Chemical synthesis and characterization of hydroxyapatite (HAp)-poly (ethylene co vinyl alcohol) (EVA) nanocomposite using a phosphonic acid coupling agent for orthopedic applications

A novel bio-analogue hydroxyapatite (HAp)-poly (ethylene co vinyl alcohol) (EVA) nanocomposite has been synthesized by a solution-based chemical methodology with varying HAp contents from 10 to 60% (w/w). The surface of HAp particles has been modified with 2-carboxyethylphosphonic acid in order to enhance the interfacial bonding interaction between HAp and EVA, and hence to improve the mechanical properties of the composite. The interfacial modification has been investigated through Fourier transform infrared absorption spectra (FTIR), X-ray diffraction (XRD) and thermal analyses. The surface morphology of the composite and the homogeneous dispersion of nanoparticles in the polymer matrix have been investigated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. The use of phosphonic acid coupling agent promotes the uniform dispersion of HAp particles in the polymer matrix with strong particle–polymer interfacial bonding, which leads to a significant improvement in mechanical properties of the composite. The cell viability test indicates that the HAp-EVA nanocomposite is cytocompatible. The developed HAp-EVA nanocomposite may be potentially used as bone substitutes.     

Rod-shaped polyaniline-barium ferrite nanocomposite: preparation, characterization and properties

Rod-shaped polyaniline (PANI)-barium ferrite nanocomposite was synthesized by in situ polymerization of aniline in the presence of BaFe(12)O(19) nanoparticles with diameters of 60-80?nm. The structure, morphology and properties of the nanocomposite were measured using powder x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometry. Different ferrite/PANI ratios were selected in order to study magnetic and conductive properties. The results indicated that there were some interactions between PANI chains and ferrite particles. The saturation magnetization and the coercivity varied with the ferrite content. The conductivity at room temperature decreased from 43.35 to 6.9 × 10(-2)?S?cm(-1) when the ferrite content changed from 0 to 50?wt%. The composite has excellent electromagnetic parameters which indicates potential application in high performance adsorbing materials in broadband and high frequency ranges. The polymerization mechanism and interactions in the nanocomposites were also studied.     

Preparation and characterization of hydroxyapatite/collagen nanocomposite gel

The self-organized hydroxyapatite/colagen (HAp/Col) nanocomposite fiber (79.6/20.4 weight ratio) was synthesized by a co-precipitation method using Ca(OH)2, H3PO4, and Col as starting substances. The gelation of the nanocomposite is essential in the application of the scaffold for bone tissue engineering. We successfully prepared HAp/Col nanocomposite gels by a facile novel method using a sodium phosphate buffer at pH 6.8. The water-insoluble nanocomposite was homogeneously dispersed in the buffer to form a viscous mixture, and gels were obtained after incubating of the mixture at 37 degrees C. The mechanical strength of the gels was analyzed against the incubation time. The demineralized gel with EDTA had the typical nanostructure of native type I Col fibers from the results of scanning electron microscopy (SEM) and atomic force microscopy (AFM); the dense network of type I Col nano-fibers below 100 nm in diameter, and the periodic pattern of 68.8+/-4.4 nm (mean +/- SD) along the fibers were observed. The gelation of the HAp/Col nanocomposite in the buffer is attributed to the physical cross-linking through entanglement of the reconstituted Col fibrils.     

Synthesis and field emission of single-crystalline copper vanadate nanobelts

Single-crystalline nanobelts of a nonstoichiometric compound Cu(1.55)V(2)O(6.55), with a thickness of 40-60?nm, width of 50-300?nm and length of several micrometers, have been synthesized on a large scale by a hydrothermal method. The structures and morphologies of the nanobelts were characterized by x-ray powder diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. A probable growth mechanism has also been discussed. The nanobelts exhibit a turn-on field of 11.0?V?μm(-1), which is defined as the macroscopic field required to produce a current density of 10?μA?cm(-2). It is anticipated that the nanobelts can serve as a candidate material for future field emitters.     

Thermally assisted semiconductor-like to insulator transition in gold-poly(methyl methacrylate) nanocomposites

Gold-polymethylmethacrylate (PMMA) nanocomposites were fabricated by mixing gold nanoparticles capped with oleylamine in polymethylmethacrylate. The samples were analysed using UV-vis absorption spectroscopy, transmission electron microscopy, small angle x-ray scattering, Fourier transform infrared spectrometry (FTIR) and x-ray photoelectron spectroscopy (XPS). Electrical resistivity of nanocomposite samples was measured by a four-probe technique in the 70-300?K range. The nanocomposites showed a transition with an onset at ～160-165?K. They exhibited a semiconductor-like conductivity at higher temperatures and nearly temperature independent conductivity at lower temperatures. The interfacial interaction of Au nanoparticles and PMMA polymer is investigated using FTIR and XPS. A ligand-exchange process occurs when capped gold nanoparticles are incorporated in PMMA polymer.     

Synthesis of PbS/poly (vinyl-pyrrolidone) nanocomposite

A simple solution growth method for synthesis of nanocomposite of PbS nanoparticles in poly(vinyl-pyrrolidone) (PVP) polymer is described. The nanocomposite is prepared from methanolic solution of lead acetate (PbAc), thiourea (TU) and PVP at room temperature (∼27 °C). Optical absorption spectrum of PbS/PVP nanocomposite solution shows strong absorption from 300 to 650 nm with significant bands at 400 and 590 nm which is characteristic of nanoscale PbS. Spin-coated nanocomposite films on glass have an absorption edge at ∼650 nm with band gap of 2.55 eV. Fourier transform infrared (FTIR) spectroscopy of PbS/PVP nanocomposite and PVP shows strong chemical bond between PbS nanoparticles and host PVP polymer. The transmission electron microscope (TEM) images reveal that 5-10 nm PbS particles are evenly embedded in PVP polymer. The formation of PbS is confirmed by selective area electron diffraction (SAED) of a typical nanoparticle.     

Stoichiometry of alloy nanoparticles from laser ablation of PtIr in acetone and their electrophoretic deposition on PtIr electrodes

Charged Pt-Ir alloy nanoparticles are generated through femtosecond laser ablation of a Pt?Ir target in acetone without using chemical precursors or stabilizing agents. Preservation of the target's stoichiometry in the colloidal nanoparticles is confirmed by transmission electron microscopy (TEM)-energy-dispersive x-ray spectroscopy (EDX), high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM)-EDX elemental maps, high resolution TEM and selected area electron diffraction (SAED) measurements. Results are discussed with reference to thermophysical properties and the phase diagram. The nanoparticles show a lognormal size distribution with a mean Feret particle size of 26 nm. The zeta potential of -45 mV indicates high stability of the colloid with a hydrodynamic diameter of 63 nm. The charge of the particles enables electrophoretic deposition of nanoparticles, creating nanoscale roughness on three-dimensional PtIr neural electrodes within a minute. In contrast to coating with Pt or Ir oxides, this method allows modification of the surface roughness without changing the chemical composition of PtIr.     

Microwave-assisted rapid synthesis of anisotropic Ag nanoparticles by solid state transformation

Anisotropic silver nanoparticles (NPs) have been synthesized rapidly using microwave irradiation by the decomposition of silver oxalate in a glycol medium using polyvinyl pyrolidone (PVP) as the capping agent. The obtained Ag nanoparticles have been characterized by UV-visible spectroscopy, powder x-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) studies. Anisotropic Ag nanoparticles of average size around 30?nm have been observed in the case of microwave irradiation for 75?s whereas spherical particles of a size around 5-6?nm are formed for 60?s of irradiation. The texture coefficient and particle size calculated from XRD patterns of anisotropic nanoparticles reveal the preferential orientation of (111) facets in the Ag sample. Ethylene glycol is found to be a more suitable medium than diethylene glycol. A plausible mechanism has been proposed for the formation of anisotropic Ag nanoparticles from silver oxalate.     

Pt nanostructure electrodes pulse electrodeposited in PVP for electrochemical power sources

In this work, we demonstrated that Pt nanostructure electrodes could be obtained by the pulse electrodeposition method in polyvinylpyrrolidone (PVP). The nanocrystal particles were confirmed by scanning electron microscopy, transmission electron microscopy and x-ray diffraction methods. The average size of Pt nanoparticles deposited in additive PVP with low and high molecular weight is 3.4 and 2.9?nm, respectively, whereas that of Pt electrodeposited without PVP is 360?nm. This means that the size of Pt nanoparticles can be controlled by PVP, resulting in an increased electrochemical surface area. The resulting Pt nanostructure electrodes showed such an improved performance for both direct methanol fuel cells and dye-sensitized solar cells.     

Enhanced x-ray irradiation-induced cancer cell damage by gold nanoparticles treated by a new synthesis method of polyethylene glycol modification

We explored a very interesting gold nanoparticle system-pegylated gold in colloidal solution-and analyzed its uptake by mice colorectal adenocarcinoma CT26 tumor cells and the impact on the cell's response to x-ray irradiation. We found that exposure to polyethylene glycol (PEG) modified ('pegylated') 4.7 ± 2.6?nm gold nanoparticles synthesized by a novel synchrotron-based method enhances the response of CT26 cells to x-ray irradiation. Transmission electron microscopy (TEM) and confocal microscopy revealed that substantial amounts of such nanoparticles are taken up and absorbed by the cells and this conclusion is supported by quantitative induced coupled plasma (ICP) results. Standard tests indicated that the internalized particles are highly biocompatible but strongly enhance the cell damage induced by x-ray irradiation. Synchrotron radiation Fourier transform infrared (SR-FTIR) spectromicroscopy analyzed the chemical aspects of this phenomenon: the appearance of C = O stretching bond spectral features could be used as a marker for cell damage and confirmed the enhancement of the radiation-induced toxicity for cells.     

Low-temperature sol-gel-derived nanosilver-embedded silane coating as biofilm inhibitor

Silver nanocomposite coatings are prepared by the sol-gel method for the prevention of biofilm formation on the surface of medical implanted devices. High-temperature processing of such coatings can lead to diffusion of nanosilver and reduce the amount of available silver particles for long-term effects. Using a low-temperature sol-gel method, we have successfully prepared silane-based matrices, phenyltriethoxysilane (PhTEOS), containing different amounts of Ag nanoparticles. The incorporation of a silver salt into the sol-gel matrix resulted in a desired silver release rate, i.e. high initial release rate followed by a lower sustained release for more than 15 days, as determined by inductively coupled plasma mass spectrometry (ICP-MS). Scanning electron microscopy (SEM) has been employed to investigate the morphology of the film surfaces before and after immersion in a nutrient-rich bacterial suspension of approximately 10? CFU ml?1, which was incubated for up to 30 days at 37?°C. It was found that thin films containing 35 nm particles could prevent the formation of biofilm for over 30 days. The presence of surface silver before and after 3, 9 and 15 days immersion was confirmed by x-ray photoelectron spectroscopy (XPS).     

Synthesis of WO(3) nanoparticles using a biopolymer as a template for electrocatalytic hydrogen evolution

Tungsten trioxide nanoparticles were prepared by a simple approach using chitosan biopolymer as a template. These nanoparticles were characterized using x-ray diffraction, Raman spectroscopy, transmission electron microscopy and high resolution transmission electron microscopy. The average size of the WO(3) nanoparticles is 42?nm, and they intercalate a larger amount of hydrogen than tungsten trioxide, which is prepared without chitosan. The materials are tested for their electrocatalytic hydrogen evolution in a sulfuric acid medium, where WO(3) nanoparticles show a fourfold higher activity than bulk tungsten trioxide.     

Synthesis and characterization of a nanocomposite NiO/SiO2 from a sustainable source of SiO2

ABSTRACT

The search for raw materials obtained from renewable sources is necessary for the sustainable development in the production of engineering materials. In this study, we present the hydrothermal synthesis of biogenic silica extracted from rice husk for the production of NiO/SiO₂ nanocomposite by Pechini method and employed an alternative strategy for the use of tetraethylorthosilicate as precursor agent. The synthesized nanocomposite presents amorphous SiO₂ nanoparticles dispersed in a NiO matrix as observed in the x-ray diffraction patterns and by scanning electron microscopy characterization. The average size of the crystallite measured by XRD was 11?nm. The formation of the aimed composite containing 83% of NiO crystalline phase and 17% of SiO₂ in amorphous phase was confirmed by Infrared and Raman spectroscopic analyses. These results demonstrate that it is possible to develop synthetic routes to produce new materials using several raw materials from sustainable sources and thus reducing environmental impact.     

Synthesis of AgBr/ZnO nanocomposite with visible light-driven photocatalytic activity

AgBr/ZnO nanocomposite was synthesized via chemical precipitation from pure ZnO nanowires, AgNO₃, and NaBr. Inductively coupled plasma optical emission spectroscopy, X-ray diffraction, and high resolution transmission electron microscopy results confirmed the forming of AgBr/ZnO nanocomposite. High resolution transmission electron microscopy results of the as-synthesized AgBr/ZnO nanocomposite revealed that AgBr nanoparticles were attached to the surface of ZnO nanowires. UV-vis diffuse reflectance spectra of both pure ZnO and AgBr/ZnO nanocomposite displayed a band gap edge at about 350-380 nm. However, compared with pure ZnO, an additional broad tail from approximately 400 nm to 700 nm appeared in the UV-vis diffuse reflectance spectrum of AgBr/ZnO nanocomposite. The photocatalytic studies indicated that the as-synthesized AgBr/ZnO nanocomposite was a kind of promising photocatalyst in remediation of water polluted by some chemically stable azo dyes under visible light.     

Facile aqueous synthesis and growth mechanism of CdTe nanorods

Single-crystal CdTe nanorods with diameters of 50-100?nm were synthesized under a surfactant-assisted hydrothermal condition. The experimental results indicated that with a temporal dependence the morphologies of CdTe nanocrystallites changed from nanoparticles to smooth surface nanorods. The crystal structure, morphology and optical properties of the products were investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and fluorescence spectrophotometer. Furthermore, the formation mechanisms of the nanorods were investigated and discussed on the basis of the experimental results.     

Synthesis of nanosize single-crystal hydroxyapatite via mechanochemical method

Single-crystal hydroxyapatite (HAp) nanorods and nanogranules have been synthesized successfully by a mechanochemical process using two distinct experimental procedures. The experimental outcomes are characterized by transmission electron microscopy (TEM), and powder X-ray diffraction (XRD) techniques. In this work, the feasibility of using polymeric milling media to prepare hydroxyapatite nanoparticles is described. The resulting hydroxyapatite powder exhibits an average size of about 20 to 23 nm. Final results indicate that the proposed synthesis strategy provides a facile pathway to obtain single-crystal HAp with high quality and suitable morphology.     

Preparation, characterization and photocatalytic properties of CdS nanoparticles dotted on the surface of carbon nanotubes

Cadmium sulfide (CdS) nanoparticles dotted on the surface of multiwalled carbon nanotubes (MWCNTs) have been synthesized by the polyol method. The as-prepared materials were characterized by x-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, and Brunauer-Emmett-Teller adsorption analysis. The results indicate that CdS nanoparticles with diameter of 5-8?nm are thickly and uniformly coated on the surface of the MWCNTs. The photodegradation of azo dye using these materials was evaluated by the degradation of Brilliant Red X-3B under visible light. The coated nanotubes show higher photocatalytic activity than both CdS alone and a CdS/activated carbon sample; in addition, there is an optimum content of MWCNTs. The presence of MWCNTs can also hamper the photocorrosion of CdS. The mechanism for the enhancement of MWCNTs on the adsorption and photocatalytic property of CdS is investigated for the first time.     

Room temperature ferromagnetism in CoO nanoparticles obtained from sonochemically synthesized precursors

In this paper we report the magnetic properties of nanosized CoO particles, prepared from sonochemically synthesized precursors and characterized using x-ray diffraction (XRD), conventional transmission electron microscopy (TEM) and scanning tunneling electron microscopy combined with energy dispersive x-ray analysis (STEM-EDX) techniques. The nanoparticles were faceted and the sizes varied between 30 and 60?nm depending on the time of annealing. They were stable even in the absence of any organic coating on them. Magnetic measurements reveal the presence of ferromagnetic interactions at low temperatures in the CoO nanoparticles synthesized after 2 and 4?h of annealing of the sonochemically synthesized precursor under nitrogen. However, after 6?h of annealing, the nanoparticles show hysteresis not only at low temperatures (1.5?K) but also at higher temperatures (100?K and room temperature), indicating the presence of room temperature ferromagnetism.     

Hydroxyapatite/ovalbumin composite particles as model protein carriers for bone tissue engineering: I. Synthesis and characterization

Hydroxyapatite (HAp) nanoparticles were synthesized from the co-precipitation reaction between calcium oxide from discarded egg shells and phosphoric acid in the absence and the presence of ovalbumin (OVA). 2-Amino-2-hydroxymethyl-propane-1,3-diol (tris-base) was used to control the pH during the co-precipitation (i.e., 7–9). The formation of HAp was confirmed by X-ray diffraction analysis, while both the Fourier-transform infrared spectroscopy and the thermogravimetric analysis confirmed the existence of OVA within the HAp–OVA particles. The crystallite sizes of the individual crystalline entities within the HAp and the HAp–OVA particles were approximated from the (002) reflection peaks by means of the Scherrer's equation. The average particle sizes of the HAp and the HAp–OVA particles were measured by particle size analysis. Transmission electron microscopy revealed that these particles were aggregates of rod-like HAp nanocrystals, whereas scanning electron microscopy revealed that these particles ultimately formed into larger aggregates. Lastly, the decrease in the pH during the precipitation process and the presence of OVA were responsible for the observed increase in the values of pore size, BET specific surface area, and pore volume of the resulting HAp particles.     

Synthesis and characterization of a new trifunctional magnetic-photoluminescent-oxygen-sensing nanomaterial

Magnetic Fe(2)O(3) nanoparticles coated with SiO(2) chemically doped with a Ru(II) complex were prepared using a simple solution based method. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) showed that the Fe(2)O(3) nanoparticles with a mean diameter of ～115?nm were successfully coated with Ru(II) complex-chemically doped SiO(2) shell with a thickness of ～30?nm. The obtained nanocomposite material showed a strong magnetic response to a varying magnetic field, exhibited the bright red triplet metal-to-ligand charge transfer ((3)MLCT) emission, and its photoluminescent intensity was sensitive to oxygen concentration. Compared with the Ru(II) complex in silica gels, the Ru(II) complex in the magnetic-optical-oxygen-sensing nanocomposite demonstrated improved thermodynamic stability of emissions. These nanocomposites are also nontoxic and easily conjugated with biomolecules. Their magnetic, photoluminescent and oxygen-sensing properties make them promising candidates for cell separation, biomarkers and optical oxygen sensors, which can measure the O(2) concentration in biological bodies.