Modeling of the solid-state packing of charged chains (PEDOT) in the presence of the counterions (TSA) and the solvent (DEG)

Molecular mechanics and ab-initio calculations are performed in the framework of the interaction between the charged poly(ethylenedioxythiophene) (PEDOT), the p-toluensulphonic acid (TSA), and the diethylene glycol (DEG). Different possibilities of positioning the counterion along the conjugated polymer are studied. For each possibility (or orientation), the influence of relative position of the counterion on the stability of these charged interfaces is considered. The results indicate that the perpendicular orientation corresponds to the most stable structure of the PEDOT/TSA complex. The influence of the counterion on the charge distribution in the PEDOT is also investigated indicating that a strong influence of the interionic correlation on the stability of PEDOT by TSA. Further the packing of doped chains with their counterions is also determined. In the larger aggregates, the effect of the solvent is considered. These results give a new insight about the molecular arrangements of PEDOT/TSA interactions and allow to understand how charge transport along the stacks can take place.     

Effect of (3‐glycidyloxypropyl)trimethoxysilane (GOPS) on the electrical properties of PEDOT:PSS films

Poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) has been reported as a successful functional material in a broad variety of applications. One of the most important advantages of PEDOT:PSS is its water‐solubility, which enables simple and environmental friendly manufacturing processes. Unfortunately, this also implies that pristine PEDOT:PSS films are unsuitable for applications in aqueous environments. To reach stability in polar solvents, (3‐glycidyloxypropyl)trimethoxysilane (GOPS) is typically used to cross‐link PEDOT:PSS. Although this strategy is widely used, its mechanism and effect on PEDOT:PSS performance have not been articulated yet. Here, we present a broad study that provides a better understanding of the effect of GOPS on the electrical and electronic properties of PEDOT:PSS. We show that the GOPS reacts with the sulfonic acid group of the excess PSS, causing a change in the PEDOT:PSS film morphology, while the oxidation level of PEDOT remains unaffected. This is at the origin of the observed conductivity changes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 814–820     

Effective charge propagation and storage in hybrid films of tungsten oxide and poly(3,4-ethylenedioxythiophene)

Hybrid (composite) electroactive films consisting of such an organic conducting polymer as poly(3,4-ethylenedioxythiophene), PEDOT, and such a polynuclear inorganic compound as amorphous tungsten oxide, WO₃/H _x WO₃ were fabricated on carbon electrodes through electrodeposition by voltammetric potential in acid solution containing EDOT monomer and sodium tungstate. Electrostatic interactions between the negatively charged tungstic units (existing within WO₃) and the oxidized positively charged conductive polymer (oxidized PEDOT) sites create a robust hybrid structure which cannot be considered as a simple mixture of the organic and inorganic components. It is apparent from scanning electron microscopy that hybrid structures are granular but fairly dense. Because PEDOT and mixed-valence tungsten oxides are electronically conducting, the resulting hybrid films are capable of fast propagation. The reversible and fast redox reactions of tungsten oxide component lie in the potential range where PEDOT matrix is conductive. Furthermore, the hybrid films exhibit good mediating capabilities towards electron transfers between model redox couples such as cationic iron(III,II) and anionic hexacyanoferrate(III,II). Since the films accumulate effectively charge and show high current densities at electrochemical interfaces, they could be of importance to electrocatalysis and to construction of redox capacitors.     

Poly(pyrrole) versus poly(3,4-ethylenedioxythiophene): amperometric cholesterol biosensor matrices

Two conducting polymers, poly(pyrrole) (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) were used as immobilization matrices for cholesterol oxidase (ChOx). The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H₂O₂ at +0.7 V in the absence of a mediator. Kinetic parameters, such as K _m and I _max, operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. K _m values are found as 7.9 and 1.3 mM for PPy and PEDOT enzyme electrodes, respectively; it can be interpreted that ChOx immobilized in PEDOT shows higher affinity towards the substrate.     

Fabrication of poly(vinyl alcohol)‐graphene quantum dots coated with poly(3,4‐ethylenedioxythiophene) for supercapacitor

Conducting nanofiber composed of poly(vinyl alcohol) (PVA), graphene quantum dots (GQDs) and poly(3,4‐ethylenedioxythiophene) (PEDOT) was prepared for symmetrical supercapacitor through electrospinning and electropolymerization techniques. The formation of PVA nanofibers with the addition of GQDs was excellently prepared with the average diameter of 55.66 ± 27 nm. Field emission scanning electron microscopy images revealed that cauliflower‐like structure of PEDOT was successfully coated on PVA‐GQD electrospun nanofibers. PVA‐GQD/PEDOT nanocomposite exhibited the highest specific capacitance of 291.86 F/g compared with PVA/PEDOT (220.73 F/g) and PEDOT (161.48 F/g). PVA‐GQD/PEDOT also demonstrated a high specific energy and specific power of 16.95 and 984.48 W/kg, respectively, at 2.0 A/g current density. PVA‐GQD/PEDOT exhibited the lowest resistance of charge transfer (R_ct) and equivalent series resistance compared with PEDOT and PVA/PEDOT, indicating that the fast ion diffusion between the electrode and electrolyte interface. PVA‐GQD/PEDOT nanocomposite also showed an excellent stability with retention of 98% after 1000 cycles. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 50–58     

Secondary doping in poly(3,4‐ethylenedioxythiophene):Poly(4‐styrenesulfonate) thin films

The electrical and structural properties of poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) thin films deposited from aqueous dispersion using different concentrations of selected secondary dopants are studied in detail. An improvement of the electrical conductivity by three orders of magnitude is achieved for dimethyl sulfoxide, sorbitol, ethylene glycol, and N,N‐dimethylformamide, and the secondary dopant concentration dependence of the conductivity exhibits almost identical behavior for all investigated secondary dopants. Detailed analysis of the surface morphology and Raman spectra reveals no presence of the secondary dopant in fabricated films, and thus the dopants are truly causing the secondary doping effect. Although the ratio of benzenoid and quinoid vibrations in Raman spectra is unaffected by doping, the phase transition in PEDOT:PSS films owing to doping is confirmed. Further analysis of temperature‐dependent conductivity reveals 1D variable range hopping (VRH) charge transport for undoped PEDOT:PSS, whereas highly conductive doped PEDOT:PSS films exhibit 3D VRH charge transport. We demonstrate that the charge ‐ hopping dimensionality change should be a fundamental reason for the conductivity enhancement. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1139–1146     

The Simplest Model for Doped Poly(3,4-ethylenedioxythiophene) (PEDOT): Single-crystalline EDOT Dimer Radical Cation Salts

Although doped poly(3,4-ethylenedioxythiophene) (PEDOT) is extensively used in electronic devices, their molecular-weight distributions and inadequately defined structures have hindered the elucidation of their underlying conduction mechanism. In this study, we introduce the simplest discrete oligomer models: EDOT dimer radical cation salts. Single-crystal structural analyses revealed their one-dimensional (1D) columnar structures, in which the donors were uniformly stacked. Band calculations identified 1D metallic band structures with a strong intracolumnar orbital interaction (band width W≈1 eV), implying the origin of the high conductivity of doped PEDOT. Interestingly, the salts exhibited semiconducting behavior reminiscent of genuine Mott states as a result of electron–electron repulsion (U) dominant over W. This study realized basic models with tunable W and U to understand the conduction mechanism of doped PEDOT through structural modification in oligomers, including the conjugation length.     

Electrochromic enhancement of poly(3,4‐ethylenedioxythiophene) films functionalized with hydroxymethyl and ethylene oxide

2‐((2,3‐Dihydrothieno[3,4‐b]dioxin‐2‐yl)methoxy)methyl oxirane (EDOT‐MO) was successfully synthesized by the reaction of epichlorohydrin with hydroxymethylated‐3,4‐ethylenedioxylthiophene (EDOT‐MeOH), which was synthesized via a simple four‐step sequence. Poly(hydroxymethylated‐3,4‐ethylenedioxylthiophene) (PEDOT‐MeOH) and poly(2‐((2,3‐dihydrothieno[3,4‐b]dioxin‐2‐yl)methoxy)methyl oxirane) (PEDOT‐MO) were electrosynthesized through electropolymerization of EDOT‐MeOH and EDOT‐MO, respectively. Structural, electrochemical, optical, and thermal properties of as‐formed polymers were investigated by FTIR, cyclic voltammetry, UV–vis, and thermogravimetry. Spectroelectrochemistry studies demonstrated that PEDOT‐MeOH and PEDOT‐MO could be reversibly oxidized and reduced accompany with obvious color changes. Further kinetic studies demonstrated that the introduction of hydroxymethyl or ethylene oxide group significantly improved electrochromic properties of 3,4‐ethylenedioxythiophene (PEDOT) and resulted in high contrast ratios (57.3% at 585 nm) and coloration efficiencies (338.5 cm² C^?1), low switching voltages, and fast response time. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1989–1999     

Growth of poly(3,4‐ethylenedioxythiophene) films prepared by base‐inhibited vapor phase polymerization

Transparent [90% transmittance at 550 nm at a sheet resistance (R_s) of 279 Ω sq^?1] poly(3,4‐ethylenedioxythiophene) (PEDOT) films with electrical conductivities up to 1354 S cm^?1 are prepared using base‐inhibited vapor phase polymerization at atmospheric pressure. The influence of reaction conditions, such as temperature and growth time, on the film formation is investigated. A simple and convenient two‐electrode method is used for the in situ measurement of resistance, enabling to investigate the growth mechanism of polymer films and the influence of different parameters (relative humidity and the amount of oxidant) on the film growth. Low humidity exerts a detrimental effect on film growth and conductivity. In situ R_s measurements suggest that a large structural change occurs upon washing the PEDOT‐oxidant film. © 2014 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2014 , 52, 561–571     

A platform to synthesize a soluble poly(3,4‐ethylenedioxythiophene) analogue

Alkyl‐substituted polyhedral oligomeric silsesquioxane (POSS) cage is combined with 3,4‐ethylenedioxythiophene under the same roof. The corresponding monomer called EDOT‐POSS is used to get soluble poly(3,4‐ethylenedioxythiophene) (PEDOT‐POSS) analogue. Both chemically and electrochemically obtained polymers are soluble in common organic solvents like dichloromethane, chloroform, tetrahydrofuran, and so forth. The PEDOT‐POSS has somewhat higher band gap (1.71 eV at 618 nm) than its parent PEDOT (1.60 eV at 627 nm) and as expected the PEDOT‐POSS exhibits higher optical contrast (74% at 618 nm) and coloration efficiency (582 cm²/C for 100% switching), lower switching time (0.9 s), higher electrochemical stability (93% of its electroactivity retains after 5000 cycles under ambient conditions) when compared to the PEDOT. A number of advantages of the PEDOT‐POSS over the PEDOT can make it a promising material in the areas of electro‐optical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3935–3941     

Selective Electroanalysis of Ascorbic Acid Using a Nickel Hexacyanoferrate and Poly(3,4‐ethylenedioxythiophene) Hybrid Film Modified Electrode

The mixed‐valent nickel hexacyanoferrate (NiHCF) and poly(3,4‐ethylenedioxythiophene) (PEDOT) hybrid film (NiHCF‐PEDOT) was prepared on a glassy carbon electrode (GCE) by multiple scan cyclic voltammetry. The films were characterized using atomic force microscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, X‐ray diffraction, and electrochemical impedance spectroscopy (AC impedance). The advantages of these films were demonstrated for the detection of ascorbic acid (AA) using cyclic voltammetry and amperometric techniques. The electrocatalytic oxidation of AA at different electrode surfaces, such as the bare GCE, the NiHCF/GCE, and the NiHCF‐PEDOT/GCE modified electrodes, was determined in phosphate buffer solution (pH 7). The AA electrochemical sensor exhibited a linear response from 5×10⁻⁶ to 1.5×10⁻⁴ M (R²=0.9973) and from 1.55×10⁻⁴ to 3×10⁻⁴ M (R²=0.9983), detection limit=1×10⁻⁶ M, with a fast response time (3 s) for AA determination. In addition, the NiHCF‐PEDOT/GCE was advantageous in terms of its simple preparation, specificity, stability and reproducibility.     

Effects of Supporting Electrolytes on Spectroelectrochemical and Electrochromic Properties of Polyaniline‐poly(styrene sulfonic acid) and Poly(ethylenedioxythiophene)‐poly(styrene sulfonic acid)‐based Electrochromic Device

Electrochromic devices are fabricated by using polyaniline (PANI) doped with poly(styrene sulfonic acid) (PSS) as coloring electrodes, poly(ethylenedioxythiophene)‐poly(styrene sulfonic acid) (PEDOT‐PSS) as complementary electrodes, and hybrid polymer electrolytes as gel electrolytes. The device based on LiClO₄‐based electrolyte (weight ratio of PMMA:PC:LiClO₄ = 0.7:1.1:0.3) shows the highest optical contrast and coloration efficiency (333 cm²/C) after 1200 cycles in these devices, and the color changes from pale yellow (?0.5 V) to dark blue (+2.5 V). The spectroelectrochemical and electrochromic switching properties of electrochromic devices are investigated, the maximum optical contrast (ΔT%) of electrochromic device for ITO|PANI‐PSS‖PMMA‐PC‐LiClO₄‐SiO₂‖PEDOT‐PSS|ITO are 31.5% at 640 nm, and electrochromic device based on LiClO₄‐based electrolyte with SiO₂ shows faster response time than that based on LiClO₄‐based electrolyte without SiO₂.     

Room temperature polymerization of poly(3,4‐ethylenedioxythiophene) as transparent counter electrodes for dye‐sensitized solar cells

Poly(3,4‐ethylenedioxythiophene) (PEDOT) counter electrode is prepared with in situ polymerization of 3,4‐ethylenedioxythiophene on a fluorine‐doped tin oxide over‐layer glass at room temperature. The cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization are measured to evaluate the catalytic activity of PEDOT counter electrode for I₃^?/I^? redox couple. Comparing the data with that of traditional thermal decomposed Pt counter electrode, it is found that PEDOT has higher catalytic activity than that of Pt counterpart. Power conversion efficiency of the dye‐sensitized solar cell (DSC) with PEDOT counter electrode can attain to 7.713%, a little higher than that of the cell with Pt counter electrode (7.300%). Taking the advantage of high transparency of PEDOT counter electrode, an Ag mirror is put on the back side of PEDOT counter electrode of the DSC to reflect light back for power conversion. Power conversion efficiency of the DSC with this special structure can be further enhanced to 8.359%, which mainly stems from the improved short‐circuit current density by the increased irradiated light intensity. Copyright © 2014 John Wiley & Sons, Ltd.     

Efficient enhancement of the thermoelectric performance of vapor phase polymerized poly(3,4‐ethylenedioxythiophene) films with poly(ethyleneimine)

Tuning the molecular rearrangement and oxidation level has been proven to be effective strategies for optimizing the thermoelectric (TE) performance of PEDOT. It is difficult to achieve these effects simultaneously via a one‐step process, however. In this work, we combined vapor phase polymerization (VPP) and H₂SO₄ post‐treatment to obtain a highly conductive PEDOT film. A novel strategy using polyethylenemine (PEI) as an effective reducing agent was employed to enhance the thermopower of the PEDOT film. Grazing‐Incidence Wide‐Angle X‐ray Scattering analysis and the changes in the oxidation level allow us to elucidate the role of PEI and its transport mechanism. It is demonstrated that the thermopower of well‐ordered crystallites in the PEDOT film significantly increases more than five times (from 11 to 59 μV K^?1) by the PEI‐DMF solution immersion process, while the electrical conductivity is maintained at 100 S cm^?1. The promising method connecting VPP, H₂SO₄, and PEI shows great potential for effectively tuning the thermopower of organic TE materials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 257–265     

Preparation and spectroelectrochemical characterization of composite films of poly(3,4-ethylenedioxythiophene) with 4-(pyrrole-1-yl) benzoic acid

The possibility of incorporation of 4-(pyrrole-1-yl) benzoic acid, PyBA, during electrodeposition of poly(3,4-ethylenedioxythiophene), PEDOT, is demonstrated here. The resulting novel composite material has been fabricated as moderately thin (ca 200–300 nm thick) PEDOT/PyBA film on electrode surface. As evidenced from scanning tunneling microscopy (STM) and scanning electron microscopy (SEM), morphology of the composite film is dense and granular, and it is composed of larger granules in comparison to the PyBA-free PEDOT film. It is apparent from infrared reflectance absorption spectroscopy and spectroelectrochemical measurements that the PEDOT/PyBA composite film cannot be viewed as simple mixtures of PEDOT and PyBA components. Some specific (chemical) interactions between PEDOT and PyBA can be expected. The conducting polymer serves as a robust, positively charged conductive polmer matrix for anionic (carboxylate-group derivatized) partially polymerized PyBA structures. Upon incorporation of PyBA, the overall stability of PEDOT film (resistance to dissolution during prolonged voltammetric potential cycling) has been improved. The fact, that the composite PEDOT/PyBA film is capable of preconcentrating (under open circuit conditions) both cations (Cu²⁺) or anions implies the presence of both free (available for binding) carboxylate groups and positively charged PEDOT sites. The presence of PyBA in PEDOT seems to facilitate charge propagation in the composite film. “Contribution to the International Workshop on Electrochemistry of Electroactive Materials (WEEM-2006), Repino, Russia, 24–29 June 2006”.     

Synthesis of high performance,conductive PEDOT‐coated polyester yarns by OCVD technique

Production of high performance conductive textile yarn fibers for different electronic applications has become a prominent area of many research groups throughout the world. We have used oxidative chemical vapor deposition (OCVD) technique to coat flexible and high strength polyester yarns with conjugated polymer, poly(3,4‐ethylenedioxythiophene) (PEDOT) in presence of ferric (III) chloride (FeCl₃) oxidant. OCVD is an efficient solvent free technique used to get uniform, thin, and highly conductive polymer layers on different substrates. In this paper, PEDOT‐coated polyester (PET) yarns were prepared under specific reaction conditions, and the electrical, mechanical and thermal properties were compared to previously studied PEDOT‐coated viscose yarns. Scanning electron microscopy (SEM) and FT‐IR analysis revealed that polymerization of PEDOT on the surface of the polyester yarns has been taken place successfully and structural analysis showed that PEDOT has strong interactions with viscose yarns as compared to PET yarns. The voltage–current (V–I) characteristics showed that PET yarns are more conductive than PEDOT‐coated viscose yarns. The variation in the conductivity of PEDOT‐coated yarns and the heat generation properties during the flow of current through coated yarns for longer period of time, was studied by time–current (t–I) characteristics. Thermogravimeteric analysis (TGA) was employed to investigate the thermal properties and the amount of PEDOT in PEDOT‐coated PET yarns compared to PEDOT‐coated viscose. The effect of PEDOT coating and ferric (III) chloride concentration on the mechanical properties of coated yarns was evaluated by tensile testing. The obtained PEDOT‐coated conductive polyester yarns could be used in smart clothing for medical and military applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Mechanism of oxidation of cyclohexanehexol (inositol) by quinquevalent vanadium

The oxidation of inositol by quinquevalent vandadium in acid medium is a first-order reaction both in vanadium (V) and inositol. The stoichiometry of the reaction is consistent with the use of two equivalents of vanadium (V) per mole of inositol with the formation of one mole of inosose. The reaction is catalyzed both by sulfuric and perchloric acid, but the rate is faster in sulfuric acid than in perchloric acid. In 1M–6M perchloric acid solutions the reaction has shown a variable order in H⁺, but in solutions of 2M–5M sulfuric and perchloric acid of constant ionic strength, the rate has a linear dependence on [H⁺]². There is also a linear correlation between the rate and bisulfate ions in sulfuric acid at constant hydrogen ion concentration. The energy of activation is found to be 19 kcal/mole and a negative entropy value of ? 14 e.u. A suitable mechanism, consistent with the kinetics in 2M–5M acid solutions, is suggested and the values of various rate constants are evaluated.     

Properties of In situ polymerized poly(3,4‐ethylenedioxythiophene)/alumina composites for energy storage applications

Composites formed by poly(3,4‐ethylenedioxythiophene) and alumina (PEDOT/Al₂O₃) have been prepared by in situ anodic polymerization. For this purpose, the stability of 1:1 and 4:1 monomer:alumina aqueous solutions has been examined as a function of the pH (2.3, 4.0, 7.0, 8.8, or 10.8). Results indicate that the monomer behaves as a dispersant that remains stable at the studied basic pHs despite they are close to the isoelectric point of alumina. Although the thermal stability of the composites is considerably affected by the pH of the reaction medium, its influence on the surface morphology is very small. Independently, of the synthetic conditions, the electrochemical properties were better for PEDOT/Al₂O₃ than for pure PEDOT, reflecting that alumina particles promote the charge mobility. The highest specific capacitance (SC; 141 F/g), which was 55% higher than that obtained for pure PEDOT, was achieved for the composite prepared at pH = 8.8 using a 4:1 monomer:alumina ratio. These conditions favor the participation of OH^– groups as secondary doping agents without degrading the polymer matrix and enhance the specific surface of the films, facilitating the ionic mobility. On the other hand, application of a multi‐step polymerization strategy has shown that interfaces originated by consecutive steps enhance the SC. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1131–1141     

Poly (3,4‐ethylenedioxythiophene) γ‐Fe2O3 polymer composite–super paramagnetic behavior and variable range hopping 1D conduction mechanism–synthesis and characterization

The present paper reports the preparation of poly (3,4‐ethylenedioxythiophene) (PEDOT) ferrimagnetic conducting polymer composite by incorporation of ferrite particles in the polymer matrix by emulsion polymerization. Synthesis of PEDOT–γ‐Fe₂O₃ composite was carried out by chemical oxidative polymerization of EDOT with ferrite particles in the presence of dodecylbenzenesulfonic acid (DBSA) that works as dopant as well as surfactant in aqueous medium. The resulting conducting composite possesses saturation magnetization (Ms) value of 20.56 emu/g with a conductivity of 0.4 Scm^?1, which was determined by VSM and four probe technique, respectively. B‐H curve reveals that ferrimagnetic particles of γ‐Fe₂O₃ show super‐paramagnetic behavior at room temperature which was also observed in PEDOT–γ‐Fe₂O₃ composite. The resulting conducting ferrimagnetic composite shows microwave absorption loss of 18.7–22.8 dB in the frequency range of 12.4–18 GHz. Thermogravimetric analysis of the composite revealed that the composite is thermally stable up to 230°C. The characterization of the PEDOT–γ‐Fe₂O₃ composite was carried out using XRD and FTIR spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd.     

The oxalic acid catalysed oxidation of bis(2,4,6-tripyridyl-1,3,5-triazine)-iron(II) by chromium(VI) in acetate buffer

Summary The reaction between bis(2,4,6-tripyridyl-1,3,5-triazine)-iron(II), Fe(TPTZ) _inf2 ^sup2+ and chromium(VI) in acetate buffers is very slow. However, in the presence of oxalic acid (catalyst) it is very fast and is completed within 10s. The reaction was studied in the 3.6–5.6 pH range using stopped-flow spectrophotometry. The reaction is first order in the substrate and zero order in the oxidant. The rate of the reaction increases with the increase in pH. Kinetic evidence for complexation between the substrate and the catalyst was obtained and a mechanism involving the formation of an ion-pair between Fe(TPTZ) _inf2 ^sup2+ and the oxalate ion is proposed.