Showing papers in "Journal of Nanoscience and Nanotechnology in 2012"

Nanofibers: effective generation by electrospinning and their applications.

Abstract: Electrospinning is the most versatile technology in use today, for the generation of polymer nanoscale fibers. The nano materials generated using this technology have a large surface area and are highly porous making it very useful in many applications in diverse fields such as energy storage, healthcare, biotechnology, environmental engineering, defense and security. The production of the fibers and the morphology can be easily controlled by modifications to the processing parameters. The relatively high production rate and simplicity of the setup makes electrospinning highly attractive. This review summarizes the effect of various processing parameters on the effective generation of nanofibers. By simple modifications to the electric field inside the electrospinning chamber the fiber collection can be easily controlled. In addition, the various applications of electrospun fibers in electronic devices, environmental sensors and filters, energy storage, and in biomedicine such as in tissue engineering, drug delivery and enzyme encapsulation are examined and the current research in each field is also explored in this review.

Investigation of Al2O3-MWCNTs hybrid dispersion in water and their thermal characterization.

Abstract: Synthesis of water based Al2O3-MWCNTs hybrid nanofluids have been investigated and characterized. Al2O3-MWCNTs nanoparticles in weight proportion of 97.5:2.5 to 90:10 have been studied over 1% to 6% weight concentration. Dispersion quality of nanofluids is assured by additional synthesis process like acids treatment and grinding of MWCNTs by planetary ball mill. The effects of ground and non-ground MWCNTs over dispersion quality and thermal conductivity have been investigated. Sedimentation effect of hybrid nanofluids with time length has been studied by sample visualization and TEM micrographs. The augmentative absorbance and thermal conductivity of hybrid nanofluids have been compared with pure Al2O3/water nanofluids. The overall result shows that the enhancement in normalized thermal conductivity of hybrid nanofluids is still not so sharp though the absorbance and other qualities show much better comparing mono type nanofluids. Hybrid nanofluids with spherical particles show a smaller increase in thermal conductivity comparing cylindrical shape particles.

Redox-based resistive switching memories.

Abstract: This review covers resistive random access memories which utilize redox processes and ionic motion on the nanoscale as their storage principle (ReRAM). Generic aspects are described in order to provide the physics and chemistry background for the explanation of the microscopic switching mechanism and of the high nonlinearity in the switching kinetics. The valence change memory (VCM) effect is elaborated in more detail. As common features, ReRAM typically show very short switching times, low switching energies, and long data retention times. In addition, they offer a scalability potential down to feature sizes in the order of 5 nm and below.

Antimicrobial activity of zirconia (ZrO2) nanoparticles and zirconium complexes.

Abstract: The antimicrobial activities of zirconia (ZrO2) nanoparticles and zirconium mixed ligand complexes were studied on bacterial strains of E. coli, S. aureus and fungal strain of A. niger. The nanoparticles of zirconia and Zr(IV) complexes with different amino acids as ligands were synthesized by hydrothermal method. X-ray diffraction (XRD) and HRTEM confirmed the crystalline nature and morphology of the synthesized products. The antimicrobial studies revealed that the zirconia exhibits activity only against the E. coli, whereas, the Zr(IV) complexes exhibits activity against both the bacteria: gram -ve E. coli and gram +ve S. aureus as well as fungal strains. The Zr(IV) complexes are found to possess significant antifungal activity against A. niger. The results are indicative of crystal plane-dependent antimicrobial activity of zirconia nanoparticles and complexes. The observed difference in the antibacterial activity of ZrO2 crystals and Zr(IV) complexes may be ascribed to the atomic arrangements of different exposed surfaces. On the basis of the study, it could be speculated that the ZrO2 nanoparticles with the same surface areas but with different shapes i.e., different active facets will show different antimicrobial activity.

Effect of carbon nanomaterials on the germination and growth of rice plants.

Abstract: For the successful diverse applications of different nanomaterials in life sciences, it is necessary to understand the ultimate fate, distribution and potential environmental impacts of manufactured nanomaterials. Phytotoxicity studies using higher plants is an important criterion for understanding the toxicity of engineered nanomaterials. We studied the effects of engineered carbon nanomaterials of various dimensionalities (carbon nanotubes, C60, graphene) on the germination of rice seeds. A pronounced increase in the rate of germination was observed for rice seeds in the presence of some of these carbon nanostructures, in particular the nanotubes. Increased water content was observed in the carbon nanomaterial treated seeds during germination compared to controls. The germinated seeds were then grown in a basal growth medium supplemented with carbon nanomaterials for studying their impact on further seedling growth. Treated seedlings appeared to be healthier with well-developed root and shoot systems compared to control seedlings. Our results indicate the possible use for carbon nanomaterials as enhancers in the growth of rice seedlings.

Mesoporous silica nanoparticles carrier for urea: potential applications in agrochemical delivery systems.

Abstract: Nanotechnology-based agrochemical delivery systems would ensure efficient and economical utilization of these very important agricultural inputs. In this study, mesoporous silica nanoparticles with particle diameters of -150 nm and pore sizes of -2.5 nm were synthesized via liquid crystal templating mechanism. Urea, as a model agrochemical molecule, was entrapped in the mesopores of the siliceous material by simple immersion loading using aqueous urea solutions. About 15.5% (w/w) of urea was loaded inside the pores mainly by physisorption while the total adsorption capacity of mesoporous silica nanoparticles could reach up to 80% (w/w). Highly concentrated urea solution was found to be more effective due to high driving concentration gradient generated. Release process of the urea-loaded mesoporous silica nanoparticles in water and soil indicated a two stage sustained slow release-profile. The findings for soil release studies revealed at least fivefold improvement in the release period. By the ability to entrap urea guest molecules into its mesopores and release them in a controlled manner, mesoporous silica nanoparticles demonstrated its great potential as a nanocarrier for agrochemicals.

The Gibbs equation versus the Kelvin and the Gibbs-Thomson equations to describe nucleation and equilibrium of nano-materials.

Abstract: The Kelvin equation, the Gibbs equation and the Gibbs-Thomson equation are compared. It is shown that the Kelvin equation (on equilibrium vapor pressure above nano-droplets) can be derived if the inner pressure due to the curvature (from the Laplace equation) is substituted incorrectly into the external pressure term of the Gibbs equation. Thus, the Kelvin equation is excluded in its present form. The Gibbs-Thomson equation (on so-called equilibrium melting point of a nano-crystal) is an analog of the Kelvin equation, and thus it is also excluded in its present form. The contradiction between the critical nucleus size (from the Gibbs equation) and the so-called equilibrium melting point of nano-crystals (from the Gibbs-Thomson equation) is explained. The contradiction is resolved if the Gibbs equation is applied to study both nucleation and equilibrium of nano-crystals. Thus, the difference in the behavior of nano-systems compared to macro-systems is due to their high specific surface area (Gibbs) and not to the high curvature of their interface (Kelvin). Modified versions of the Kelvin equation and the Gibbs-Thomson equation are derived from the Gibbs equation for phases with a general shape and for a spherical phase.

Preparation and biomedical applications of core-shell silica/magnetic nanoparticle composites.

Abstract: Core-shell structured silica/magnetic nanoparticle composites have recently been subjected to extensive research since the shells could offer protection to the cores and introduce new properties to the hybrid structures, which endue them with great application potentials in various fields. Several approaches have been studied for the synthesis of SiO2 coated on magnetic nanoparticles. These approaches include Stober process, microemulsion, sodium silicate and tetraethoxysilane hydrolysis, aerosol pyrolysis, layer-by-layer strategy, polymer-templating and sonochemical deposition. This review is focused on describing state-of-the-art synthetic routes and methods for the preparation of silica/magnetic nanoparticle composites. Furthermore, we also introduce main applications of these nanoparticle composites in biomedical scopes and address some challenges in the synthesis of high-quality magnetic nanoparticles.

Preparation of graphene quantum dots for bioimaging application.

Abstract: In this communication, preparation of graphene quantum dots (GQDs) with size about 10 nm by vigorous oxidation of graphite is reported. Thus obtained GQDs exhibit good physiological solubility, high photostability, low cytotoxicity, and yellow-green fluorescence with quantum yield about 7%. Furthermore, the feasibility of the GQDs for cell imaging application is demosntrated.

Repeated oral dose toxicity of iron oxide nanoparticles: biochemical and histopathological alterations in different tissues of rats.

Abstract: Iron oxide (Fe2O3) nanoparticles are widely used in different fields of nanotechnology. However, studies on its toxicological effects in humans and the environment are scarce. Therefore in this investigation 28 days repeated dose oral toxicity studies were conducted on Fe2O3-30 nanoparticles and its counterpart Fe2O3-Bulk with special reference to target biochemical enzymes and histopathological changes in different tissues of female albino Wistar rats. The alterations observed after Fe2O3-30 treatment in various tissues of exposed rats were dose dependent. Low dose was less effective than medium and high doses with low dose demonstrating "no observed adverse effect" (NOAEL). Further, high dose treated rats showed toxic sign and symptoms but no mortality. Due to the repeated doses of Fe2O3-30 nanoparticles, significant inhibition was observed in total, Na(+)-K+, Mg2+ and Ca(2+)-ATPases in brain of exposed rats. Similarly, significant inhibition was recorded in RBC and brain acetylcholinesterase indicating that both synaptic transmission and nerve conduction were affected by this compound. Fe2O3-30 significantly increased aspartate amino transferase, alanine amino transferase and lactate dehydrogenase in serum and liver, whereas, these enzymes were significantly decreased in kidney indicating tissue necrosis and possible leakage of these enzymes into the blood stream. Increased levels of these enzymes in liver as well as in serum might be an adaptive mechanism due to the stress of iron nanoparticles. High dose treated rats of Fe2O3-30 showed dilated central vein, perivascular round cell collections in liver along with focal areas of necrosis, whereas kidney showed focal tubular damage and red pulp congestion, whereas prominent white pulp indices were observed in spleen. However, histopathological analysis of heart and brain tissues failed to show any adverse changes in their architecture exposed to repeated doses of Fe2O3-30 when compared with controls. Fe2O3-Bulk did not induce any adverse effects in either biochemical parameters or histopathology in the treated rats and the changes observed were near to controls and mostly insignificant, indicating that the counter part of nanoparticles i.e., bulk material is less potent than the nanoparticles in causing toxicity in the exposed animals. These results suggested that as particle size decreases, this iron nanoparticle showed increased toxicity, even though the same material is relatively inert in bulk form. The changes observed in these target enzyme activities could be useful as biomarkers of exposure to nanoparticles.

In vitro degradation behavior of silica nanoparticles under physiological conditions.

Abstract: Understanding the degradability of silica nanoparticles is significant for the rational design of desired nanomaterials for various biomedical applications. However, the effect of the intrinsic properties of silica nanoparticles, such as particle shape, surface chemistry, and porosity, on kinetic degradation process under different extrinsic conditions has still received little attention. Herein, mesoporous silica nanoparticles (MSNs) with different aspect ratios (ARs, 1, 2, and 4), the corresponding PEG-functionalized MSNs, and amorphous Stober spherical silica nanoparticles were specially designed and their degradation was evaluated in in vitro simulated physiological media. The results show that shape, surface properties and porosity of nanoparticles, as well as the component of simulated physiological media, play important roles in tuning the degradation kinetics and behaviors. Sphere-shaped MSNs have a faster degradation rate than rod-shaped counterparts. Naked MSNs are eroded from particle external surface, while PEGylated MSNs from interior of particles. And spherical MSNs display more extensive degradation than amorphous silica nanoparticles. The presence of fetal bovine serum (FBS) in Dulbecco's Modified Eagle's Medium (DMEM) can accelerate the degradation process. These results can provide useful guidelines for the rational design of silica nanoparticles for biomedical applications.

Removal of fluoride from water using iron oxide-hydroxide nanoparticles.

Abstract: A novel and facile method for the synthesis of uniform stoichiometric powder form of non-magnetic iron oxide-hydroxide nanoparticles with spherical morphology and its application for defluoridation of drinking water is reported. X-ray powder diffraction analysis (XRD), BET surface area, FTIR, field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) images were used to characterize nanoscale iron oxide-hydroxide. Transmission electron microscopy (TEM) image revealed the formation of iron oxide-hydroxide nanoparticles with spherical morphology. The iron oxide-hydroxide nanoparticles showed an excellent ability to remove fluoride (F − from contaminated water over a wide range of pH. The influences of temperature, stirring speed, pH, adsorbent dose and contact time were studied. The equilibrium data were tested with various isotherm models and finally, a calculation procedure was reported for the calculation of adsorbent requirement. The fluoride adsorbed nanoparticles was regenerated upto 70% using sodium hydroxide or hydrochloric acid solution. The iron oxide-hydroxide nanoparticles can be used as an effective and replicable adsorbent media for defluoridation of water in presence of competing anions like chloride, iodate, iodide and sulphate.

Antimicrobial finish of textiles by chitosan UV-curing.

Abstract: The purpose of this research work was to develop a textile finish based on the radical UV-curing of chitosan on textiles to confer antimicrobial properties. Chitosan is a biopolymer with unique properties such as biodegradability, non-toxicity, antimicrobial activity. In this work cotton or silk fabrics and synthetic filter fabrics were impregnated with an acid solution of chitosan added of the photoinitiator in the proper amount and cured at room temperature by exposure to UV lamp. Process conditions such as percentage add-on, dilution, chitosan-fabric contact time, irradiation time and power, were optimized. The antimicrobial activity of finished fabrics was tested according to ASTM E 2149-01 standard test performed with Escherichia Coli ATCC 8739. Moreover dyeing test with Turquoise Telon dye were carried out to evaluate the treatment homogeneity while the amino group content was determined by ninhydrin assay. Moreover on cotton and silk fabrics the treatment fastness to domestic laundering was tested, according to UNI EN ISO105-C01. Obtained results showed a strong antimicrobial activity conferred by the treatment, homogeneous on fabric surface. It is evident already at low add-on, without affecting the hand properties of natural fabrics and the filtration characteristics of the synthetic filter fabrics. Finally, washing fastness was better for samples prepared with a better penetration of chitosan inside the fibers.

Future prospects of NAND flash memory technology--the evolution from floating gate to charge trapping to 3D stacking.

Abstract: NAND Flash memory has scaled at phenomenal speed in the last decade and conventional floating gate (FG) Flash memory has now commenced volume production in the 2X nm node. Despite this stunning success, the technology challenges are formidable below 20 nm. Charge-trapping (CT) devices are promising to scale beyond 20 nm but below 10 nm both CT and FG devices hold too few electrons for robust MLC (Multi-level Cell, or more than one bit storage per cell) storage. The simpler structure and its more robust storage (not sensitive to tunnel oxide defects since charges are stored in deep trap levels) also make CT suitable for 3D stacking. Optimistically, 3D CT Flash memory may allow the density increase to continue for at least another decade beyond the 1X nm node. In this paper, we review the current status of FG devices, their scaling challenges, and the operation principles of CT devices and several variations such as TANOS and BE-SONOS. We will then discuss various 3D memory architectures, technology challenges and address the poly-silicon thin film transistor (TFT) issues.

Nanoscale ZnO induces cytotoxicity and DNA damage in human cell lines and rat primary neuronal cells.

Abstract: The toxic effects of ZnO nanoparticles (nano-ZnO) (1-100 microg/mL) suspended in DMEM were examined in human A549 cells, HepG2 cells, human skin fibroblast cells, human skin keratinocytes, and rat primary neuronal cells for 24 h Nano-ZnO induced dose dependent cytotoxicity and damaged cell membranes Cell death was not mediated by reactive oxygen species (ROS) or apoptosis Nano-ZnO induced DNA damage in rat primary neuronal cells, human fibroblasts, and A549 cells The cytotoxicity of nano-ZnO in DMEM supplemented with 10% FBS, instead of serum free DMEM, was also examined in the A549 cells, human skin fibroblast cells, and human skin keratinocytes The levels of cytotoxicity induced were similar to those tested without FBS; in addition, ROS was observed These results indicate that the cause of cytotoxicity is medium dependent and imply that cellular growth conditions may play a significant role in induction of cytotoxicity and DNA damage by nano-ZnO

Effect of the drying conditions on the microstructure of silica based xerogels and aerogels.

Abstract: Nanostructured silica based xerogels and aerogels are prepared by sol-gel technology, using methyltrimethoxysilane as precursor. The influence of the drying method and conditions on the microstructure of the obtained materials is investigated, since the drying stage has a critical influence on their porosity. Two types of drying methods were used: atmospheric pressure drying (evaporative), to produce xerogels, and supercritical fluids drying, to obtain aerogels. Although the supercritical fluids drying technique is more expensive and hazardous than the atmospheric pressure drying, it is well known that aerogels are less dense than the xerogels due to less pore shrinkage. However, the ideal situation would be to use atmospheric pressure drying in conditions that minimize the pore collapse. Therefore, in this work, different temperature cycles for atmospheric pressure drying and two heating rates for the supercritical fluids drying are tested to study the gels' shrinkage by analyzing the density and porosity properties of the final materials. The best materials obtained are aerogels dried with the lower heating rate (approximately 80 degrees C/h), since they exhibit very low bulk density (approximately 50 kg/m3), high porosity (95%)-mainly micro and mesopores, high surface area (approximately 500 m2/g), moderate flexibility and a remarkable hydrophobic character (>140 degrees). It was proved that the temperature cycles of atmospheric pressure drying can be tuned to obtain xerogels with properties comparable to those of aerogels, having a bulk density only approximately15 kg/m3 higher. All the synthesized materials fulfill the requirements for application as insulators in Space environments.

Comparisons between TiO2- and SiO2-flux assisted TIG welding processes.

Abstract: This study investigates the effects of flux compounds on the weld shape, ferrite content, and hardness profile in the tungsten inert gas (TIG) welding of 6 mm-thick austenitic 316 L stainless steel plates, using TiO2 and SiO2 powders as the activated fluxes. The metallurgical characterizations of weld metal produced with the oxide powders were evaluated using ferritoscope, optical microscopy, and Vickers microhardness test. Under the same welding parameters, the penetration capability of TIG welding with TiO2 and SiO2 fluxes was approximately 240% and 292%, respectively. A plasma column made with SiO2 flux exhibited greater constriction than that made with TiO2 flux. In addition, an anode root made with SiO2 flux exhibited more condensation than that made with TiO2 flux. Results indicate that energy density of SiO2-flux assisted TIG welding is higher than that of TiO2-flux assisted TIG welding.

Morphological modification of MWCNT functionalized with HNO3/H2SO4 mixtures.

Abstract: The acidic oxidation with HNO3/H2SO4 mixtures is widely reported as an effective method to functionalize multi-walled carbon nanotubes (MWCNT). Although effective, a bad control of the oxidation conditions frequently cause serious modifications of carbon nanotube network, limiting further potential applications. Investigations about the effect of functionalization operating conditions on the morphological, chemical and chemical-physical properties of MWCNT can be useful for a proper setting of oxidation reactions of MWCNT according to their specific applications. In this work the effect of HNO3/H2SO4 ratio on the morphological and chemical-physical properties and on the degree of functionalization of MWCNT was investigated. Electron microscopy, thermogravimetric, X-ray diffraction, titration and water dispersion analyses clearly revealed that the increase of the amount of concentrated sulphuric acid in the HNO3/H2SO4 mixture lead to an increase of the amount of functional groups on the MWCNT surface but also to an increase of structural damage in terms of tube cutting and generation of additional defects in the graphitic network of pristine.

Synthesis, characterization, and antimicrobial activity of nano-hydroxyapatite-zinc for bone tissue engineering applications.

Abstract: The bone implants used in tissue repair are susceptible to infections caused by staphylococci, specifically Staphylococcus aureus. Hence, the development of better biological materials that provide antimicrobial activity in bone tissue engineering is required. The nanoparticles of hydroxyapatite (nHAp) and nHAp dopped with Zn (nHAp-Zn) were prepared by the wet chemical method and the ion exchange method, respectively. They were characterized using SEM, AFM, FTIR and XRD. The antibacterial activity of nHAp and nHAp-Zn was determined with Gram-negative and Gram-positive bacterial strains. The results indicated that nHAp alone was acting as an inert matrix and when substituted with Zn, it showed better antibacterial activity. The nHAp-Zn was found to be non-toxic to osteoprogenitor cells. Thus, due to the antimicrobial property of nHAp-Zn nanoparticles, we suggest that they would have potential applications towards bone tissue engineering.

Optimizing hemocompatibility of surfactant-coated silver nanoparticles in human erythrocytes.

Abstract: Several recent biological science studies have been focused on nanotechnology and nanomaterials due to their potential use in biomedicine. Drug delivery systems are an example of biomedical applications utilizing nanoparticles. Silver nanoparticles (AgNPs) can be used for these drug delivery systems. However, the effects of cytotoxicity caused by AgNPs are not fully understood. Determining the optimal characteristics to facilitate the biocompatibility of AgNPs is an important subject for application. In the present study, human erythrocytes were used as an in vitro model to examine the size, dose, and coating surfactant-dependent cytotoxicity of AgNPs. Our results demonstrated that polyvinylpyrrolidone (PVP) was a more suitable surfactant than polyethylene glycol (PEG) for AgNPs capping. In addition, we determined the appropriate particular size and dosage of AgNPs to reduce human erythrocytes hemolysis. Membrane damages including hemolysis, potassium efflux, protein leakage, and alterations in cell shape and membrane fragility were minimized with 100-nm AgNP particles. This study provides novel insights into AgNPs cytotoxicity and a basis for utilizing AgNPs for diagnostic and therapeutic applications.

Actuating and Sensing Properties of Nanoporous Gold

Abstract: We show that variations in the relative humidity give rise to reversible macroscopic dimensional changes in nanoporous gold exposed to ambient air. The macroscopic strain is the consequence of changes in the nanoporous gold surface stress. We have measured reversible strain amplitudes up to 0.02% in response to a 15% change in relative humidity. The direct conversion into mechanical work of the energy involved in the liquid to vapor phase transition of water is attractive for environmentally friendly short-stroke actuator and sensor applications.

Nanoemulsions as delivery systems for lipophilic drugs.

Abstract: Nanoemulsions have received a growing attention as colloidal drug carriers for pharmaceutical applications. Their advantages over conventional formulations include drug enhanced solubility and bioavailability, protection from toxicity, improved pharmacological activity and stability, more sustained delivery and protection from physical and chemical degradation. Nanoemulsions can be prepared by two major techniques, high-energy and low-energy emulsification. Both these emulsification methods have proved to be efficient to obtain stable nanoemulsions with small and highly uniform droplets. Further research into nanoemulsions is important to develop novel liquid formulations with more efficient results in therapeutic.

Characterization of surface accumulation and release of nanosilica during irradiation of polymer nanocomposites by ultraviolet light.

Abstract: Polymer nanocomposites are increasingly used in applications that are subjected to harsh environments. Owing to polymer's susceptibility to photodegradation, nanofillers in a polymer nanocomposite may be released into the environments during the composite's life cycle. Such release potentially poses an environmental health and safety problem and may hinder commercialization of these advanced materials. This study investigated the fate and release of nanosilica from epoxy/nanosilica composites. Specially-designed holders containing nanocomposite specimens were irradiated with UV light in a well-controlled environmental chamber. UV irradiated samples were removed for measurements of polymer chemical degradation, mass loss, surface morphology, nanosilica accumulation on the composite surface, and nanosilica release. Epoxy matrix underwent rapid photodegradation, resulting in substantial accumulation of silica nanofillers on the composite surface and also release from the composite. A conceptual model for surface accumulation and release of nanosilica during UV irradiation of epoxy nanocomposites is presented.

Gold-coated iron oxide nanoparticles as a T2 contrast agent in magnetic resonance imaging.

Abstract: Gold-coated iron oxide (Fe3O4) nanoparticles were synthesized for use as a T2 contrast agent in magnetic resonance imaging (MRI). The coated nanoparticles were spherical in shape with an average diameter of 20 nm. The gold shell was about 2 nm thick. The bonding status of the gold on the nanoparticle surfaces was checked using a Fourier transform infrared spectrometer (FTIR). The FTIR spectra confirmed the attachment of homocysteine, in the form of thiolates, to the Au shell of the Au-Fe3O4 nanoparticles. The relaxivity ratio, R2/R1, for the coated nanoparticles was 3-fold higher than that of a commercial contrast agent, Resovist, which showed the potential for their use as a T2 contrast agent with high efficacy. In animal experiments, the presence of the nanoparticles in rat liver resulted in a 71% decrease in signal intensity in T2-weighted MR images, indicating that our gold-coated iron oxide nanoparticles are suitable for use as a T2 contrast agent in MRI.

Fullerene C60 prevents neurotoxicity induced by intrahippocampal microinjection of amyloid-beta peptide.

Abstract: The dynamics of the state of hippocampal pyramidal neurons after intrahippocampal microinjections of (1) amyloid-beta25-35 (1.6 nmol/1 microl), (2) an aqueous molecule-colloidal solution of C60 (0.46 nmol/1 microl) and (3) an aqueous molecule-colloidal solution of C60 before amyloid-beta25-35 administration were analysed in rats. This model allowed us to study the role of amyloid-beta25-35 in the pathogenesis of Alzheimer's disease and to test anti-amyloid substances. Methods of fluorescent (acridine orange) and brightfield (cresyl violet and immunohistochemistry) microscopy were used. Acridine orange staining indicated changes in protein synthesis intensity due to alterations in the rRNA state of neuron ribosomes. One day after administration of amyloid-beta25-35, the intensity of protein synthesis in the population of morphologically intact cells decreased by 45%. By day 14, degeneration occurred in the majority of pyramidal cells, and amyloid-beta25-35 deposits were observed in the neuronal cytoplasm. In necrotic cells, acridine orange staining of the cytoplasm was drastically increased as a result of RNA degradation rather than due to an increase in protein synthesis. Because amyloid-beta25-35 administration provoked oxidative stress, we assumed that an aqueous molecule-colloidal solution of C60 administered before amyloid-beta25-35 prevented protein synthesis changes on day 1, while acting as an antioxidant, and by day 14 it inhibited neurodegeneration and amyloid-beta25-35 accumulation. Based on the data that an aqueous molecule-colloidal solution of C60 prevented amyloid-beta25-35 aggregation in in vitro experiments and based on our present evidence on the antitoxicity of an aqueous molecule-colloidal solution of C60, we suggest that functionalised C60 prevents/diminishes amyloid-beta25-35 aggregation in vivo as well. Thus, an aqueous molecule-colloidal solution of C60 administered at a low concentration before amyloid-beta2-35, prevented disturbances in protein synthesis, neurodegeneration and formation amyloid-beta25-35 deposits in hippocampal pyramidal neurons in vivo. This evidence gives promise that functionalised C60 can be used to develop anti-amyloid drugs combining antioxidant and anti-aggregative properties.

Ni doped Fe3O4 magnetic nanoparticles.

Abstract: In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.

Chemical Vapor Deposition Synthesis of Carbon Nanotube-Graphene Nanosheet Hybrids and Their Application in Polymer Composites

Abstract: Both carbon nanotubes (CNTs) and graphene nanosheets (GNs) have potential applications in polymer composites. Combining them may induce a synergistic effect on enhancing the properties of composites. Herein, CNT-GN 3D hybrids were prepared by liquid injection chemical vapor deposition through a spray containing both carbon feedstocks and catalyst precursors. Vertically aligned CNTs were self-organized on the GNs. The morphology of hybrids could be well controlled as a function of the synthesis parameters. The unique 3D geometry of the CNT-GN hybrids provided composites with a higher electrical conductivity as compared to composites solely reinforced by CNTs or GNs. However, the thermal stability of the neat poly(vinylidene fluoride) matrix was found to decrease upon the addition of these hybrid fillers.

Development of novel guava puree films containing chitosan nanoparticles.

Abstract: One of the overall goals of industries is to use packages that do not cause environmental problems at disposal time, but that have the same properties as the conventional ones. The goal of this study is to synthesize edible films based on hydroxypropyl methylcellulose (HPMC) with guava puree and chitosan (CS) nanoparticles. This was divided into two stages, the first is the synthesis of chitosan nanoparticles and the second is the production of the films. For the nanoparticles, average size and zeta potential measurements were performed. The characterizations of mechanical and thermal properties, solubility and water vapor permeability tests were conducted in the films. It was observed that when the nanoparticles were added to HPMC and guava puree films, they improved their mechanical and thermal properties, as well as decreased the films solubility and permeability. The potential application of the films prepared would be in edible films with flavor and odor to extend the shelf life of products.

Artemisia capillaris extracts as a green factory for the synthesis of silver nanoparticles with antibacterial activities.

Abstract: We report a green synthesis of silver nanoparticles that uses extracts from the aerial part of Artemisia capillaris. Both water and 70% ethanol extracts successfully generated silver nanoparticles. The formation of silver nanoparticles was confirmed by surface plasmon resonance bands, Fourier transform-infrared spectra, high resolution-transmission electron and atomic force microscopic images. Various shapes of silver nanoparticles were generated with an average diameter of 29.71 nm with water extract and 29.62 nm with 70% ethanol extract. An improvement in antibacterial activity (MIC 8.35-16.7 microg/mL) was observed against a total of twenty different strains of Gram-negative and Gram-positive bacteria. A remarkable enhancement (approximately 12-fold) was observed against Pseudomonas aeruginosa, Escherichia coli, Enterobacter cloacae, Klebsiella oxytoca, and Klebsiella areogenes when compared with the extract alone. Silver nanoparticles produced by the 70% ethanol extract showed slightly higher antibacterial activity than those generated with the water extract. The correlation between total flavonoid content of each extract and the antibacterial activity did not exert any significant relationships. This report suggests that plant extracts have the potential to be used as powerful reducing agents for the production of biocompatible silver nanoparticles possessing enhanced antibacterial activities.

Synthesis and characterizations of Cd-doped ZnO multipods for environmental remediation application.

Abstract: Well-crystalline Cd-doped ZnO multipods were synthesized by simple and facile hydrothermal process by using zinc chloride, cadmium chloride, hexamethylenetetramine and ammonium hydroxide at low-temperature. The synthesized materials were characterized in terms of their morphological, structural, compositional and optical properties. The morphological investigations done by field emission scanning electron microscopy (FESEM) reveal that the synthesized products are multipods shaped and grown in high density. The structural and compositional properties, observed by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) attached with FESEM and Fourier transform infrared (FTIR) spectroscopy exhibit that the synthesized multipods are well-crystalline and possessing wurtzite hexagonal phase pure Cd-doped ZnO. The as-synthesized Cd-doped ZnO multipods exhibited good optical properties as was confirmed by UV-vis. spectroscopy. Finally, the as-synthesized Cd-doped ZnO multipods were used environmental remediation application. For this, the synthesized multipods were used as an effective photocatalyst for the photocatalytic degradation of acridine orange (AO) which exhibit similar to 92.4% degradation within 90 min. This work demonstrates that doped ZnO materials could be used as efficient photocatalyst for the photocatalytic degradation of various organic dyes and chemicals.