Electrically conducting polymers as templating interfaces for fabrication of copper nanotubes.

Submicrometer tubes have been fabricated by a polymer-based template approach using electroless deposition. The copper was deposited on polystyrene fibers functionalized with an interfacial electrically conducting polyaniline thin film layer. Thermal degradation of the functionalized fiber templates resulted in copper tubes of diameter 1600 ± 50 nm with wall thicknesses ranging between 100 and 200 nm. The morphology and elemental analysis of copper coaxial fibers was analyzed using SEM and EDS. Electrical properties were analyzed using FTIR and PXRD was used to study crystal structure of copper nanotubes.

Perspectives on the Development of Filter Media for Point of Use Water Filters: Case Study of Arsenate Removal.

The demand for access to clean water will continue to increase as the world population increases. For sustainable development and embracement of technological advancement, it is plausible to consider a filter material development approach that uses locally abundant natural resources as the raw material and nanotechnology techniques for material fabrication. The review and research paper will present a perspective of the authors on how to embrace nanotechnology for filter media development with key focus on the remediation of arsenate. Drinking water contaminated with arsenic is an emerging global challenge. Continuous exposure to drinking water with high levels arsenic could result in several types of cancer. With this in mind, the US EPA in 2001 set 10 ppb as the maximum contaminant level of arsenic from the initial 50 ppb. Therefore, arsenic remediation is key in mitigating these health risks in people residing near water bodies with elevated arsenic levels. Adsorption is considered to be the cheapest. However, from literature, majority of the adsorbents cannot be used in field applications due to challenges associated with low adsorption capacity and a high level of particle leaching into purified water thus posing health dangers. Therefore, it means that many of these adsorbents are economically non-viable. A new chitosan, aluminium, titanium, iron and zirconium (CTS-Al-Ti-Fe-Zr) hybrid was fabricated through the sol-gel process. The material was characterized by scanning electron microscopy, Brunauer-Emmett-Teller and Fourier Transform Infrared spectroscopy before and after adsorption. Batch adsorption properties towards As(V) were separately studied as a function of the effect of adsorbent dose, pH, initial concentration, contact time and competing ions. Characterization results show that the material is a polycrystalline with a specific surface area of 56.4 m2g-1. Further, FTIR and SEM-EDAX showed adsorption of arsenate on the surface of the nanocomposite. Research findings suggest that with only 100 mg of the adsorbent arsenate can be reduced to less than 10 ppb from an initial concentration of 300 ppb respectively. The maximum adsorption capacity for arsenate removal was recorded as 123 mg/g. The presence of SiO3 2-, CO3 2-, and HCO3 - ions resulted in a slight decline in the adsorption efficiency of arsenate. The equilibrium data fitted well with the Langmuir isotherm 0.99518. Data from the fabricated prototype Point-of-use filter showed that with 60.0 g of the nanocomposite, it is possible to reduce 650 L of drinking water with an arsenate initial concentration of 300 ppb to less 10 ppb. In conclusion, the research findings suggest that the nanocomposite material is capable of removal of arsenate from contaminated drinking water to WHO acceptable levels with a potential to be up scaled for commercial applications.

Enhancement of antibacterial activity through phyto-fabrication of silver nanoparticles with Ficus thonningii aqueous extracts.

The World Health Organisation reports higher levels of bacterial resistance to cephalosporins and carbapenems of above 54%. The sufficient redox capabilities of Ficus thonningii phytochemicals for Ag+  reduction to Ag0 and ultimately aggregation to nucleation are exploited for the first time in attempting to enhance the antibacterial activity. Solution colour change to brown due to surface plasmon resonance phenomenon confirmed nanoparticle fabrication with a UV/Vis absorption peak at 426 nm. Fourier Transform Infrared spectra revealed functional groups (C=C at 1620-1680 cm-1 ; C=H at 1400-1600 cm-1 aromatics) for encapsulation, stabilisation, and reduction of the silver ion. The Dynamic Light Scattering technique verified F. thonningii encapsulated silver nanoparticles particle size of 57.84 nm with a negative zeta potential (-19.8 mV) as proof of stability. The surface, shape and topographical features were shown by Scanning Electron Microscopy as spherical orientations. An enhanced antimicrobial efficacy was displayed by the nanoparticles (inhibition zones of 26.1, 24.1 and 15.2 mm from 11.5, 10.6 and 6.5 mm) for Staphylococcus aureus, Streptococcus pyrogenes and Escherichia coli, respectively, compared to Flucloxacillin standard that was in the ranges of 21.5, 23.5 and 25.7 mm. The enhanced potency provides a basis for diversified approaches of generating novel drugs for treating bacterial infections.

Polyacrylonitrile-based carbonized fibers and metal-carbonized fiber nanocomposites for thermal transport.

This work examines the fabrication and thermal analysis of metal-carbon composite fibers prepared via an electrospinning process. The metal-carbon composite fibers of silver, copper, gold, and nickel were prepared by electrospinning of a composite solution of polyacrylonitrile (PAN) and metal precursor followed by heat treatment in air, nitrogen to 1000 degrees C and in 6% H2, respectively. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy dispersive spectroscopy (EDS) and Scanning thermal microscopy (SThM) were applied to characterize the metal-carbon fibers. TEM analysis showed a relatively uniform, contact-free distribution of the nanoparticles on the surface of the carbon fibers with size range of 3 nm-10 nm. Thermal analysis data showed an enhancement in the thermal conductivity of the nanomaterials when compared with the model PAN-based carbonized fibers. This was attributed to the incorporation of metal nanoparticles in the fiber matrix and on the surface.

Green Synthesis and Characterization of Silver Nanoparticles Using Citrullus lanatus Fruit Rind Extract.

The wide-scale application of silver nanoparticles (AgNPs) in areas such as chemical sensing, nanomedicine, and electronics has led to their increased demand. Current methods of AgNPs synthesis involve the use of hazardous reagents and toxic solvents. There is a need for the development of new methods of synthesizing AgNPs that use environmentally safe reagents and solvents. This work reports a green method where silver nanoparticles (AgNPs) were synthesized using silver nitrate and the aqueous extract of Citrullus lanatus fruit rind as the reductant and the capping agent. The optimized conditions for the AgNPs synthesis were a temperature of 80°C, pH 10, 0.001 M AgNO3, 250 g/L watermelon rind extract (WMRE), and a reactant ratio of 4 : 5 (AgNO3 to WMRE). The AgNPs were characterized by Ultraviolet-Visible (UV-Vis) spectroscopy exhibiting a λmax at 404 nm which was consistent with the spectra of spherical AgNPs within the wavelength range of 380-450 nm, and Cyclic Voltammetry (CV) results showed a distinct oxidation peak at +291 mV while the standard reference AgNPs (20 nm diameter) oxidation peak occurred at +290 mV, and Transmission Electron Microscopy (TEM) revealed spherical shaped AgNPs. The AgNPs were found to have an average diameter of 17.96 ± 0.16 nm.

Templated synthesis of amphiphilic nanoparticles at the liquid-liquid interface.

A simple and reliable method is described to produce inorganic nanoparticles functionalized asymmetrically with domains of hydrophobic and hydrophilic ligands on their respective hemispheres. These amphiphilic, Janus-type particles form spontaneously by a thermodynamically controlled process, in which the particle cores and two competing ligands assemble at the interface between two immiscible liquids to reduce the interfacial energy. The asymmetric surface chemistry resulting from this process was confirmed using contact angle measurements of water droplets on nanoparticle monolayers deposited onto hydrophobic and hydrophilic substrates-particles presenting their hydrophobic face give contact angles of ∼96°, those presenting their hydrophilic face ∼19°. The spontaneous assembly process is rationalized by a thermodynamic model, which accounts both for the energetic contributions driving the assembly and for the entropic penalties that must be overcome. Consistent with the model, amphiphilic NPs form only when there is sufficient interfacial area to accommodate them; however, this potential limitation is easily overcome by mechanical agitation of the two-phase mixture. While it is straightforward to vary the ratio of hydrophobic and hydrophilic ligands, the accumulation of amphiphilic particles at the interface is maximal for ligand ratios near 1:1. In addition to gold nanoparticles and thiolate ligands, we demonstrate the generality of this approach by extending it to the preparation of amphiphilic iron oxide nanoparticles using two types of diol-terminated ligands. Depending on the material properties of the inorganic cores, the resulting amphiphilic particles should find applications as responsive particle surfactants that respond dynamically to optical (plasmonic particles) and/or magnetic (magnetic particles) fields.

Synthesis and optical properties of co-doped ZnO submicrometer tubes from electrospun fiber templates.

Submicrometer ZnO tubes have been synthesized by a polymer based template approach using sol-gel deposition. Zinc acetate, a precursor to ZnO, was deposited on catalytically active electrospun polycarbonate fibers approximately 250+/-100 nm in diameter. Thermal degradation of the core fibers resulted in the oxidation of zinc acetate to produce ZnO nanotubes with diameters of approximately 500+/-100 nm and an average wall thickness of approximately 100+/-50 nm. Scanning electron microscopy (SEM), Energy dispersive spectroscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and UV-visible spectroscopy were used to characterize the composition, structure, and morphology of the tubes. Powder X-ray diffraction results showed that a wurtzite crystalline phase was obtained. The UV-visible absorption spectrum was red-shifted by 25 nm due to narrowing of the ZnO band gap (approximately 3.22 eV) as a result of Co doping. Similarly, green band emission was not observed in the emission spectrum, while emission lifetime was determined to be 620 ps from photoluminescence studies.