Electroactive Properties Research Articles

Solution processable poly(vinylidene fluoride)-based ferroelectric polymers for flexible electronics

Since the discovery of piezoelectricity in poly(vinylidene fluoride) (PVDF) 50 years ago, ferroelectric polymers have established their own areas for research and applications due to their unique properties in comparison to single crystals and inorganics. PVDF is a semicrystalline polymer that can crystallize into five different polymorphs. Among them, the polar β-phase is the most interesting one for electroactive properties because it has the highest dipolar moment and the highest piezoelectric response. In the early days, the β-PVDF was typically produced by melt processing, limiting its form to free-standing films. The rapid development of flexible electronics, however, highly requires β-PVDF fabricated from solutions under mild conditions. The objective of this perspective is to summarize the effective methods to produce β-PVDF from solution, to present the approaches for enhancing the electroactive properties through morphological controls, and to discuss the applications of PVDF-based ferroelectric polymers in flexible electronics. In addition, current challenges that may impede the further development of this field are pointed out.

Unexpected formation of 1,2- and 1,4-bismethoxyl Sc3N@I h-C80 derivatives via regioselective anion addition: an unambiguous structural identification and mechanism study.

An attempt to achieve heterocyclic cycloadducts of Sc3N@Ih-C80via reaction with Ph2C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O, PhC Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CPh or PhCN in the presence of tetrabutylammonium hydroxide (TBAOH) stored in CH3OH led to the formation of the unexpected bismethoxyl adducts of Sc3N@Ih-C80 (1 and 2). Further studies reveal that TBAOH in CH3OH can boost the CH3O− addition efficiently, regardless of the presence of other reagents. Single-crystal X-ray diffraction results firmly assign the molecular structures of 1 and 2 as respective 1,4- and 1,2-bismethoxyl adducts, and reveal unusual relationships between the internal Sc3N cluster and the addition modes, in addition to the unusual packing mode in view of the orientation of the methoxyl groups. Electrochemical results demonstrate smaller electrochemical gaps for 1 and 2, relative to that of Sc3N@Ih-C80, confirming their better electroactive properties. Finally, a plausible reaction mechanism involving anion addition and a radical reaction was proposed, presenting new insights into the highly selective reactions between the methoxyl anion and metallofullerenes. 1 and 2 represent the first examples of methoxyl derivatives of metallofullerenes. This work not only presents a novel and facile strategy for the controllable synthesis of alkoxylated metallofullerene derivatives, but also provides new non-cycloadducts for the potential applications of EMFs.

Lignin biopolymer: the material of choice for advanced lithium-based batteries.

Lignin, an aromatic polymer, offers interesting electroactive redox properties and abundant active functional groups. Due to its quinone functionality, it fulfils the requirement of erratic electrical energy storage by only providing adequate charge density. Research on the use of lignin as a renewable material in energy storage applications has been published in the form of reviews and scientific articles. Lignin has been used as a binder, polymer electrolyte and an electrode material, i.e. organic composite electrodes/hybrid lignin-polymer combination in different battery systems depending on the principal charge of quinone and hydroquinone. Furthermore, lignin-derived carbons have gained much popularity. The aim of this review is to depict the meticulous follow-ups of the vital challenges and progress linked to lignin usage in different lithium-based conventional and next-generation batteries as a valuable, ecological and low-cost material. The key factor of this new finding is to open a new path towards sustainable and renewable future lithium-based batteries for practical/industrial applications.

Towards the Translation of Electroconductive Organic Materials for Regeneration of Neural Tissues

Electroconductive materials, such as conductive polymers and carbon-nanomaterials, have been studied since the 1970s for use in a broad range of applications. These materials showcase electrical properties that are similar to those of commonly used metals, while providing other benefits such as processing flexibility, ability to modify, and ease of synthesis. Conductive polymers (e.g., polypyrrole, polythiophene, polyaniline) as well as carbon-based nanomaterials (e.g., graphene, fullerenes) are organic in nature. This makes them ideal candidates to be augmented to create biocompatible materials while maintaining electroactive properties at functional levels that match endogenous electrical tissue activity. In this review, we focus on the uses of these electroconductive materials in the context of the nervous system, specifically recent studies in the brain, eye, ear, spinal cord, and peripheral nerve. We also highlight in vivo studies and clinical trials, as well as provide a brief look at emerging electroconductive materials.

Influence of annealing temperature on the existence of polar domain in uniaxially stretched polyvinylidene-co-hexafluoropropylene for energy harvesting applications

The structural and electroactive properties of the as-prepared random copolymer polyvinylidene-co-hexafluoropropylene thin film are explored as a function of thermal treatment at various temperature regions. The thermal treatment of the polymer thin film not only changes the structural conformations that is very natural but establishes a polar domain in the non-polar α-phase. Here, we discover an anomalous temperature-dependent crossover behavior from the non-polar α-phase to an appreciable enhancement in ferroelectric and piezoelectric responses. The maximum unipolar strain (Smax=−5.01%), an ultrahigh value of normalized piezoelectric coefficient (d33∗=−556pm/V), high electromechanical coupling factor (Kp=0.78) factor including the high dielectric constant (ϵ′=23at100Hz) at a relatively low electric field of 900 kV/cm may, therefore, be an effect of the established polar domain for the sample annealed at 105 °C. The direct piezoelectric charge coefficient (d33), a key factor for the performance of a prepared polymer thin film system as an energy harvester, lies in the range of −10±2pC/N. Also, the annealed sample exhibited a persistent polarization after several cumulative cycles of applied stress.

Linker Deficiency, Aromatic Ring Fusion, and Electrocatalysis in a Porous Ni8-Pyrazolate Network.

The cruciform linker molecule here features two designer functions: the pyrazole donors for framework construction, and the vicinal alkynyl units for benzannulation to form nanographene units into the Ni8-pyrazolate scaffold. Unlike the full 12 connections of the Ni8(OH)4(H2O)2 clusters in other Ni8-pyrazolate networks, significant linker deficiency was observed here, leaving about half of the Ni(II) sites capped by acetate ligands, which can be potentially removed to open the metal sites for reactivity. The crystalline Ni8-pyrazolate scaffold also retains the crystalline order even after thermal treatments (up to 300 °C) that served to partially graphitize the neighboring alkyne units. The resultant nanographene components enhance the electroactive properties of the porous hosts, achieving hydrogen evolution reaction (HER) activity that rivals that of topical nickel/palladium-enabled materials.

Acidic triggering of reversible electrochemical activity in a pyrenetetraone-based 2D polymer

In this communication, a novel two-dimensional polymer network (DAPT-TFP) has been synthesized based on pyrenetetraone moieties connected through robust enamine functional groups. Results show that DAPT-TFP exhibit high thermal and chemical stability, even after subjecting the material to a basic or acidic media for certain time (1 M H2SO4 or 1 M NaOH, respectively). An application to conductive additive-free electrode is detailed, as a proof of the ideal interaction between the ions of the neutral aqueous electrolyte and the molecular polymer nanostructure activated by simple acidic treatment. Thus, the study indicates that the redox properties of new organic electrode materials exhibiting limited electroactive properties can be boosted by a straightforward acidic treatment.

Micro‐Structuration of Piezoelectric Composites Using Dielectrophoresis: Toward Application in Condition Monitoring of Bearings

Piezoelectric soft material based on inorganic/organic composites suitable for aerospace and aeronautical monitoring sensors is fabricated. The designed material is a piezoelectric composite made of lead zirconate titanate (PZT) filler embedded in a poly(dimethyl siloxane) (PDMS) matrix. To improve the piezoelectric properties of the film, the connectivity of the ceramic filler is increased via electric field‐assisted structuration, which leads to columnar arrangement of the filler across the thickness. This structure (1–3) shows higher piezoelectricity than one with randomly dispersed filler (0–3). Piezoelectric and dielectric activities of PZT/PDMS in 0–3 and 1–3 configurations at different volume fractions are compared. The results confirm that the 1–3 connectivity leads to superior piezoelectric behavior. Thermal stability of electroactive properties and high temperature X‐ray diffraction (XRD) analyses are performed: the composites maintain a good piezoelectric response, even at 200 °C. Following a process optimization, the piezoelectric behavior of this new class of composites approaches the fluorinated ferroelectric polymers one, with the advantages of piezoelectric properties stability preserved at a higher temperature and a lower poling electric field. In conclusion, there is potential for the integration of the designed sensor in aircraft ball bearings for condition monitoring.

Dielectric Elastomers UV-Cured from Poly(dimethylsiloxane) Solution in Vinyl Acetate.

Poly(dimethylsiloxane) (PDMS) has been extensively used as an electroactive polymer material because it exhibits not only excellent moldability but also mechanical properties sufficient enough for electroactive performance despite low dielectric permittivity. Its low dielectric property is due to its molecular non-polarity. Here, we introduce a polar group into a PDMS elastomer by using vinyl acetate (VAc) as a crosslinker to improve the dielectric permittivity. We synthesized a high-molecular weight PDMS copolymer containing vinyl groups, namely poly(dimethylsiloxane-co-methylvinylsiloxane) (VPDMS), and prepared several of the VPDMS solutions in VAc. We obtained transparent PDMS films by UV curing of the solution layers. Electromechanical actuation-related physical properties of one of the UV-cured films were almost equivalent to or superior to those of platinum-catalyzed hydrosilylation-cured PDMS films. In addition, saponification of the UV-cured film significantly improved the electrical and mechanical properties (ɛ′ ~ 44.1 pF/m at 10 kHz, E ~ 350 kPa, ɛ ~ 320%). The chemical introduction of VAc into PDMS main chains followed by saponification would offer an efficacious method of enhancing the electroactive properties of PDMS elastomers.

The Rapid and Practical Route to Cu@PCR Sensor: Modification of Copper Nanoparticles Upon Conducting Polymer for a Sensitive Non‐Enzymatic Glucose Sensor

AbstractIn this work, rapid, sensitive, practical, and economical strategy for non‐enzymatic glucose sensor has been reported based on a modification of copper nanoparticles upon conducting polymer with high surface area (Cu@PCR). Firstly, PCR conducting polymer electrode (PCR) has been successfully fabricated by electrochemical polymerization of a specially synthesized and characterized star‐shaped carbazole derivative. Then copper nanoparticles have been successfully electrodeposited on the PCR as a practical method with cyclic voltammetry. The morphologies of the synthesized materials have been characterized by scanning electron microscopy (SEM) and energy‐dispersive spectroscopy (EDS) measurements. The Cu@PCR sensor platform has been displayed a synergistic effect of high catalytical properties of copper nanoparticles and high electroactive properties of PCR towards the glucose oxidation in alkaline medium. The Cu@PCR sensor platform has shown high sensitivity of 847 μAmM−1cm−2, good stability (10 weeks), a low detection limit of 0.043 μM, and a fast response of 3 s for the non‐enzymatic electrochemical detection of glucose. This organic−inorganic hybrid composite sensor is a promising candidate for the fabrication of a highly sensitive and rapid glucose‐sensing with the simple preparation procedure and use of a low‐cost precursor.

The State of the Art of Energy Harvesting and Storage in Silk Fibroin-Based Wearable and Implantable Devices

The energy autonomy of self-powered wearable electronics depends on the adequate development of new technologies for energy harvesting and energy storage devices based on textile fibers to facilitate the integration with truly flexible and wearable devices. Silk fiber-based systems are attractive for the design of biomedical devices, lithium-ion batteries and flexible supercapacitors, due to their nitrogen-rich structure (for preparation of hierarchical carbon-based structures), and available surface for chemical modification reinforcing electroactive properties for use in batteries and supercapacitors. Herein, this paper reviews recent advances on silk fiber-based systems for harvesting and the storage of energy and the corresponding strategies to reinforce the physical and chemical properties of the resulting composites applied as electrodes and battery separators.

Dimensional effect of SrTiO3 particles on functional performance optimization of polydimethylsiloxane-based composites for dielectric elastomer actuators

Dielectric elastomer materials have a great application potential in electromechanical sensing and energy-harvesting fields. However, the realization of high electro-actuation properties under a relatively low electric field is still a critical challenge. Herein two series of polydimethylsiloxane (PDMS)-based dielectric elastomer composites incorporated SrTiO3 (STO) with distinguishing diameters were prepared through solution-blending and compression moulding methods. The resultant STO/PDMS composites showed significantly enhanced dielectric permittivity and Young’s modulus. Moreover, the PDMS-based composite filled with 4 vol.% nano-scaled STO exhibited an improved electro-actuation strain of 3.3% at a very low electric field of 24 V μm−1, which was 30% larger than that of the neat PDMS. The experimental results revealed that the electro-active performance of dielectric elastomer composite under low electric fields can be influenced by the size of incorporating functional units, and be also successfully optimized by regulating the fillers-matrix interfacial interaction. This study provides a promising strategy to design and fabricate novel dielectric elastomers with advanced low-field driving electro-active properties.

The influence of the addition of tungsten trioxide nanoparticle size on structure, thermal, and electroactivity properties of hybrid material–reinforced PANI

Nanomaterials are synthetized by aniline with different contents of WO3 nanoparticles using a chemical oxidative polymerization method. FTIR, ultraviolet–visible, XPS, SEM, and XRD confirmed the successful synthesis of the three PANI@WO3 samples. Thermogravimetric analysis shows an improved thermal stability by the presence of WO3 in nanocomposites compared with PANI. Interestingly, the analysis of the band gap shows lowest value of optical band gap of 1.88 eV for PANI@WO3 (0.5) compared with PANI@WO3 (1.0) and PANI@WO3 (1.5) with 1.91 eV and 1.98 eV, respectively. In addition, the electroactivity properties were investigated by cyclic voltammetry to explore the benefits of these types of hybrid materials in electrochemical applications.

Electrospun Hydrophobic Polyaniline/Silk Fibroin Electrochromic Nanofibers with Low Electrical Resistance.

Electronic textiles (E-textiles) have been an area of intense industrial and academic research for years due to their advanced applications. Thus, the goal of this study was to develop highly conductive silk fibroin electrochromic nanofibers for use in E-textiles. The silk nanofibers were prepared by an electrospinning technique, and the conductive polyaniline (PANI) was added to impart the electrical conductivity and electroactive property to the resultant electrospun silk composite nanofibers. The experimental results showed that tuning the electrospinning procedure could control the morphology of the composite nanofibers, thus altering their mechanical properties and surface wettability. Furthermore, the developed PANI/silk composite fibers possess electroactive and electrochromic properties, such as adjusting the applied voltage. The developed strategy demonstrated the feasibility of incorporating not only electrical functionality but also electroactivity into sustainable silk nanofibers using electrospinning technique.

Preparation and characterization of electro-active shape memory PCL/SEBS-g-MA/MWCNT nanocomposites

In this work, novel thermally responsive shape memory polymer (SMP) blends of poly(caprolactone) (PCL) and maleic anhydride grafted polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene (SEBS-g-MA) blends and electro-active PCL/SEBS-g-MA/multi walled carbon nanotube (MWCNT) nanocomposites with different compositions were prepared by melt blending technique. The effects of the PCL content (30-40-50%) on morphological, thermal, mechanical and shape memory properties were investigated. Based on SEM analysis, co-continuous morphology was observed in the blend having the weight ratio of 50:50 (50 PCL-50MA). The thermally triggered shape memory properties which were characterized by a dynamic mechanical analyzer (DMA) showed that the 50 PCL-50MA exhibited the highest fixing (Rf 98.28%) and recovery ratios (Rr 87.97%) among the SMP blends. In the second part of the study, the 50 PCL-50MA blend nanocomposites were produced with different amounts of multiwalled carbon nanotubes (MWCNTs) and their thermal, mechanical, morphological, electrical and electro-active shape memory properties were investigated. The blend nanocomposite including 10 phr CNT indicated the lowest volume resistivity value (3.82 Ω cm). The same nanocomposite also showed elecro-active shape memory property generating Joule heat under 40 V voltage with the shortest recovery time (56 s). The nanocomposite also exhibited sensor behaviour when it was subjected to finger bending deformation.

Electrochemical Biosensors Based on Nanomaterials for Early Detection of Alzheimer's Disease.

Alzheimer’s disease (AD) is an untreatable neurodegenerative disease that initially manifests as difficulty to remember recent events and gradually progresses to cognitive impairment. The incidence of AD is growing yearly as life expectancy increases, thus early detection is essential to ensure a better quality of life for diagnosed patients. To reach that purpose, electrochemical biosensing has emerged as a cost-effective alternative to traditional diagnostic techniques, due to its high sensitivity and selectivity. Of special relevance is the incorporation of nanomaterials in biosensors, as they contribute to enhance electron transfer while promoting the immobilization of biological recognition elements. Moreover, nanomaterials have also been employed as labels, due to their unique electroactive and electrocatalytic properties. The aim of this review is to add value in the advances achieved in the detection of AD biomarkers, the strategies followed for the incorporation of nanomaterials and its effect in biosensors performance.

Overcoming the potential drop in conducting polymer artificial muscles through metallization of electrospun nanofibers by electroplating process

Electrochemical actuators made of conducting polymers are one of the major types of artificial muscles that have attracted much attention in recent years. However, these artificial muscles suffer from potential drop along the length, which undermines their performance in applications requiring longer muscles. This study is aimed at enhancing the performance of this type of artificial muscles through overcoming the potential drop along the length. This is implemented using copper electroplating and creating a full-length highly conductive nanofibrous layer. Polyurethane/copper/polypyrrole (PU/Cu/PPy) nanofibrous artificial muscles were fabricated by combining electrospinning, electroplating and electrochemical polymerization. The copper electroplating affected many features of the PU nanofibrous layer including surface morphology of nanofibers, thermal, mechanical and electrical properties. Average diameter of the PU nanofibers was measured as 306 ± 48 nm, which increased significantly by increasing the duration of copper electroplating. By copper electroplating for 20 s, the onset temperature of nanofibers thermal decomposition was increased from 249 to 302 °C. Additionally, using this process, the sample Young’s modulus was increased from 2.20 ± 0.21 to 62.32 ± 5.42 MPa while its elongation at break was decreased from 173.84 ± 14.22 to 94.81 ± 10.96. After copper electroplating for duration as low as 20 s, the electrical conductivity of nanofibers was increased by more than 200 times from 48.90 ± 1.10 to 10 103.06 ± 14.28 S cm−1. Electrochemical polymerization of pyrrole on the surface of metalized nanofibers increased the average diameter of produced nanofibers to 1030 ± 102 nm. Providing an electrical connection along the entire length of artificial muscle resulted in enhanced electroactive property and hence final bending actuation of 88° for a cycle potential between −0.8 V and 0.5 V at a scan rate of 5 mV s−1 was observed. The nanofibrous artificial muscle fabricated by the proposed method has immense potential for use in practical applications.

Flexible piezoelectric PVDF/NDs nanocomposite films: improved electroactive properties at low concentration of nanofiller and numerical simulation using finite element method

In the present work, flexible poly (vinylidene fluoride)/Diamond nanoparticles nanocomposite films with improved electroactive properties at low filler concentration were developed. The combination of nanofiller doping and mechanical stretching was employed to obtain the films with significantly improved electroactive phase at low nanodiamond (ND) concentration, making them the interesting materials for several applications in the electronic devices. The nanocomposite films with different nanofiller concentration were prepared and then stretched under different stretch ratios. The polar phase content of all films was calculated and compared. It was found that the polar phase fraction of the films was significantly enhanced by increasing the nanofiller concentration and the stretch ratio. Moreover, a finite element model was constructed to determine the true value of the strain during the tensile process and to calibrate the stretch ratio. Development of such nanocomposite films with improved piezoelectric properties at low nanofiller concentration can extend their applications for practical usage.

Optimization of the compositions of polyanionic sodium-ion battery cathode NaFe2−xVx(PO4)(SO4)2

Sodium (Na) super ionic conductor (NASICON) polyanionic compounds have recently attracted much attention from the battery community because of their electroactive properties and reasonably high ionic conductivities, leading to their use as a cathode in sodium-ion batteries. This article describes the compositional optimizations, crystallographic evaluations, and electrochemical behavior of a new mixed NASICON polyanionic compound, NaFe2−xVx(PO4)(SO4)2. By doping the characteristic Fe3+ sites of the FeO6 octahedrons with varying amounts of V3+, the electrochemical stability and charge transport in NaFe2(PO4)(SO4)2 were enhanced. The resulting best composition, with crystal structure NaFe1.4V0.6(PO4)(SO4)2 resolved through the Rietveld method, exhibited a stable capacity compared with the other synthesized compositions. In situ powder x-ray diffraction measurements, a single-phase intercalation/deintercalation mechanism of the NASICON structure in the measured sodium concentration window was observed with no impurity phase formation. Further electrochemical assessments revealed the interfacial charge transfer kinetics to be the rate-limiting step in the sodium concentration window. Also, the measured sodium-ion diffusivity values in the range of 6 × 10−11 to 7 × 10−11 cm2/s in the measured sodium concentration range. The results reported here highlight the potential of compositionally and morphologically optimized NaFe1.4V0.6(PO4)(SO4)2 with higher particle surface areas as a cathode material for high-performance sodium-ion batteries.

Electrochemistry of redox probes at thin films of carbon nano-onions produced by thermal annealing of nanodiamonds

Electrochemical data for pristine carbon nano-onions (CNO), radio frequency Ar/O2 plasma oxidized CNO (CNO-RF) and chemically oxidized CNO (CNO-OXI) cast on glassy carbon electrodes (GCE) are presented. The electrochemical response was evaluated by cyclic voltammetry using [Fe(CN)6]3-, [Ru(NH3)6]3+, [Fe(H2O)6]2+ and ferrocenemethanol (FcCH2OH) as redox probes. The electron transfer kinetics for these probes was influenced by the nature of functional groups on the electrode material, adsorption processes and the electrostatic interactions between the redox probes and the surface of the different carbon nano-onions. The electrocatalytic properties for the reduction of O2 to H2O2 at CNO, CNO-RF and CNO-OXI modified electrodes were also evaluated using linear sweep voltammetry. The electroreduction of O2 shifted to more positive potential (up to −0.16 V vs Ag/AgCl) as the oxidation degree of CNO increased. In the same way, the sensitivity for the electrochemical detection of H2O2 was enhanced up to 50-fold respect to unmodified GC electrode. Furthermore, the electrocatalytic oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA) was studied by cyclic voltammetry and differential pulse voltammetry at CNO, CNO-RF and CNO-OXI modified electrodes. The electrodes displayed excellent electrocatalytic activity for the oxidation of AA, DA and UA. These results demonstrate that CNO enhance the electroactive properties of redox probes and are thus promising materials for electrochemical detection and metal-free electrocatalysts of different reactions. Additionally, the electrochemical data obtained here can serve to understand the performance of carbon nano-onion thin films as electrode materials.