m2 g-1. The study of the electrical properties as a function of temperature and frequency exhibited semiconducting behavior with conduction activation energy of 0.45 eV. Kinetic analysis of non-isothermal TG curves, using three different computational integral methods revealed an activation energy value, for the titanate formation, of 240 kJ mol-1 according to the phase boundary controlled mechanism (R2).

The preparation of Sr1-xNdx(MnSn)0.5Fe11O19 M-type hexaferrites powders by a citrate sol-gel method was investigated. The samples were determined by X-ray diffraction (XRD) and transmission electron microscope (TEM). Microwave absorption properties of hexaferrite- acrylic resin composites were measured using SWR (standing-wave-ratio) method in the range of 12 to 20 GHz. It was shown that small amounts of Nd+3 substitution could significantly modify the microwave electromagnetic parameters. Furthermore, the investigation indicated that substitution of Nd+3 ions for Sr+2 ions in Sr(MnSn)0.5Fe11O19 resonant frequency would move toward higher frequency. The results showed that the powder possesses excellent microwave absorption properties. A minimum reflection loss of -43 dB was observed for the composite, where x = 0.03. A broad bandwidth of microwave absorption (with a -10 dB reflection loss as a reference) is predicted in the composite samples containing the ferrite powders of x=0.02, and x=0.03 in Ku-band frequencies.

La-doped Barium-ferrite/Poly-m-toluidine composites with electromagnetic behavior were prepared by in situ polymerization of m-toluidine in the presence of La-doped Barium-ferrite particles. The structures, morphologies and properties of composites were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), four-probe conductivity tester and vibrating sample magnetometer (VSM). FTIR and XRD spectra demonstrated that there were interactions between ferrite and poly-m-toluidine (PMT). TEM studies showed that the composites presented the core-shell structure. Under applied magnetic field, nanocomposite exhibited the hysteretic loops of the ferromagnetic behavior. The magnetic parameter saturation magnetization of composites depends on the content of La-doped barium-ferrite particles.

In this article free convective peristaltic motion of MHD Jeffrey nano fluid in an irregular channel is considered. Convective surface boundary conditions are incorporated for the thermal flow analysis. Energy equation exhibits the viscous dissipation. The problem prescribed under long wavelength and low Reynold's number approximation. HPM (homotopy perturbation method) is used to developed the solutions for nano particle fraction and heat transfer phenomena, while exact solutions are calculated for stream function and pressure gradient. The obtained results grip on “convection Biot number Bi, Hartmann number M, , Jeffrey fluid parameter λ, thermophoresis parameter Nt and Brownian motion parameter Nb”. The assets of different parameters on the flow quantities of observation are analyzed. As a concluding point, the streamlines are plotted and examined.

In this research, the refinement behavior of scrap silicon during mechanical milling with varying time was observed. Initial premilled Si powder with 106µm size was milled using high energy ball milling equipment in order to produce commercially applicable 10 µm target Si powders. Milling time was changed from 1 min to 60min while the characteristics and morphological changes of the powders according to the milling time were observed by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray diffractometer (XRD). The average particle size was found to have reached 10μm after a short milling time of 20~30 min, while 60min of milling yielded fine spherical particles of around 3.5 µm, surrounded by fine nanoparticles. In addition, it has also been found that there is presence of nano Si particles after 60 minutes of milling. The refinement mechanism suggests that the longer the milling time, the finer the powder size becomes with identifiable stages observed in between.

The problem of an axisymmetric flow of a nanofluid over a radially permeable shrinking sheet with convective surface boundary condition is studied numerically. The governing partial differential equations are transformed into ordinary differential equations by a similarity transformation, before being solved numerically using a shooting method. The effects of the Lewis number Le , Brownian motion parameter Nb , thermophoresis parameter Nt , and the Biot number Bi on the heat and mass transfer characteristics are studied. It is found that the solution exists only if adequate suction through the permeable sheet is introduced. Moreover, unique, dual and triple solutions are found to exist for a certain range of the suction parameter. Furthermore, increasing the Lewis number and the Brownian motion parameter are to decrease the heat transfer rate at the surface but increase the mass transfer rate. Both the heat and mass transfer rates at the surface decrease with increasing values of the thermophoresis parameter.

Exogenous nucleotide supplementation during times of rapid growth and stress is preferred because de novo synthesis is insufficient and energetically a costly process. To overcome inefficient utilization of dietary nucleotides due to intestinal cell repulsion and dependency on pH, an efficient controlled delivery system based on chitosan nanoparticles (NPs) was developed. The effects of these (0.2% and 0.4%) RNA-loaded chitosan NPs (Chitosan: RNA ratio 2:1), 0.4% bare RNA, and 0.8% chitosan NPs on productive efficiency (growth rate, feed conversion and protein efficiency ratio), body composition, organo-somatic indices, haemato-biochemical and immune responses (WBC count, phagocytic activity, serum lysozyme, serum total protein and albumin : globulin ratio) and survival of Labeo rohita fish fingerlings, following challenge with pathogenic bacteria were evaluated. Dietary chitosan NPs were found not to affect productive efficiency, but improved (P < 0.01) immunity by increasing WBC and phagocytic activity. Dietary RNA significantly improved (P < 0.01) productive efficiency, immunity and survival, which was further potentiated (P < 0.01) by its nanosized delivery by loading onto chitosan NPs. Blood glucose, haemoglobin, RBC count, serum uric acid and whole body composition were unaffected (P > 0.05) by dietary treatments. RNA-loaded chitosan NPs increased hepato- and viscerosomatic indices. The activity of metabolic enzymes (intestinal and liver alkaline phosphatase, alanine- and aspartateamino transferases, lactate- and malate-dehydrogeneases) corresponded with the performance of the respective diets. As growth, immunity and disease resistance in fish given dietary nano-sized RNA were significantly higher than in those given bare RNA or chitosan alone, and as nanoformulation reduced the usage of individual components by half, the use of RNA-loaded chitosan NPs can be favoured in the feed/food industry over chitosan and RNA alone.