Electroconducting Properties Research Articles

Micrometer-thick and porous nanocomposite coating for electrochemical sensors with exceptional antifouling and electroconducting properties

Development of coating technologies for electrochemical sensors that consistently exhibit antifouling activities in diverse and complex biological environments over extended time is vital for effective medical devices and diagnostics. Here, we describe a micrometer-thick, porous nanocomposite coating with both antifouling and electroconducting properties that enhances the sensitivity of electrochemical sensors. Nozzle printing of oil-in-water emulsion is used to create a 1 micrometer thick coating composed of cross-linked albumin with interconnected pores and gold nanowires. The layer resists biofouling and maintains rapid electron transfer kinetics for over one month when exposed directly to complex biological fluids, including serum and nasopharyngeal secretions. Compared to a thinner (nanometer thick) antifouling coating made with drop casting or a spin coating of the same thickness, the thick porous nanocomposite sensor exhibits sensitivities that are enhanced by 3.75- to 17-fold when three different target biomolecules are tested. As a result, emulsion-coated, multiplexed electrochemical sensors can carry out simultaneous detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid, antigen, and host antibody in clinical specimens with high sensitivity and specificity. This thick porous emulsion coating technology holds promise in addressing hurdles currently restricting the application of electrochemical sensors for point-of-care diagnostics, implantable devices, and other healthcare monitoring systems.

Graphene-integrated thermoplastic vulcanizates: Effects of in-situ vulcanization on structural, thermal, mechanical and electrical properties

Gaining considerable attention as valuable plastic static-dissipative materials, conductive polymer blends are used as supercapacitors, light emitting diodes, artificial muscles and biosensors. Thermoplastic vulcanizates (PECVs) were prepared by blending ethylene propylene diene monomer (EPDM) and polypropylene (PP) thermoplastic via in-situ compatibilization technique by using a suitable compatibilizer and curing system. Electrically conducting graphene filler was incorporated into the blend to impart electroconducting properties. Maintaining a constant PP/EPDM ratio of 80:20 for all specimens, PECVs containing different loadings of graphene filler were prepared through in-situ compatibilization method. Fourier-transform infrared spectroscopy analysis was performed to investigate chemical changes ensued as a result of compatibilization reactions. Addition of graphene into the blended PECVs slightly improved their processability and thermally stable as confirmed by tests performed on Differential Scanning Calorimetery and Thermogravimetric Analyser. Mechanical aspects of the blends, inspected by operating Universal Testing Machine and Rockwell Hardness Tester, were substantially improved on account of blend compatibilization and addition of graphene. Their electrical properties measured through four-probe technique revealed significant improvement in electrical conductivity of compatibilized PECVs due to incorporation of graphene filler.

Impedance Spectroscopy Study of Ni-Zn Electrochemical Alkaline Systems with Anode of Nano-sized ZnO Doped with Conducting Ceramics B(Pb)SCCO 2212

For the purpose of electrochemical applications (such as Ni-Zn batteries), we have experimentally studied the electrical impedimetric response of electrochemical systems (ECSs), in which the anodes were fabricated from nano-sized ZnO material doped with high-temperature superconducting ceramics Bi1.7Pb0.3Sr2CaCu2Oy (B(Pb)SCCO 2212) at concentration of either 5, 7, or 10 wt%. The electro-conducting properties of such ECSs with alkaline electrolyte were characterized at ambient temperature by measurements with electrochemical impedance spectroscopy in the frequency range 0.1 Hz –100 kHz. The effect from the ceramics additives on both complex electrical impedance and electrical conductivity of the examined ECSs was estimated.

Polymer (PEO)-liquid crystal (LC E8) composites: The effect from the LC inclusion

The effect from the inclusion of nematic liquid crystal (LC) E8 into the polymer poly(ethylene oxide) (PEO) was inspected by studying of structural and electrical properties of PEO-E8 composites at weight percentage of E8 ranging from 10 % to 50 %. Flexible PEO-E8 films with a thickness of 0.1 mm were structurally characterized by X-ray diffraction and X-ray photo-electron spectroscopy. The results obtained by our analyses indicate that a polymer-LC intermolecular complex is formed by inclusion of E8 LC molecules in the PEO host at a certain their concentration level. The structural properties of PEO-E8 composites were correlated with their electro-conducting properties as depending on the E8 LC concentration. By the amount of the LC fraction one can achieve a controlled modification of the structural and electro-conducting properties of the PEO-E8 material. As compared to PEO, the inclusion of E8 LC in the PEO polymer matrix can lead to a considerably enhanced electrical conductivity of PEO-E8 composites.

First hybrid radical-cation salts with halogen substituted iron bis(dicarbollide) anions – synthesis, structure, properties

New radical-cation salts based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) were synthesized: (ЕТ)2[8,8′-Br2-3,3′-Fe(1,2-C2B9H10)2] (1) and (ЕТ)[8,8′-I2-3,3′-Fe(1,2-C2B9H10)2] (2). Their crystal structures were studied by X-ray analysis, electroconducting and magnetic properties were measured in a wide temperature range. Salts (1) and (2) appeared to be the first radical-cation salts with [8,8′-I2-3,3′-Fe(1,2-C2B9H10)2]- and [8,8′-Br2-3,3′-Fe(1,2-C2B9H10)2]- anions, respectively. In the literature [8,8′-I2-3,3′-Fe(1,2-C2B9H10)2]- and [8,8′-Br2-3,3′-Fe(1,2-C2B9H10)2]- anions are presented for the first time. Salts (1) and (2) were found to be paramagnetic. Their room temperature conductivities were 2 and 1·10−6 Ohm−1cm−1, respectively.

Defect-Rich Metallic Titania (TiO1.23)—An Efficient Hydrogen Evolution Catalyst for Electrochemical Water Splitting

As a promising alternative hydrogen evolution electro-catalyst to platinum, a classical and earth-abundant “titania” is investigated. Herein, the paradigm of electro-inactive titania has been surmounted by exploiting defect engineering as a tool, which tailors the local atomic structure of nonconductive titania via electrochemical cathodization strategy. The enhanced electro-conducting properties along with favorable surface energetics for Hads of reduced titania (TiO1.23) ensures ultrafast HER kinetics. Because of the proximity with the benchmark Pt, the reduced titania exhibits excellent HER catalytic activity in an acidic electrolyte by exhibiting low onset potential of 75 mV versus RHE and a Tafel slope of 88 mV·dec–1, and it demonstrates 10 mA·cm–2 at a potential of 198 mV versus RHE. Furthermore, the cathodization process also endows “magic effects” by effectively exposing the (111) close-packed plane with extravagant texture coefficient and makes the structure more thermodynamically stable. The long-term durability studies (5000 cycles of cyclic sweeping, 40 h of static polarization) confirm the extremely stable HER catalytic activity of TiO1.23. These findings suggest that by tuning oxygen vacancies in the lattice and its concomitant cumulative strained configuration, reduced titania can be an effective HER electro-catalyst for electrochemical water splitting.

BEDT-TTF-based organic conductors with [MBr4]2− anions, M = Cd, Co, Zn, Mn, Hg. Effect of solvent

New layered conductors of (BEDT-TTF)4(Anion)(solvent) and (BEDT-TTF)3(Anion) stoichiometery (BEDT-TTF=bis(ethylenedithio) tetrathiafulvalene) with double-charged anions of tetrahedral geometry, [MBr4]2−, M=Cd, Co, Zn, Mn, Hg, have been synthesized using 2-halogenotoluenes, fluorobenzene and chlorocycloalkanes as solvents. The effect of solvent on composition and electroconducting properties of the compounds has been traced. Crystal structure of θ-(BEDT-TTF)4CdBr4(C7H7Br) and (BEDT-TTF)3CoBr4 has been determined. In the first compound, conducting layers show similar structure but differ in the direction of the BEDT-TTF stacks. In the second one, two crystallographically independent BEDT-TTF layers are considerably different from each other. In layer I, radical cations are linked in ribbons by side-to-side type. In layer II, BEDT-TTF forms dimers stacked with a fan-shaped offset. The ESR linewidths for (BEDT-TTF)4(MBr4)(solvent), solvent=C7H7Cl, C6H5F are close to the linewidth for θ-(BEDT-TTF)4CdBr4(C7H7Br) that allows one to assume similar structural packing motifs.

Magnetite (Fe3O4)-filled carbon nanofibers as electro-conducting/superparamagnetic nanohybrids and their multifunctional polymer composites

A mild-temperature, nonchemical technique is used to produce a nanohybrid multifunctional (electro-conducting and magnetic) powder material by intercalating iron oxide nanoparticles in large aspect ratio, open-ended, hollow-core carbon nanofibers (CNFs). Single-crystal, superparamagnetic Fe3O4 nanoparticles (10 nm average diameter) filled the CNF internal cavity (diameter <100 nm) after successive steps starting with dispersion of CNFs and magnetite nanoparticles in aqueous or organic solvents, sequencing or combining sonication-assisted capillary imbibition and concentration-driven diffusion, and finally drying at mild temperatures. The influence of several process parameters—such as sonication type and duration, concentration of solids dispersed in solvent, CNF-to-nanoparticle mass ratio, and drying temperature—on intercalation efficiency (evaluated in terms of particle packing in the CNF cavity) was studied using electron microscopy. The magnetic CNF powder was used as a low-concentration filler in poly(methyl methacrylate) to demonstrate thin free-standing polymer films with simultaneous magnetic and electro-conducting properties. Such films could be implemented in sensors, optoelectromagnetic devices, or electromagnetic interference shields.

Syntheses, structures, and electroconductivity of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and bis(methylenedithio)tetrathiafulvalene (BMDT-TTF) salts with cobalt 8,8′-dichloro-3,3′-bis(1,2-dicarbollide)

Radical cation salts of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and bis(methylenedithio)tetrathiafulvalene (BMDT-TTF) with the 8,8′-dichloro derivative of cobalt bis(1,2-dicarbollide) (BEDT-TTF)2[8,8′-Cl2-3,3′-Co(1,2-C2B9H10)2] (1) and (BMDT-TTF)4[8,8′-Cl2-3,3′-Co(1,2-C2B9H10)2] (2) were synthesized and their crystal structures and electrocon-ducting properties were determined. The synthesized radical cation salts are semiconductors with the conductivity σ293 = 1.5 and 2.0 Ohm−1 cm−1, respectively. A decrease in the size of the substituent in a series of (BEDT-TTF)2[8,8′-X2-3,3′-Co(1,2-C2B9H10)2] and (BMDT-TTF)4[8,8′-X2-3,3′-Co(1,2-C2B9H10)2] (X = I, Br, Cl) results in the compression of the anion sublattice of the crystal and compaction of the radical cation packing of the conducting layer, which, in turn, increases the conductivity of the crystals.

Black anatase titania enabling ultra high cycling rates for rechargeable lithium batteries

In this work we report the synthesis and the characterization of black anatase TiO2. We show that this material displays a nanostructured architecture, with an electro-conducting trivalent Ti. The presence of trivalent Ti in this structure narrows the inherent high band gap energy to a semiconductor level, reaching a value as low as 1.8 eV, resulting in the very high electrical conductivity of 8 × 10−2 S cm−1. These extraordinary electro-conducting physical properties ensure an ultra fast Li+ insertion into and extraction from the host structure of anatase TiO2 making it a unique, high rate electrode, delivering at a 100 C-rate (20 A g−1) a discharge capacity of 127 mA h (g-TiO2)−1 with approximately 86% retention during 100 charge–discharge cycles at 25 °C and approximately 84% retention at −20 °C.

Hybrid, Nano-Structurized Materials of Special Purpose on the Basis of Silicon Dioxide

Highly disperse powders of complex morphology, micro- and nanostructure were obtained by treatment of quartz in a planetary-centrifugal mill of a dynamic action in the presence of different organic substances. The surface layer with the thickness of 10-70nm modifying the particle of quartz after mechanochemical treatment is a polymer with encapsulated nanosized particles of iron. Powder material from such highly disperse composition particles of modified quartz is characterized by ferromagnetic and electroconducting properties. A galvanic effect in a nanosize scale is possible to take place on the surface of particles consisting of a polymer nanostucturized film with sites supersaturated with metallic and carbon clusters. The practical realization of such structures is promising when producing highly active sorbents as well as for collecting of oil products spills on the surface of water.

Experimental studies of cation-anion-deficient Nd1 − x Sr x MnO3 − y (x = 0.45) films with various thicknesses

The magnetic and electroconducting properties of Nd1 − xSrxMnO3 − y films with various thicknesses are studied. It is shown that all the films exhibit considerably high conductivity at a temperature of 300 K and that they are not a paramagnetic insulator as should be the case according to the phase diagram of this compound. The temperature dependence of the resistance exhibits a semiconductor behavior with decreasing temperature and has a maximum Rmax at the temperature Tmax being significantly different from the Curie point. A negative magnetic moment is observed in all the studied films at high temperatures. The possible causes of this phenomenon are discussed.

Lithium-Ion conducting oxides: Synthesis, structure, and electroconducting properties

The properties of perovskite type ABO3 lithium-ion conducting oxides based on lanthanum lithium titanate (La,Li)TiO3, lanthanum lithium niobate and tantalate, and Li5La3M2O12 (M = Nb, Ta) garnets were considered. Approaches to modification of the properties of these oxides, as well as the charge-compensation mechanisms associated with nonisovalent doping were discussed. Special consideration was given to phase formation and crystal structure in relation to the composition and preparation conditions of the oxides.

Improving Electrical Performances of Wool Textiles: Synthesis of Conducting Polypyrrole on the Fiber Surface

Antistatic treatments lower the electrical resistivity of textiles and facilitate charge dissipation avoiding high potential electrical discharges. Moreover, low surface resistivity gives textiles electro-conducting, soil release, thermal and electromagnetic shielding properties. A new way of producing electrically conducting textiles consists of treatments with organic conducting polymers. Unfortunately, conducting polymers have a low level of processability because of their poor mechanical and physical properties. These problems have been overcome by simple in situ depositions of conducting polymers on different substrates in order to produce composite materials with good mechanical properties. Polypyrrole (PPy) is one of the most promising candidates because it exhibits high conductivity and good environmental stability. In situ PPy synthesis on wool and on other animal fibers is presented in this work. A preliminary oxidative treatment (e.g. shrink-proofing, bleaching or depigmentation) improves the electrical properties of the resulting conductive composite textiles significantly.

The Ion Conducting Properties of Perovskite-Type Solid Solutions (La&lt;sub&gt;0.5&lt;/sub&gt;Li&lt;sub&gt;0.5&lt;/sub&gt;) [Ti&lt;sub&gt;1-x&lt;/sub&gt;(M&lt;sub&gt;0.5&lt;/sub&gt;Nb&lt;sub&gt;0.5&lt;/sub&gt;)&lt;sub&gt;x&lt;/sub&gt;]O&lt;sub&gt;3&lt;/sub&gt; (M = Al, Ga)

The influence of B-site substitution on electroconducting properties of perovskite-type solid solutions (La0.5Li0.5)[Ti1-x(M0.5Nb0.5)x]O3 with M = Al, Ga, have been studied. A decrease in the conductivity due to the unit cell contraction with increasing x in case of M = Al has been revealed. In case of Ga and Nb substitutions for Ti the unit cell volume has been found to increase with increasing x while the conductivity decreases due to the impurity phases presence. The high and low temperature anomalies on the temperature dependences of dielectric characteristic related to both the relaxation effect and phase transitions have been revealed.

Oxygen Permeability of Mixed Conducting Perovskite Lanthanum Gallate-Based Ceramics

The structure, microstructure, electric transport and oxygen permeation properties of (La,Sr)(Ga,Mg,Fe)O3-δ ceramics with perovskite or brownmillerite structures have been studied. Oxygen permeability values of ~0.1 cm3/cm2·min has been revealed at 1000 K for the ceramics studied. The correlation of electroconducting properties of the LaGaO3-based ceramics with perovskite and brownmillerite structures to their oxygen permeability characteristics has been proved.

Synthesis, crystal structure and electroconducting properties of a new molecular semiconductor (ET) 5[Ho(NCS) 7]]·EtOH

The new molecular semiconductor (ET)5[Ho(NCS)7]·EtOH was synthesised by the electrochemical oxidation of bis(ethylenedithio) tetrathiafulvalene (ET); its crystal structure and electroconducting properties were studied.

ETHYNETHIOL-BASED POLYENEPOLYSULFIDES FROM ACETYLENE AND ELEMENTAL SULFUR: SYNTHESIS AND PROPERTIES

Ethynethiol-based polysulfide polymers [Cssize 2}H2S x ] (x = 1-6) have been synthesized by the reaction of sodium acetylides and elemental sulfur in liquid ammonia with the following hydrolysis of sodium ethynethiolates and spontaneous polymerization of ethynethiols thus formed. The polymers are brown powders (up to 87% sulfur content), possessing electroconducting (10−13–10−14 S · cm−1), paramagnetic (1018 spin · g−1) and redox properties. Application of the polymers as active cathode materials provides for a stable cycling of model lithium batteries. * Now Sion Power Corporation.

Crystal structure and molecular packing in a new organic semiconductor penta[bis(ethylenedithio)tetrathiafulvalene]-hexathiocyanatomononitratoyttrium(III)-ethanol

A new radical cation (ET) 5[Y(NCS) 6NO 3]·C 2H 5OH salt was prepared by electrochemical oxidation of ET in a chlorobenzene–ethanol solution. Its crystal structure and conducting properties were examined. The salt has a layered crystal structure with a new type of molecular packing in the radical cation layer, which was called the ω-type. The observed electroconducting properties suggest that this salt is a semiconductor.

Electron paramagnetic resonance studies on oxidative polymerization mechanism of furan derivatives

The oxidative polymerization of furan, 3-methylfuran and 2,2′,5′,2″-terfuran, induced by iodine in organic solvents having different donicity, was investigated by time-resolved electron paramagnetic resonance (EPR) spectroscopy. The reaction was monitored starting from the onset of the process and radical species arising from the monomers in early stages of the polymerization reaction were detected. The comparison between experimental and theoretical hyperfine coupling constants, obtained by simulated EPR spectra and theoretical ab initio calculations, respectively, allowed one to structurally characterize the above radical species, thus enabling mechanistic conclusions about oxidative coupling. Moreover, the analysis of the time evolution of EPR spectrum during the oxidative polymerization process was used for evaluating the relative amount of localized and mobile radical species along the polymer backbone, thus getting preliminary information about conjugation extent and electroconducting properties of the final material. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1901–1910, 1998