Current Nanoscience - Volume 9, Issue 5, 2013

Iron oxide nanomaterials have been gaining excessive importance because of their magnetic characteristics and wide applications. Iron oxides magnetic nanoparticles with appropriate surface chemistry are prepared either by wet chemical method such as colloid chemical or sol-gel methods or by dry processes such as vapor deposition techniques. Iron oxides in nano-scale have exhibited great potential for their applications as catalytic materials, wastewater treatment adsorbents, pigments, coatings, gas sensors, ion exchangers, magnetic recording devices, magnetic data storage devices, magnetic resonance imaging, bioseparation and as a soft ferrite. This review summarizes study of the methods for the preparation of iron oxide magnetic nanoparticles with a control over the size, morphology and the magnetic properties and some recent bio-engineering, commercial, and industrial applications.

Nanotechnology is essentially related with the synthesis of nanoparticles of varying size and shapes. With the search of environment- friendly protocols for the synthesis of nanoparticles a diverse group of biological agents have been emerged. These biological agents are safe, eco-friendly and lead to green synthesis of nanoparticles. The present review focuses on the role of biological agent(s) towards the development of green nanotechnology, the applications of nanoparticles in different fields of science and technology, and also the toxicological effects of nanoparticles.

Cerium oxide or ceria is an inorganic compound of Cerium, a rare earth element of lanthanide series. Due to the unique ability of cerium to switch oxidation states between +3 and +4 it has various applications as ultraviolet light absorbers, catalytic converters for automobile exhaust systems, solar cells, optics, oxygen sensors and other commercial and biomedical applications. Cerium oxide nanoparticles popularly known as nanoceria are efficient free radical scavengers and are considered as a potent therapeutic option for the treatment of ROS mediated disorders like neurodegenerative disorders, retinal disorders, cancer and can also act as a potent drug delivery agent. Engineered nanoparticles have the potential to revolutionize diagnosis and treatment of many diseases which require the synthesis of nanoceria with biocompatibility so as to enhance its therapeutic potential without inducing any cytotoxicity. Here we review the various methods for synthesis of nanoceria for biomedical applications and we discuss the challenges to realize the potential of nanoceria in therapeutics.

In this study, we developed poly(lactide)-poly(ethylene glycol) (PLA-PEG) blend nanoparticles with variable molecular PEG weights (2, 10, or 20 kDa) to encapsulate antifungal amphotericin B (AmB) and to evaluate its in vitro efficacy in strains of Candida sp. and in vitro cytotoxicity in human erythrocytes. The nanoparticles were prepared using an emulsification/solvent evaporation technique and were characterized with respect to size, size distribution, AmB entrapment efficiency, AmB state of aggregation, and AmB in vitro release profile. The mean particle size was 241 nm, and AmB encapsulation efficiency was above 68.9%. The AmB in vitro release profile demonstrated a burst effect within the first 24 h, which released approximately 20% of AmB, followed by a sustained release of approximately 29.5% of AmB over 26 days. The nanoparticles protected the erythrocytes from lysis caused by AmB within the first 12 h, and AmB was efficacious against strains of Candida sp. in its sustained release profile. The PEG molecular weight did not demonstrate an effect on the physicochemical and biological parameters. Thus, PLA-PEG blend nanoparticles may function as potential carriers for AmB.

In the present work, magnetic nanoparticles coated with silica or ORMOSIL are prepared in a two step process. In the first step, SPIONs with 6 nm average diameter are produced by a reduction-precipitation process conducted in air and in the second one, SPIONs were used as seeds for silica/ORMOSIL growth (below 30 nm), in situ by a modified Stober sol-gel method. SPIONs and silica/ ORMOSIL magnetic core-shell nanostructures were characterized by X-Ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), Mossbauer spectroscopy and SQUID magnetometry. TEM observations of SPIONs and silica/ORMOSIL SPIONs allow determining size and shape. FTIR allows determining silica/ORMOSIL structural fingerprints. X-ray and Mossbauer spectroscopy allow determining the magnetite/maghemite ratio, discussed as a nanosized constrained. SPIONs and silica/ORMOSIL SPIONs show superparamagnetic properties making them appropriated to biomedical applications.

Systematic investigations of magnetization behavior performed on planar arrays of 30 nm wide Fe-nanowires (NW) fabricated on oxidized step-bunched Si (111) templates reveal that the NW arrays exhibit an uniaxial anisotropy dominated by the shape of the wires, that facilitates in retaining the magnetization in-plane with easy axis parallel to the wires. The NWs possess polycrystalline character with bcc-crystal structure, and present an oxidized interface when capped with MgO. From the temperature dependent magnetization studies we find that for thick wires (>4.5 nm) the magnetization reversal is governed by the curling reversal mode. Whereas, for thin wires the reversal is dominated by thermal activation.

A low cast, full efficient and short term procedure for magnetization of carboxylated short multi-walled carbon nanotubes c- SMWCNTs was innovated in this work. Carboxylic acid groups were functionalized on SMWCNTs by refluxing in concentrated mixture of HNO3 and H2SO4 (1:3, v/v) solution. The remaining acid of the solution was neutralized by NaOH base until pH value reached 11 and then Fe3O4 nanoparticles were attached on the outer surfaces of c-SMWCNTs by co-precipitation. Different analyses were used to confirm the decoration of c-SMWCNTs with Fe3O4 nanoparticles. Fourier transform infrared (FTIR) spectroscopy, which is used to evaluate chemical bonds, confirmed that the carboxylic acid groups generated on the SMWNTs while scanning electron microscopy (SEM). Investigation of FTIR peaks of O–H and C=O bonds and shift of X-ray diffraction (XRD) peaks demonstrated that the Fe3O4 nanoparticles were attached on the c-SMWCNTs. Energy-dispersive X-ray (EDX) analytical technique was also used to investigate identity and quantity of the elements.

Carbon Nanotubes (CNTs) are purified by Dynamic-oxidation (D-oxidation) technique to enhance the field emission behavior of CNT field emitters. In D-oxidation method, Carbon-type (C-type) impurities are removed out by selective oxidation by heating at constantly increasing temperature in air. It is observed that the turn-on voltage of D-oxidized CNTs is decreased from 4.4 V/μm to 3.6 V/μm, the current density is enhanced from 0.014 mA/cm2 to 1.12 mA/cm2 at an electric field of 6.4 V/μm and effective emitting area is increased from ∼ 2.18 x10-12 cm2 to 1.09 x10-9 cm2. These findings may be due to the removal of C-type impurities from the surface of CNTs during D-oxidation which exposes the large effective area for emission of electrons leading to enhanced emission current even at low turn-on voltage.

Sudan dyes are toxic or carcinogenic even at low concentrations, which are illegally used as additives in food products to maintain their red color and thus stimulate sales of these products in the market recently. A facile adsorption procedure for the removal of Sudan I and II in n-hexane using oxidized multi-walled carbon nanotubes (O-MWCNTs) is presented in this paper. The effect of absorption conditions including absorption time, amount of adsorbent, initial concentration of Sudan I and II was examined. Two isotherm models were used to describe the adsorption equilibrium, while three kinetic models were applied to evaluate the adsorption process. The adsorption process and equilibrium for Sudan I and II were all proved to be fitted by the Langmuir model and second-order kinetic model. The O-MWCNTs possessed fast kinetics for Sudan I and II from n-hexane solvent with each saturation time of <30 min, and correspondingly the maximum adsorption capacities for Sudan I and II were 41.408 mg/g and 47.037 mg/g, respectively.

In this paper, multi-walled carbon nanotubes (MWCNTs) were oxidized by 30 w% hydrogen peroxide to introduce hydroxyl groups and carboxyl groups on it. Catalyzed by p-toluenesulfonic acid, D-tartaric acid (DTA) was grafted onto MWCNTs by an esterification reaction. Fourier transform infrared spectroscopy and high resolution transmission electron microscopy were used to elucidate the introduced groups and the morphologies changes of the MWCNTs samples. The D-tartaric acid modified MWCNTs were used as chiral im pregnating reagents for thin-layer chromatography for enantioseparation of propranolol enantiomers, and the chiral separation factor was achieved over 7.23 by a mixed solvent of acetonitrile-tert-butanol-acetic acid (volume ratio is 49:49:2) as developing solvent.

We demonstrate a method to fabricate flexible field effect transistors based on mask-free inkjet printed silver micro-electrodes and wet-transfer of chemical vapor deposition grown graphene. The process is simple, low-cost and repeatable. The transistor shows a field-effect hole mobility of 33 cm2/Vs and on/off ratio of 2.1 with high drain current of 54 mA, which is the highest reported in air at room temperature.

The objective of this paper is to provide a systematic investigation on design or evaluation for W/Al interface structure in micro/ nano electronic manufacturing. To understand the basic mechanical properties of the W/Al interface structure, the elastic modulus and the hardness of the sample were investigated by nanoindentation. To investigate the integrating characteristics of the sample in progress, the effect of thermal loading and no-thermal loading on the integrating force of the W/Al interface is tested by nanoscratch. The interfacial bonding force between the films can be obtained for understanding the integrating characteristics. The results show that the interfacial bonding force can be improved by thermal loading, which means the mechanical properties of W/Al interface can be modulated and modified by using thermal loading. It is significant for design and industrial manufacturing process of W/Al interface structure.

Vildagliptin-loaded mucoadhesive nanoparticles using Carbopol 934 P (CVN) as mucoadhesive polymer were prepared by Buchi Nano Spray Dryer to retain the drug in the stomach for a prolonged period of time and to provide sustainable release. The morphological properties of the nanoparticles were studied by scanning electron microscopy and found to have smoother surface with shriveled shape. Drug loading and the percentage recovery werefound to be 89.2 ± 0.5 and 96 ± 0.4 respectively. Bimodal particle size distribution with a mean of 355.8 nm and 80.15 nm was noticed. Angle of repose for CVN particles was relatively good with  < 32.4°. The percent swelling of CVN formulation was found to be 181±9%. In vivo studies in rats suggest that the vildagliptin was retained in the gastrointestinal tract(GIT) for prolonged period of time (∼12 h) and standard group was reduced significantly (∼3 h). Stability studies witnessed no changes when stored at 3-5°C or 15 – 25°C, except that the agglutinative phenomenon which was observed at 37°C and RH 75%. This study validates the mucoadhesive nanoparticles as one of the most appropriate drug delivery approaches for the effective delivery of vildagliptin.

In this investigation anelectrospunsulfonated poly(ethylene terephthalate) (SPET) nanofibrous mat was prepared by electrospinning of the SPET solution in trifluoroaceticacid (TFA)/dichloromethane (DCM) mixture. The produced nanofibers had average diameter of 133nm. The performance of the aforementioned membrane for removal ofFe3+,Mg2+ and Ca2+under different conditions of applied pH and pressure wasstudied. The cross flow recirculation ultrafiltration set-up was employed.Under optimum conditions (pH 1.5 and pressure of 1.2 bar) the removal of Fe3+, Mg2+ and Ca2+were 87.1, 77.14 and 34.92, respectively. The filtration mechanism was also determined through blocking laws and permeate volume data. Subsequently, an acceptable agreement (98%) was achieved for internal pore blocking mechanism. Two equilibrium adsorption isotherms: Langmuir and Freundlich were fitted to the salts’ equilibrium sorption data on SPET membrane at different feed concentrations. The Freundlich isotherm was found to well represent the measured adsorption data based on the higher coefficientof determination (r2).

The present work aims at optimizing the nano size of the particles of γ-alumina to generate micro- and meso-porous structures and improve the efficiency of dehydrogenation catalysts. Following this trend, two different kinds of γ-alumina were prepared using low and high concentration of cetyl tri-methyl ammonium bromide surfactant (CTAB). Both kinds of alumina were characterized by XRD, TG, DTA, SEM and TEM in addition to surface characterization. SEM and TEM images showed that the alumina prepared with the low concentration of CTAB has groups of ultra fine nanoparticles with size ∼ 7 nm assembled into a strong agglomeration with creating micro- and meso-porous structures and high surface area (256.9 m2/g). With the high concentration of CTAB, the nano size of alumina increased to become ∼100 nm creating only meso-porous structure. These results indicated that the spherical particles of alumina with the nano size below 10 nm adhere to two or three other particles creating the cavities between the globules and providing micro- and mesoporous structures. On the other hand, the aggregates of the nanoparticles above 10 nm produce only mesoporous structures. Our results conclude that the size of the globules determines the specific surface area of the solids, its pore volume and the diameters of its pores. Development of the dehydrogenation catalyst was achieved by supporting 0.6 wt.% platinum metal over the micro-and mesoporous structure of the prepared γ-alumina. The results of catalytic activity concluded that the prepared nanocatalyst is selective toward cyclohexane dehydrogenation reaction with catalytic conversion of cyclohexane 87% at 450 °C.

According to the self-similarity of powder particle breakage, multi fractal model which could simulate the process of powder particle breakage and aggregation has been built and also has been discussed the simulation process by using methods of number theory and matrix. The comparative analysis of the simulation results and the statistical results, shows that the multi fractal model can be used to accurately describe the breaking process and distribution of powder particles and may have the duality of static state (contribution of powder particles) and dynamic state (fragmentizing course). According to the fractal dimension obtained from the expression of fractal dimension have the uniqueness, which show multiple fractal about process of powder particle breakage and aggregation have the uniqueness. Matrix model based on multi fractal parameters could describe and forecast the breaking process and distribution of powder particles, and is expected to be insensitive to resolution and sampling length of measuring instrument, so this model is more reasonable and effective than the traditional model based on statistical analysis.

CdS hollow nanospheres with enhanced photocatalytic performance have been prepared by employing SiO2 nanospheres as templates with a simple and mild solution reaction at room temperature. Field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) analyses confirmed that these CdS hollow nanospheres possess 370 nm diameter and the wall thickness less than about 30 nm. UV-Vis absorption spectra show that the as-synthesized hollow CdS nanospheres display better light absorption ability than the contracted solid CdS nanospheres. Furthermore, the hollow CdS nanospheres exhibit enhanced activity toward decomposition of target organic pollutant such as Rhodamine B (RhB), under Xe arc lamp irradiation. The calculated rate constants for hollow CdS nanospheres are 5.5 times larger than that of solid CdS nanospheres, which could be ascribed to the improved light absorption ability, adsorption capability due to the hollow structure, and higher charge separation efficiency achieved by shortening the charge transporting path with thinner hollow CdS shell.

The thermal boundary layer of nanofluids over an unsteady stretching sheet with a convective surface boundary condition is investigated. Two types of water based Newtonian nanofluids containing metallic or nonmetallic nanoparticles such as Copper (Cu) and Alumina (Al2O3) are considered from a theoretical viewpoint and for a range of nanoparticle volume fractions. Using a similarity transformation the governing time dependent nonlinear boundary layer equations for momentum and thermal energy are reduced to a set of nonlinear ordinary differential equations. The resulting four-parameter problem is solved numerically using fourth order Runge-Kutta integration scheme with shooting technique for some representative values of the unsteadiness parameter (A), the Prandtl number (Pr), local Biot number (Bi) and solid volume fraction parameter (φ). It is shown the both the shear stress and heat transfer rate at the sheet surface are higher for Cu-water as compared to Al2O3-water. Besides, it is found that the heat transfer rate at the surface decreases with increasing flow unsteadiness (A) and increases with increasing with increasing Bi and φ. A comparison with a previous study available in the literature has been done and we found an excellent agreement with them.

PVDF-based nanocomposites with insulating BaTiO3, semiconducting SiC and conducting graphite nanoplatelets (GNPs) and with hybridization of these nanofillers were fabricated by simple solution mixing and compression molding. The electrical properties of such composite materials were characterized using AC impedance spectroscopy with frequencies ranging from 50 to 5x106 Hz. The results showed that the solution mixing process enables homogeneous dispersion of nanofillers in the PVDF matrix. The dielectric constant of the PVDF-based nancomposites was found to increase with nanofiller content, particularly for the composites with SiC and GNP fillers. The addition of conductive fillers was shown to have a strong effect on the dielectric relaxations of PVDF in low frequency region. Furthermore, the modulus formalism can well describe the relaxation phenomenon of the PVDF-based nanocomposites. The reduced activation energy derived from the isothermal relaxations indicates facile reorientation of the PVDF dipoles to applied external frequencies.

There remains a great need for improved imaging technology in oncology both for screening, localization, and to follow the progress of treatments. With the exception of gadolinium, which has a history of use in MRI, other rare earth elements have been largely under-used for in vivo imaging. The unique properties of this class of elements are described and the possibilities for their application in cancer imaging illustrated. Furthermore, recent discoveries show how rare earth elements can provide novel therapeutics in the fight against cancer.