Conducting Polymer Layer Research Articles

Characteristics of Love Waves in a Functionally Graded Conductive Polymer Layer Perfectly Bonded with a Piezoelectric Substrate under an Impulsive Point Source

Characteristics of Love Waves in a Functionally Graded Conductive Polymer Layer Perfectly Bonded with a Piezoelectric Substrate under an Impulsive Point Source

An antifouling electrochemical sensor based on a U-shaped four-in-one peptide and poly(3,4-ethylenedioxythiophene) for vancomycin detection in fresh goat milk

Nonspecific adsorption of biomolecules (notably, proteins) and bacteria from unsterilized food may occur on sensor surfaces, which is still a challenge for food safety sensing. To achieve sensitive detection of unsterilized raw-food materials, in this study, a U-shaped four-in-one peptide with the sequence Ac-FLKLLKKLL-DOPA3-PPPPEEKDQDKEKaa that exhibited anchoring, antifouling, antibacterial, and recognition properties was designed. The peptide-modified sensor surface effectively prevented bacterial adhesion and proliferation while resisting biomolecule adsorption (signal inhibition rate as low as 0.51 % in single-protein solutions). A highly conductive polymer layer of poly(3,4-ethylenedioxythiophene) was introduced to improve the electrochemical performance before U-shaped four-in-one peptide anchoring. The proposed sensor could accurately detect vancomycin, with a wide linear range and limit of detection of 0.05–10 μg mL−1 and 2.06 ng mL−1 (S/N = 3), respectively. Satisfactory recovery rates (101.3–105.3 %) were achieved using diluted fresh goat milk.

Toward coupling across inorganic/organic hybrid interfaces: polyaniline-coated gold nanoparticles with 4-aminothiophenol as gold-anchoring moieties

AbstractThe chemical binding between metal nanoparticles and (semi-)conductive polymer layers is essential to control the (opto-)electronic properties of such hybrid materials. Current approaches that achieve a conjugated binding of organic (semi-)conductive ligands to metal nanoparticles demonstrated promising functional properties, but are based on tedious multi-step organic synthesis to incorporate the required binding moieties at the chain ends of targeted macromolecular species. Herein, we explore the pre-functionalization of gold nanoparticles with p-aminothiophenol and subsequent surfactant-assisted formation of a poly(aniline) (PANI) shell as a means to access gold/PANI core–shell-type nanoparticles with enhanced conductive properties. Controlled surface deposition of these hybrid nanoparticles is achieved via template-assisted self-assembly. For these surface-deposited nanoparticles, charge transport properties are characterized at the nanoscale by conductive atomic force microscopy measurements and show a significant conductivity increase of our core–shell particles as compared to reference particles formed by conventional surfactant-assisted PANI-shell formation. Graphical Abstract

Sealing porous carbon via surface-initiated polymerization achieves low-surface-area Si-C microparticles for Li-ion batteries

Porous Si-carbon composite architecture represents an effective design for lithium-ion batteries (LIBs) anodes. However, the high specific surface area (SSA) greatly negates cell initial Coulombic efficiency (ICE), and the function of porous carbon is challenged by practical conditions such as calendaring and high-mass-loading cycling. Here, we report a crosslinked conductive polymer layer as sealing layer for porous Si-C particles to enable high ICE and stable cycling of densified Si-anodes. A surface-initiated polymerization was adopted to form a conformal polymeric skin that can greatly lower the SSA and improve ICE of porous Si-C particles (94.8 vs. 5.7 m2/g, and 77.3% vs. 84.4%). The “sealed” Si-C particle maintains desirable intraparticle porosity to digest the volume changes during Li insertion, while the polymeric skin is key to shield off electrolyte penetration into the particles interior and to mechanically package the porous secondary particles throughout calendaring and cycling. The Si-C graphite mixtures anode (650 mAh/g) retains 70.8% capacity after 500 cycles. Adopting high-mass-loading NCM622, the full cell with stringent electrode metrics (anode at 1.2 g/cm3, NCM622 at 3.1 g/cm3, 3.4 mAh/cm2) demonstrates 65.9% capacity retention after 100 cycles. This study opens up a pathway to produce low-SSA porous anodes for practical LIBs.

Enhancing the attraction of positively charged precursors of conductive polymer poly(3,4-ethylenedioxythiophene) by anchoring sulfonate groups in cellulose fibres

Interfacial interactions are key to the development of high-performance coatings such as conductive polymer layers on fibrous materials. In this work, we present an approach of strengthening the interaction by forming ionic bonds between cellulose fibres and the conductive polymer layer by introducing a sulfonate group on cellulose fibres. The ionic bonds are formed between anchored sulfonate group and the positively charged precursor 3,4-ethylenedioxythiophene (EDOT), followed by the deposition and polymerisation of poly(3,4-ethylenedioxythiophene):sulfate (PEDOT:SO4) on the fibrous substrate surface. The conductance of the PEDOT:SO4 coated substrate with anchored sulfonate groups coated may be 1.7 times higher compared to the conductance of the unmodified cellulose substrate depending on experimental conditions. EDX measurements confirm the presence of sulfur and a shift of zeta potential at lower pH supports the evidence of the anionic anchored groups on the fibre surface. Our study therefore provides a new way to enhance the affinity of fibrous cellulose materials towards polymer conductive coatings.

Ultrasensitive detection of chloramphenicol in water using functionalized polymers with an aluminium organic framework

Metal-Organic Frameworks (MOFs) are extensively used as electrode material in various sensing applications due to their efficacious porous nature and tunable properties. However, pristine MOFs lack conductive attributes that hinder their wide usage in electrochemical applications. Electropolymerization of several aromatic monomers has been a widely used strategy for preparing conducting electrode materials for various sensing applications in the past decades. Herein, we report a similar approach by employing the electropolymerization method to create a functional polymer layer to enhance the sensitivity of an Aluminium Organic Framework (DUT-4) for the selective detection of Chloramphenicol (CAP) antibiotic in aqueous environment. The combined strategy using the conducting polymer layer with the porous Al MOF provides surpassing electrochemical performance for sensing CAP with regard to the very low detection limit (LOD = 39 nM) and exceptionally high sensitivity (11943 μA mM−1 cm−2). In addition, the fabricated sensor exhibited good selectivity, reproducibility and stability. The developed method was successfully evaluated in various real samples including lake water and river water for CAP detection with good recovery percentages even at lower concentrations.

Optimization of a Conductive Polymer Layer on MOF-Derived Carbon Materials for High-Performance Supercapacitor Electrodes

Optimization of a Conductive Polymer Layer on MOF-Derived Carbon Materials for High-Performance Supercapacitor Electrodes

Ugradnja grafenova oksida u sloj vodljivog polimera i naknadna elektrokemijska redukcija

U ovom radu provedena je elektrokemijska sinteza poli(3,4-etilendioksitiofena) (PEDOT) sloja i kompozitnog sloja PEDOT/grafenov oksid (GO). Sinteza je provedena iz elektrolita koji je sadržavao 3,4-etilendiokstiofen (EDOT) u otopini poli(natrij 4-stirensulfonata) (PSS) ili smjesi PSS/GO. Rezultati su pokazali da se dobra pseudokapacitivna svojstva PEDOT slojeva postižu elektrokemijskom sintezom kod 1,00 V te pri trajanju sinteze do 600 s. Za optimalnu koncentraciju PSS određena je vrijednost od 0,01 mol dm<sup>–3</sup>. Ugradnja GO-a u strukturu vodljivog polimera dokazana je rezultatima UV/Vis spektrofotometrije. Radna elektroda sa slojem PEDOT/GO negativno je polarizirana pri −1,4 V u 0,1 mol dm<sup>–3</sup> otopini KCl. Tim postupkom GO je preveden u vodljivi oblik odnosno reducirani grafenov oksid. Poboljšana pseudokapacitivna svojstva ukazala su na uspješno provedenu elektrokemijsku redukciju GO-a u sloju vodljivog polimera. Sintetizirani vodljivi polimeri ispitani su metodom cikličke voltametrije.

An electrografted monolayer of polyaniline as a tuneable platform for a glucose biosensor.

Polyaniline (PANI), a nanostructured conducting polymer, has shown significant potential in optical and bioelectrochemical devices. However, its performance and stability on various substrates are hindered by weak adhesion to the surface. In this study, a strongly adherent polyaniline conducting polymer layer with a thickness of five nanometers was electrografted onto an initiating monolayer on gold and tin-doped indium oxide substrates. These electrografted monolayers consist of vertically oriented fully oxidized-protonated (pernigraniline salt) and deprotonated (pernigraniline base) forms of polyaniline. The monolayer exhibits pH-dependent colour changes and it is suitable for enzyme compatibility. In light of these findings, we have developed and characterized an electrochemical glucose biosensor based on the monolayer of polyaniline on a gold electrode. The biosensor utilizes glucose oxidase as the biorecognition element for the selective detection of glucose concentrations in real blood plasma samples.

Beyond Flexibility: Transparent Silver Nanowire Electrodes on Patterned Surfaces for Reconfigurable Devices

Silver nanowire (AgNW) emerges as a next‐generation transparent electrode material, offering enhanced flexibility and ease of fabrication compared to traditional transparent electrode materials, such as metallic oxides. In the previous research, the uniform deposition of AgNWs on flat surfaces is demonstrated, exhibiting high conductivity, flexibility, and excellent transmittance. However, the evolution of nano‐electronics technology necessitates the fabrication of transparent electrodes on non‐flat surfaces, such as those found in zenithal bistable devices and reconfigurable Fresnel lenses. In this study, a method is proposed to deposit AgNW material on uneven surfaces using the Mylar‐bar‐coating method, with a polyvinyl chloride (PVC)‐based Fresnel lens serving as the target surface. Additionally, the impact of varying AgNW suspension concentrations on transmittance and sheet resistance is investigated. To further reduce sheet resistance, a layer of conductive polymer, poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), is deposited on the AgNWs. The measurements reveal that a 2 mg mL−1 sample exhibits a sheet resistance of 187.83 W W−1 with 87.4% transmittance at 550 nm. After the PEDOT:PSS process, the sheet resistance decreases to 122.84 W W−1 with 84.4% transmittance. In this research, a solution is offered for the uniform deposition of AgNWs on patterned surfaces, paving the way for the next generation of optical devices.

Dielectric optical waveguide fabricated on a transparent substrate

Transparent glass substrates are routinely used in the fabrication of metasurfaces, augmented reality (AR), virtual reality (VR), and holographic devices. While readily compatible with photolithographic patterning methods, when electron beam (E-Beam) techniques are used, field distortion and stitching errors can result due to the buildup of charge. A common approach to overcome this issue is to deposit a thin conductive polymer layer (E-Spacer). However, if high-voltage E-Beam is used to achieve nano-features, the polymer conductivity is not sufficient. We have shown that by using chromium (Cr) as an overcoating conductive layer on the resist, we can achieve accurate and seamless patterning in multiple writing fields and used the method to fabricate on-chip Si3N4 waveguides on SiO2. This technique has the potential to enable the fabrication of large-scale integrated photonic systems on transparent or dielectric substrates.

Conductive Polymer-Based Interactive Shelving System for Real-Time Inventory Management.

Stockouts constitute a major challenge in the retail industry. Stockouts are caused by errors related to manual stockkeeping and by the misplacement of items on shelves. Such errors account for up to 4% of lost sales. Real-time inventory management systems for misplaced items or missing stock detection in retail stores are limited. Accordingly, a conductive polymer-based interactive shelving system for real-time inventory management is developed. The system comprises an 80 × 48 sensor array fabricated by screen-printing a piezoresistive carbon-based conductive polymer layer onto gold interdigitated electrodes deposited on a flexible substrate. Each sensing pixel has dimensions of 5 mm × 5 mm and a sensing area of 4 mm × 4 mm. The sensor mat can detect the shape and weight features of stockkeeping units (SKUs), which can then be analyzed by a TensorFlow model for SKU identification. The developed system is characterized for functional resistance range, uniformity, repeatability, and durability. The accuracy of SKU identification achieved using shape features only and the accuracy of SKU identification achieved using both shape and weight features is 95% and 99.2%, respectively. The key novelty of the work is the development of a deep learning-embedded interactive smart shelving system for retail inventory management by using the shape and weight features of SKU. Also, the developed system helps to detect the SKU if they are stacked one over the other. Furthermore, multiple sensor mats implemented on various shelves in a retail store can be modularized and integrated for monitoring under the control of a single PC. Accordingly, the proposed retail inventory tracking system can facilitate the development of automated "humanless" shops.

Induced Wettability Switch in Thin Films of Conductive Polymer Coatings Exhibiting Hydrophobic/Hydrophilic Interactions.

The hydrophobic/hydrophilic character of some conductive polymer (CP) coatings can be switched in the function of the working conditions of these adaptive materials. We studied the influence of electrical stimuli and intrinsic physical characteristics (nature of the polymerizable core, dopants, the droplet dimension and physical properties, surface roughness, etc.) on the CP wettability. A simulation strategy was developed for determining the contact angle (CA) of a liquid droplet on a CP layer with roughness. The method was tested for new reported CP composites, but with new dopants. The results indicate that the influences on the material wettability are correlated, and in practice, modification of more than one parameter converges to a wanted behavior of the material. E.g., the CP porous film of poly(3-hexylthiophene) (P3HT) + [6,6]-phenyl-C61-butyricacid-methyl-ester (PCBM) changes its wettability at voltages of up to 26 V, but if doping ions are inserted and the roughness geometry is modified, the voltage decreases twice. Our multi-parametrical study points out that the polymer wettability type is driven by the voltage, but this effect is tuned differently by each internal parameter. The thin films' effect and the dopants (in-situ and ex-situ) significantly decrease the actuation voltage. We also illustrated that the wettability type does not change for specific sets of parameters.

Development of Smart Potentiometric Sensors Covered with Non-Biofouling Layer for Detection of Early Stages of Inflammatory Processes Around Joint Replacements

One of the problems occurring after the joint replacement is connected with the post-surgery infections which are caused by bacteria that form biofilms on surfaces and are referred to as biofilm-related infections (BRI). It is also worth noting that due to the bioresponse, strong pathophysiological changes in the microclimate of an affected surface occur (decrease in pH, formation of various reactive oxygen species (ROS), depletion of Fe ions, and increase in the concentration of Ca ions). In this work we have prepared a robust selective potentiometric sensor of ROS and pH sensor for the detection of pH changes caused by sterile inflammation and bacterial and fungal infections. The ROS sensor consists of a conductive polymer layer based on polythiophene with an incorporated porphyrin-metal complex that potentiometrically detects the presence of ROS (H2O2 and ClO– ions). This sensor is connected by the covalent bonds with a non-biofouling layer of poly(2-methyl-2-oxazoline), which works as a bio-compa­tibilizer. It was shown that the potentiometric sensor shows a rapid response to hydrogen peroxide, does not record any interference with bovine serum albumin as a model serum protein, and is able to fully reversibly detect ROS with a linear response within a wide range of biological relevant concentrations (from 0.05 μM to 10 μM). The sensing electrode based on polyaniline and poly(2-methyl-2-oxazoline) on a titanium alloy support was developed for the potentiometric detection of peri-implant pH changes to enable early detection of the aforementioned pathologies. The developed electrodes show the changing of pH in the range between 5 and 8 for the individual pathogenic bacteria or pathogenic yeast, with a Nernstian slope of −59.6/pH.

Spherical Sulfur-Infiltrated Carbon Cathode with a Tunable Poly(3,4-ethylenedioxythiophene) Layer for Lithium-Sulfur Batteries.

Li-S batteries have received significant attention owing to their high energy density, nontoxicity, low cost, and eco-friendliness. However, the dissolution of lithium polysulfide during the charge/discharge process and its extremely low electron conductivity hinder practical applications of Li-S batteries. Herein, we report a sulfur-infiltrated carbon cathode material with a spherical morphology and conductive polymer coating. The material was produced via a facile polymerization process that forms a robust nanostructured layer and physically prevents the dissolution of lithium polysulfide. The thin double layer composed of carbon and poly(3,4-ethylenedioxythiophene) provides sufficient space for sulfur storage and effectively prevents the elution of polysulfide during continuous cycling, thereby playing an essential role in increasing the sulfur utilization rate and significantly improving the electrochemical performance of the battery. Sulfur-infiltrated hollow carbon spheres with a conductive polymer layer demonstrate a stable cycle life and reduced internal resistance. The as-fabricated battery demonstrated an excellent capacity of 970 mA h g-1 at 0.5 C and a stable cycle performance, exhibiting ∼78% of the initial discharge capacity after 50 cycles. This study provides a promising approach to significantly improve the electrochemical performance of Li-S batteries and render them as valuable and safe energy devices for large-scale energy storage systems.

Smart fire-safety cotton fabric with fire-warning capability via dual working mechanisms

Increasing demand for fire safety has aroused the enthusiasm of researchers for exploring early-stage fire-warning materials. Herein, an early-stage fire-warning cotton fabric (denoted as CF-CP-FR) was designed with a two-layered structure: conducting polymer layer and flame-retardant layer, through in-situ chemical oxidation polymerization of polypyrrole (PPy) and dip coating of the compound of montmorillonite and ammonium polyphosphate (MMT@APP), respectively. Based on the thermoelectric effect of the PPy, CF-CP-FR was endowed with accurate temperature sensing capability below 100 °C. When encountering fire, CF-CP-FR showed excellent fire-warning response as fast as 1.0 s and displayed repeatable fire-warning capability under the protection of the MMT@APP. Via the mechanism of thermo-induced resistance change, the coated cotton fabric could also trigger the fire warning circuit at ca. 2.0 s. Meanwhile, the flame retardancy and thermal stability of CF-CP-FR were significantly enhanced, owing to the synergetic effect of MMT and APP. This work is promising in fabricating multifunctional clothing with efficient fire safety and smart fire-warning capability.

Resistance measurements for the wireless evaluation of electrocatalytic activity

Electrochemical water-splitting is one of the key reactions that lay the basis for the storage of energy produced by sustainable sources. The development of fast methods to evaluate the electrocatalytic activity of electrode materials with respect to the oxidation and reduction of water are therefore required to make further progress in this exciting field of research. Here, we present a novel method based on bipolar electrochemistry, which allows evaluating the electrocatalytic activity of a material towards hydrogen and oxygen evolution (HER and OER, respectively) with a single device. This method is based on the capability of a conducting polymer layer to behave as a variable-resistance switch as a function of its electrochemical doping. This approach was used to evaluate the electrocatalytic activity of Au, Pt and Ni surfaces towards HER and OER in terms of the half-wave electric field, ε1/2, obtained during the insulating/conducting transition of poly-3,4-ortho-xylen-dioxythiophene (PXDOT). The trends of ε1/2 variations are in agreement with data reported with classical electrochemical methods. In this work, we developed an easy and straightforward method to evaluate the electrocatalytic activity of electrode materials for water-splitting.

Water-Borne Carbonaceous Coatings on Conducting Polymer-Modified Cotton Fabrics To Attenuate Electromagnetic Radiation

Textile-based shielding materials are gaining much importance for electromagnetic interference (EMI) shielding because of their increased flexibility compared to most existing materials. The multilayer-like architectures realized by coating textiles can be used strategically to enhance the attenuation of microwaves. Herein, we report a water-borne conductive coating capable of shielding both EM and UV radiation with good thermal stability for potential applications as smart textiles. This work tries to understand the effect of different textile pre-treatments to maximize the enhancements in properties. Cotton fabrics were initially subjected to in situ polymerization of aniline and pyrrole and subsequently coated with a carbonaceous layer containing graphene nanoplatelets and carbon nanofibers on both the sides. It was seen that both the conducting polymer layer and the carbonaceous coating work in tandem to enhance the thermal stability, UV blocking, and EMI shielding. The coated fabrics shows a shielding effectiveness of −22 dB at a thickness of 1.2 mm over a wide frequency range of 2.6–26.5 GHz, a limiting oxygen index of 26%, and remarkable UV-blocking properties with a blocking of 99.99%. Both the coating and the pre-treatment do not alter the fabric’s wettability─the surface remains hydrophilic. The coating rendered the fabric with conductivity values showing a four-order jump from the control sample. The samples show a shielding effectiveness of −22 dB, accounting for more than 99% of the incident radiation being attenuated. The attenuation happens via an absorption-dominated mechanism. The coated textile exhibits excellent heat dissipation properties, with temperatures dropping from as high as 147 to 41 °C in just 60 s.

Using electrochemical impedance spectroscopy to study biofilm growth in a 3D-printed flow cell system

Biofilm contamination is a widespread issue that can occur anywhere when organisms attach to surfaces in the presence of water. In industrial environments, formation of biofilms can lead to component failure, material degradation, and biofouling or spoilage, which collectively come with significant economic costs. Microfabricated electrochemical impedance spectroscopy (EIS) sensors have emerged as a promising tool for monitoring biofilm as EIS sensors capture information about biofilm growth autonomously in real-time; however, sensors suffer from drift, and the technique lacks temporal interpretation of dynamic biofilm processes. In this work, microfabricated sensors featuring gold micro-interdigitated electrodes (μIDEs) were modified with an electrically conductive polymer layer resulting in EIS measurement variability that was significantly reduced compared to unmodified sensors, and enabled highly stable, time-resolved EIS measurements. EIS characterization of Pseudomonas aeruginosa biofilm in parallel with high-resolution confocal laser scanning microscopy (CLSM) was performed using a novel 3D-printed flow cell system, resulting in distinct changes to EIS data corresponding with consistent biofilm growth. We have shown that EIS microsensors can detect four stages of biofilm: (i) initial biofilm attachment to the sensor substrate, (ii) early-stage irreversible biofilm proliferation characterized by sparse biofilm coverage, (iii) mature biofilm detection characterized by uniform biofilm coverage, and (iv) changes due to detachment and regrowth of biofilm.

Nanocomposite Materials based on Metal Nanoparticles for the Electrochemical Sensing of Neurotransmitters

Neurotransmitters (NTs) are known as endogenous chemical messengers with important roles in the normal functioning of central and peripheral nervous systems. Abnormal levels of certain NTs, such as dopamine, serotonin and epinephrine, have been linked with several neurodegenerative diseases (such as Alzheimer’s disease, Parkinson’s disease and Huntington’s disease). To date, various strategies have been employed for the quantitative determination of NTs, and nanocomposite materials based on conducting polymers and metal nanoparticles constitute a cornerstone for the development of electrochemical sensors with low costs, stability, fast response rates and high selectivity and sensitivity. The preparation and analytical applications of nanocomposite materials based on metal nanoparticles in the electrochemical sensing of neurotransmitters are discussed in this paper. Recent developments in the electrochemical sensing of neurotransmitters are also discussed with emphasis on the benefits brought by metal nanoparticles in improving the sensitivity of the analytical measurements. The electrochemical synthesis methods for the in situ generation of metal nanoparticles within conducting polymer layers are reviewed. The analytical applications of the nanocomposite-sensing materials towards the detection of neurotransmitters such as dopamine, epinephrine and serotonin are discussed in terms of detection and quantification limits, linear response range, sensitivity and selectivity.