Unexpected Interaction between PEDOT and Phosphonium Ionic Liquids

Molecular-Orbital Delocalization Enhances Charge Transfer in π-Conjugated Organic Semiconductors

π-Conjugated organic semiconductors are promising materials for surface-enhanced Raman scattering (SERS)-active substrates based on the tunability of electronic structures and molecular orbitals. Herein, we investigate the effect of the temperature-mediated resonance-structure transitions of poly(3,4-ethylenedioxythiophene) (PEDOT) in poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT : PSS) films on the interactions between substrate and probe molecules, thereby affecting the SERS activity. Absorption spectroscopy and density functional theory calculations show that this effect occurs mainly due to delocalization of the electron distribution in molecular orbitals, effectively promoting the charge transfer between the semiconductor and probe molecules. In this work, we investigate for the first time the effect of electron delocalization in molecular orbitals on SERS activity, which will provide new design ideas for the development of highly sensitive SERS substrates.

Rational design and microwave-assisted synthesis of a novel terthiophene derivative for facile preparation of binder-free polymer/metal oxide-based binary composite electrodes with high electrochemical performance

A simple and effective approach was reported for the preparation of binder-free conducting polymer/metal oxide binary composite electrode materials.

A novel approach to improve the oil miscibility and incorporate multifunctionality in ionic liquids as lubricant additives

Recently ionic liquids (ILs) have shown promising tribological properties as additives in base oils; however their lack of miscibility is a problem, with very few ILs being compatible with lubricant oil formulation (non-polar base oils). This work shows the use of a surfactant which can increase the range of available ILs that are stable when added to these base oils. In this study a range of tetraalkylphosphonium based ILs were successfully blended with a PIBSA surfactant and these blends were all shown to be miscible in a non-polar base oil. Without the PIBSA a number of the ILs were immiscible in the base oil. The tribological properties of IL additives that are miscible in the non-polar base oils were compared with and without the surfactant present and showed that the presence of the PIBSA did not affect the IL additives performance. Additionally, two ILs that are immiscible without the surfactant showed the greatest reduction in friction and wear. SEM analysis showed an increase in the amount of phosphorus on the wear surface when the surfactant was present, suggesting that the PIBSA enhances tribo-film formation. NMR, FTIR, DLS and TEM investigations into the interactions between the PIBSA and the ILs showed that the improved stability in the base oil may be due to intermolecular interactions such as hydrophobic, van der Waals, dipole-dipole or ion-dipole that reduce the size distribution of the previously immiscible ILs. The presence of the ILs was also shown to improve the resistance to corrosion. Prior to this study the ILs available for use as lubricant additives was severely limited and compromised, mostly based upon their miscibility. Here the use of PIBSA to increase the range of ILs available as lubricant additives has vastly improved the promise that they represent in this area.

Mixed Ionic-Electronic Conductors Based on PEDOT:PolyDADMA and Organic Ionic Plastic Crystals

Mixed ionic-electronic conductors, such as poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) are postulated to be the next generation materials in energy storage and electronic devices. Although many studies have aimed to enhance the electronic conductivity and mechanical properties of these materials, there has been little focus on ionic conductivity. In this work, blends based on PEDOT stabilized by the polyelectrolyte poly(diallyldimethylammonium) (PolyDADMA X) are reported, where the X anion is either chloride (Cl), bis(fluorosulfonyl)imide (FSI), bis(trifluoromethylsulfonyl)imide (TFSI), triflate (CF3SO3) or tosylate (Tos). Electronic conductivity values of 0.6 S cm-1 were achieved in films of PEDOT:PolyDADMA FSI (without any post-treatment), with an ionic conductivity of 5 × 10-6 S cm-1 at 70 °C. Organic ionic plastic crystals (OIPCs) based on the cation N-ethyl-N-methylpyrrolidinium (C2mpyr+) with similar anions were added to synergistically enhance both electronic and ionic conductivities. PEDOT:PolyDADMA X / [C2mpyr][X] composites (80/20 wt%) resulted in higher ionic conductivity values (e.g., 2 × 10-5 S cm-1 at 70 °C for PEDOT:PolyDADMA FSI/[C2mpyr][FSI]) and improved electrochemical performance versus the neat PEDOT:PolyDADMA X with no OIPC. Herein, new materials are presented and discussed including new PEDOT:PolyDADMA and organic ionic plastic crystal blends highlighting their promising properties for energy storage applications.

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.

Substitution effect in reversible gel-liquid phase transformation polyoxometalate ionic liquid compounds

The substitution effect on a series of POM-type ionic liquids, has been investigated. The physicochemical properties of the ILs are highly related to their structures. When protons are substituted for ammonium, high conductivity and better thermostability are observed.

An organic hydrophilic dye for water-based dye-sensitized solar cells

In this study we report the first organic hydrophilic dye employed for 100% water-based electrolyte DSSCs. We show that the replacement of alkyl by glycolic chains in the dye structure is able to provide excellent wettability, resulting in an efficient system with remarkably reduced desorption problems that allowed us to perform tests over a wide pH range. By changing the electrolyte composition, employing chenodeoxycholic acid as a co-adsorbent and using PEDOT counter-electrodes, 3% power conversion efficiency under 1-sun illumination was obtained. We show that chenodeoxycholic acid does not significantly increase the wettability, and we provide new insights into the higher performance resulting from its co-adsorption.

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

Solid-state proton activity sensors capable of measuring the proton activity of non-aqueous media and ionic liquids regardless of their hydrophobicity and water content were miniaturised and simplified.

Electrocatalytic reduction of carbon dioxide on a cobalt tetrakis(4-aminophenyl)porphyrin modified electrode in BMImBF4

Electro-catalytic reduction of CO₂ at −0.8 V vs. Ag/AgCl has been studied with poly-Co(ii)-porphyrin on ITO in BMImBF₄ as reaction media.