Nanostructured conducting polymers for energy applications: towards a sustainable platform

An eco-friendly polycaprolactone/graphite composite as a robust freestanding electrode platform for supercapacitive energy storage

We present the successful development and characterization of a novel eco-friendly polycaprolactone-graphite (PCLGr) composite as a freestanding platform, serving as a bulk conducting chip electrode for supercapacitor applications. Notably, this is the first report of using this biodegradable polymer for making such a self-standing conductive platform. Traditional polymer and carbon-based electrodes often rely on insulating supports or non-eco-friendly materials, which we have addressed in our work. Direct deposition of the redox material, polyaniline (PANI), onto the electrode via the galvanostatic method has been achieved. The specific capacitance of PANI demonstrates comparability to previous studies utilizing conventional current collectors. Notably, the electrode exhibits exceptional stability in highly acidic environments. Comprehensive characterization utilizing bulk conductivity measurements, XRD, TGA, DSC, SEM, and stress-strain analyses shows advanced properties of the electrode. It complements the evaluation of PANI's supercapacitive performance through cyclic voltammetry, charge-discharge measurements, and impedance spectroscopy. We achieved a specific capacitance of ≈162 F g-1 at 0.5 A g-1. This innovative electrode presents a promising alternative to conventional counterparts across various electrochemical applications.

Enhanced Electrocatalytic Performance of the FePt/PPy-C Composite toward Methanol Oxidation

A novel FePt/PPy-C composite nanomaterial has been designed and investigated as a methanol oxidation reaction (MOR) electrocatalyst. The FePt nanoparticles with an average diameter of about 3 nm have been prepared by the co-reduction method and then loaded onto the PPy-C composite support. The electrocatalytic performance is affected by the composition of the FePt nanoparticles. The experimental results indicated that the Fe1.5Pt1/PPy-C catalyst exhibited excellent catalytic activity and stability for MOR, with mass activity and specific activity of 1.76 A mgPt-1 and 2.71 mA cm-2, respectively, which are 5.18 and 4.60 times higher than that of the commercial Pt/C catalyst. Density functional theory (DFT) has been employed to simulate the electrical structures of catalyst supports, and the mechanism of the methanol oxidation process has been further analyzed. The heterojunctions of the PPy-C interface could accelerate the electron migration from the electrocatalytic center to the electrodes. The possibility of methanol oxidation has been improved effectively, which can be confirmed by the d-band center and CO adsorption energy on FePt nanoparticles in the DFT calculation results.

Green synthesis and characterization of silver and copper nanoparticles and their use as an effective adsorbent for chromium removal and recovery from wastewater

Chromium (Cr) is one of the hazardous heavy metals that is naturally carcinogenic and causes various health problems. Metallic nanoparticles such as silver and copper nanoparticles (Ag NPs and Cu NPs) have gained great attention because of their unique chemical, physical, and biological attributes, serving diverse and significant role in various useful and sustainable applications. In the present study, both of these NPs were synthesized by green method in which Azadirachta indica plant extract was used. These nanoparticles were characterized by using advanced instrumental techniques such as Fourier transmission infrared (FTIR), X-ray diffraction (XRD), scanning electron microscope attached with energy-dispersive spectroscopy (SEM-EDS), and elemental mapping. These environmentally friendly nanoparticles were utilized for the batch removal of Cr from the wastewater. For analysis of adsorption behaviour, a range of kinetic isotherm models (Freundlich, Temkin, Dubinin, and Langmuir) and kinetic models (pseudo-first-order and pseudo-second-order) were used for the Cu-NPs and Ag-NPs. Cu NPs exhibited the highest Cr removal efficiency (96%) within a contact time of 10-15 min, closely followed by Ag NPs which achieved a removal efficiency of 94% under the similar conditions. These optimal outcomes were observed at a sorbent dose of 0.5 g/L for Ag NPs and 0.7 g/L for Cu NPs. After effectively capturing Cr using these nanoparticles, the sorbates were examined through SEM-EDX analysis to observe how much Cr metal was attached to the nanoparticles, potentially for future use. The analysis found that Ag-NPs captured 18% of Cr, while Cu-NPs captured 12% from the aqueous solution. More precise experimental conditions are needed for higher Cr removal from wastewater and determination of the best conditions for industrial-level Cr reuse. Although nanomaterial exhibit high efficiency and selectivity for Cr removal and recovery from wastewater, more research is necessary to optimize their synthesis and performance for industrial-scale applications and develop efficient methods for Cr removal and recovery.

A di-electrophoretic simulation procedure of iron-oxide micro-particle drug attachment system for leukemia treatment using COMSOL software: a potential treatment reference for LMICs

Background

Leukemia encompasses various subtypes, each with unique characteristics and treatment approaches. The challenge lies in developing targeted therapies that can effectively address the specific genetic mutations or abnormalities associated with each subtype. Some leukemia cases may become resistant to existing treatments over time making them less susceptible to chemotherapy or other standard therapies.

Objective

Developing new treatment strategies to overcome resistance is an ongoing challenge particularly in Low and Middle Income Countries (LMICs). Computational studies using COMSOL software could provide an economical, fast and resourceful approach to the treatment of complicated cancers like leukemia.

Methods

Using COMSOL Multiphysics software, a continuous flow microfluidic device capable of delivering anti-leukemia drugs to early-stage leukemia cells has been computationally modeled using dielectrophoresis (DEP).

Results

The cell size difference enabled the micro-particle drug attachment to the leukemia cells using hydrodynamic focusing from the dielectrophoretic force. This point of care application produced a low voltage from numerically calculated electrical field and flow speed simulations.

Conclusion

Therefore, such a dielectrophoretic low voltage application model can be used as a computational treatment reference for early-stage leukemia cells with an approximate size of 5 μm.

Aqueous Processable One-Dimensional Polypyrrole Nanostructured by Lignocellulose Nanofibril: A Conductive Interfacing Biomaterial

One-dimensional (1D) nanomaterials of conductive polypyrrole (PPy) are competitive biomaterials for constructing bioelectronics to interface with biological systems. Synergistic synthesis using lignocellulose nanofibrils (LCNF) as a structural template in chemical oxidation of pyrrole with Fe(III) ions facilitates surface-confined polymerization of pyrrole on the nanofibril surface within a submicrometer- and micrometer-scale fibril length. It yields a core-shell nanocomposite of PPy@LCNF, wherein the surface of each individual fibril is coated with a thin nanoscale layer of PPy. A highly positive surface charge originating from protonated PPy gives this 1D nanomaterial a durable aqueous dispersity. The fibril-fibril entanglement in the PPy@LCNFs facilely supported versatile downstream processing, e.g., spray thin-coating on glass, flexible membranes with robust mechanics, or three-dimensional cryogels. A high electrical conductivity in the magnitude of several to 12 S·cm-1 was confirmed for the solid-form PPy@LCNFs. The PPy@LCNFs are electroactive and show potential cycling capacity, encompassing a large capacitance. Dynamic control of the doping/undoping process by applying an electric field combines electronic and ionic conductivity through the PPy@LCNFs. The low cytotoxicity of the material is confirmed in noncontact cell culture of human dermal fibroblasts. This study underpins the promises for this nanocomposite PPy@LCNF as a smart platform nanomaterial in constructing interfacing bioelectronics.

Role of Efficient Charge Transfer at the Interface between Mixed-Phase Copper-Cuprous Oxide and Conducting Polymer Nanostructures for Photocatalytic Water Splitting

Photocatalytic hydrogen generation from water splitting is regarded as a sustainable technology capable of producing green solar fuels. However, the low charge separation efficiencies and the requirement of lowering redox potentials are unresolved challenges. Herein, a multiphase copper-cuprous oxide/polypyrrole (PPy) heterostructure has been designed to identify the role of multiple oxidation states of metal oxides in water reduction and oxidation. The presence of a mixed phase in PPy heterostructures enabled an exceptionally high photocatalytic H₂ generation rate of 41 mmol h^-1 with an apparent quantum efficiency of 7.2% under visible light irradiation, which is a 7-fold augmentation in contrast to the pure polymer. Interestingly, the copper-cuprous oxide/PPy heterostructures exhibited higher charge carrier density, low resistivity, and 6 times higher photocurrent density compared to Cu₂O/PPy. Formation of a p-p-n junction between polymer and mixed-phase metal oxide interfaces induce a built-in electric field which influences directional charge transfer that improves the catalytic activity. Notably, photoexcited charge separation and transfer have been significantly improved between copper-cuprous oxide nanocubes and PPy nanofibers, as revealed by femtosecond transient absorption spectroscopy. Additionally, the photocatalyst demonstrates excellent stability without loss of catalytic activity during cycling tests. The present study highlights a superior strategy to boost photocatalytic redox reactions using a mixed-phase metal oxide in the heterostructure to achieve enhanced light absorption, longer charge carrier lifetimes, and highly efficient photocatalytic H₂ and O₂ generation.

Preparation of Anionic Surfactant-Based One-Dimensional Nanostructured Polyaniline Fibers for Hydrogen Storage Applications

Polyaniline fibers were prepared in the presence of anionic surfactant in an ice medium to nucleate in one dimension and were compared to bulk polyaniline prepared at an optimum temperature. Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD) were used to investigate the structural analysis of the prepared samples. A conductivity study reveals that polyaniline fibers have high conductivity compared to bulk polyaniline. Hydrogen storage measurements confirm that the polyaniline fibers adsorbed approximately 86% of the total actual capacity of 8–8.5 wt% in less than 9 min, and desorption occurs at a lower temperature, releasing approximately 1.5 wt% of the hydrogen gases when the pressure is reduced further to 1 bar.

Nanostructured Conducting Polymers and Their Applications in Energy Storage Devices

Due to the energy requirements for various human activities, and the need for a substantial change in the energy matrix, it is important to research and design new materials that allow the availability of appropriate technologies. In this sense, together with proposals that advocate a reduction in the conversion, storage, and feeding of clean energies, such as fuel cells and electrochemical capacitors energy consumption, there is an approach that is based on the development of better applications for and batteries. An alternative to commonly used inorganic materials is conducting polymers (CP). Strategies based on the formation of composite materials and nanostructures allow outstanding performances in electrochemical energy storage devices such as those mentioned. Particularly, the nanostructuring of CP stands out because, in the last two decades, there has been an important evolution in the design of various types of nanostructures, with a strong focus on their synergistic combination with other types of materials. This bibliographic compilation reviews state of the art in this area, with a special focus on how nanostructured CP would contribute to the search for new materials for the development of energy storage devices, based mainly on the morphology they present and on their versatility to be combined with other materials, which allows notable improvements in aspects such as reduction in ionic diffusion trajectories and electronic transport, optimization of spaces for ion penetration, a greater number of electrochemically active sites and better stability in charge/discharge cycles.

Intrinsically Conducting Polymer Composites as Active Masses in Supercapacitors

Intrinsically conducting polymers ICPs can be combined with further electrochemically active materials into composites for use as active masses in supercapacitor electrodes. Typical examples are inspected with particular attention to the various roles played by the constituents of the composites and to conceivable synergistic effects. Stability of composite electrode materials, as an essential property for practical application, is addressed, taking into account the observed causes and effects of materials degradation.

Synthesis of Nanoparticles and Theoretical Model of Their Retention in Plasma of RF Capacitive Discharge with Vertically Arranged Electrodes in Acetylene

In the present research, experiments on the formation and retention of nanoparticles (NPs) in the plasma of radio frequency (RF) capacitive discharge in acetylene were carried out with vertically positioned internal electrodes. It has been shown via SEM and TEM techniques that NPs found on the horizontal tube wall after the discharge operation have a spherical shape with a predominant diameter of approximately 400-600 nm. HRTEM analysis reveals their amorphous structure. At the same time, such NPs were not found on vertical electrodes, only a polymer film was deposited. To elucidate the possibility of NPs leaving the plasma in the direction of vertical electrodes, a model of NP retention in the near-electrode sheath of an RF capacitive discharge was elaborated. The model has shown that nanometer- and even micrometer-sized particles formed in the plasma cannot cross the near-electrode sheath and reach the electrode surface. For the plasma consisting of three charged components (positive ions, electrons, and NPs), an analytical model of ambipolar diffusion was developed. Applying this model, it has been shown that the ambipolar electric field can keep the micrometer-sized NPs in the plasma if their concentration is low. However, in the case of a high concentration of NPs, they can be retained with a diameter of no more than a few hundred nanometers due to a significant decrease in the ambipolar electric field. The calculation results are in agreement with our experimental data.

Polypyrrole Nanomaterials: Structure, Preparation and Application

In the past decade, nanostructured polypyrrole (PPy) has been widely studied because of its many specific properties, which have obvious advantages over bulk-structured PPy. This review outlines the main structures, preparation methods, physicochemical properties, potential applications, and future prospects of PPy nanomaterials. The preparation approaches include the soft micellar template method, hard physical template method and templateless method. Due to their excellent electrical conductivity, biocompatibility, environmental stability and reversible redox properties, PPy nanomaterials have potential applications in the fields of energy storage, biomedicine, sensors, adsorption and impurity removal, electromagnetic shielding, and corrosion resistant. Finally, the current difficulties and future opportunities in this research area are discussed.

The Frontiers of Functionalized Nanocellulose-Based Composites and Their Application as Chemical Sensors

Chemical sensors are a rapidly developing technology that has received much attention in diverse industries such as military, medicine, environmental surveillance, automotive power and mobility, food manufacturing, infrastructure construction, product packaging and many more. The mass production of low-cost devices and components for use as chemical sensors is a major driving force for improvements in each of these industries. Recently, studies have found that using renewable and eco-friendly materials would be advantageous for both manufacturers and consumers. Thus, nanotechnology has led to the investigation of nanocellulose, an emerging and desirable bio-material for use as a chemical sensor. The inherent properties of nanocellulose, its high tensile strength, large specific surface area and good porous structure have many advantages in its use as a composite material for chemical sensors, intended to decrease response time by minimizing barriers to mass transport between an analyte and the immobilized indicator in the sensor. Besides which, the piezoelectric effect from aligned fibers in nanocellulose composites is beneficial for application in chemical sensors. Therefore, this review presents a discussion on recent progress and achievements made in the area of nanocellulose composites for chemical sensing applications. Important aspects regarding the preparation of nanocellulose composites using different functionalization with other compounds are also critically discussed in this review.

A Biodegradable Polymer-Based Plastic Chip Electrode as a Current Collector in Supercapacitor Application

Here, we report the performance of a biodegradable polymer-based Plastic chip Electrode (PCE) as a current collector in supercapacitor applications. Its production was evaluated using two redox materials (conducting polymers polyaniline and poly(3,4-ethylene dioxythiophene)) and a layered material, rGO. The conducting polymers were directly deposited over the Eco-friendly PCE (EPCE) using the galvanostatic method. The rGO was prepared in the conventional way and loaded over the EPCE using a binder. Both conducting polymers and rGO showed proper specific capacitance compared to previous studies with regular current collectors. Electrodes were found highly stable during experiments in high acidic medium. The supercapacitive performance was evaluated with cyclic voltammetry, charge–discharge measurements, and impedance spectroscopy. The supercapacitive materials were also characterized for their electrical and microscopic properties. Polyaniline and PEDOT were deposited over EPCEs showing >150 Fg−1 and >120 Fg−1 specific capacitance, respectively, at 0.5 Ag−1. rGO continued to show higher particular capacitance of >250 Fg−1 with excellent charge–discharge cyclic stability. The study concludes that EPCs can be used as promising electrodes for electrical energy storage applications.

In-depth probing of thermally-driven phase separation behavior of lamella-forming PS-b-PMMA films by infrared nanoscopy

A non-invasive, image-based analytic method utilizing scattering-type scanning near-field optical microscopy (s-SNOM) is suggested to evaluate the phase separation behavior of lamella-forming polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymer films. Taking advantage of the penetrability of the tip-enhanced IR signal into the films, the spatio-spectral maps of each component are constructed. Subsequently, the effect of a sole and combinatorial applications of the self-assembly procedures, such as solvent vapor annealing (SVA) and/or thermal annealing (TA), on the spatial distribution of PS or PMMA components is quantitatively assessed in terms of the areal portions of the PS domain, PMMA domain, and the mixed zone that is adjacent to the domain border. Additionally, by statistically comparing the local concentration profiles, the chemical contrast between the domains turns out to be dependent upon the annealing procedures (namely, SVA and SVA + TA). This technique can pave the way to an uncomplicated but precise investigation of the polymer nanostructure-based thin film devices whose performances are critically governed by the spatial arrangement of the chemical elements.

Electrochemical Investigation of PANI:PPy/AC and PANI:PEDOT/AC Composites as Electrode Materials in Supercapacitors

The electrochemical deposition of the composites polyaniline (PANI):polypyrrole (PPy)/activated carbon (AC) and polyaniline (PANI): 3, 4-polyethylenedioxythiophene (PEDOT)/AC films is carried out in this work. The electrochemical character of the fabricated samples is investigated via cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) using a three-electrode setup. The values of the specific capacitance of the composites PANI:PPy/AC and PANI:PEDOT/AC at a current density of 1 Ag⁻¹ are evaluated as 586 Fg⁻¹ and 611 Fg⁻¹, respectively. The values of energy density are 40 Whkg⁻¹ and 2094 Wkg⁻¹, whereas power density is recorded as 44 Whkg⁻¹ and 2160 Wkg⁻¹ for respective composites PANI:PPy/AC and PANI:PEDOT/AC. Moreover, the respective composites appeared to retain cyclic stabilities of 92% and 90%. This study points to the potential of the prepared composites for application as electrodes in supercapacitors.

Electrosynthesis of Biocompatible Free-Standing PEDOT Thin Films at a Polarized Liquid|Liquid Interface

Conducting polymers (CPs) find applications in energy conversion and storage, sensors, and biomedical technologies once processed into thin films. Hydrophobic CPs, like poly(3,4-ethylenedioxythiophene) (PEDOT), typically require surfactant additives, such as poly(styrenesulfonate) (PSS), to aid their aqueous processability as thin films. However, excess PSS diminishes CP electrochemical performance, biocompatibility, and device stability. Here, we report the electrosynthesis of PEDOT thin films at a polarized liquid|liquid interface, a method nonreliant on conductive solid substrates that produces free-standing, additive-free, biocompatible, easily transferrable, and scalable 2D PEDOT thin films of any shape or size in a single step at ambient conditions. Electrochemical control of thin film nucleation and growth at the polarized liquid|liquid interface allows control over the morphology, transitioning from 2D (flat on both sides with a thickness of <50 nm) to “Janus” 3D (with flat and rough sides, each showing distinct physical properties, and a thickness of >850 nm) films. The PEDOT thin films were p-doped (approaching the theoretical limit), showed high π–π conjugation, were processed directly as thin films without insulating PSS and were thus highly conductive without post-processing. This work demonstrates that interfacial electrosynthesis directly produces PEDOT thin films with distinctive molecular architectures inaccessible in bulk solution or at solid electrode–electrolyte interfaces and emergent properties that facilitate technological advances. In this regard, we demonstrate the PEDOT thin film’s superior biocompatibility as scaffolds for cellular growth, opening immediate applications in organic electrochemical transistor (OECT) devices for monitoring cell behavior over extended time periods, bioscaffolds, and medical devices, without needing physiologically unstable and poorly biocompatible PSS.

Free-standing hybrid film for separation of dye pollutant with self-cleaning ability under visible light

The development of low cost and environmental-friendly materials has long been an ambition for effective removal of dye pollutants in complex water environments. In this study, a free-standing separation film of bacterial cellulose reinforced/functionalized by graphitic phase carbon nitride is developed by a facile suction filtration strategy, of which the former is precoated by polypyrrole, and the latter is pre-doped by oxygen to endow the as-obtained film an enhanced photocatalytic performance and self-cleaning ability. The as-obtained film exhibits a high tensile stress of 51.8 ± 1.1 MPa, and a high resistance to cold, heat, acid and alkali. For typical dyes of methylene blue and rhodamine B, a high dye rejection rate of 99.9% at 138 L/m²•h•bar feed flux is obtained by the as-obtained film. Even at a salt concentration higher than 5%, it still maintained high dye removal rates and achieves effective separation of dye and salt. Simultaneously, a high dye photocatalytic degradation of the composite films rates up to 98% in only 90 min, and a high self-cleaning ability demonstrated by recovery of flux after light treatment in cyclic tests. The density functional theory calculation validates the beneficial effects of improved light response range and separated photogenerated electron/holes for the effective degradation of dyes by oxygen-doped carbon nitride coupled with one-dimensional polypyrrole chains. Overall, this study proposes a new direction for the separation of dye pollutants with a high visible-light self-cleaning capacity by structural tailoring of bacterial cellulose with carbon nitride.

Aqueous Multivalent Charge Storage Mechanism in Aromatic Diamine-Based Organic Electrodes

Rechargeable batteries employing aqueous electrolytes are more reliable and cost-effective as well as possess high ionic conductivity compared to the flammable organic electrolyte solutions. Among these types of batteries, aqueous batteries with multivalent ions attract more attention in terms of providing high energy density. Herein, electrochemical behavior of an organic electrode based on a highly aromatic polymer containing 2,3-diaminophenazine repeating unit, namely poly(ortho-phenylenediamine) (PoPD), is tested in two different multivalent ions (Zn²⁺ and Al³⁺) containing aqueous electrolytes, that is, in zinc sulfate and aluminum chloride solutions. PoPD is synthesized via electropolymerization, and its ion transport and storage mechanism are comprehensively investigated by structural and electrochemical analyses. The electrochemical quartz crystal microbalance, time-dependent Fourier transform infrared, and electrochemical impedance spectroscopy analyses as well as ex situ X-ray diffraction observations established that along with the Zn²⁺ or Al³⁺ ions, reversible proton insertion/extraction also takes place. Contrary to the most of the organic electrodes that requires the use of conductive carbon additives, the electrodeposited PoPD electrode is intrinsically electrically conductive enough, resulting in a binder and additive free electrode assembly. In addition, its discharge products do not dissolve in aqueous medium. As a whole, the resulting PoPD electrode delivers excellent rate performances with prolonged cycle life in which discharge capacities of ∼110 mAh g^-1 in 0.25 M AlCl₃ and ∼93 mAh g^-1 in 1 M ZnSO₄ aqueous electrolyte after 1000 cycles at a current density of 5C have been achieved.

Strong Bathochromic Shift of Conjugated Polymer Nanowires Assembled with a Liquid Crystalline Alkyl Benzoic Acid via a Film Dispersion Process

We present aqueous dispersions of conjugated polymer nanowires (CPNWs) with improved light absorption properties aimed at aqueous-based applications. We assembled films of a donor-acceptor-type conjugated polymer and liquid crystalline 4-n-octylbenzoic acid by removing a cosolvent of their mixture solutions, followed by annealing of the films, and then formed aqueous-dispersed CPNWs with an aspect ratio >1000 by dispersing the films under ultrasonication at a basic pH. X-ray and spectroscopy studies showed that the polymer and liquid crystal molecules form independent domains in film assemblies and highly organized layer structures in CPNWs. Our ordered molecular assemblies in films and aqueous dispersions of CPNWs open up a new route to fabricate nanowires of low-band-gap linear conjugated polymers with the absorption maximum at 794 nm remarkably red-shifted from 666 nm of CPNWs prepared by an emulsion process. Our results suggest the presence of semicrystalline polymorphs β1 and β2 phases in CPNWs due to long-range π-π stacking of conjugated backbones in compactly organized lamellar structures. The resulting delocalization with a reduced energy bang gap should be beneficial for enhancing charge transfer and energy-conversion efficiencies in aqueous-based applications such as photocatalysis.

Recent advances in piezocatalytic polymer nanocomposites for wastewater remediation

Among several forms of water pollutants, common pesticides, herbicides, organic dyes and heavy metals present serious and persistent threats to human health due to their severe toxicity. Recently, piezocatalysis based removal of pollutants has become a promising field of research to combat such pollutions by virtue of the piezoelectric effect. In reality, piezoelectric materials can produce electron-hole separation upon external vibration, which greatly enhances the production of various reactive oxygen species (ROS) and further increases the pollutant degradation rate. Piezocatalysis does not alter the quality or composition of water, like several other conventional techniques (adsorption and photocatalysis), which makes this technique non-invasive. The simplicity and tremendously high efficacy of piezocatalysis have attracted researchers worldwide and thus various functional materials are employed for piezocatalytic wastewater remediation. In this frontier, we highlight and demonstrate recent developments on polymer based piezocatalytic nanocomposites to treat industrial wastewater in a facile manner that holds strong potential to be translated into a clean and green technology.

Flexible Nanowire Conductive Elastomers for Applications in Fully Polymeric Bioelectronic Devices. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021;2021:5872-5875. [PMID: 34892455 DOI: 10.1109/embc46164.2021.9629903]

Soft, flexible polymer-based bioelectronics are a promising approach to minimize the chronic inflammatory reactions associated with metallic devices, impairing long-term device reliability and functionality. This work demonstrates the fabrication of conductive elastomers (CEs) consisting of chemically synthesized poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires embedded within a polyurethane (PU) elastomeric matrix, resulting in soft and flexible, fully polymeric electrode materials. Increasing PEDOT nanowire loadings resulted in an improvement in electrochemical properties and conductivity, an increased Young's modulus and reduced strain at failure. Nanowire CEs were also found to have significantly improved electrochemical performance compared to one of the standard electrode materials, platinum (Pt). Indirect in vitro cytocompatibility test was carried out to investigate the effect of leachable substances from the CE on primary rodent cells. Nanowire CEs provide a promising alternative to metals for the fabrication of soft bioelectronics.

One-step synthesis, characterization and properties of novel hybrid electromagnetic nanomaterials based on polydiphenylamine and Co-Fe particles in the absence and presence of single-walled carbon nanotubes

A one-step preparation method for hybrid electromagnetic nanomaterials based on polydiphenylamine (PDPA) and bimetallic Co-Fe particles in the absence and presence of single-walled carbon nanotubes (SWCNT) was proposed. During IR heating of PDPA in the presence of Co(ii) and Fe(iii) salts in an inert atmosphere at T = 450-600 °C, the polycondensation of diphenylamine (DPA) oligomers and dehydrogenation of phenyleneamine units of the polymer with the formation of C[double bond, length as m-dash]N bonds and reduction of metals by evolved hydrogen with the formation of bimetallic Co-Fe particles dispersed in a polymer matrix occur simultaneously. When carbon nanotubes are introduced into the reaction system, a nanocomposite material is formed, in which bimetallic Co-Fe particles immobilized on SWCNT are distributed in the matrix of the polymer. According to XRD data, reflection peaks of bimetallic Co-Fe particles at diffraction scattering angles 2θ = 69.04° and 106.5° correspond to a solid solution based on the fcc-Co crystal lattice. According to SEM and TEM data, a mixture of particles with sizes of 8-30 nm and 400-800 nm (Co-Fe/PDPA) and 23-50 nm and 400-1100 nm (Co-Fe/SWCNT/PDPA) is formed in the nanocomposites. The obtained multifunctional Co-Fe/PDPA and Co-Fe/SWCNT/PDPA nanomaterials demonstrate good thermal, electrical and magnetic properties. The saturation magnetization of the nanomaterials is M S = 14.99-31.32 emu g-1 (Co-Fe/PDPA) and M S = 29.48-48.84 emu g-1 (Co-Fe/SWCNT/PDPA). The electrical conductivity of the nanomaterials reaches 3.5 × 10-3 S cm-1 (Co-Fe/PDPA) and 1.3 S cm-1 (Co-Fe/SWCNT/PDPA). In an inert medium, at 1000 °C the residue is 71-77%.

Electrochemical Polymerization Induced Chirality Fixation of Crystalline Pillararene-Based Polymer and Its Application in Interfacial Chiral Sensing

A new strategy has been developed for the direct chirality fixation, which is induced by electrochemical polymerization, of macrocyclic hosts pillar[5]arene. Taking advantage of electrochemical polymerization, thiophene-modified pillar[5]arene monomers (Th-P[5]A) have been regularly arranged under the action of an electric field to form chiral nanofiber-like crystalline pillar[5]arene-based polymers (poly-Th-P[5]A), showing a significant circular dichroism (CD) signal. With the active photochemical properties, poly-Th-P[5]A is first used as a photoelectrochemical (PEC) chiral sensor for the identification and determination of l- and d-ascorbic acid (l-AA, d-AA) without adding any extra photoactive probes. Importantly, the chiral recognition between poly-Th-P[5]A and l-AA also triggers a polarity conversion for the photocurrent of the polymer, and it greatly results in a broad chiral detection range for l-AA, crossing 6 orders of magnitude. This work provides a promotional strategy for building a PEC chiral recognition platform based on pillararenes.

Nanoarchitectured Porous Conducting Polymers: From Controlled Synthesis to Advanced Applications

Conductive polymers (CPs) integrate the inherent characteristics of conventional polymers and the unique electrical properties of metals. They have aroused tremendous interest over the last decade owing to their high conductivity, robust and flexible properties, facile fabrication, and cost-effectiveness. Compared to bulk CPs, porous CPs with well-defined nano- or microstructures possess open porous architectures, high specific surface areas, more exposed reactive sites, and remarkably enhanced activities. These attractive features have led to their applications in sensors, energy storage and conversion devices, biomedical devices, and so on. In this review article, the different strategies for synthesizing porous CPs, including template-free and template-based methods, are summarized, and the importance of tuning the morphology and pore structure of porous CPs to optimize their functional performance is highlighted. Moreover, their representative applications (energy storage devices, sensors, biomedical devices, etc.) are also discussed. The review is concluded by discussing the current challenges and future development trend in this field.

Electrospun PEO/PEDOT:PSS Nanofibers for Wearable Physiological Flex Sensors

Flexible sensors are fundamental devices for human body monitoring. The mechanical strain and physiological parameters coupled sensing have attracted increasing interest in this field. However, integration of different sensors in one platform usually involves complex fabrication process-flows. Simplification, even if essential, remains a challenge. Here, we investigate a piezoresistive and electrochemical active electrospun nanofibers (NFs) mat as the sensitive element of the wearable physiological flex sensing platform. The use of one material sensitive to the two kinds of stimuli reduces the process-flow to two steps. We demonstrate that the final NFs pH-Flex Sensor can be used to monitor the deformation of a human body joint as well as the pH of the skin. A unique approach has been selected for pH sensing, based on Electrochemical Impedance Spectroscopy (EIS). A linear dependence of the both the double layer capacitance and charge transfer re-sistance with the pH value was obtained by EIS, as well as a linear trend of the electrical resistance with the bending deformation. Gauge factors values calculated after the bending test were 45.84 in traction and 208.55 in compression mode, reflecting the extraordinary piezoresistive behavior of our nanostructured NFs.

Assemble of Bi-doped TiO2 onto 2D MoS2: an efficient p-n heterojunction for photocatalytic H2 generation under visible light

Fabrication of noble-metal-free, efficient and stable hybrid photocatalyst is essential to address the rapidly growing energy crisis and environmental pollution. Here, MoS₂ has been used as the co-catalyst on Bi-doped TiO₂ to form a novel heterostructure to increase the utilization of the photogenerated charge carriers for improving photocatalytic H₂ evolution activity through water reduction. Significantly increased photocatalytic H₂ generation has been achieved on the optimized MoS₂/Bi-TiO₂ nanocomposite (∼512 μmol g^-1) after 4 h of visible light illumination, which is nine times higher than that of the pristine TiO₂ (∼57 μmol g^-1). The measurements of photocurrent, charge transfer resistance and photo-stability of MoS₂/Bi-TiO₂ photoanode imply that charge separation efficiency has been improved in comparison to the pure MoS₂ and TiO₂ photoanodes. Further, the Mott-Schottky study confirmed that a p-n heterojunction has been formed between n-type MoS₂ and p-type Bi-doped TiO₂, which provides a potential gradient to increase charge separation and transfer efficiency. On the basis of these experimental results, this enhanced photocatalytic activity of MoS₂/Bi-TiO₂ heterostructures could be ascribed to the significant visible light absorption and the efficient charge carrier separation. Thus, this work demonstrates the effect of p-n junction for achieving high H₂ evolution activity and photoelectrochemical water oxidation under visible light illumination.

Preparation of a polymer nanocomposite via the polymerization of pyrrole : biphenyldisulfonic acid : pyrrole as a two-monomer-connected precursor on MoS2 for electrochemical energy storage

We prepared a poly(pyrrole : biphenyldisulfonic acid : pyrrole (Py:BPDSA:Py)) nanocomposite of molybdenum disulfide (MoS₂), P(Py:BPDSA:Py)-MoS₂, with high crystallinity. The composite is synthesized by oxidative polymerization of Py:BPDSA:Py as a two-monomer-connected precursor (TMCP) linked by ionic bonding on a molybdenum disulfide (MoS₂) monolayer. The chemical, structural and morphological characterization of this composite is confirmed by Raman spectroscopy, FT-IR, X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), and scanning electron microscopy (SEM). The crystal structure is analysed by X-ray diffraction (XRD) and high-voltage electron microscopy (HVEM), which shows a face-centered cubic (FCC) crystal structure for the composite. Nitrogen adsorption-desorption isotherms show an improved specific surface area (91.3 m² g^-1). The electrochemical properties of the composite with a unique crystal structure and a large specific surface area are analysed through cyclic voltammetry (CV), which shows a specific capacitance of 681 F g^-1 demonstrating that the composite can be used as an efficient electrode active material for electrochemical energy storage systems.

Conjugated polymer nanostructures displaying highly photoactivated antimicrobial and antibiofilm functionalities

This work reports the use of conjugated polymer nanostructures (CPNs) as photoactivated antimicrobial compounds against Gram-positive and Gram-negative microorganisms. Two representative CPNs of polythiophene (PEDOT) and polyaniline (PANI) were prepared as nanofibres with an average diameter of 40 nm and length in the micrometer range. Both CPNs exhibited strong antimicrobial activity under UVA irradiation with the same fluence rate as the UVA component of the solar spectrum. The effect was tested using the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Escherichia coli. The reduction of colony forming units (CFUs) reached >6 log for PEDOT concentrations as low as 33 ng mL-1. For PEDOT nanofibers, a complete inhibition of S. aureus and E. coli growth was reached at 883 ng mL-1 and 333 ng mL-1 respectively. The photoactivation effect of PANI nanofibres on S. aureus and E. coli was also high, with a CFU reduction of about 7 log and 4 log respectively for an exposure concentration of 33 ng mL-1. The antimicrobial activity was only high under light irradiation and was almost negligible for bulk PEDOT and PANI. The effect of polymeric nanofibers could be attributed to the photoinduced generation of reactive oxygen species, which may induce cell membrane damage, eventually leading to bacterial impairment and inhibition of their biofilm forming capacity. CPN PEDOT and PANI coatings were able to keep surfaces free of bacterial attachment and growth even after 20 h of previous contact with exponentially growing cultures in the dark. PEDOT and PANI CPNs demonstrated good cytocompatibility with human fibroblasts and the absence of hemolytic activity. The materials demonstrated advantages in terms of broad antibacterial spectrum, biofilm inhibition, and the absence of acute toxicity for biomedical applications.

Conducting Polymer-Based Nanohybrids for Fuel Cell Application

Carbon materials such as carbon graphitic structures, carbon nanotubes, and graphene nanosheets are extensively used as supports for electrocatalysts in fuel cells. Alternatively, conducting polymers displayed ultrahigh electrical conductivity and high chemical stability havegenerated an intense research interest as catalysts support for polymer electrolyte membrane fuel cells (PEMFCs) as well as microbial fuel cells (MFCs). Moreover, metal or metal oxides catalysts can be immobilized on the pure polymer or the functionalized polymer surface to generate conducting polymer-based nanohybrids (CPNHs) with improved catalytic performance and stability. Metal oxides generally have large surface area and/or porous structures and showed unique synergistic effects with CPs. Therefore, a stable, environmentally friendly bio/electro-catalyst can be obtained with CPNHs along with better catalytic activity and enhanced electron-transfer rate. The mass activity of Pd/polypyrrole (PPy) CPNHs as an anode material for ethanol oxidation is 7.5 and 78 times higher than that of commercial Pd/C and bulk Pd/PPy. The Pd rich multimetallic alloys incorporated on PPy nanofibers exhibited an excellent electrocatalytic activity which is approximately 5.5 times higher than monometallic counter parts. Similarly, binary and ternary Pt-rich electrocatalysts demonstrated superior catalytic activity for the methanol oxidation, and the catalytic activity of Pt24Pd26Au50/PPy significantly improved up to 12.5 A per mg Pt, which is approximately15 times higher than commercial Pt/C (0.85 A per mg Pt). The recent progress on CPNH materials as anode/cathode and membranes for fuel cell has been systematically reviewed, with detailed understandings into the characteristics, modifications, and performances of the electrode materials.

Boosting the Utilization and Electrochemical Performances of Polyaniline by Forming a Binder-Free Nanoscale Coaxially Coated Polyaniline/Carbon Nanotube/Carbon Fiber Paper Hierarchical 3D Microstructure Composite as a Supercapacitor Electrode

Nanoscale polyaniline (PANI) is formed on a hierarchical 3D microstructure carbon nanotubes (CNTs)/carbon fiber paper (CFP) substrate via a one-step electrochemical polymerization method. The chemical and structural properties of the binder-free PANI/CNTs/CFP electrode are characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. The specific capacitance of PANI/CNTs/CFP tested in a symmetric two-electrode system reaches 731.6 mF·cm^-2 (1354.7 F·g^-1) at a current density of 1 mA·cm^-2 (1.8 A·g^-1). The symmetric supercapacitor device demonstrates excellent cycling performance up to 10,000 cycles with a capacitance retention of 81.4% at a current density of 1 mA·cm^-2 (1.8 A·g^-1). The results demonstrate that the binder-free CNTs/CFP composite is a strong backbone for depositing ultrathin PANI layers at a high mass loading. The hierarchical 3D microstructure PANI/CNTs/CFP provides enough space and transporting channels to form an efficient electrode-electrolyte interface for the supercapacitance reaction. The formed nanoscale PANI film coaxially coated on the sidewalls of CNTs enables efficient charge transfer and a shortened diffusion length. Hence, the utilization efficiency and electrochemical performances of PANI are significantly improved. The rational design strategy of a CNT-based binder-free hierarchical 3D microstructure can be used in preparing various advanced energy-storage electrodes for electrochemical energy-storage and conversion systems.

True Meaning of Pseudocapacitors and Their Performance Metrics: Asymmetric versus Hybrid Supercapacitors

The development of pseudocapacitive materials for energy-oriented applications has stimulated considerable interest in recent years due to their high energy-storing capacity with high power outputs. Nevertheless, the utilization of nanosized active materials in batteries leads to fast redox kinetics due to the improved surface area and short diffusion pathways, which shifts their electrochemical signatures from battery-like to the pseudocapacitive-like behavior. As a result, it becomes challenging to distinguish "pseudocapacitive" and "battery" materials. Such misconceptions have further impacted on the final device configurations. This Review is an earnest effort to clarify the confusion between the battery and pseudocapacitive materials by providing their true meanings and correct performance metrics. A method to distinguish battery-type and pseudocapacitive materials using the electrochemical signatures and quantitative kinetics analysis is outlined. Taking solid-state supercapacitors (SSCs, only polymer gel electrolytes) as an example, the distinction between asymmetric and hybrid supercapacitors is discussed. The state-of-the-art progress in the engineering of active materials is summarized, which will guide for the development of real-pseudocapacitive energy storage systems.

Nanostructured Carbon-Nitrogen-Sulfur-Nickel Networks Derived From Polyaniline as Bifunctional Catalysts for Water Splitting

The development of reliable production routes for sustainable hydrogen (H₂), which is an essential feedstock for industrial processes and energy carrier for fuel cells, is needed. It appears to be an unavoidable alternative to significantly reduce the dependence on conventional energy sources based on fossil fuels without increasing the atmospheric CO₂ levels. Among the different power-to-X scenarios to access high purity H₂, the electrochemical approach based on electrolysis looks to be a promising sustainable solution at both the small and large industrial scales. However, the practical realization of this important opportunity faces several challenges, including the efficient design of cost-effective catalytic materials to be used as a cathode with improved intrinsic and durable activity. In this contribution, we report the design and development of efficient nanostructured catalysts for the electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in aqueous media, whereby noble metal-free elements are embedded in a matrix of a conducting polymer, polyaniline (PANI). To increase the electrical conductivity and further the electrocatalytic ability toward HER of the chemically polymerized PANI in the presence of nickel (II) salt (nitrate), the PANI-based materials have first been stabilized at a mild temperature of 250-350°C in air and then carbonized at 800-1,000°C under nitrogen gas to convert the chemical species into nitrogen, sulfur, nickel, and carbon nanostructured networks (CNNs). Different physicochemical (TGA-DSC, Raman spectroscopy, XRD, SEM, EDX, ICP, CHNS, BET, and XPS) and electrochemical (voltammetry and electrochemical impedance spectrometry) methods have been integrated to characterize the as-synthesized CNNs materials and interrogate the relationship of material-to-performance. It has been found that those synthesis conditions allow for the substantial increase of the electrocatalytic performance toward HER and OER in alkaline media in terms of the onset potential and charge transfer resistance and overpotential at the specific activity of 10 milliamps per square centimeter, thus ranking the present materials among the most efficient noble metal-free catalysts and making them possible candidates for integration in practical low-energy consumption alkaline electrolyzers.

Synthesis and Characterization of Hollow-Sphered Poly(N-methyaniline) for Enhanced Electrical Conductivity Based on the Anionic Surfactant Templates and Doping

Poly(N-methylaniline) (PNMA) is a polyaniline derivative with a methyl substituent on the nitrogen atom. PNMA is of interest owing to its higher solubility in organic solvents when compared to the unsubstituted polyaniline. However, the electrical conductivity of polyaniline derivatives suffers from chemical substitution. PNMA was synthesized via emulsion polymerization using three different anionic surfactants, namely sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and dioctyl sodium sulfosuccinate (AOT). The effects of surfactant structures and concentrations on electrical conductivity, doping level, crystallinity, morphology, and thermal stability were investigated. The re-doping step using perchloric acid (HClO₄) as a dopant was sequentially proceeded to enhance electrical conductivity. PNMA synthesized in SDBS at five times its critical micelle concentration (CMC) demonstrated the highest electrical conductivity, doping level, and thermal stability among all surfactants at identical concentrations. Scanning electron microscopy (SEM) images revealed that the PNMA particle shapes and sizes critically depended on the surfactant types and concentrations, and the doping mole ratios in the re-doping step. The highest electrical conductivity of 109.84 ± 20.44 S cm⁻¹ and a doping level of 52.45% were attained at the doping mole ratio of 50:1.

Carbon Gels-Modified TiO2: Promising Materials for Photocatalysis Applications

Carbon gels are a kind of porous organic polymer, which play pivotal roles in electrode, supercapacitor, hydrogen storage, and catalysis. Carbon gels are commonly prepared by the condensation of resorcinol and formaldehyde. The as-prepared polymers are further aged and sintered at a high temperature in an inert atmosphere to form cross-linked and intertwined porous structures. Owing to its large specific area and narrow pore size distribution, this kind of material is very appropriate for mass transfer, substrate absorption, and product desorption from the pores. In recent years, carbon gels have been discovered to function as effective hybrid materials with TiO₂ for photocatalytic applications. They could act as efficient deep-traps for photo-induced holes, which decreases the recombination probability of photo-induced carriers and lengthens their lifetime. In this mini-review, we will discuss the state-of-the-art paragon examples of carbon gels/TiO₂ composite materials applied in photo(electro)catalysis. The major challenges and gaps of its application in this field will also be emphasized.

Conducting Polymer Grafting: Recent and Key Developments

Since the discovery of conductive polyacetylene, conductive electroactive polymers are at the focal point of technology generation and biocommunication materials. The reasons why this research never stops growing, are twofold: first, the demands from the advanced technology towards more sophistication, precision, durability, processability and cost-effectiveness; and second, the shaping of conducting polymer research in accordance with the above demand. One of the major challenges in conducting polymer research is addressing the processability issue without sacrificing the electroactive properties. Therefore, new synthetic designs and use of post-modification techniques become crucial than ever. This quest is not only advancing the field but also giving birth of new hybrid materials integrating merits of multiple functional motifs. The present review article is an attempt to discuss the recent progress in conducting polymer grafting, which is not entirely new, but relatively lesser developed area for this class of polymers to fine-tune their physicochemical properties. Apart from conventional covalent grafting techniques, non-covalent approach, which is relatively new but has worth creation potential, will also be discussed. The aim is to bring together novel molecular designs and strategies to stimulate the existing conducting polymer synthesis methodologies in order to enrich its fascinating chemistry dedicated toward real-life applications.

TiO2 nanofibres decorated with green-synthesized PAu/Ag@CQDs for the efficient photocatalytic degradation of organic dyes and pharmaceutical drugs

Organic pollutants such as dyes and pharmaceutical drugs have become an environmental menace, particularly in water bodies owing to their unregulated discharge. It is thus required to develop an economically viable and environment-friendly approach for their degradation in water bodies. In this study, for the first time, we report green route-synthesized plasmonic nanostructures (PM-CQDs (where M: Au and Ag)) decorated onto TiO2 nanofibers for the treatment of toxic dye- and pharmaceutical drug-based wastewater. PM-CQDs are efficaciously synthesized using carbon quantum dots (CQDs) as the sole reducing and capping agent, wherein CQDs are derived via a green synthesis approach from Citrus limetta waste. The characteristic electron-donating property of CQDs played a key role in the reduction of Au3+ to Au0 and Ag+ to Ag0 under visible light irradiation to obtain PAu-CQDs and PAg-CQDs, respectively. Thus, the obtained CQDs, PAu-CQDs, and PAg-CQDs are loaded onto TiO2 nanofibers to obtain a PM-CQD/TiO2 nanocomposite (NC), and are further probed via transmission electron microscopy, scanning electron microscopy and UV-visible spectrophotometry. The degradation of organic pollutants and pharmaceutical drugs using methylene blue and erythromycin as model pollutants is mapped with UV-vis and NMR spectroscopy. The results demonstrate the complete MB dye degradation in 20 minutes with 1 mg mL-1 of PAu-CQD/TiO2 NC, which otherwise is 30 minutes for PAg@CQD/TiO2 dose under visible light irradiation. Similarly, the pharmaceutical drug was found to degrade in 150 minutes with PAu-CQD/TiO2 photocatalysts. These findings reveal the enhanced photocatalytic performance of the green-synthesized Au decorated with TiO2 nanofibers and are attributed to the boosted SPR effect and aqueous-phase stability of Au nanostructures. This study opens a new domain of utilizing waste-derived and green-synthesized plasmonic nanostructures for the degradation of toxic/hazardous dyes and pharmaceutical pollutants in water.

Manipulating nanoscale structure to control functionality in printed organic photovoltaic, transistor and bioelectronic devices

Printed electronics is simultaneously one of the most intensely studied emerging research areas in science and technology and one of the fastest growing commercial markets in the world today. For the past decade the potential for organic electronic (OE) materials to revolutionize this printed electronics space has been widely promoted. Such conviction in the potential of these carbon-based semiconducting materials arises from their ability to be dissolved in solution, and thus the exciting possibility of simply printing a range of multifunctional devices onto flexible substrates at high speeds for very low cost using standard roll-to-roll printing techniques. However, the transition from promising laboratory innovations to large scale prototypes requires precise control of nanoscale material and device structure across large areas during printing fabrication. Maintaining this nanoscale material control during printing presents a significant new challenge that demands the coupling of OE materials and devices with clever nanoscience fabrication approaches that are adapted to the limited thermodynamic levers available. In this review we present an update on the strategies and capabilities that are required in order to manipulate the nanoscale structure of large area printed organic photovoltaic (OPV), transistor and bioelectronics devices in order to control their device functionality. This discussion covers a range of efforts to manipulate the electroactive ink materials and their nanostructured assembly into devices, and also device processing strategies to tune the nanoscale material properties and assembly routes through printing fabrication. The review finishes by highlighting progress in printed OE devices that provide a feedback loop between laboratory nanoscience innovations and their feasibility in adapting to large scale printing fabrication. The ability to control material properties on the nanoscale whilst simultaneously printing functional devices on the square metre scale is prompting innovative developments in the targeted nanoscience required for OPV, transistor and biofunctional devices.