Electrochemistry of conducting polymers--persistent models and new concepts

Selective non-enzymatic uric acid sensing in the presence of dopamine: electropolymerized poly-pyrrole modified with a reduced graphene oxide/PEDOT:PSS composite

A molecularly imprinted polymer (MIP) with uric acid cavities increases the selectivity of uric acid measurement in the presence of dopamine as an interferent.

Evaluation of Electrochromic Properties of Polypyrrole/Poly(Methylene Blue) Layer Doped by Polysaccharides

Polypyrrole (Ppy) and poly(methylene blue) (PMB) heterostructure (Ppy-PMB) was electrochemically formed on the indium tin oxide (ITO) coated glass slides, which served as working electrodes. For electropolymerization, a solution containing pyrrole, methylene blue, and a saccharide (lactose, sucrose, or heparin) that served as dopant was used. The aim of this study was to compare the effect of the saccharides (lactose, sucrose, and heparin) on the electrochromic properties of the Ppy-PMB layer. AFM and SEM have been used for the analysis of the surface dominant features of the Ppy-PMB layers. From these images, it was concluded that the saccharides used in this study have a moderate effect on the surface morphology. Electrochromic properties were analyzed with respect to the changes of absorbance of the layer at two wavelengths (668 nm and 750 nm) by changing the pH of the surrounding solution and the potential between +0.8 V and -0.8 V. It was demonstrated that the highest absorbance changes are characteristic for all layers in the acidic media. Meanwhile, the absorbance changes of the layers were decreased in the more alkaline media. It was determined that the Ppy-PMB layers with heparin as a dopant were more mechanically stable in comparison to the layers doped with lactose and sucrose. Therefore, the Ppy-PMB layer doped with heparin was selected for the further experiment and it was applied in the design of electrochromic sensors for the determination of three xanthine derivatives: caffeine, theobromine, and theophylline. A linear relationship of ΔA (∆A = A_+0.8V - A_-0.8V) vs. concentration was determined for all three xanthine derivatives studied. The largest change in optical absorption was observed in the case of theophylline determination.

Solid-state dye-sensitized solar cells using polymeric hole conductors

The present review presents the application of electronically conducting polymers (conducting polymers) as hole conductors in solid-state dye solar cells (S-DSSCs). At first, the basic principles of dye solar cell operation are presented. The next section deals with the principles of electrochemical polymerisation and its photoelectrochemical variety, the latter being an important, frequently-used technique for generating conducting polymers and hole conductors in DSSCs. Finally, two varieties of S-DSSC configurations, those of dry S-DSSC and of S-DSSCs incorporating a liquid electrolyte, are discussed.

Electrochemical Synthesis of Unique Nanomaterials in Ionic Liquids

The review considers the features of the processes of the electrochemical synthesis of nanostructures in ionic liquids (ILs), including the production of carbon nanomaterials, silicon and germanium nanoparticles, metallic nanoparticles, nanomaterials and surface nanostructures based on oxides. In addition, the analysis of works on the synthesis of nanoscale polymer films of conductive polymers prepared using ionic liquids by electrochemical methods is given. The purpose of the review is to dwell upon an aspect of the applicability of ILs that is usually not fully reflected in modern literature, the synthesis of nanostructures (including unique ones that cannot be obtained in other electrolytes). The current underestimation of ILs as an electrochemical medium for the synthesis of nanomaterials may limit our understanding and the scope of their potential application. Another purpose of our review is to expand their possible application and to show the relative simplicity of the experimental part of the work.

Constant Potential and Constant Current Electrolysis: An Introduction and Comparison of Different Techniques for Organic Electrosynthesis

Electrosynthesis involves transferring charge between two electrodes to promote chemical reactions by applying potential. The modes of controlling the current and potential can affect the reaction mechanism, product distribution and yields, and add a control factor for reaction optimization. In this Synopsis, theoretical discussion is applied to specific case studies from the literature to illustrate methods of adjusting and tracking electrical parameters for the optimization and monitoring of electroorganic reactions.

In Situ Spectroelectrochemical-Conductance Measurements as an Efficient Tool for the Evaluation of Charge Trapping in Conducting Polymers

In situ UV-vis-NIR spectroelectrochemistry has been intensively used to evaluate the electronic transitions during the charging/discharging process of π-conjugated polymers. However, the type of charge carrier and the mechanisms of their transport, remains still a point of discussion. Herein, the coupling between UV-vis-NIR spectroscopy and in situ electrochemical-conductance measurements is proposed to compare the doping process of three different thiophene-based conducting polymers. The simultaneous monitoring of electrical and absorption properties, associated with low energy electronic transitions characteristic for polarons and bipolarons, was achieved. In addition, this method allows evaluating the reversible charge trapping mechanism of poly-3,4-o-xylendioxythiophene (PXDOT), caused by the formation of σ-dimers, making it a very useful tool to determine relevant physicochemical properties of conductive materials.

Tuning Organic Electrochemical Transistor (OECT) Transconductance toward Zero Gate Voltage in the Faradaic Mode

In this work, we investigate material design criteria for low-powered/self-powered and efficient organic electrochemical transistors (OECTs) to be operated in the faradaic mode (detection at the gate electrode occurs via electron transfer events). To rationalize device design principles, we adopt a Marcus-Gerischer perspective for electrochemical processes at both the gate and channel interfaces. This perspective considers density of states (DOS) for the semiconductor channel, the gate electrode, and the electrolyte. We complement our approach with energy band offsets of relevant electrochemical potentials that can be independently measured from transistor geometry using conventional electrochemical methods as well as an approach to measure electrolyte potential in an operating OECT. By systematically changing the relative redox property offsets between the redox-active electrolyte and semiconducting polymer channel, we demonstrate a first-order design principle that necessary gate voltage is minimized by good DOS overlap of the two redox processes at the gate and channel. Specifically, for p-type turn-on OECTs, the voltage-dependent, electrochemically active semiconductor DOS should overlap with the oxidant form of the electrolyte to minimize the onset voltage for transconductance. A special case where the electrolyte can be used to spontaneously dope the polymer via charge transfer is also considered. Collectively, our results provide material design pathways toward the development of simple, robust, power-saving, and high-throughput OECT biosensors.

Molecularly Imprinted Polymers (MIPs) in Sensors for Environmental and Biomedical Applications: A Review

Molecular imprinted polymers are custom made materials with specific recognition sites for a target molecule. Their specificity and the variety of materials and physical shapes in which they can be fabricated make them ideal components for sensing platforms. Despite their excellent properties, MIP-based sensors have rarely left the academic laboratory environment. This work presents a comprehensive review of recent reports in the environmental and biomedical fields, with a focus on electrochemical and optical signaling mechanisms. The discussion aims to identify knowledge gaps that hinder the translation of MIP-based technology from research laboratories to commercialization.

Hybrid light-emitting devices for the straightforward readout of chiral information

Bipolar electrochemistry has gained increasing attention in recent years as an attractive transduction concept in analytical chemistry in general and, more specifically, in the frame of chiral recognition. Herein, we use this concept of wireless electrochemistry, based on the combination of the enantioselective oxidation of a chiral probe with the emission of light from a light-emitting diode (LED), as an alternative for an easy and straightforward readout of the presence of chiral molecules in solution. A hybrid polymer-microelectronic device was designed, using an inherently chiral oligomer, that is, oligo-(3,3'-dibenzothiophene) and a polypyrrole strip as the anode and cathode of a miniaturized LED. The wireless induced redox reactions trigger light emission when the probe with the right chirality is present in solution, whereas no light emission is observed for the opposite enantiomer. The average light intensity shows a linear correlation with the analyte concentration, and the concept opens the possibility to quantify the enantiomeric excess in mixtures of the molecular antipodes.

Video Speed Switching of Plasmonic Structural Colors with High Contrast and Superior Lifetime

Reflective displays or "electronic paper" technologies provide a solution to the high energy consumption of emissive displays by simply utilizing ambient light. However, it has proven challenging to develop electronic paper with competitive image quality and video speed capabilities. Here, the first technology that provides video speed switching of structural colors with high contrast over the whole visible is shown. Importantly, this is achieved with a broadband-absorbing polarization-insensitive electrochromic polymer instead of liquid crystals, which makes it possible to maintain high reflectivity. It is shown that promoting electrophoretic ion transport (drift motion) improves the switch speed. In combination with new nanostructures that have high surface curvature, this enables video speed switching (20 ms) at high contrast (50% reflectivity change). A detailed analysis of the optical signal during switching shows that the polaron formation starts to obey first order reaction kinetics in the video speed regime. Additionally, the system still operates at ultralow power consumption during video speed switching (<1 mW cm^-2 ) and has negligible power consumption (<1 µW cm^-2 ) in bistability mode. Finally, the fast switching increases device lifetime to at least 10⁷ cycles, an order of magnitude more than state-of-the-art.

Prediction of the standard potentials for one-electron oxidation of N,N,N',N' tetrasubstituted p-phenylenediamines by calculation

The formal potentials for the reversible one-electron oxidation of N,N,N',N' tetrasubstituted p-phenylenediamines in acetonitrile have been applied as a test set for benchmarking computational methods for a series of compounds with only small structural differences. The aim of the study is to propose a simple method for calculating the standard oxidation potentials, and therefore, the protocol is progressively developed by adding more terms in the energy expression. In addition, the effect of including implicit solvation models (IEFPCM, CPCM, and SMD), larger basis sets, and correlation methods are investigated. The oxidation potentials calculated using the G3MP2B3 approach with IEFPCM resulted in the best fit (R² = 0.9624), but the slope of the correlation line, 0.74, is far from the optimal value, 1.00. B3LYP/6-311++G(d,p) and TPSSh/6-311++G(2d,p) yielded only slightly less consistent data (R² = 0.9388 and R² = 0.9425), but with much better slopes, 1.00 and 0.94, respectively. We conclude that it is important to investigate the basis set size and treatment of electron correlation when calculating oxidation potentials for N,N,N',N' tetrasubstituted p-phenylenediamines.

Modulating the Enantiodiscrimination Features of Inherently Chiral Selectors by Molecular Design: A HPLC and Voltammetry Study Case with Atropisomeric 2,2'-Biindole-Based Monomers and Oligomer Films

A family of inherently chiral electroactive selectors based on the 2,2'-biindole atropisomeric scaffold, of easy synthesis and modulable functional properties, is studied in cascade in two enantioselection contexts. They are at first investigated as probes in enantioselective HPLC, studying molecular structure and temperature effects, and achieving very efficient semipreparative enantioseparation. The enantiomers thus obtained, of remarkable chiroptical features (optical rotation as well as circular dichroism), are successfully applied as selectors in chiral voltammetry in different media for discrimination of the enantiomers of chiral electroactive probes, either by conversion into enantiopure electroactive electrode surfaces by electrooligomerization on glassy carbon substrate (the two monomers with shorter alkyl chains), or as chiral additive in achiral ionic liquid (the monomer with longest alkyl chains). Discrimination is conveniently and reproducibly achieved in terms of significant potential differences for the two enantiomers, specularly inverting either probe or selector configuration. In one case successful discrimination is also observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios.

Effect of Electrosynthesis Potential on Nucleation, Growth, Adhesion, and Electronic Properties of Polypyrrole Thin Films on Fluorine-Doped Tin Oxide (FTO)

Polypyrrole (PPy) is one of the most attractive conducting polymers for thin film applications due to its good electrical conductivity, stability, optical properties, and biocompatibility. Among the technologies in which PPy has gained prominence are optoelectronics and solar energy conversion, where transparent electrodes such as fluorine-doped tin oxide (FTO) or indium tin oxide (ITO) are frequently used. However, FTO substrates have the notable advantage that their components are widely available in nature, unlike those of ITO. Recognizing the importance that the FTO/polypyrrole system has gained in various applications, here, we studied for the first time the nucleation and growth mechanism of electro-synthesized PPy on FTO. Additionally, the effect of the synthesis potential (0.9, 1.0, 1.1, and 1.2 V vs. Ag/AgCl) on the homogeneity, adhesion, conductivity, and HOMO energy levels of PPy films was determined. From current–time transients and scanning electron microscopy, it was found that films synthesized at 0.9 and 1.0 V exhibit 3D growth with progressive nucleation (as well as lower homogeneity and higher adhesion to FTO). In contrast, films synthesized at 1.1 and 1.2 V follow 2D growth with instantaneous nucleation. It was also evident that increasing the polymerization potential leads to polymers with lower conductivity and more negative HOMO levels (versus vacuum). These findings are relevant to encourage the use of electro-synthesized PPy in thin film applications that require a high control of material properties.

Highly Strained 1,8-Naphthalene-Bridged Cyclic Oligophenylenes and Their Open-Shell Diradical Dications

The synthesis and characterization of two 1,8-naphthalene-bridged cyclic oligo-para-phenylenes with four or eight phenylene units are reported. Both molecules exhibit a highly strained structure with two nearly face-to-face arranged p,p'-biphenylylene/p,p'-quaterphenylylene chains. Their dications were obtained by chemical oxidation with NO·SbF₆, and both showed open-shell singlet diradical character with a small singlet-triplet energy gap.

Photoinduced Electron Transfer between DNA and Water-Soluble Porphyrins

Photophysical properties of five kinds of porphyrins (H₂TMPyP, ZnTMPyP, PdTMPyP, H₂TPPS, and ZnTPPS) complexed with model DNAs (ctDNA and dGMP) have been investigated using steady-state absorption, circular dichroism (CD), and femtosecond transient absorption spectroscopy. Upon addition of ctDNA (or dGMP), larger hypochromism and red shifts are observed for H₂TMPyP and PdTMPyP compared to the other samples. The steady-state measurements have suggested that the binding modes of H₂TMPyP-ctDNA and PdTMPyP-ctDNA are partial intercalation and full intercalation, respectively, while ZnTMPyP-ctDNA shows outside groove binding. No significant interaction was observed between both H₂TPPS and ZnTPPS with two kinds of DNA. Upon excitation of the porphyrins into the higher excited state S₂ (Soret band), the appearance of the transient absorption from ∼500 to ∼620 nm at about 0.05 ps in H₂TMPyP-ctDNA, H₂TMPyP-dGMP, and PdTMPyP-dGMP indicates the occurrence of the electron transfer (ET) from guanine to H₂TMPyP and PdTMPyP. The forward ET are extremely fast (k_f ≥ 1.0 × 10¹³ s^-1), and the backward ET rates are ∼5.6 × 10¹² and ∼4.0 × 10¹² s^-1, respectively. The complexation with DNA may lead to the shorter lifetime of the fluorescence of H₂TMPyP and PdTMPyP.

Fabrication of Robust, Highly Conductive, and Elastic Hybrid Carbon Foam Platform for High-Performance Compressible Asymmetry Supercapacitors

Highly conductive and elastic three-dimensional (3D) porous carbon materials are ideal platforms to fabricate electrodes for high-performance compressible supercapacitors. Herein, a robust, highly conductive, and elastic carbon foam (CF) hybrid material is reported, which is fabricated by integrating cellulose nanofiber/multiwalled carbon nanotube (CNF/MWCNT) aerogel sheets with a melamine sponge (MS), followed by carbonization. The carbonized CNF/MWCNT aerogel sheets contribute to the high conductivity and specific surface area of the CF, and the 3D network-like skeleton derived from the carbonization of the MS enhances the elasticity and stability of the CF. More importantly, the CF possesses good scalability, allowing the introduction of electroactive materials such as polypyrrole (PPy) and Fe₃O₄ to fabricate high-performance compressible PPy-CF and Fe₃O₄-CF electrodes. Moreover, an assembled PPy-CF//Fe₃O₄-CF device shows reversible charging-discharging at a voltage of 1.6 V and demonstrates a high specific capacitance (172.5 F/g) and an outstanding energy density (59.9 W h/kg). The device exhibits capacitance retention rates reaching 98.3% and stable energy storage characteristics even under different degrees of compressive deformation. This study offers a scalable strategy for fabricating high-performance compressible supercapacitors, thereby providing a new means of satisfying the energy storage needs of portable electronic devices that are prone to deformation.

A Novel Cobalt Metallopolymer with Redox-Matched Conjugated Organic Backbone via Electropolymerization of a Readily Available N4 Cobalt Complex

Fast and reversible cobalt-centered redox reactions in metallopolymers are the key to using these materials in energy storage, electrocatalytic, and sensing applications. Metal-centered electrochemical activity can be enhanced via redox matching of the conjugated organic backbone and cobalt centers. In this study, we present a novel approach to redox matching via modification of the cobalt coordination site: a conductive electrochemically active polymer was electro-synthesized from [Co(Amben)] complex (Amben = N,N′-bis(o-aminobenzylidene)ethylenediamine) for the first time. The poly-[Co(Amben)] films were investigated by cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM), in situ UV-vis-NIR spectroelectrochemistry, and in situ conductance measurements between −0.9 and 1.3 V vs. Ag/Ag⁺. The polymer displayed multistep redox processes involving reversible transfer of the total of 1.25 electrons per repeat unit. The findings indicate consecutive formation of three redox states during reversible electrochemical oxidation of the polymer film, which were identified as benzidine radical cations, Co(III) ions, and benzidine di-cations. The Co(II)/Co(III) redox switching is retained in the thick polymer films because it occurs at potentials of high polymer conductivity due to the optimum redox matching of the Co(II)/Co(III) redox pair with the organic conjugated backbone. It makes poly-[Co(Amben)] suitable for various practical applications based on cobalt-mediated redox reactions.

Molecular Imprinting Technology for Determination of Uric Acid

The review focuses on the overview of electrochemical sensors based on molecularly imprinted polymers (MIPs) for the determination of uric acid. The importance of robust and precise determination of uric acid is highlighted, a short description of the principles of molecular imprinting technology is presented, and advantages over the others affinity-based analytical methods are discussed. The review is mainly concerned with the electro-analytical methods like cyclic voltammetry, electrochemical impedance spectroscopy, amperometry, etc. Moreover, there are some scattered notes to the other electrochemistry-related analytical methods, which are capable of providing additional information and to solve some challenges that are not achievable using standard electrochemical methods. The significance of these overviewed methods is highlighted. The overview of the research that is employing MIPs imprinted with uric acid is mainly targeted to address these topics: (i) type of polymers, which are used to design uric acid imprint structures; (ii) types of working electrodes and/or other parts of signal transducing systems applied for the registration of analytical signal; (iii) the description of the uric acid extraction procedures applied for the design of final MIP-structure; (iv) advantages and disadvantages of electrochemical methods and other signal transducing methods used for the registration of the analytical signal; (vi) overview of types of interfering molecules, which were analyzed to evaluate the selectivity; (vi) comparison of analytical characteristics such as linear range, limits of detection and quantification, reusability, reproducibility, repeatability, and stability. Some insights in future development of uric acid sensors are discussed in this review.

Syntheses and Physical Properties of Cationic BN-Embedded Polycyclic Aromatic Hydrocarbons

Cationic BN-embedded polycyclic aromatic hydrocarbons (BN-PAH⁺ s) were synthesized from a nitrogen-containing macrocycle via pyridine-directed tandem C-H borylation. Incorporating BN into PAH⁺ resulted in a remarkable hypsochromic shift due to an increase in the LUMO energy and the symmetry changes of the HOMO and LUMO. Electrophilic substitution or anion exchange of BN-PAH⁺ possessing tetrabromoborate as a counter anion (BN⁺ [BBr₄ ^- ]) afforded air-stable BN-PAH/PAH⁺ s. Of these, BN⁺ [TfO^- ] allowed reversible two-electron reduction and the formation of two-dimensional brickwork-type π-electronic ion pair with 1,2,3,4,5-pentacyanocyclopentadienyl anion, demonstrating the potential application of BN-PAH⁺ as electronic materials.

Nickel(II) Complex of N4 Schiff Base Ligand as a Building Block for a Conducting Metallopolymer with Multiple Redox States

Metal–ligand interactions in monomeric and polymeric transition metal complexes of Schiff base ligands largely define their functional properties and perspective applications. In this study, redox behavior of a nickel(II) N₄-anilinosalen complex, [NiAmben] (where H₂Amben = N,N′-bis(o-aminobenzylidene)ethylenediamine) was studied by cyclic voltammetry in solvents of different Lewis basicity. A poly-[NiAmben] film electrochemically synthesized from a 1,2-dichloroethane-based electrolyte was investigated by a combination of cyclic voltammetry, electrochemical quartz crystal microbalance, in situ UV-Vis spectroelectrochemistry, and in situ conductance measurements between −0.9 and 1.3 V vs. Ag/Ag⁺. The polymer displayed multistep redox processes involving reversible transfer of the total of ca. 1.6 electrons per repeat unit, electrical conductivity over a wide potential range, and multiple color changes in correlation with electrochemical processes. Performance advantages of poly-[NiAmben] over its nickel(II) N₂O₂ Schiff base analogue were identified and related to the increased number of accessible redox states in the polymer due to the higher extent of electronic communication between metal ions and ligand segments in the nickel(II) N₄-anilinosalen system. The obtained results suggest that electrosynthesized poly-[NiAmben] films may be viable candidates for energy storage and saving applications.

Cost-Effective, Flexible, and Colorful Dynamic Displays: Removing Underlying Conducting Layers from Polymer-Based Electrochromic Devices

Electrochromic (EC) materials and devices provide a user-controlled, dynamic way of displaying information using low power, making them interesting for a range of applications in numerous markets, including logistics, retail, consumer goods, and health care. To optimize the cost while simplifying the production, expanding the color space, and enhancing the contrast and vibrancy of EC displays aimed for cost-sensitive products, we sought to reduce the number of layers as well as remove the underlying conducting layer that accounts for a substantial fraction of the cost of a printed label. Here, we show how conjugated electrochromic polymers, which are inherently semiconducting, can be used to accomplish this goal and afford printable EC displays with a flexible form factor. Using a combination of electrochemical probes, in situ spectroscopy, solid-state conductivity, and in situ conductance measurements, we have studied and compared five different EC polymers with conductivities spanning multiple orders of magnitude and colors that span most of the visible range, identifying polymers and properties that allow for switching from the colored to the clear state without an underlying conducting layer. Finally, we incorporate these EC polymers into optimized flexible devices without an underlying conductor and demonstrate that they are able to provide on-demand, reversible colored-to-clear switching on the order of seconds to minutes, with operating voltages below ±1 V, optical memories exceeding 60 min, and a shelf-life exceeding 12 months.

Wavy graphene sheets from electrochemical sewing of corannulene

The presence of non-hexagonal rings in the honeycomb carbon arrangement of graphene produces rippled graphene layers with valuable chemical and physical properties. In principle, a bottom-up approach to introducing distortion from planarity of a graphene sheet can be achieved by careful insertion of curved polyaromatic hydrocarbons during the growth of the lattice. Corannulene, the archetype of such non-planar polyaromatic hydrocarbons, can act as an ideal wrinkling motif in 2D carbon nanostructures. Herein we report an electrochemical bottom-up method to obtain egg-box shaped nanographene structures through a polycondensation of corannulene that produces a new conducting layered material. Characterization of this new polymeric material by electrochemistry, spectroscopy, electron microscopy (SEM and TEM), scanning probe microscopy, and laser desorption-ionization time of flight mass spectrometry provides strong evidence that the anodic polymerization of corannulene, combined with electrochemically induced oxidative cyclodehydrogenations (Scholl reactions), leads to polycorannulene with a wavy graphene-like structure.

A bottom-up synthesis of wavy graphene structures obtained through an anodic polymerization process, combined with an electrochemically triggered oxidative cyclodehydrogenation, of the bowl-shaped polyaromatic hydrocarbon corannulene.

Electricity-Driven Post-Functionalization of Conducting Polymers

Electrochemical doping of conducting polymers (CPs) generates polarons (radical ionic species) and bipolarons (ionic species) in their backbone via multi-electron transfer between an electrode and the CP. In the electrochemical polymer reaction (ePR), these generated ionic species are regarded as reactive intermediates for further transformation of the chemical structures of CPs. This electrochemical post-functionalization can easily be used to control the degree of reactions by turning a power supply on/off, as well as tuning the applied electrode potential, which leads to fine-tuning of the various properties of the CPs, such as the HOMO/LUMO level and PL properties. This Account summarizes recent developments in the electrochemical post-functionalization of CPs. In particular, we focus on reaction design for the ePR, with respect to the preparation and structure of the precursor polymers, applicable functional groups, efficient reaction conditions, and electrolytic methodologies.

Electrochemically Triggered Chain Reactions for the Conversion of Furan Derivatives

We report an electrochemical method for coupling biomass-derived C5/C6 compounds to value-added fuel precursors. Using only 2 % of equivalent charges, 2-methylfuran (2-MF) was oxidized to yield a cation radical, which readily reacted with 3-hexene-2,5-dione, a derivate of 2,5-dimethylfuran, to produce 3-(5-methylfuran-2-yl)hexane-2,5-dione. The product was converted to 4-ethylnonane (a component of biodiesel/jet fuel) in a single step in excellent yield. Importantly, the reaction was not sensitive to oxygen, and a trace amount of water was found to promote the reaction. Detailed mechanistic studies confirmed the proposed reaction pathways. Key to the mechanism is the radical generation that is enabled by electrochemistry. The radical is regenerated at the end of a reaction cycle to ensure chain propagation for an average of ca. 47 times, resulting in an apparent Faradaic efficiency of 4700 %.

Textile Chemical Sensors Based on Conductive Polymers for the Analysis of Sweat

Wearable textile chemical sensors are promising devices due to the potential applications in medicine, sports activities and occupational safety and health. Reaching the maturity required for commercialization is a technology challenge that mainly involves material science because these sensors should be adapted to flexible and light-weight substrates to preserve the comfort of the wearer. Conductive polymers (CPs) are a fascinating solution to meet this demand, as they exhibit the mechanical properties of polymers, with an electrical conductivity typical of semiconductors. Moreover, their biocompatibility makes them promising candidates for effectively interfacing the human body. In particular, sweat analysis is very attractive to wearable technologies as perspiration is a naturally occurring process and sweat can be sampled non-invasively and continuously over time. This review discusses the role of CPs in the development of textile electrochemical sensors specifically designed for real-time sweat monitoring and the main challenges related to this topic.

Electrochemical bubble generation via hydrazine oxidation for the in situ control of an electrodeposited conducting polymer micro/-nanostructure

Herein, a simple, in situ, on step and highly repeatable electrochemical method that allows controlling the nanostructure of electrodeposited polymer films is reported. As an example, the tuning of the electrodeposited polypyrrole nanostructures using inert gas bubbles as the template at the electrode surface generated by the electrochemical oxidation of hydrazine is shown. The hydrazine discharge occurs at a lower potential regarding the beginning of pyrrole electropolymerization process, which allows the modulation of the density and size of the bubbles on the surface electrode controlling electrochemical parameters (applied potential, concentration, time, etc.). Subsequently, the applied potential is moved to where the pyrrole polymerization begins, which induces the material discharges around the bubble template producing polypyrrole hollow structures with definite patterns on the electrode surface. This methodology is proposed as a simple model for the electrodeposition with the morphological control of a wide range of conductive polymers.

An electrochemical method to manipulate the size and density of electrodeposited polypyrrole structures at the micro-nanoscale by the discharge of hydrazine.

Remediation of heavy metal-contaminated soils by electrokinetic technology: Mechanisms and applicability

Electrokinetic remediation is a widely admitted technology forrectifying heavy metal-contaminated soil. Various technologies have been effectively developed to improve the metal removal efficiency of contaminated soil by electrochemical treatment alone or in combination with other remediation technologies. The working components for electrokinetic system, such as supplying power for electric fields, installing electrodes to generate electric fields, introducing electrolytes and other potential materials as a reactive medium are crucial. This review focuses on the specific functions of the working components in electrokinetic systems and their effects on the efficiency of heavy metal removal using electrochemical process. The advancements in working components were systematically summarized, such as power for electric fields, electrodes, electrolytes and ion exchange membrane, which have various impacts on the effectiveness of electrokinetic remediation. Additionally, this study introduces the application of dominating technologies at present coupled with electrokinetics. Overall, a judicious design and reasonable operation in the application of electrokinetic-coupled remediation should be implemented to enhance the removal process of heavy metals from contaminated soil.

2D and 3D Immobilization of Carbon Nanomaterials into PEDOT via Electropolymerization of a Functional Bis-EDOT Monomer

Carbon nanomaterials (CNMs) and conjugated polymers (CPs) are actively investigated in applications such as optics, catalysis, solar cells, and tissue engineering. Generally, CNMs are implemented in devices where the relationship between the active elements and the micro and nanostructure has a crucial role. However, they present some limitations related to solubility, processibility and release or degradability that affect their manufacturing. CPs, such as poly(3,4-ethylenedioxythiophene) (PEDOT) or derivatives can hide this limitation by electrodeposition onto an electrode. In this work we have explored two different CNMs immobilization methods in 2D and 3D structures. First, CNM/CP hybrid 2D films with enhanced electrochemical properties have been developed using bis-malonyl PEDOT and fullerene C60. The resulting 2D films nanoparticulate present novel electrochromic properties. Secondly, 3D porous self-standing scaffolds were prepared, containing carbon nanotubes and PEDOT by using the same bis-EDOT co-monomer, which show porosity and topography dependence on the composition. This article shows the validity of electropolymerization to obtain 2D and 3D materials including different carbon nanomaterials and conductive polymers.

Conducting polymers: a comprehensive review on recent advances in synthesis, properties and applications

Conducting polymers are extensively studied due to their outstanding properties, including tunable electrical property, optical and high mechanical properties, easy synthesis and effortless fabrication and high environmental stability over conventional inorganic materials. Although conducting polymers have a lot of limitations in their pristine form, hybridization with other materials overcomes these limitations. The synergetic effects of conducting polymer composites give them wide applications in electrical, electronics and optoelectronic fields. An in-depth analysis of composites of conducting polymers with carbonaceous materials, metal oxides, transition metals and transition metal dichalcogenides etc. is used to study them effectively. Here in this review we seek to describe the transport models which help to explain the conduction mechanism, relevant synthesis approaches, and physical properties, including electrical, optical and mechanical properties. Recent developments in their applications in the fields of energy storage, photocatalysis, anti-corrosion coatings, biomedical applications and sensing applications are also explained. Structural properties play an important role in the performance of the composites.