Prestressed natural fibre spun yarn reinforced polymer-matrix composites

Abstract We report that a prestressing technique similar to that traditionally used in prestressed concrete can improve the mechanical performance of flax fibre spun yarn reinforced polymer-matrix composites. Prestressing a low twist yarn not only introduces tension to the constituent fibres and compressive stress to the matrix similar as in prestressed concretes, but also causes changes to the yarn structure that lead to the rearrangement of fibres within the yarn. Prestressing increases the fibre packing density in yarn, causes fibre straightening, and reduces fibre obliquity in yarn (improved fibre alignment along yarn axis). All these changes contribute positively to the mechanical properties of the natural fibre yarn reinforced composites. Crown

The underlying assumption in chemistry education

The underlying assumption in chemistry education is that chemistry is real, distinct discipline, clearly differentiable from other sciences. Chemistry is the study of matter and its interactions with other matter and with energy, but the aspects which distinguish chemistry are: macroscopic observations and descriptions of properties and change; understanding in terms of atoms and molecules; abstract representations to describe and communicate chemical concepts; and occupational health and safety. These aspects are not unique to chemistry, but their combination make chemistry unique. Over the last three years, there have been major reviews of school science education through the formulation of the Australian National Curriculum and of undergraduate education through the Learning and Teaching Academic Standards Project. In both cases, individual RACI members and chemistry professionals, including school teachers, and RACI working party and workshop, have articulated the unique nature of chemistry and the need for chemistry education as a separate subject.

In situ synthesis of natural rubber latex-supported gold nanoparticles for flexible SERS substrates

Natural rubber latex (NRL) from Hevea brasiliensis was used as a matrix to synthesize gold nanoparticles (AuNPs), leading to an organic-inorganic hybrid latex of NRL-supported AuNPs (AuNPs@NRL). The in situ and environmentally friendly preparation of AuNPs in an NRL matrix was developed by thermal treatment without using any other reducing agents or stabilizers because natural rubber particles and non-rubber components present in serum can serve as supporters for the synthesized AuNPs. As a result, the nanosized and well-dispersed AuNPs not only are decorated on the surface of natural rubber particles, but also can be found in the serum of NRL. The size of the AuNPs presented in NRL matrix can be controlled by adjusting the concentration of NRL. Furthermore, the flexible surface-enhanced Raman scattering (SERS) substrates made from the AuNPs@NRL through vacuum filtration presented good enhancement of the Raman probe molecule of 4-mercaptopyridine and outstanding SERS reproducibility. The capability of synthesizing the bio-supported nanohybrid latex provides a novel green and simple approach for the fabrication of flexible and effective SERS substrates.

An organic ionic plastic crystal electrolyte for rate capability and stability of ambient temperature lithium batteries

Reliable, safe and high performance solid electrolytes are a critical step in the advancement of high energy density secondary batteries. In the present work we demonstrate a novel solid electrolyte based on the organic ionic plastic crystal (OIPC) triisobutyl(methyl)phosphonium bis(fluorosulfonyl)imide (P1444FSI). With the addition of 4 mol% LiFSI, the OIPC shows a high conductivity of 0.26 mS cm-1 at 22 °C. The ion transport mechanisms have been rationalized by compiling thermal phase behaviour and crystal structure information obtained by variable temperature synchrotron X-ray diffraction. With a large electrochemical window (ca. 6 V) and importantly, the formation of a stable and highly conductive solid electrolyte interphase (SEI), we were able to cycle lithium cells (LiLiFePO4) at 30 °C and 20 °C at rates of up to 1 C with good capacity retention. At the 0.1 C rate, about 160 mA h g-1 discharge capacity was achieved at 20 °C, which is the highest for OIPC based cells to date. It is anticipated that these small phosphonium cation and [FSI] anion based OIPCs will show increasing significance in the field of solid electrolytes.

Aquatic toxicity of manufactured nanomaterials: challenges and recommendations for future toxicity testing

 Aquatic nanotoxicologists and ecotoxicologists have begun to identify the unique properties of the nanomaterials (NMs) that potentially affect the health of wildlife. In this review the scientific aims are to discuss the main challenges nanotoxicologists currently face in aquatic toxicity testing, including the transformations of NMs in aquatic test media (dissolution, aggregation and small molecule interactions), and modes of NM interference (optical interference, adsorption to assay components and generation of reactive oxygen species) on common toxicity assays. Three of the major OECD (Organisation for Economic Co-operation and Development) priority materials, titanium dioxide (TiO2), zinc oxide (ZnO) and silver (Ag) NMs, studied recently by the Natural Sciences and Engineering Research Council of Canada (NSERC), National Research Council of Canada (NRC) and the Business Development Bank of Canada (BDC) Nanotechnology Initiative (NNBNI), a Canadian consortium, have been identified to cause both bulk effect, dissolution-based (i.e. free metal), or NM-specific toxicity in aquatic organisms. TiO2 NMs are most toxic to algae, with toxicity being NM size-dependent and principally associated with binding of the materials to the organism. Conversely, dissolution of Zn and Ag NMs and the subsequent release of their ionic metal counterparts appear to represent the primary mode of toxicity to aquatic organisms for these NMs. In recent years, our understanding of the toxicological properties of these specific OECD relevant materials has increased significantly. Specifically, researchers have begun to alter their experimental design to identify the different behaviour of these materials as colloids and, by introducing appropriate controls and NM characterisation, aquatic nanotoxicologists are now beginning to possess a clearer understanding of the chemical and physical properties of these materials in solution, and how these materials may interact with organisms. Arming nanotoxicologists with this understanding, combined with knowledge of the physics, chemistry and biology of these materials is essential for maintaining the accuracy of all future toxicological assessments.

Dynamic nuclear polarisation enhanced (14)N overtone MAS NMR spectroscopy.

Dynamic nuclear polarisation (DNP) has been used to obtain magic angle spinning (14)N(OT) (nitrogen-14 overtone) solid-state NMR spectra from several model amino acids, with both direct and indirect observation of the (14)N(OT) signal. The crystalline solids were impregnated with biradical solutions of organic liquids that do not dissolve the crystalline phase. The bulk phase was then polarized via(1)H spin diffusion from the highly-polarized surface (1)H nuclei, resulting in (1)H DNP signal enhancements of around two orders of magnitude. Cross polarisation from (1)H nuclei directly to the (14)N overtone transition is demonstrated under magic angle spinning, using a standard pulse sequence with a relatively short contact time (on the order of 100 μs). This method can be used to acquire (14)N overtone MAS powder patterns that match closely with simulated line shapes, allowing isotropic chemical shifts and quadrupolar parameters to be measured. DNP enhancement also allows the rapid acquisition of 2D (14)N(OT) heteronuclear correlation spectra from natural abundance powder samples. (1)H-(14)N(OT) HETCOR and (13)C-(14)N(OT) HMQC pulse sequences were used to observe all single-bond H-N and C-N correlations in histidine hydrochloride monohydrate, with the spectra obtained in a matter of hours. Due to the high natural abundance of the (14)N isotope (99.6%) and the advantages of observing the overtone transition, these methods provide an attractive route to the observation of C-N correlations from samples at natural isotopic abundance and enable the high resolution measurement of (14)N chemical shifts and quadrupolar interaction parameters.

Silver nanoparticles prepared by gamma irradiation across metal-organic framework templates

In this study, we demonstrate for the first time the successful fabrication of well-dispersed ultrafine silver nanoparticles inside metal-organic frameworks through a single step gamma irradiation at room temperature. HKUST-1 crystals are soaked in silver nitrate aqueous solution and irradiated with a Cobalt 60 source across a range of irradiation doses to synthesize highly uniformly distributed silver nano-particles. The average size of the silver nanoparticles across the Ag@HKUST-1 materials is found to vary between 1.4 and 3 nm for dose exposures between 1 and 200 kGy, respectively. The Ag@HKUST-1 hybrid crystals exhibit strong surface plasmon resonance and are highly durable and efficient catalytic materials for the reduction of 4-nitrophenol to 4-aminophenol (up to 14.46 × 10-3 s-1 for 1 kGy Ag@HKUST-1). The crystals can be easily recycled for at least five successive cycles of reaction with a conversion efficiency higher than 99.9%. The gamma irradiation is demonstrated to be an effective and environmental friendly process for the synthesis of nano-particles across confined metal-organic frameworks at room temperature with potential applications in environmental science.

Comparative analyses of cadmium and zinc uptake correlated with changes in natural resistance-associated macrophage protein (NRAMP) expression in Solanum nigrum L. and Brassica rapa

Environmental context Soils contaminated with metals can pose both environmental and human health risks. This study showed that a common crop vegetable grown in the presence of cadmium and zinc readily accumulated these metals, and thus could be a source of toxicity when eaten. The work highlights potential health risks from consuming crops grown on contaminated soils. Abstract Ingestion of plants grown in heavy metal contaminated soils can cause toxicity because of metal accumulation. We compared Cd and Zn levels in Brassica rapa, a widely grown crop vegetable, with that of the hyperaccumulator Solanum nigrum L. Solanum nigrum contained 4 times more Zn and 12 times more Cd than B. rapa, relative to dry mass. In S. nigrum Cd and Zn preferentially accumulated in the roots whereas in B. rapa Cd and Zn were concentrated more in the shoots than in the roots. The different distribution of Cd and Zn in B. rapa and S. nigrum suggests the presence of distinct metal uptake mechanisms. We correlated plant metal content with the expression of a conserved putative natural resistance-associated macrophage protein (NRAMP) metal transporter in both plants. Treatment of both plants with either Cd or Zn increased expression of the NRAMP, with expression levels being higher in the roots than in the shoots. These findings provide insights into the molecular mechanisms of heavy metal processing by S. nigrum L. and the crop vegetable B. rapa that could assist in application of these plants for phytoremediation. These investigations also highlight potential health risks associated with the consumption of crops grown on contaminated soils.

Ionic liquids for energy, materials, and medicine.

As highlighted by the recent ChemComm web themed issue on ionic liquids, this field continues to develop beyond the concept of interesting new solvents for application in the greening of the chemical industry. Here some current research trends in the field will be discussed which show that ionic liquids research is still aimed squarely at solving major societal issues by taking advantage of new fundamental understanding of the nature of these salts in their low temperature liquid state. This article discusses current research trends in applications of ionic liquids to energy, materials, and medicines to provide some insight into the directions, motivations, challenges, and successes being achieved with ionic liquids today.

A study of phase behavior and conductivity of mixtures of the organic ionic plastic crystal N-methyl-N-methyl-pyrrolidinium dicyanamide with sodium dicyanamide

We report on the thermal, structural and conductivity properties of the organic ionic plastic crystal (OIPC) N-methyl-N-methyl-pyrrolidinium dicyanamide [C1mpyr][N(CN)2] mixed with the sodium salt Na[N(CN)2]. The DSC thermal traces indicate that an isothermal transition, which may be a eutectic melting, occurs at ~ 89 °C, below which all compositions are entirely in the solid phase. At 20 mol% Na[N(CN)2], this transition is the final melt for this mixture, and a new liquidus peak grows beyond 20 mol% Na[N(CN)2]. The III- > II solid-solid phase transition continues to be evident at ~- 2 °C. The microstructure for all the mixtures indicated a phase separated morphology where precipitates can be clearly observed. Most likely, these precipitates consist of a Na-rich second phase. This was also suggested from the vibrational spectroscopy and the 23Na NMR spectra. The lower concentrations of Na[N(CN)2] present complex 23Na MAS spectra, suggesting more than one sodium ion environment is present in these mixtures consistent with complex phase behavior. Unlike other OIPCs where the ionic conductivity usually increases upon doping or mixing in a second component, the conductivity of these mixtures remains relatively constant and above 10- 4 S cm- 1 at ∼ 80 °C, even in the solid state. Such high conductivities suggest these materials may be promising to be used for all solid-state electrochemical devices.

Thermally flexible epoxy/cellulose blends mediated by an ionic liquid

Blends between the widely used thermoset resin, epoxy, and the most abundant organic material, natural cellulose are demonstrated for the first time. The blending modification induced by charge transfer complexes using a room temperature ionic liquid, leads to the formation of thermally flexible thermoset materials. The blend materials containing low concentrations of cellulose were optically transparent which indicates the miscibility at these compositions. We observed the existence of intermolecular hydrogen bonding between epoxy and cellulose in the presence of the ionic liquid, leading to partial miscibility between these two polymers. The addition of cellulose improves the tensile mechanical properties of epoxy. This study reveals the use of ionic liquids as a compatible processing medium to prepare epoxy thermosets modified with natural polymers.

Probing the tunable surface chemistry of graphene oxide

The determination of oxygen content, hydrophobicity and reduction efficiency of graphene oxide (GO) are difficult tasks because of its heterogeneous structure. Herein, we describe a novel approach for the detailed understanding of the surface chemistry of GO by studying the interactions between [Ru(bpy)3](2+) and GO.

Rhodium(II) azavinyl carbenes and their recent application to organic synthesis

This highlight solely focusses on the synthetic applications of azavinyl rhodium(II) carbenes derived from N-sulfonyl triazoles. An overview of their use in intermolecular reactions to form a variety of heterocycles is examined, in addition to intramolecular annulations and rearrangements.

Metal and metalloid containing natural products and a brief overview of their applications in biology, biotechnology and biomedicine

Bioinorganic natural product chemistry is a relatively unexplored but rapidly developing field with enormous potential for applications in biology, biotechnology (especially in regards to nanomaterial development, synthesis and environmental cleanup) and biomedicine. In this review the occurrence of metals and metalloids in natural products and their synthetic derivatives are reviewed. A broad overview of the area is provided followed by a discussion on the more common metals and metalloids found in natural sources, and an overview of the requirements for future research. Special attention is given to metal hyperaccumulating plants and their use in chemical synthesis and bioremediation, as well as the potential uses of metals and metalloids as therapeutic agents. The potential future applications and development in the field are also discussed.

One-pot synthesis of aminated multi-walled carbon nanotube using thiol-ene click chemistry for improvement of epoxy nanocomposites properties

A non-oxidative method based on thiol-ene click chemistry for functionalization of multi-walled carbon nanotube (CNT) was performed in order to improve the interfacial interactions between epoxy matrix and CNT. In this way, the CNT was aminated using 2-aminoethanethiol hydrochloride radicals thermally produced by a peroxide radical initiator. The aminated CNT (CNT-NH2) was characterized by FTIR, TGA, and solubility evaluations, confirming that thiol radicals are successfully grafted onto the CNT surface with a proper yield. Various percentages of pure CNT (p-CNT) and CNT-NH2 were then incorporated into epoxy matrix to evaluate the effect of the functionalization of CNT on thermal, mechanical, and morphological properties. The nanocomposites were characterized by DMA, tensile testing, and TGA. Results showed that glass transition temperature, tensile properties and thermal stability of epoxy nanocomposites containing CNT-NH2 improves significantly compared to those containing unmodified CNT. These results prove the role of amino-functionalization in improving the interfacial adhesion between epoxy and CNT, which was further confirmed by morphological observations of fracture surfaces of the nanocomposites.