Repairing Peripheral Nerves:Is there a Role for Carbon Nanotubes?

Peripheral nerve injury continues to be a major global health problem that can result in debilitating neurological deficits and neuropathic pain. Current state-of-the-art treatment involves reforming the damaged nerve pathway using a nerve autograft. Engineered nerve repair conduits can provide an alternative to the nerve autograft avoiding the inevitable tissue damage caused at the graft donor site. Commercially available nerve repair conduits are currently only considered suitable for repairing small nerve lesions; the design and performance of engineered conduits requires significant improvements to enable their use for repairing larger nerve defects

Carbon-cryogel hierarchical composites as effective and scalable filters for removal of trace organic pollutants from water

Effective technologies are required to remove organic micropollutants from large fluid volumes to overcome present and future challenges in water and effluent treatment. A novel hierarchical composite filter material for rapid and effective removal of polar organic contaminants from water was developed. The composite is fabricated from phenolic resin-derived carbon microbeads with controllable porous structure and specific surface area embedded in a monolithic, flow permeable, poly(vinyl alcohol) cryogel. The bead-embedded monolithic composite filter retains the bulk of the high adsorptive capacity of the carbon microbeads while improving pore diffusion rates of organic pollutants. Water spiked with organic contaminants, both at environmentally relevant concentrations and at high levels of contamination, was used to determine the purification limits of the filter. Flow through tests using water spiked with the pesticides atrazine (32 mg/L) and malathion (16 mg/L) indicated maximum adsorptive capacities of 641 and 591 mg pollutant/g carbon, respectively. Over 400 bed volumes of water contaminated with 32 mg atrazine/L, and over 27,400 bed volumes of water contaminated with 2 μg atrazine/L, were treated before pesticide guideline values of 0.1 μg/L were exceeded. High adsorptive capacity was maintained when using water with high total organic carbon (TOC) levels and high salinity. The toxicity of water filtrates was tested in vitro with human epithelial cells with no evidence of cytotoxicity after initial washing

Use of iron-based technologies in contaminated land and groundwater remediation: a review

Reactions involving iron play a major role in the environmental cycling of a wide range of important organic, inorganic and radioactive contaminants. Consequently, a range of environmental clean-up technologies have been proposed or developed which utilise iron chemistry to remediate contaminated land and surface and subsurface waters, e.g. the use of injected zero zero-valent iron nanoparticles to remediate organic contaminant plumes; the generation of iron oxyhydroxide-based substrates for arsenic removal from contaminated waters; etc. This paper reviews some of the latest iron-based technologies in contaminated land and groundwater remediation, their current state of development, and their potential applications and limitations

Effect of undensified silica fume on the dispersion of carbon nanotubes within a cementitious composite

The synergistic effect of multi-walled carbon nanotubes (MWCNTs) and Undensified Silica Fume (USF) on the microstructure of cementitious composites has been studied. In the current work, USF was used to enhance the dispersion of nanotubes throughout the composite and prevent the re-agglomeration of nanotubes by providing a physical barrier of particles of small size. Ultrasonication was employed to disperse MWCNTs in water in the presence of polycarboxylate-based superplasticizer (PCE) as a dispersion agent. The results indicate that incorporation of USF considerably improves the dispersion of nanotubes in the composites, with subsequent enhancement of composite packing density. This enhancement can be attributed to the synergistic effect of MWCNTs and USF in reducing the volume of pores through the cementitious composites

Effect of high-intensity sonication on the dispersion of carbon-based nanofilaments in cementitious composites, and its impact on mechanical performance

Carbon-based nanofilaments are promising materials for improving the mechanical performance of cementitious composites. To date, the main challenge in their effective use has been controlling the dispersion of these additives in water and in the resulting mixed composites due to their strong van der Waals self-attraction and hydrophobic surfaces. This study uses high-intensity sonication to disperse different nanofilament types in water, and assesses their resulting reinforcing efficiency in cementitious composites. The proportion of nanofilaments used (in this case, multiwall carbon nanotubes MWCNTs, functionalized multiwall carbon nanotubes F-MWCNTs, and carbon nanofibres CNFs) was 0.025% by weight of cement. Aqueous dispersions were examined using transmission electron microscopy (TEM) and optical microscopy, and ultraviolet-visible (UV–vis) spectroscopy. Compressive, flexural and splitting tensile strengths tests, and porosity and density measurements, were used to evaluate the mechanical properties of the composites. High-intensity sonication over short durations significantly improved the dispersion, and reinforcing and filling effects, of carbon-based nanofilaments in cementitious composites, with increases in compressive strength of 24–32%, splitting tensile strength of 45–50%, and flexural toughness factor of 30–40%, observed after 28 days curing. A 17–26% reduction in the porosity of the composite materials was also recorded

High efficiency removal of dissolved As(III) using iron nanoparticle-embedded macroporous polymer composites

Novel nanocomposite materials where iron nanoparticles are embedded into the walls of a macroporous polymer were produced and their efficiency for the removal of As(III) from aqueous media was studied. Nanocomposite gels containing ?-Fe2O3 and Fe3O4 nanoparticles were prepared by cryopolymerisation resulting in a monolithic structure with large interconnected pores up to 100 ?m in diameter and possessing a high permeability (ca. 3 × 10?3 m s?1). The nanocomposite devices showed excellent capability for the removal of trace concentrations of As(III) from solution, with a total capacity of up to 3 mg As/g of nanoparticles. The leaching of iron was minimal and the device could operate in a pH range 3–9 without diminishing removal efficiency. The effect of competing ions such as SO42? and PO43? was negligible. The macroporous composites can be easily configured into a variety of shapes and structures and the polymer matrix can be selected from a variety of monomers, offering high potential as flexible metal cation remediation devices

Creation of 3-dimensional carbon nanostructures from UV irradiation of carbon dioxide at room temperature

A method is presented for the production of carbon nanomaterials from carbon dioxide in a low temperature process. In this method, carbon dioxide is irradiated with an ultraviolet laser at the conditions of critical opalescence where light is scattered and absorbed. Spherical carbon nanoparticles are obtained under these conditions on metal substrates without any additional catalyst near room temperature. The particles are of approximately uniform shape and size of around 100 nm. Some of the particles form clusters. The method is reproducible on different substrates. Quantum chemical calculations have been employed in order to elucidate the role of critical opalescence and of the substrate. The calculations show that the presence of molecular clusters at the critical point is essential in decreasing the excitation energy. The dissociation reaction most likely occurs on the surface of the substrate, where the excitation energy is decreased even further

Interactions of single and multi-layer graphene oxides with water, methane, organic solvents and HCl studied by 1H NMR

Abstract Contemporary characterisation techniques for graphenes are often performed for samples in a dried state or vacuum, which can lead to significant structural changes and difficulty in assessing the actual physical or physicochemical characteristics of graphenes in a colloid state. The interfacial phenomena between water or mixtures (of water with benzene, methane, or HCl) bound to single-layer graphene oxide (SLGO) and multi-layer graphene oxide (MLGO) in different dispersion media (CDCl3, CCl4, CDCl3/DMSO, air) were studied using low-temperature (200–280K) 1H NMR spectroscopy. Use of the NMR cryoporometry method allows determination of the textural characteristics of SLGO and MLGO depending on their hydration degree. It was found that SLGO in diluted suspensions is more agglomerated after freezing-thawing. This effect could be assigned to cryogelation of carbon sheets leading to a decrease in the specific surface area (from 1841 to 533m2/g) representing the area of sheets that are accessible for water that is unfrozen at subzero temperatures. The results obtained show that the cryoporometry method is appropriate for the investigation of the texture of both wetted and suspended graphene oxides

Morphological and chemical features of nano and macroscale carbons affecting hydrogen peroxide decomposition in aqueous media

Chemical and structural factors of carbon materials affect their activity in adsorption and surface reactions in aqueous media. Decomposition of hydrogen peroxide studied is a probe reaction for exploring parameters of carbons that might be involved, such as specific surface area, nitrogen and oxygen doping and conformational changes. To date, a detailed comparison of the behavior of carbon nanoscale (Carbon Nanotubes, CNT, Single Layer Graphene Oxide, SLGO) with macroscale (Activated carbons, AC) materials in this reaction has not been forthcoming. Herein, we demonstrate that on their first cycle, ACs in doped and undoped forms outperform all nanoscale carbons tested in the H2O2 decomposition. Among the nanocarbons, nitrogen-doped CNT exhibited the highest activity in this reaction. However, subsequent recycling of each carbon, without chemical regeneration between uses, reveals SLGO exhibits greater reaction rate stability over an extended number of cycles (n > 8) than other carbons including nitrogen-doped CNT and ACs. The effects of pH, temperature and concentration on the reaction were analyzed. Quantum-chemical modeling and reaction kinetics analysis reveal key processes likely involved in hydrogen peroxide decomposition and show evidence that the reaction rate is linked to active sites with N-and O-containing functionalities