Electroactive Elements Research Articles

Conductive polymers and derivatives as recognition element for electrochemical sensing of food and drug additives: A brief perspective.

Conducting polymers (CPs) are a distinct category of polymeric materials characterised by conjugated main chains that display adjustable electrical and optical properties. By regulating their doping states, these characteristics can be enhanced for many applications. CPs have demonstrated stability in aquatic conditions, rendering them suitable as electroactive and recognition elements in chemointerfaces and as electrode materials, particularly in water-based systems. This paper examines the use of CPs and CP-based nanocomposites in electrochemical sensors, specifically their application in identifying contaminants in food and pharmaceuticals. This research offers a thorough examination of the mechanics underlying CP-based electrochemical sensors, elucidating the origin of their detecting abilities and the characteristics that render them suitable for various applications. It encompasses the theoretical understanding foundation of electrochemical sensing, providing insights into the principal frameworks and prevalent conducting polymers and their derivatives utilised in sensor development. Alongside the concepts of electrochemical sensing, we examine diverse electroanalytical techniques, including chronoamperometry, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry, which are presented in a tabular format. These techniques are extensively employed for the detection and quantification of pharmaceuticals and food adulterants. We briefly highlight CP-based nanocomposites that improve sensitivity and reduce detection limits of these sensors, with this information compiled in a comprehensive table. In summary, electrodes constructed from CP-based nanocomposites typically exceed the performance of those built from pristine CPs. Nevertheless, additional systematic research is required to enhance the comprehension of the design and optimisation of nanocomposite-based electrodes for more effective sensing performance.

Simulation of Interaction Processes of C20 Fullerene with Graphene

Graphene, a carbon sheet one atom thick, with carbon atoms arranged in a two-dimensional honeycomb configuration, has a number of intriguing properties. Fullerenes are a promising material for creating electro-active elements in solar cells and active layers in thin-film organic transistors. A computer model of the C20 fullerene molecule was constructed using the energy minimization method with the second-generation Brenner potential (REBO). A computer model of "infinite" defect-free graphene was built, designed to consider the process of adsorption of a C20 fullerene molecule on its surface. To study adsorption process computer models of fullerene and "infinite" graphene were approached to the required distance with a different set of geometric arrangement of fullerene with respect to the graphene surface. It has been established that the adsorption of fullerene C20 on the surface of graphene can be carried out in three different ways, differing in the number of interacting fullerene and graphene atoms. The binding energies and adsorption lengths for C20 fullerene molecules adsorbed on the graphene surface in different ways are calculated. The way of adsorption corresponding to the highest binding energy and the shortest adsorption length was revealed.

Highly Efficient Piezoelectrets through Ultra-Soft Elastomeric Spacers.

Piezoelectrets are artificial ferroelectrics that are produced from non-polar air-filled porous polymers by symmetry breaking through high-voltage-induced Paschen breakdown in air. A new strategy for three-layer polymer sandwiches is introduced by separating the electrical from the mechanical response. A 3D-printed grid of periodically spaced thermoplastic polyurethane (TPU) spacers and air channels was sandwiched between two thin fluoroethylene propylene (FEP) films. After corona charging, the air-filled sections acted as electroactive elements, while the ultra-soft TPU sections determined the mechanical stiffness. Due to the ultra-soft TPU sections, very high quasi-static (22,000 pC N−1) and dynamic (7500 pC N−1) coefficients were achieved. The isothermal stability of the coefficients showed a strong dependence on poling temperature. Furthermore, the thermally stimulated discharge currents revealed well-known instability of positive charge carriers in FEP, thereby offering the possibility of stabilization by high-temperature poling. The dependences of the dynamic coefficient on seismic mass and acceleration showed high coefficients, even at accelerations approaching that of gravity. An advanced analytical model rationalizes the magnitude of the obtained quasi-static coefficients of the suggested structure indicating a potential for further optimization.

Electrochemical biosensors by in situ dissolution of self-assembled nanolabels into small monomers on electrode surface

Nanomaterials composed of electroactive elements have increasingly being used as the signal labels of electrochemical biosensors. In this work, we proposed a novel strategy for the preparation of signal labels used for electrochemical biosensors. The method is based on the signal amplification of self-assembled nanomaterials of small molecules and the in situ dissolution of nanostrutures into electroactive elements on electrode surface. Ferrocenoyl phenylalanine (Fc-F) nanoparticles (FcFNPs) were prepared and used as the example of signal labels. The FcFNPs captured by sensor electrode were in situ disassembled into tens or hundreds of monomers by methnol. After evaporation of methnol, the released Fc-F monomers were concentrated on electrode surface to produce a strong electrochemical signal. With prostate specific antigen and cancer cells as the model analytes, the target concentration as low as 1 pg/mL or 10 cells can be readily measured. This work should be valuable for designing of novel nanolabels and development of sensitive sensing platforms.

Electrochemical reactivity of In-Pb solid solution as a negative electrode for rechargeable Mg-ion batteries

A composite In-Pb:carbon was successfully synthetized by a two-step mechanochemical synthesis in order to obtain an adequate particles size and structure to investigate the electrochemical reactivity of the In-Pb solid solution towards Mg. A potential synergetic coupling of electroactive elements In and Pb was examined using electrochemical and ex situ X-ray diffraction analyses. The potential profile of the solid solution indicates the formation of Mg2Pb and MgIn. However, the diffraction study suggests a peculiar electrochemically-driven amorphization of MgIn during the magnesiation, in strong contrast to MgIn crystallization in In-based and InBi-based electrodes reported in the literature. Combining In and Pb favors the amorphization of MgIn and a high first magnesiation capacity of about 550 mAh g−1, but is thereafter detrimental to the material’s reversibility. These results emphasize the possible influence of electrochemically-driven amorphization and crystallization processes on electrochemical performance of battery materials.

High Magnetic Field-Engineered Bunched Zn-Co-S Yolk-Shell Balls Intercalated within S, N Codoped CNT/Graphene Films for Free-Standing Supercapacitors.

The abundant mass and charge transfer involved in Faradaic redox reactions are largely determined by microstructures including the surface area and porosity, elemental composition and electrical conductivity of bimetallic sulfides. Here, a high magnetic field (HMF) was introduced to tune these intrinsic characters for superior supercapacitor electrodes. We developed a novel HMF-controlled anion-exchange methodology to prepare the one-dimensional (1D) bunched Zn-Co-S yolk-shell balls (ZCS6T BYSBs). The HMF-induced directional growth and alignment of Zn0.76Co0.24S drive the directional 1D assembly. The as-obtained ZCS6T BYSBs possess larger surface area/pore volume, higher crystallinity and electrical conductivity, richer electroactive elements, and favorable axial electron and ion transport because of HMF-enhanced favorable ion diffusion and exchange kinetics. Flexible S, N codoped carbon nanotubes/graphene films embedded with the ZCS6T BYSBs (CZS6T/CNTs/SNGS) were fabricated by vacuum filtration and one-step S, N codoping and reduction of graphene oxides to improve structural stability and charge transport. The CZS6T/CNTs/SNGS electrode displayed impressive enhanced specific capacitance and rate capability with 78.7% capacitance retention at 30 A g-1. Furthermore, the CZS6T/CNTs/SNGS//CNTs/SNGS asymmetric supercapacitor delivered remarkable cycling stability with a high energy density of 41.1 W h kg-1 at a large power density of 9022 W kg-1.

Electrochromism of Ferrocene- and Viologen-Based Redox-Active Ionic Liquids Composite.

Redox-active ionic liquids (RAILs) require no other additional reagents such as solvent and supporting electrolyte for electrochemical reactions under undiluted condition. Viologen-based RAILs are one of the electrochromic (EC) ionic liquids with sharp color contrast and high chemical stability. An operation of an EC cell requires two electroactive elements, an EC material and a charge compensating material. In this study, an equimolar composite of a viologen-based RAIL as the EC material and a ferrocene-based RAIL as the charge compensation material, was synthesized and applied to an EC cell. The EC cell with the composite RAIL of as high concentration as 0.92 M each redox species showed good coloration efficiency (91.4 cm2 C-1 at 540 nm on 1.0 V). The coloration process of the EC cell was diffusion-limited process. The current and absorbance of the EC cell reached constant values at large enough bias voltage because of the charge recombination between reduced viologens and oxidized ferrocenes. The recombination affected rapid color erasing process. Almost no deterioration of the composite RAIL was found by 1H NMR after 13 000 potential cycle durability experiment.

Pseudocapacitive Behavior of Polycationic Oxides for Electrochemical Capacitors

Electrochemical double-layer capacitors (EDLCs) represent the most important family of today’s commercially available Electrochemical Capacitors (ECs). Such systems can store charges electrostatically in the electrochemical double-layer that arises from the separation of charges at the electrode / organic electrolyte interfaces when polarizing the electrodes, and exhibit an excellent cycling stability combined with fair gravimetric and volumetric energy densities. Other types of ECs use “pseudocapacitive” materials, i.e. materials that use fast and reversible surface redox (faradaic) reactions to store energy. To combine the advantages of both organic EDLCs and aqueous symmetric systems, the design of aqueous asymmetric supercapacitors was proposed. These devices comprise either two pseudocapacitive materials, or a pseudocapacitive and a capacitive carbon-based material which exhibit complementary electroactive windows. As a result, operating cell voltages approaching 2 V can be obtained, leading to competitive energy densities without the disadvantages of using an organic electrolyte. Both specific energy and power densities have to be increased and improving the volumetric capacitance of supercapacitors, which is one of the limiting factors of today’s stationary applications, is essential. In order to meet these requirements, solid state chemistry is an powerful tool to design new materials. Our strategy was based on the study of polycationic oxide materials. They can combine transition metals such as Fe or Mn, that are known to be electrochemically active in aqueous media, with dense elements such as W, Bi,… The Fe/W/O has a peculiar interest since our recent studies have shown that FeWO4 exhibit excellent electrochemical properties [1,2]. Its pseudocapacitive behaviour has been demonstrated by operando XAS experiments with the use of a special cell designed in our lab [3]. The use of low-temperature synthesis methods in order to get nanosized particles with high specific surface areas is also required. Synthesis conditions and materials characterizations of the electrodes and also of full devices will be detailed in the presentation, highlighting the crucial role of the electroactive elements, the crystallographic structure, and the morphology of the synthesized materials on their electrochemical performance. [1] N. Goubard-Bretesché, O. Crosnier, C. Payen, F. Favier, T. Brousse, Electrochem. Commun. 57 (2015) 61. [2] N. Goubard-Bretesché, O. Crosnier, F. Favier, T. Brousse, Electrochim. Acta 206 (2016), 458. [3] N. Goubard-Bretesché, O. Crosnier, C. Douard, A. Iadecola, R. Retoux, C. Payen, F. Favier, M.-L. Doublet, T. Brousse, in preparation.

Microbial synthesis of metallic molybdenum nanoparticles

The production of nanoparticles through biosynthesis is a reliable, non-toxic, and sustainable alternative to conventional chemical and physical methods of production. While noble metals, such as palladium, gold, and silver, have been formed via bioreduction, biologically-induced reduction of electroactive elements to a metallic state has not been reported previously. Herein, we report the reduction of an electroactive element, molybdenum, via microbial reduction using Clostridium pasteurianum. C. pasteurianum was able to reduce 88% of the added Mo6+ ions. The bioreduced molybdenum was shown to be metallically bonded in a prototypical crystal structure with an average particle size of 15 nm. C. pasteurianum was previously shown to degrade azo dyes using in situ formed Pd nanoparticles, but this study shows that in situ formed Mo particles also act as catalysts for degradation of azo dyes. C. pasteurianum cultures with the bioformed Mo nanoparticles were able completely degrade 155 μM methyl orange within 6 min, while controls with no Mo took 36 min. This research demonstrates, for the first time, that the bioreduction of active elements and formation of catalytic particles is achievable.

Pseudocapacitive Polycationic Oxides for Supercapacitors Operating in Aqueous Electrolytes

Electrochemical double-layer capacitors (EDLCs) represent the most important family of today’s commercially available Electrochemical Capacitors (ECs). Such systems store charges electrostatically in the electrochemical double-layer that arises from the separation of charges at the electrode / organic electrolyte interfaces when polarizing the electrodes, and exhibit an excellent cycling stability combined with fair gravimetric and volumetric energy densities. Other types of ECs use “pseudocapacitive” materials, i.e. materials that use fast and reversible surface redox (faradic) reactions to store energy. To combine the advantages of both organic EDLCs and aqueous symmetric systems, the design of aqueous asymmetric supercapacitors was proposed. These devices comprise either two pseudocapacitive materials, or a pseudocapacitive and a capacitive carbon-based material which exhibit complementary electroactive windows. As a result, operating cell voltages approaching 2 V can be obtained, leading to competitive energy densities without the disadvantages of using an organic electrolyte [1]. Both specific energy and power densities have to be increased and improving the volumetric capacitance of supercapacitors, which is one of the limiting factors of today’s stationary applications, is essential [2]. In order to meet those requirements, solid state chemistry is an extremely powerful tool to design new materials. Our strategy was based on the study of materials that are electrochemically active in aqueous media, with transition metals and/or high density elements, with the possibility to use low-temperature synthesis methods in order to get nanosized particles with high specific surface areas, and the possibility to have several redox couples that could be involved in the charge storage mechanism. Among the studied materials, our interest has focused on different materials such as transition metal oxides (MnO2, Fe3O4,…) and polycationic oxides MWO4 (M=Fe, Mn, Co,…) [3]. Synthesis conditions and materials characterizations of the electrodes and also of full devices will be detailed in the presentation, highlighting the crucial role of the electroactive elements, the crystallographic structure, and the morphology of the synthesized materials on their electrochemical performance. J.W. Long et al., MRS Bulletin., 36, 513 (2011).N. Goubard-Bretesché et al., Electrochem. Commun., 57, 61 (2015).N. Goubard-Bretesché et al., Electrochim. Acta 206, 458 (2016).

Back Cover: Nanoscale Measurements of Lithium‐Ion‐Battery Materials using Scanning Probe Techniques (ChemElectroChem 1/2017)

The Back Cover picture represents a paper in which scanning probe microscopy methods applied to energy conversion and storage devices (specifically lithium-ion batteries) are reviewed, with an emphasis on the electroactive elements. More information can be found in the Review by S. B. Schougaard, J. Mauzeroll, and co-workers on page 6 in Issue 1, 2017 (DOI: 10.1002/celc.201600571).

Pressure-Induced Capillary Encapsulation Protocol for Ultrahigh Loading of Sulfur and Selenium Inside Carbon Nanotubes: Application as High Performance Cathode in Li–S/Se Rechargeable Batteries

There has been a paradigm shift in research foci toward elemental electrodes from the conventional intercalation compound-based electrochemical storage. Replacing intercalation transition metal (oxide) compounds with elemental cathodes (e.g., sulfur, oxygen) theoretically raises the storage capacities by more than one order in magnitude. The insulating nature and complexities of the redox reaction associated with electroactive elements necessitates their housing inside an electronic conductor, which has been mainly carbon. Efficiency of the electrochemical storage using such elemental electrodes, besides depending on factors related to the electrolyte, solid-state diffusion, mainly depends on characteristics of the carbon host. We report here a novel, simple, and efficient pressure-induced capillary encapsulation protocol for the confinement of chalcogens, sulfur (S) and selenium (Se), inside carbon nanotubes (CNTs). Confinement led to lowering of the surface tension of molten S/Se, resulting in superior ...

Nanoscale Measurements of Lithium‐Ion‐Battery Materials using Scanning Probe Techniques

AbstractState‐of‐the‐art scanning probe microscopy (SPM) methods as applied to energy conversion and storage devices, specifically lithium‐ion batteries, are reviewed with an emphasis on the electroactive elements. The unique ability of SPM‐based methods to provide localized information has proven highly valuable for the in‐depth understanding of the fundamental mechanisms, processes, and degradation of lithium‐ion batteries (LIBs). As such, SPM analysis is poised to play a strong role in the competition for new higher performing LIBs, especially given the unprecedented choice and availability of SPM techniques tailored to provide physical and chemical information at the nanoscale.

Characterization of LiMn<sub>0.3</sub>Co<sub>0.3</sub>Ni<sub>0.3</sub>Cr<sub>0.1</sub>O<sub>2</sub> and LiMn<sub>0.333</sub>Co<sub>0.333</sub>Ni<sub>0.333</sub>O<sub>2</sub> Synthesized <i>via</i> Sol-Gel Method: XRD, SEM and XPS Studies

One of the aspects most intensively researched in the continuing improvisation of lithium battery is the search for high capacity, high energy density and high performance cathode materials. Substitution of the electroactive elements with heteroatoms is one of the promising methods. In this study, a potential cathode material with a layered structure was successfully synthesized via a sol-gel method. As a comparison, the well-known LiMn1/3Co1/3Ni1/3O2(LiMn0.333Co0.333Ni0.333O2) was also synthesized using exactly the same method and conditions. Both materials were characterized using simultaneous thermogravimetric analysis (STA), X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS). The stoichiometries of the compounds were also confirmed through energy-dispersive X-ray spectroscopy (EDX) measurement. XRD results show that both compounds are single phase and impurity-free with well-ordered hexagonal layered structure characteristics of R-3m space group. Both compounds also show similar morphologies with well-formed crystals and clean surfaces as depicted by the SEM images. XPS measurement reveals that the introduction of chromium into LiMn1/3Co1/3Ni1/3O2results in a considerable change in the chemical environment as observed by significant changes in the binding energies (BE) of manganese, cobalt and nickel respectively.

Optimization of Secondary Battery Electrodes by Monitoring the Architecture of Electroactive and Conductive Elements: Application to Nickel Hydroxide

not Available.

Screen printing as a holistic manufacturing method for multifunctional microsystems and microreactors

Microsystems are commonly manufactured by photolithographic or injection moulding techniques in a variety of realizations and on almost any material. A perennial problem in the manufacturing of microsystems is the difficulty to obtain hybrid devices that incorporate distinct materials with different functionalities. In most of the cases, cumbersome prototyping and high investment needed for manufacturing are additional problems that add to the cost of the final product. Such drawbacks are true not only for lab-on-a-chip but also for certain microreactor applications. Most importantly, in many commercial applications where an intermediate product between full fluidics control and a ‘strip’ is needed, such restraints prohibit the feasibility of reduction to practice. Screen printing on the other hand is a low cost technique that has been used for years in mass producing two-dimensional low cost reproductions of a mask pattern for circuits and art incorporates prototyping in production and allows the use of an almost limitless variety of materials as ‘inks’. In this work it is demonstrated that taking advantage of the deposited ink's three-dimensional nature, screen printing can be used as a versatile and low cost technique for the fabrication of microchannels. Microchannels with dimensions in the order of 100 µm were fabricated that could readily incorporate functionalities through the choice of the materials used to create the microstructure. Variables have been investigated through a factorial experimental design as important process parameters that affect the resolution and print thickness of the resulting microchannels that incorporate electroactive elements. Such studies can lead to the optimization of the process for custom applications.

The synthesis of novel core-substituted naphthalene diimides via Suzuki cross-coupling and their properties

This paper reports the efficient core-substitution of halogenated naphthalene diimides utilizing the Suzuki cross-coupling reaction to install various aryl substituents at the 2,6 positions. The UV-visible spectra of these compounds show a clear absorbance red shift and an enhanced fluorescence output, making them potential candidates for solar-cell dyes and electroactive elements for supramolecular materials.

Ordered array of diamond ultramicroband electrodes for electrochemical analysis

Boron-doped diamond ultramicroband arrays with different array densities and interelement spacings were fabricated using silicon technology and selective diamond deposition (SAD) technique to yield microvoltammetric electrodes. The electroactive ultramicroband elements were designed with one microscopic critical dimension to impart microelectrode behavior while the other dimension was made larger to yield an increase in signal current. Cyclic voltammetry studies in this work showed that with sufficient interelement separation, the ultramicroband arrays display sigmoidal pseudo-steady-state cyclic voltammograms characteristic of microband electrodes. The ultramicroband arrays yielded higher faradaic current per unit area, than either square ultramicroelectrode array or conventional planar diamond electrode from earlier reported work. This is due to enhanced mass transport to the ultramicroband elements at slow scan rates. Larger current density and higher signal-to-noise (S/N) ratio leads to better limits of detection, making it possible to fabricate a more sensitive electrode for applications such as electroanalysis, electrocatalysis, trace element analysis, mechanistic and fast transfer kinetics studies, electrochemistry in highly resistive media, as well as sensors in flow and biological system.

Modulation of electroosmotic flows in electron-conducting microchannels by coupled quasi-reversible faradaic and adsorption-mediated depolarization

A theoretical model is proposed for the description of steady electroosmotic flows within a cylindrical electron-conducting microchannel that is depolarized by faradaic and adsorption-mediated processes. The bipolar electron-transfer (e.t.) reactions are examined in the general situation where the electrolyte contains a quasi-reversible redox couple. The rate of the e.t. reactions is governed by transversal convective diffusion of the electroactive species to/from the surface and a position-dependent degree of reversibility. The nonuniform distribution of the electric field in solution, that is intimately coupled to that of the local faradaic current density, alters the double layer composition along the conducting surface via the occurrence of simultaneous electronic and ionic double layer charging processes. This in turn generates a nonlinear distribution of the zeta potential, which affects the electroosmotic flow. The highly coupled spatial profiles for the concentrations of the electroactive species, the faradaic current density, the electrokinetic potential, the electric field and the electroosmotic velocity in/along the metallic channel are solved by consistent numerical analysis of (i) the convective-diffusion equation, (ii) the generalized Butler–Volmer expression that includes mass transport and electron-transfer kinetic contributions, (iii) the continuity and Navier–Stokes equations, and (iv) the Poisson equation for finite currents. The results reported as a function of the surface properties of the channel and the kinetic characteristics of the e.t. reaction illustrate the deviations of the electroosmotic flow profiles as compared to the typical pluglike distribution predicted by Smoluchowski's equation and encountered for homogeneous and dielectric channels. Manipulation of the flow patterns by bipolar electrochemical means is a promising way to control and optimize the local detection and separation of electroactive molecules or molecules dyed with electroactive elements.

Synthesis of spherical Li[Ni (1/3− z) Co (1/3− z) Mn (1/3− z) Mg z]O 2 as positive electrode material for lithium-ion battery

Li[Ni (1/3− z) Co (1/3− z) Mn (1/3− z) Mg z ]O 2 ( z = 0, 0.04) positive electrode materials were synthesized via a co-precipitation method. These materials have α-NaFeO 2 ( R 3 ¯ m ) structure, as confirmed by X-ray diffraction (XRD) studies. Cation mixing in Li layer seemed to be decreased by Mg substitution as examined by Rietveld refinements of XRD data. Spherical morphologies were observed for the as-synthesized final products by scanning electron microscopy. Their electrochemical properties during charge and discharge were discussed. When magnesium ions are substituted, the initial reversible capacity reduced. However, the substitution for Mn sites in Li[Ni 1/3Co 1/3Mn 1/3]O 2 did not decrease the capacity because Mn sites substitution did not result in loss of electroactive elements in the compound. Differential scanning calorimetric studies showed the exothermic peaks of the charged electrode Li[Ni (1/3− z) Co (1/3− z) Mn (1/3− z) Mg z ]O 2 ( z = 0.04) were significantly smaller than that of Li[Ni 1/3Co 1/3Mn 1/3]O 2, which means that thermal stability was greatly improved by Mg substitution even at highly delithiated state.