An investigation of polypyrrole coated conductive textiles: this research aimed at clarifying some issues occurred in the research project on coloured conductive textiles

Coloured conducting textiles have shown a wide range of potential applications in heating fabrics, electromagnetic wave absorption, and wearable optoelectronic devices. This research aimed at clarifying some issues occurred in the research project on coloured conductive textiles. The investigation firstly clarified a possible chemical reaction that took place between a commercial dispersing dye (Terasil Red G) and the conducting polymer polypyrrole, through chemical separation, structural identification and spectrum characterisations. Then, a series of acidic dyes were introduced into polypyrrole matrix during the vapour coating of conducting polymer on the wool fabrics. Colour and thermal stability studies were conducted. Finally, the polypyrrole nanoparticles (particle size several~200nm) were prepared by a microemulsion polymerisation technique. An acid dye was used as the dopant to re-dope the nanoparticles. The effect of the acidic dye on the optical absorption of nanoparticles was studied. Applying the conducting nanoparticles on wool fabrics may open an alternative path to achieve the coloured conducting textiles.

Identification of a by-product of nitric oxide synthase activity in human acute brain injury with in vivo proton magnetic resonance spectroscopy

BACKGROUND AND PURPOSE: Laboratory studies have been used to identify nitric oxide as a notable mediator in neuronal death after acute brain injury. To our knowledge, this has not previously been confirmed with in vivo study in humans. Our purpose was to seek in vivo evidence for the induction of nitric oxide synthase (NOS) in human acute brain injury by using proton MR spectroscopy.

METHODS: In vitro proton MR spectra were obtained in neural extracts from 30 human cadavers, and in vivo spectra were obtained in 20 patients with acute brain injury and in a similar number of control subjects.

RESULTS: We identified a unique peak at 3.15 ppm by using in vivo proton MR spectroscopy in eight of 20 patients with acute brain injury but not in 20 healthy volunteers (P < .002). On the basis of in vitro data, we have tentatively assigned this peak to citrulline, a NOS by-product.

CONCLUSION: To our knowledge, our findings suggest, for the first time, that excitotoxicity may occur in human acute brain injury. Confirmation with the acquisition of spectra in very early acute cerebral injury would provide a rationale for the use of neuroprotective agents in these conditions, as well as a new noninvasive method for quantification.

Effect of nano-Al2O3 addition on the densification of YSZ electrolytes

This work investigates the effect of nanosized Al2O3 addition on the sinterability of YSZ electrolyte. (1-x)YSZ + Al2O3 ceramics with compositions x = 0 to 0.01 were prepared by the conventional mixed oxide route from a commercial powder suspension (particle size <50 nm), and sintered at 1200 to 1500 degrees C for 2 hours in air. Densification, phase evolution, and microstructure were characterized by SEM/EDS and XRD. An improvement in sintered density was observed for the samples with 0.2 to 0.5 mol% Al2O3, though depending on the sintering temperature. Only cubic zirconia was detected as crystalline phase, although XRD features suggested chemical interactions depending upon the amount of Al2O3. The grain size of YSZ was homogeneous and no second phase segregation was detected in the tested range of incorporated nano-Al2O3 and sintering temperatures.

Lithium doped N,N-dimethyl pyrrolidinium tetrafluoroborate organic ionic plastic crystal electrolytes for solid state lithium batteries

The organic ionic plastic crystal material N,N-dimethyl pyrrolidinium tetrafluoroborate ([C1mpyr][BF4]) has been mixed with LiBF4 from 0 to 8 wt% and shown to exhibit enhanced ionic conductivity, especially in the higher temperature plastic crystal phases (phases II and I). The materials retain their solid state well above 100 °C with the melt not being observed up to 300 °C. Interestingly the conductivity enhancement is highest with the lowest level of LiBF4 addition in phase II, but then the order of enhancement is reversed in phase I. In all cases, a conductivity drop is observed at the II → I phase transition (105 °C) which is associated with increased order in the pure matrix, as previously reported, although the conductivity drop is least for the highest LiBF4 amount (8 wt%). The 8 wt% sample displays different conductivity behaviours compared to the lower LiBF4 concentrations, with a sharp increase above 50 °C, which is apparently not related to the formation of an amorphous phase, based on XRD data up to 120 °C. Symmetric cells, Li/OIPC/Li, were prepared and cycled at 50 °C and showed evidence of significant preconditioning with continued cycling, leading to a lower over-potential and a concomitant decrease in the cell resistivity as measured by EIS. An SEM investigation of the Li/OIPC interfaces before and after cycling suggested significant grain refinement was responsible for the decrease in cell resistance upon cycling, possibly as a result of an increased grain boundary phase.

Substrate-induced coagulation (SIC) of nano-disperse carbon black in non-aqueous media : a method of manufacturing highly conductive cathode materials for Li-ion batteries by self-assembly

Substrate-induced coagulation (SIC) is a coating process based on self-assembly for coating different surfaces with fine particulate materials. The particles are dispersed in a suitable solvent and the stability of the dispersion is adjusted by additives. When a surface, pre-treated with a flocculant e.g. a polyelectrolyte, is dipped into the dispersion, it induces coagulation resulting in the deposition of the particles on the surface. A non-aqueous SIC process for carbon coating is presented, which can be performed in polar, aprotic solvents such as N-Methyl-2- pyrrolidinone (NMP). Polyvinylalcohol (PVA) is used to condition the surface of substrates such as mica, copperfoil, silicon-wafers and lithiumcobalt oxide powder, a cathode material used for Li-ion batteries. The subsequent SIC carbon coating produces uniform layers on the substrates and causes the conductivity of lithiumcobalt oxide to increase drastically, while retaining a high percentage of active battery material.

One-step vapour-phase formation of patternable, electrically conductive, superamphiphobic coatings on fibrous materials

Patternable, electrically conductive coatings having a superhydrophobic and superoleophobic surface have been prepared by one-step vapour-phase polymerisation of polypyrrole in the presence of a fluorinated alkyl silane directly on fibrous substrates. The coated fabrics showed a surface resistance of 0.5-0.8 kΩ □^-1 with water and hexadecane contact angles of 165° and 154°, respectively.

An organic ionic plastic crystal electrolyte based on the triflate anion exhibiting high proton transport

A novel organic ionic plastic crystal (OIPC) electrolyte based on a quaternary ammonium cation and the triflate anion has been synthesized, which shows fast proton transport and high thermal stability in the solid state when doped with triflic acid.

Ionic liquids and organic ionic plastic crystals utilizing small phosphonium cations

The development of new liquid and solid state electrolytes is paramount for the advancement of electrochemical devices such as lithium batteries and solar cells. Ionic liquids have shown great promise in both these applications. Here we demonstrate the use of phosphonium cations with small alkyl chain substituents, in combination with a range of different anions, to produce a variety of new halide free ionic liquids that are fluid, conductive and with sufficient thermal stability for a range of electrochemical applications. Walden plot analysis of the new phosphonium ionic liquids shows that these can be classed as "good" ionic liquids, with low degrees of ion pairing and/or aggregation, and the lithium deposition and stripping from one of these ionic liquids has been demonstrated. Furthermore, for the first time phosphonium cations have been used to form a range of organic ionic plastic crystals. These materials can show significant ionic conductivity in the solid state and thus are of great interest as potential solid-state electrolyte materials.

Organic ionic plastic crystal electrolytes; a new class of electrolyte for high efficiency solid state dye-sensitized solar cells

Dye-sensitized solar cells are an increasingly promising alternative to conventional silicon solar cells as a method of converting solar energy to electricity and thus providing an effectively inexhaustible energy source. However, the most efficient of these devices currently utilize liquid electrolytes, which suffer from the associated problems of leakage and evaporation. Hence, significant research is currently focused on the development of solid state alternatives. Here we report a new class of solid state electrolyte for these devices, organic ionic plastic crystal electrolytes, that allow relatively rapid diffusion of the redox couple through the matrix, which is critical to the cell performance. A range of different organic ionic plastic crystal materials, utilizing different cation and anion structures, have been investigated and the conductivities, diffusion rates and photovoltaic performance of the electrolytes are reported. The best material, utilizing the dicyanamide anion, achieves efficiencies of more than 5%.

The effect of coordinating and non-coordinating additives on the transport properties in ionic liquid electrolytes for lithium batteries

In the present study we expand our analysis of using two contrasting organic solvent additives (toluene and THF) in an ionic liquid (IL)/Li NTf 2 electrolyte. Multinuclear Pulsed-Field Gradient (PFG) NMR, spin-lattice (T1) relaxation times and conductivity measurements over a wide temperature range are discussed in terms of transport properties and structuring of the liquid. The conductivity of both additive samples is enhanced the most at low temperatures, with THF slightly more effective than toluene. Both the anion and lithium self-diffusivity are enhanced in the same order by the additives (THF > toluene) while that of the pyrrolidinium cation is marginally enhanced. 1H spin-lattice relaxation times indicate a reasonable degree of structuring and anisotropic motion within all of the samples and both 19F and 7Li highlight the effectiveness of THF at influencing the lithium coordination within these systems.

Characterization and evaluation of BaCo0.7Fe0.2Nb0.1O3−δ as a cathode for proton-conducting solid oxide fuel cells

This study characterizes BaCo0.7Fe0.2Nb0.1O3−δ (BCFN) perovskite oxide and evaluates it as a potential cathode material for proton-conducting SOFCs with a BaZr0.1Ce0.7Y0.2O3-δ (BZCY) electrolyte. A four-probe DC conductivity measurement demonstrated that BCFN has a modest electrical conductivity of 2–15 S cm−1 in air with p-type semiconducting behavior. An electrical conductivity relaxation test showed that BCFN has higher Dchem and Kchem than the well-known Ba0.5Sr0.5Co0.8Fe0.2O3−δ oxide. In addition, it has relatively low thermal expansion coefficients (TECs) with values of 18.2 × 10−6 K−1 and 14.4 × 10−6 K−1 at temperature ranges of 30–900 °C and 30–500 °C, respectively. The phase reaction between BCFN and BZCY was investigated using powder and pellet reactions. EDX and XRD characterizations demonstrated that BCFN had lower reactivity with the BZCY electrolyte than strontium-containing perovskite oxides such as SrCo0.9Nb0.1O3-δ and Ba0.6Sr0.4Co0.9Nb0.1O3−δ. The impedance of BCFN was oxygen partial pressure dependent. Introducing water into the cathode atmosphere reduced the size of both the high-frequency and low-frequency arcs of the impedance spectra due to facilitated proton hopping. The cathode polarization resistance and overpotential at a current density of 100 mA cm−2 were 0.85 Ω cm−2 and 110 mV in dry air, which decreased to 0.43 Ω cm−2 and 52 mV, respectively, in wet air (∼3% H2O) at 650 °C. A decrease in impedance was also observed with polarization time; this was possibly caused by polarization-induced microstructure optimization. A promising peak power density of ∼585 mW cm−2 was demonstrated by an anode-supported cell with a BCFN cathode at 700 °C.