Using a selective cadmium-binding peplipid to create responsive liquid crystalline nanomaterials.

A specific metal ion-responsive lipid liquid crystalline (LLC) dispersion system was fabricated, which can work in buffer solutions. The LLC matrix was prepared from phytantriol which spontaneously forms the reversed bicontinuous cubic phase in water, and a novel peptide-lipid conjugate (peplipid) consists of a myristate alkyl chain for anchoring into the phytantriol-based cubic bilayer and a peptide sequence for capturing a specific metal ion. The peplipid in its unbound state, when added into the phytantriol-based cubic system induces a positive effect on the bilayer curvature, resulting in the formation of the lamellar phase (vesicles) and the dispersion was transparent in appearance. Upon binding of the cadmium ion, the peplipid induces a negative effect on the lipid bilayer curvature and consequently leading to the formation of cubic phase and opaque appearance. In contrast, other metal ions, including buffering salts, could not sufficiently trigger the phase transition due to weak interaction with the peplipid. The high selectivity of metal ion interaction and triggered phase transition provide potential applications, such as in colloidal-mineral separation, triggered drug release and treatment of cadmium (II) pollution.

Crystalline Structures and α → β and γ polymorphs transformation induced by nanoclay in PVDF-based nanocomposite

Poly(vinylidene fluoride) (PVDF) nanocomposites were prepared by melt-mixing. The dispersion of clay platelets and rheology of nanocomposites were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and rheometric mechanical spectrometer (RMS). The transformation of α to β and γ phase in PVDF was induced by the addition of nanoclay and subsequently the isothermal crystallization kinetics of neat PVDF and its nanocomposite have been investigated. The interaction between clay nanofillers and PVDF macromolecular chains induced the change of conformation from trans-gauche to all-trans crystal structure in PVDF segment. The isothermal crystallization of PVDF/clay nanocomposites was carried out by Differential Scanning Calorimetry (DSC) technique. The influence of clay platelets on nucleation crystallization rate and Avrami exponent were studied. PVDF/clay nanocomposite showed higher crystallization rate indicating that nanoclay has acted as an effective nucleation agent. This nucleation effect of nanoclay increased the Avrami exponent and decreased the degree of crystallinity. © 2014 World Scientific Publishing Company.

Identify kinetic features of fibers growing, branching, and bundling in microstructure engineering of crystalline fiber network

Fibers growing, branching, and bundling are essential for the development of crystalline fiber networks of molecular gels. In this work, for two typical crystalline fiber networks, i.e. the network of spherulitic domains and the interconnected fibers network, related kinetic information is obtained using dynamic rheological measurements and analysis in terms of the Avrami theory. In combination with microstructure characterizations, we establish the correlation of the Avrami derived kinetic parameter not only with the nucleation nature and growth dimensionality of fibers and branches, but also with the fiber bundles induced by fiber-fiber interactions. Our study highlights the advantage of simple dynamic rheological measurements over other spectroscopic methods used in previous studies for providing more kinetic information on fiber-fiber interactions, enabling the Avrami analyses to extract distinct kinetic features not only for fibers growing and branching, but also for bundling in the creation of strong interconnected fibers networks. This work may be helpful for the implementation of precise kinetic control of crystalline fiber network formations for achieving desirable microstructures and rheological properties for advanced applications of gel materials. This journal is © the Partner Organisations 2014.

Nature of crystalline particle assembly in ring shaped colloidal stains from concentrated dispersions

The drying of colloidal droplet suspensions is important in many realms of practical application and has sustained the interest of researchers over two decades. The arrangements of polystyrene and silica beads, both of diameter 1 μm, 10% by volume of solid deposited on normal glass (hydrophilic), and silicone (hydrophobic) surfaces evaporated from a suspension volume of 3 μL, were investigated. Doughnut shape depositions were found, imputing the influence of strong central circulation flows that resulted in three general regions. In the central region which had strong particle build-up, the top most layers of particle arrangement was confirmed to be disordered using power spectrum and radial distribution function analysis. On closer examination, this appeared more like frustrated attempts to crystallize into larger grains rather than beads arranging in a disordered fashion throughout the piling process. With an adapted micro-bulldozing operation to progressively remove layers of particles from the heap, we found that the later efforts to crystallize through lateral capillary inter-particle forces were liable to be undone once the particles contacted the disorganized particles underneath, which were formed out of the jamming of fast particles arriving at the surface. © 2014 Elsevier B.V.

Nanostructured liquid crystalline particles as next generation agrochemical delivery vehicles

A new system for delivering agrichemicals to crop plants was investigated. Nano-structured lipid particles were used as an alternative to traditional surfactants for penetrating plant surfaces. In laboratory and field trials the nanoparticles delivered chemicals effectively, caused less damage to plants, required less water and resulted in lower environmental impacts.

Nanostructured liquid crystalline particle assisted delivery of 2,4-dichlorophenoxyacetic acid to weeds, crops and model plants

Routine agricultural practices are heavily dependent on the use of surfactants, many of which are toxic to humans and detrimental to the environment. In proof of concept work we have previously shown the potential of nanostructured liquid crystalline particles (NLCP) to safely interact with plant leaf cuticular surfaces with minimal impact on epicuticular waxes. Here we demonstrate the use of NLCP to effectively deliver the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) to plant leaves in laboratory and field studies. In the laboratory, the physiological stress responses of lupin, Lupinus angustifolius (L.) (Fabaceae) towards NLCP spray applications were shown to be much reduced in comparison with application of two common surfactants. Phytotoxicity assays of 2,4-D loaded NLCP were used to validate the herbicidal effects on Arabidopsis thaliana (L.) Heynth. (Brassicaceae) and established a similarity with that of surfactant assisted 2,4-D delivery when tested at a concentration of 0.1%. Field trials were conducted to test the efficacy of NLCP-assisted delivery of 2,4-D in comparison with commercial surfactants for the control of the invasive weed wild radish, Raphanus raphanistrum (L.) (Brassicaceae), in wheat, Triticum aestivum (L.) (Poaceae) crop fields. Compared against Estercide 800, a commercially available 2,4-D formulation, NLCP assisted delivery of 2,4-D was effective at low concentrations of 0.03% and 0.06%. The crop yield remained similar for all the tested concentrations and formulations of 2,4-D loaded NLCP and Estercide 800. This is the first report to directly show that, as an alternative to conventional methods, NLCP can be used under both laboratory and field conditions to successfully delivery an agrochemical.

Electrophilic substitution of acetyltrimethylsilane with tellurium(IV) halides: A synthetic route to 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium halides

The reaction of tellurium tetrahalides, TeX4 (XCl. Br) with acetyltrimethylsilane in CCl4 at ambient temperature, unlike that of the aryltellurium trichlorides, ArTeCl3 that give the expected electrophilic substitution products, Ar(Me3SiCOCH2)TeCl2, (Ar = 1-C10H7, 2; 2,4,6-Me3C6H2, 3), afforded novel silylated heterocycles, 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium halides 1a and 1b. These Te(II) heterocyclic compounds undergo halide exchange with sodium iodide and also add dihalogens oxidatively to afford the corresponding iodide, 1c and the Te(IV) trihalides, 5a and 5b respectively. A large lowering of ν(CO) is indicative of strong Te⋯OC interactions among these heterocycles, and is also substantiated by single-crystal X-ray diffraction data for 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium chloride. The ¹²⁵Te chemical shifts for the new 10-Te-3 telluranes and 12-Te-5 pertelluranes that involve tellurium bound to two highly electronegative atoms (O, X) are among the highest (downfield) reported for organotellurium(II) and (IV) compounds.

Crystalline polymorph transition in poly(vinylidene fluoride) (PVDF)/acrylic rubber(ACM)/clay partially miscible hybrid

This study investigates the intercalation of nanoclay in partially miscible blends of poly(vinylidene fluoride) (PVDF) and acrylic rubber(ACM). Transmission electron microscopy and X-ray diffraction technique were used to investigate the formation of nanoscale polymer blend/clay hybrids. Using Infrared spectroscopy and X-ray analysis, the different polymorph formation in PVDF nanocomposite and conjugated phases of partially miscible nanocomposite was studied. Nanoclay was found to induce β and γ polymorphs while ACM tend to induce α phase in this polymer system. It was shown that PVDF chains in ACM-rich phase of partially miscible nanocomposites interact with ACM chains which in return form α polymorph in the presence of ACM. Further observations revealed that nanoclay in α polymorph is wrapped by ACM molecules.

N7-(carboxymethyl)guanine-lithium crystalline complex: a bioinspired solid electrolyte

Electrochemical device with components having direct significance to biological life processes is a potent futuristic strategy for the realization of all-round green and sustainable development. We present here synthesis design, structural analysis and ion transport of a novel solid organic electrolyte (G7Li), a compound reminiscent of ion channels, derived from regioisomeric N7-guanine-carboxylate conjugate and Li-ions. G7Li, with it's in-built supply of Li(+)-ions, exhibited remarkably high lithium-ion transference number (= 0.75) and tunable room temperature ionic conductivity spanning three decades (≈10(-7) to 10(-3) Ω(-1) cm(-1)) as a function of moisture content. The ionic conductivity show a distinct reversible transition around 80-100 °C, from a dual Li(+) and H(+) (<100 °C) to a pure Li(+) conductor (>100 °C). Systematic studies reveal a transition from water-assisted Li-ion transport to Li hopping-like mechanism involving guanine-Li coordination. While as-synthesized G7Li has potential in humidity sensors, the anhydrous G7Li is attractive for rechargeable batteries.

Quantum emission from defects in single-crystalline hexagonal boron nitride

Bulk hexagonal boron nitride (hBN) is a highly nonlinear natural hyperbolic material that attracts major attention in modern nanophotonics applications. However, studies of its optical properties in the visible part of the spectrum and quantum emitters hosted by bulk hBN have not been reported to date. In this work, we study the emission properties of hBN crystals in the red spectral range using sub-band-gap optical excitation. Quantum emission from defects is observed at room temperature and characterized in detail. Our results advance the use of hBN in quantum nanophotonics technologies and enhance our fundamental understanding of its optical properties.

Alignment and characterisation of hexagonal lyotropic liquid crystalline nanostructure for membrane synthesis

Weiwei has been devoting to the alignment and characterisation of hexagonal lyotropic liquid crystalline nanostructure to uniform orientation by applying external fields. According to the Synchrotron small angle x-ray scattering results, it has produced distinct progress. This technique is aimed for improving the filtration efficiency of nanoporous membranes.