Decoupling order and conductivity in doped conducting polymers.

Herein it is demonstrated that the high level of interchain ordering of pEDOT is not necessary for the polymer to have efficient charge transport. Resistance and order are compared during the manufacturing process, where the polymerisation step and ordering step are decoupled as separate stages of the processing. GIWAXS experiments measuring interchain order are correlated to resistivity measurements at multiple stages of the manufacturing process on single films, and it is shown that for an individual film, where percolation is achieved, having a long range ordered system offers no reduction in resistance compared to having a highly disordered state of the same film. For this system, once the chains of pEDOT are formed, it is experimentally demonstrated that for percolation to be achieved, a remarkably low 4.5% volume fraction pEDOT is required. The apparent lack of necessity for significant interchain ordering allows for a meaningful measurement of development of the charge transport during the chemical polymerisation process.

Miniaturisation and simplification of solid-state proton activity sensors for non-aqueous media and ionic liquids.

This work is the further development of the previous pH (effective) sensor work where a biologically derived proton-active redox centre - riboflavin (RFN) - was entrapped into a vapour phase polymerised poly(3,4-ethylenedioxythiophene) film and ferrocene (Fc) dissolved in the sample solution was used as an internal reference redox couple. Here, we report a disposable solid state pH (effective) sensor where we successfully incorporated both RFN and Fc into a single solid state electrode. The electrodes were then used for pH (effective) sensing where water is not required. The system was further miniaturised and simplified from a 3 electrode to a 2 electrode setup with the working electrode area being as small as 0.09 mm(2). The sensors show the ability to measure pH (effective) in both aqueous and non-aqueous media including ionic liquids (ILs) regardless of their hydrophobicity. This is an important step towards the ability to customise ILs or non-aqueous media with suitable proton activity (PA) for various applications e.g. customised ILs for biotechnological applications such as protein preservation and customised media for PA dependent reactions such as catalytic reactions.

Exploring zinc coordination in novel zinc battery electrolytes.

The coordination of zinc ions by tetraglyme has been investigated here to support the development of novel electrolytes for rechargeable zinc batteries. Zn(2+) reduction is electrochemically reversible from tetraglyme. The spectroscopic data, molar conductivity and thermal behavior as a function of zinc composition, between mole ratios [80 : 20] and [50 : 50] [tetraglyme : zinc chloride], all suggest that strong interactions take place between chloro-zinc complexes and tetraglyme. Varying the concentration of zinc chloride produces a range of zinc-chloro species (ZnClx)(2-x) in solution, which hinder full interaction between the zinc ion and tetraglyme. Both the [70 : 30] and [50 : 50] mixtures are promising electrolyte candidates for reversible zinc batteries, such as the zinc-air device.

Engineering hydrophilic conducting composites with enhanced ion mobility.

Ion mobility has a direct influence on the performance of conducting polymers in a number of applications as it dictates the operational speed of the devices. We report here the enhanced ion mobility of poly(3,4-ethylene dioxythiophene) after incorporation of gelatin. The gelatin-rich domains were seen to provide an ion pathway through the composites.

Unexpected interaction between PEDOT and phosphonium ionic liquids.

In-situ-polymerized films of poly(3,4-ethylenedioxythiophene) (PEDOT) are known to be relatively ordered materials and maintain this order under changing chemical and electrochemical conditions. It is therefore surprising that certain ionic liquids (ILs) were found to interact with PEDOT and thereby to a large extent disrupt the ordered structure. The current work demonstrates the expansion of the interlayer distance (d100) of PEDOT and the composite of PEDOT with poly(ethyleneglycol) (PEDOT(PTS):PEG) in the presence of IL mixtures containing triisobutylmethylphosphonium tosylate (P1444PTS) and water. In presence of the mixtures, the PEDOT(PTS):PEG film expands up to ~100% while the PEDOT(PTS) film expanded ~50%. The expansion did not increase the electrical resistance but increased the absorption in the π-π* range, which can be explained by increased shielding of the PEDOT chains by the IL. The incorporation of P1444PTS increased the capacitance by 350%, compared to the theoretical capacitance of PEDOT(PTS), due to the formation of additional double-layer capacitance.

A solid-state pH sensor for nonaqueous media including ionic liquids.

We describe a solid state electrode structure based on a biologically derived proton-active redox center, riboflavin (RFN). The redox reaction of RFN is a pH-dependent process that requires no water. The electrode was fabricated using our previously described 'stuffing' method to entrap RFN into vapor phase polymerized poly(3,4-ethylenedioxythiophene). The electrode is shown to be capable of measuring the proton activity in the form of an effective pH over a range of different water contents including nonaqueous systems and ionic liquids (ILs). This demonstrates that the entrapment of the redox center facilitates direct electron communication with the polymer. This work provides a miniaturizable system to determine pH (effective) in nonaqueous systems as well as in ionic liquids. The ability to measure pH (effective) is an important step toward the ability to customize ILs with suitable pH (effective) for catalytic reactions and biotechnology applications such as protein preservation.

Chelating ionic liquids for reversible zinc electrochemistry.

Advanced, high energy-density, metal-air rechargeable batteries, such as zinc-air, are of intense international interest due to their important role in energy storage applications such as electric and hybrid vehicles, and to their ability to deal with the intermittency of renewable energy sources such as solar and wind. Ionic liquids offer a number of ideal thermal and physical properties as potential electrolytes in such large-scale energy storage applications. We describe here the synthesis and characterisation of a family of novel "chelating" ILs designed to chelate and solubilize the zinc ions to create electrolytes for this type of battery. These are based on quaternary alkoxy alkyl ammonium cations of varying oligo-ether side chains and anions such as p-toluene sulfonate, bis(trifluoromethylsulfonyl)amide and dicyanoamides. This work shows that increasing the ether chain length in the cation from two to four oxygens can increase the ionic conductivity and reduce the melting point from 67 °C to 15 °C for the tosylate system. Changing the anion also plays a significant role in the nature of the zinc deposition electrochemistry. We show that zinc can be reversibly deposited from [N(222(20201))][NTf2] and [N(222(202020201))][NTf2] beginning at -1.4 V and -1.7 V vs. SHE, respectively, but not in the case of tosylate based ILs. This indicates that the [NTf2] is a weaker coordinating anion with the zinc cation, compared to the tosylate anion, allowing the coordination of the ether chain to dominate the behavior of the deposition and stripping of zinc ions.

Graphene/zinc nano-composites by electrochemical co-deposition.

We describe for the first time the electrochemical co-deposition of composites based on a reactive base metal and graphene directly from a one-pot aqueous mixture containing graphene oxide and Zn(2+). In order to overcome stability issues the Zn(2+) concentration was kept below a critical threshold concentration, ensuring stable graphene oxide suspensions in the presence of cationic base metal precursors. This approach ensures the compatibility between the cationic base metal precursor and graphene oxide, which is more challenging compared to previously reported anionic noble metal complexes. Spectroscopic evidence suggests that the reason for destabilisation is zinc complexation involving the carboxylate groups of graphene oxide. The composition of the electrodeposited co-composites can be tuned by adjusting the concentration of the precursors in the starting mixture. The nano-composites show zinc particles (<3 nm) being uniformly dispersed amongst the graphene sheets. It is also demonstrated that the composites are electrochemically active and suitable for energy storage and energy conversion applications. However, a factor limiting the discharge efficiency is the reactivity of the base metal (low reduction potential and small particle size) which undergoes rapid oxidation when exposed to aqueous electrolytes.

Direct electro-deposition of graphene from aqueous suspensions.

We describe the direct electro-chemical reduction of graphene oxide to graphene from aqueous suspension by applying reduction voltages exceeding -1.0 to -1.2 V. The conductivity of the deposition medium is of crucial importance and only values between 4-25 mS cm(-1) result in deposition. Above 25 mS cm(-1) the suspension de-stabilises while conductivities below 4 mS cm(-1) do not show a measurable deposition rate. Furthermore, we show that deposition can be carried out over a wide pH region ranging from 1.5 to 12.5. The electro-deposition process is characterised in terms of electro-chemical methods including cyclic voltammetry, quartz crystal microbalance, impedance spectroscopy, constant amperometry and potentiometric titrations, while the deposits are analysed via Raman spectroscopy, infra-red spectroscopy, X-ray photoelectron spectroscopy and X-ray diffractometry. The determined oxygen contents are similar to those of chemically reduced graphene oxide, and the conductivity of the deposits was found to be ∼20 S cm(-1).

Copolymer of Phenylene and Thiophene toward a Visible-Light-Driven Photocatalytic Oxygen Reduction to Hydrogen Peroxide.

π-Conjugated polymers including polythiophenes are emerging as promising electrode materials for (photo)electrochemical reactions, such as water reduction to H2 production and oxygen (O2) reduction to hydrogen peroxide (H2O2) production. In the current work, a copolymer of phenylene and thiophene is designed, where the phenylene ring lowers the highest occupied molecular orbital level of the polymer of visible-light-harvesting thiophene entities and works as a robust catalytic site for the O2 reduction to H2O2 production. The very high onset potential of the copolymer for O2 reduction (+1.53 V vs RHE, pH 12) allows a H2O2 production setup with a traditional water-oxidation catalyst, manganese oxide (MnO x ), as the anode. MnO x is deposited on one face of a conducting plate, and visible-light illumination of the copolymer layer formed on the other face aids steady O2 reduction to H2O2 with no bias assistance and a complete photocatalytic conversion rate of 14 000 mg (H2O2) gphotocat -1 h-1 or ≈0.2 mg (H2O2) cm-2 h-1.

Nonpolar Water Clusters: Proton Nuclear Magnetic Resonance Spectroscopic Evidence for Transformation from Polar Water to Nonpolar Water Clusters in Liquid State.

The hydrophilic/hydrophobic interactions of water are important in biological and chemical self-assembly phenomena. Water clusters in hydrophobic environments exhibit a unique morphology. Their process of formation and nonpolar properties have been extensively studied, but no direct experimental evidence has been available until now. This study provides spectroscopic evidence for the transformation of water to nonpolar configuration via clustering. Although individual water molecules form hydrogen bonds with the hydroxyl protons of n-hexanol when codissolved in a nonpolar solvent (toluene-d8), the water clusters are comprised solely of hydrogen bonds between water molecules and do not form hydrogen bonds with the hydroxyl protons of n-hexanol. This behavior indicates that the water clusters are nonpolar rather than polar. This study reports the first example of nonpolar water configuration produced via a liquid-state clustering. This property is a common and important interfacial phenomenon of water in chemistry, biology, materials science, geology, and meteorology.

Two States of Water Converge to One State below 215 K.

Anomalies of water have been explained by the two-state water model. In the model, water becomes one state upon supercooling. However, water crystallizes completely below 235 K ("no man's land"). The structural origin of the anomalous of the water is hidden in the "no man's land". To understand the properties of water, the spectroscopic experiment in "Norman's land" is inevitable. Hence, we proposed a new soft-confinement method for standard nuclear magnetic resonance spectroscopy to explore the "no man's land". We found the singularity temperature (215 K) at ambient pressure. Water exists in one state below 215 K. Above 215 K, the two states of water are supercritical states of the liquid-liquid critical point. The current study provides a perspective to determine the liquid-liquid critical point of water existing in a high-pressure condition.

Microsecond dye regeneration kinetics in efficient solid state dye-sensitized solar cells using a photoelectrochemically deposited PEDOT hole conductor.

Microsecond dye-regeneration kinetics was observed in efficient solid state dye-sensitized solar cells using photoelectrochemically deposited poly(3,4-ethylenedioxythiophene (PEDOT) hole conductors using transient absorption spectroscopy. The dye-regeneration rate is orders of magnitude slower than the case using the I(-)/I(3)(-) redox couple or commonly used small molecule hole conductor and is attributed to the low dye to PEDOT ratio within the films.

Flexible and compressible Goretex-PEDOT membrane electrodes for solid-state dye-sensitized solar cells.

A porous, flexible electrode based on a PTFE (Teflon) membrane (Goretex) coated with a metallic current collector and a conducting polymer (poly(3,4-ethylenedioxythiophene), PEDOT) has been developed for applications in solid-state dye-sensitized solar cells. Its low sheet resistance and compressibility make it an ideal electrode on uneven TiO(2) surfaces with high efficiency and reproducibility. The porous nature of the electrode enables the feed-through of reactants and treatment agents, which opens up exciting opportunities to interface these photoelectrochemical devices with electrocatalytic, energy conversion, and storage systems. Postfabrication bonding of the photoanode and the Goretex-Au-PEDOT electrode is demonstrated.

Conducting polymer enzyme alloys: electromaterials exhibiting direct electron transfer.

Glucose oxidase (GOx) is an important enzyme with great potential application for enzymatic sensing of glucose, in implantable biofuel cells for powering of medical devices in vivo and for large-scale biofuel cells for distributed energy generation. For these applications, immobilisation of GOx and direct transfer of electrons from the enzyme to an electrode material is required. This paper describes synthesis of conducting polymer (CP) structures in which GOx has been entrained such that direct electron transfer is possible between GOx and the CP. CP/enzyme composites prepared by other means show no evidence of such "wiring". These materials therefore show promise for mediator-less electronic connection of GOx into easily produced electrodes for biosensing or biofuel cell applications.

Supercooled Low-Entropy Water Clusters.

The properties of low-entropy water clusters and small bulk water domains in a hydrophobic solvent over a wide temperature range (235-333 K), including supercooling temperatures, were investigated. 1H nuclear magnetic resonance spectroscopy showed singularity temperatures at ∼300, 250, 235, and 225 K. We proposed a model to understand these singularity temperatures in which the low-entropy water cluster is a locally favored tetrahedral structure (LFTS) and the small bulk water domain contains a mixture of disordered normal-liquid structure (DNLS) and LFTS. The model showed that the LFTS and DNLS populations change with applied temperature. Above ∼300 K, all local water structures become a DNLS. The population of LFTS increases with cooling and becomes dominant below ∼250 K. At ∼225 K, all local water structures converge to LFTS. The phase-transition rate of the low-entropy water clusters and small bulk water domains increases significantly at ∼235 K. The phase transition of the low-entropy water clusters showed primary ice nucleation. Low-entropy water clusters in a hydrophobic solvent are a unique water morphology and a probe material for water investigations.

Self polymerising ionic liquid gel.

A novel self-polymerised ionic liquid (IL) gel was prepared at room temperature (RT), without light or heat or addition of initiator, using a new IL, choline formate (CF), and 2-hydroxyethyl methacrylate (HEMA).

CdS thin-film electrodeposition from a phosphonium ionic liquid.

Thin, adherent films of CdS were electrodeposited on FTO coated glass by reduction of a thiosulfate precursor in the presence of Cd(II) ions in methyltributylphosphonium (P(1,4,4,4)) tosylate ionic liquid at 130-150 degrees C. The structural properties of the deposits have been characterized by profilometry, scanning electron microscopy (SEM) and optical microscopy. Energy dispersive X-ray spectroscopy (EDX) was used to evaluate the chemical composition, which was found to be close to stoichiometric. Semiconductor properties including the band gap and flat band potential were calculated from UV-Vis and impedance spectroscopy measurements. The crystal structure was analyzed by X-ray diffraction (XRD). The data obtained from XRD and band gap measurements suggest the presence of hexagonal CdS crystals. The possible growth mechanism of the films is also addressed.

Long-lived water clusters in hydrophobic solvents investigated by standard NMR techniques.

Unusual physical characteristics of water can be easier explained and understood if properties of water clusters are revealed. Experimental investigation of water clusters has been reported by highly specialized equipment and/or harsh experimental conditions and has not determined the properties and the formation processes. In the current work, we used standard 1H-NMR as a versatile and facile tool to quantitatively investigate water clusters in the liquid phase under ambient conditions. This approach allows collection of data regarding the formation, long lifetime, stability, and physical properties of water clusters, as a cubic octamer in the liquid phase.

Plasma Modification and Synthesis of Membrane Materials-A Mechanistic Review.

Although commercial membranes are well established materials for water desalination and wastewater treatment, modification on commercial membranes is still necessary to deliver high-performance with enhanced flux and/or selectivity and fouling resistance. A modification method with plasma techniques has been extensively applied for high-performance membrane production. The paper presents a mechanistic review on the impact of plasma gas and polymerization, at either low pressure or atmospheric pressure on the material properties and performance of the modified membranes. At first, plasma conditions at low-pressure such as plasma power, gas or monomer flow rate, reactor pressure, and treatment duration which affect the chemical structure, surface hydrophilicity, morphology, as well as performance of the membranes have been discussed. The underlying mechanisms of plasma gas and polymerization have been highlighted. Thereafter, the recent research in plasma techniques toward membrane modification at atmospheric environment has been critically evaluated. The research focuses of future plasma-related membrane modification, and fabrication studies have been predicted to closely relate with the implementation of the atmospheric-pressure processes at the large-scale.