High-Performance Flexible All-Solid-State Supercapacitor from Large Free-Standing Graphene-PEDOT/PSS Films

Chirality-enhanced 2D conductive polymer for flexible electronics and chiral sensing applications

Chiral two-dimensional (2D) conductive polymers, encompassing chiral, 2D, flexible, and conductive properties, constitute a novel class of material that remains largely unexplored. The infusion of chirality into 2D conductive polymers taps into the unique characteristics associated with chirality, presenting opportunities to enhance or tailor the electronic, optical, and structural properties of materials for specific technological applications. In this study, we synthesized a chiral 2D PEDOT:PMo11V nanofilm through interfacial polymerization, effectively integrating a chiral monolayer, conductive polymer, and inorganic cluster. The inclusion of inorganic cluster serves to enhance the conductivity of the resulting chiral nanofilm. Furthermore, we demonstrated the chiral nanofilm as a capable electrochemical sensor for detecting drug enantiomers. The inherent flexibility of the chiral nanofilm also lays the groundwork for the development of chiral flexible/wearable devices.

Hybrid and Asymmetric Supercapacitors: Achieving Balanced Stored Charge across Electrode Materials

An electrochemical capacitor configuration extends its operational potential window by leveraging diverse charge storage mechanisms on the positive and negative electrodes. Beyond harnessing capacitive, pseudocapacitive, or Faradaic energy storage mechanisms and enhancing electrochemical performance at high rates, achieving a balance of stored charge across electrodes poses a significant challenge over a wide range of charge-discharge currents or sweep rates. Consequently, fabricating hybrid and asymmetric supercapacitors demands precise electrochemical evaluations of electrode materials and the development of a reliable methodology. This work provides an overview of fundamental aspects related to charge-storage mechanisms and electrochemical methods, aiming to discern the contribution of each process. Subsequently, the electrochemical properties, including the working potential windows, rate capability profiles, and stabilities, of various families of electrode materials are explored. It is then demonstrated, how charge balancing between electrodes falters across a broad range of charge-discharge currents or sweep rates. Finally, a methodology for achieving charge balance in hybrid and asymmetric supercapacitors is proposed, outlining multiple conditions dependent on loaded mass and charge-discharge current. Two step-by-step tutorials and model examples for applying this methodology are also provided. The proposed methodology is anticipated to stimulate continued dialogue among researchers, fostering advancements in achieving stable and high-performance supercapacitor devices.

Multiscale Structural Design of 2D Nanomaterials-based Flexible Electrodes for Wearable Energy Storage Applications

2D nanomaterials play a critical role in realizing high-performance flexible electrodes for wearable energy storge devices, owing to their merits of large surface area, high conductivity and high strength. The electrode is a complex system and the performance is determined by multiple and interrelated factors including the intrinsic properties of materials and the structures at different scales from macroscale to atomic scale. Multiscale design strategies have been developed to engineer the structures to exploit full potential and mitigate drawbacks of 2D materials. Analyzing the design strategies and understanding the working mechanisms are essential to facilitate the integration and harvest the synergistic effects. This review summarizes the multiscale design strategies from macroscale down to micro/nano-scale structures and atomic-scale structures for developing 2D nanomaterials-based flexible electrodes. It starts with brief introduction of 2D nanomaterials, followed by analysis of structural design strategies at different scales focusing on the elucidation of structure-property relationship, and ends with the presentation of challenges and future prospects. This review highlights the importance of integrating multiscale design strategies. Finding from this review may deepen the understanding of electrode performance and provide valuable guidelines for designing 2D nanomaterials-based flexible electrodes.

Advances in Printed Electronic Textiles

Electronic textiles (e-textiles) have emerged as a revolutionary solution for personalized healthcare, enabling the continuous collection and communication of diverse physiological parameters when seamlessly integrated with the human body. Among various methods employed to create wearable e-textiles, printing offers unparalleled flexibility and comfort, seamlessly integrating wearables into garments. This has spurred growing research interest in printed e-textiles, due to their vast design versatility, material options, fabrication techniques, and wide-ranging applications. Here, a comprehensive overview of the crucial considerations in fabricating printed e-textiles is provided, encompassing the selection of conductive materials and substrates, as well as the essential pre- and post-treatments involved. Furthermore, the diverse printing techniques and the specific requirements are discussed, highlighting the advantages and limitations of each method. Additionally, the multitude of wearable applications made possible by printed e-textiles is explored, such as their integration as various sensors, supercapacitors, and heated garments. Finally, a forward-looking perspective is provided, discussing future prospects and emerging trends in the realm of printed wearable e-textiles. As advancements in materials science, printing technologies, and design innovation continue to unfold, the transformative potential of printed e-textiles in healthcare and beyond is poised to revolutionize the way wearable technology interacts and benefits.

Enhancing electrochemical properties of a two-dimensional zeolitic imidazole framework by incorporating a conductive polymer for dopamine detection

The zeolitic imidazole framework with a leaf-shaped morphology (ZIF-L) has a wide range of promising applications in gas storage, battery materials, catalytic reactions, and optoelectronic devices due to its planar leaf-like structure and large surface area. However, the low conductivity, weak catalytic activity, and poor stability in the water dielectric medium of ZIF-L limit its further practical application. To solve these problems, we added the conductive polymer heterocyclic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to ZIF-L for the sensitive detection of dopamine (DA). The synthesized composite ZIF-L/PEDOT:PSS (ZIF-L/PEDOT) not only retained the surface morphology of ZIF-L but also exhibited excellent electrochemical properties. The higher electrical conductivity of ZIF-L/PEDOT than that of ZIF-L was due to the enhanced electron transfer at the interface between ZIF-L and PEDOT:PSS. As a result, we developed an electrochemical biosensor based on the ZIF-L/PEDOT composite, which has a limit of detection of 7 nM for DA and a wide linear range from 25 nM to 500 μM. Furthermore, the current drop was negligible after 28 days, proving that the biosensor has excellent stability. Based on the above-mentioned outstanding performance, the ZIF-L/PEDOT-based biosensor was successfully used to detect DA in human serum samples. These results demonstrated that ZIF-L/PEDOT is expected to play an essential role in disease detection.

Modern Developments for Textile-Based Supercapacitors

Smart textiles are transforming the future of wearable technology, and due to that, there has been a great deal of new research looking for alternative energy storage. Supercapacitors offer high discharge rates, flexibility, and long life cycles and can be integrated fully into a textile. Optimization of these new systems includes utilizing electrically conductive materials, employing successful electrostatic charge and/or faradaic responses, and fabricating a textile-based energy storage system without disrupting comfort, washability, and life cycle. This paper examines recent developments in fabrication methods and materials used to create textile supercapacitors and what challenges still remain.

Bipolar Electrochemical Stimulation Using Conducting Polymers for Wireless Electroceuticals and Future Directions

Electrochemistry has become a powerful strategy to modulate cellular behavior and biological activity by manipulating electrical signals. Subsequent electrical stimulus-responsive conducting polymers (CPs) have advanced traditional wired electrochemical stimulation (ES) systems and developed wireless cell stimulation systems due to their electroconductivity, biocompatibility, stability, and flexibility. Bipolar electrochemistry (BPE), i.e., wireless electrochemistry, offers an effective pathway to modify wired ES systems into a desirable contactless mode, turning out a potential technique to offer fundamental insights into neural cell stimulation and neural network formation. This review commences with a brief discussion of the BPE technique and also the advantages of a bipolar electrochemical stimulation (BPES) system compared to traditional wired ES systems and other wireless ES systems. Then, the BPES system is elucidated through four aspects: the benefits of BPES, the key factors to establish BPES platforms for cell stimulation, the limits/barriers to overcome for current rigid materials in particular metals-based systems, and a brief overview of the concept proved by CPs-based systems. Furthermore, how to refine the existing BPES system from materials/devices modification that combine CP compositions with 3D fabrication/bioprinting technologies is elaborately discussed as well. Finally, the review ends together with future research directions, picturing the potential of BPES system in biomedical applications.

Smart Electronic Textile-Based Wearable Supercapacitors

Electronic textiles (e-textiles) have drawn significant attention from the scientific and engineering community as lightweight and comfortable next-generation wearable devices due to their ability to interface with the human body, and continuously monitor, collect, and communicate various physiological parameters. However, one of the major challenges for the commercialization and further growth of e-textiles is the lack of compatible power supply units. Thin and flexible supercapacitors (SCs), among various energy storage systems, are gaining consideration due to their salient features including excellent lifetime, lightweight, and high-power density. Textile-based SCs are thus an exciting energy storage solution to power smart gadgets integrated into clothing. Here, materials, fabrications, and characterization strategies for textile-based SCs are reviewed. The recent progress of textile-based SCs is then summarized in terms of their electrochemical performances, followed by the discussion on key parameters for their wearable electronics applications, including washability, flexibility, and scalability. Finally, the perspectives on their research and technological prospects to facilitate an essential step towards moving from laboratory-based flexible and wearable SCs to industrial-scale mass production are presented.

Flexible Solid Supercapacitors of Novel Nanostructured Electrodes Outperform Most Supercapacitors

Sustainable and scalable fabrication of electrode materials with high energy and power densities is paramount for the development of future electrochemical energy storage devices. The electrode material of a supercapacitor should have high electrical conductivity, good thermal and chemical stability, and a high surface area per unit volume (or per unit mass). Researchers have made great efforts to use two-dimensional (2D) nanomaterials, but the separated 2D plates are re-stacked during processing for electrode fabrication, impeding the transport of ions and reducing the number of active sites. We developed a novel process for manufacturing thin and flexible electrodes using a 2D material (MXene,Ti₃AlC₂) and a conducting polymer (poly(3,4-ethylenedioxythiophene), PEDOT). Because the PEDOT layer is electrochemically synthesized, it does not contain the activator poly(styrene sulfonate). The electrospray deposition technique solves the restacking problem and facilitates the infilling of the gel electrolyte by forming a highly porous open structure across the entire electrode. In the PEDOT/MXene multilayered electrode, the double-layer capacitance increased substantially because of a dramatic increase in the number of accessible sites through the MXene layer. Although applied to solid supercapacitors, these new supercapacitors outperform most aqueous electrolyte supercapacitors as well as other solid supercapacitors.

Design and Testing of Autonomous Chargeable and Wearable Sweat/Ionic Liquid-Based Supercapacitors

This work demonstrates ionic liquid electrolyte-inscribed sweat-based dual electrolyte functioning supercapacitors capable of self-charging through sweat electrolyte function under a non-enzymatic route. The supercapacitor electrodes are fabricated from TREN (tris(2-aminoethyl)amine), poly-3,4-ethylenedioxythiophene, and a graphene oxide mixture with copper-mediated chelate, and this polymer-GO-metal chelate film can produce excellent energy harvest/storage performance from a sweat and ionic liquid integrated electrolyte system. The fabricated device is specifically designed to reduce deterioration using a typical planar structure. In the presence of sweat with ionic liquid, the dual electrolyte mode supercapacitor exhibits a maximum areal capacitance of 3600 mF cm^-2 , and the energy density is 450 mWhcm^-2 , which is more than 100 times greater than that from previously reported supercapacitors. The supercapacitors were fabricated/attached directly to textile fabrics as well as ITO-PET (Indium tin oxide (ITO)-polyethylene terephthalate (PET) film to study their performance on the human body during exercise. The self-charging performance with respect to sweat wetting time for the sweat@ionic liquid dual electrolyte showed that the supercapacitor performed well on both fabric and film. These devices exhibited good response for pH effect and biocompatibility, and as such present a promising multi-functional energy system as a stable power source for next-generation wearable smart electronics.

PEDOT: PSS promotes neurogenic commitment of neural crest-derived stem cells

Poly (3,4-ethylendioxythiophene) polystyrene sulphonate (PEDOT:PSS) is the workhorse of organic bioelectronics and is steadily gaining interest also in tissue engineering due to the opportunity to endow traditional biomaterials for scaffolds with conductive properties. Biomaterials capable of promoting neural stem cell differentiation by application of suitable electrical stimulation protocols are highly desirable in neural tissue engineering. In this study, we evaluated the adhesion, proliferation, maintenance of neural crest stemness markers and neurogenic commitment of neural crest-derived human dental pulp stem cells (hDPSCs) cultured on PEDOT:PSS nanostructured thin films deposited either by spin coating (SC-PEDOT) or by electropolymerization (ED-PEDOT). In addition, we evaluated the immunomodulatory properties of hDPSCs on PEDOT:PSS by investigating the expression and maintenance of the Fas ligand (FasL). We found that both SC-PEDOT and ED-PEDOT thin films supported hDPSCs adhesion and proliferation; however, the number of cells on the ED-PEDOT after 1 week of culture was significantly higher than that on SC-PEDOT. To be noted, both PEDOT:PSS films did not affect the stemness phenotype of hDPSCs, as indicated by the maintenance of the neural crest markers Nestin and SOX10. Interestingly, neurogenic induction was clearly promoted on ED-PEDOT, as indicated by the strong expression of MAP-2 and β—Tubulin-III as well as evident cytoskeletal reorganisation and appreciable morphology shift towards a neuronal-like shape. In addition, strong FasL expression was detected on both undifferentiated or undergoing neurogenic commitment hDPSCs, suggesting that ED-PEDOT supports the expression and maintenance of FasL under both expansion and differentiation conditions.

Recent Studies on Dispersion of Graphene-Polymer Composites

Graphene is an excellent 2D material that has extraordinary properties such as high surface area, electron mobility, conductivity, and high light transmission. Polymer composites are used in many applications in place of polymers. In recent years, the development of stable graphene dispersions with high graphene concentrations has attracted great attention due to their applications in energy, bio-fields, and so forth. Thus, this review essentially discusses the preparation of stable graphene-polymer composites/dispersions. Discussion on existing methods of preparing graphene is included with their merits and demerits. Among existing methods, mechanical exfoliation is widely used for the preparation of stable graphene dispersion, the theoretical background of this method is discussed briefly. Solvents, surfactants, and polymers that are used for dispersing graphene and the factors to be considered while preparing stable graphene dispersions are discussed in detail. Further, the direct applications of stable graphene dispersions are discussed briefly. Finally, a summary and prospects for the development of stable graphene dispersions are proposed.

Latex-Based Polystyrene Nanocomposites with Non-Covalently Modified Carbon Nanotubes

We prepared electrically conductive polystyrene (PS) nanocomposites by incorporating non-covalently surface-modified carbon nanotubes (CNTs) with hydrophilic polymers such as polydopamine (PDA) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Further, ethylene glycol (EG) was introduced as a second dopant to improve the electrical properties of the nanocomposites prepared with PEDOT:PSS-wrapped CNTs. All conductive PS nanocomposites were prepared through latex-based process, and the morphology and properties of the nanocomposites were investigated. The electrical properties of the nanocomposites with PEDOT:PSS-wrapped CNTs were better than those of the nanocomposites with PDA-coated CNTs owing to the conducting nature of PEDOT:PSS, although the dispersions of both types of modified CNTs in the PS matrix were excellent, as evidenced by morphology and rheology. In the case of PEDOT:PSS modification, the electrical properties of the nanocomposites with EG-doped PEDOT:PSS-wrapped CNTs were superior to those of the nanocomposites without EG treatment.

Vapor phase polymerization for electronically conductive nanopaper based on bacterial cellulose/poly(3,4-ethylenedioxythiophene)

Eco-friendly conductive polymer nanocomposites have garnered attention as an effective alternative for conventional conductive nanocomposites. Here, we report the fabrication and optimization of flexible, self-standing, and conductive bacterial cellulose/poly(3,4-ethylene dioxythiophene) (BC/PEDOT) nanocomposites using the vapor phase polymerization (VPP) method. Eco-friendly bacterial cellulose (BC) is used as a flexible matrix, and the highly conductive PEDOT polymer is introduced into the BC matrix to achieve electronic conductivity. We demonstrate that vapor phase polymerized BC/PEDOT composites exhibit more than 10 times lower sheet resistance (18 Ω/square) compared to solution polymerized BC/PEDOT (188 Ω/square). The resultant BC/PEDOT fabricated could be bent up to 100 times and completely rolled up without a notable decrease in electronic performance. Moreover, bent BC/PEDOT films enable operation of a green light-emitting diode (LED) light, indicating the flexibility and stability of conductive BC/PEDOT films. Overall, this study suggests a strategy for the development of eco-friendly, flexible, and conductive nanocomposite films.

One-Pot Hydrothermal Synthesis of Solution-Processable MoS2/PEDOT:PSS Composites for High-Performance Supercapacitors

It is challenging to hydrothermally synthesize solution-processable MoS₂, as the strong van der Waals force between MoS₂ nanosheets induces self-assembly of agglomerates. Here, we introduce poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) into the precursor to impede aggregate formation in the hydrothermal process. A hybrid MoS₂/PEDOT:PSS (MP) hydrogel is formed due to the electrostatic interactions between the negatively charged MoS₂ and positively charged PEDOT chains. This hydrogel can be easily dispersed in water for subsequent solution processing such as vacuum filtration to form free-standing flexible films or extrusion 3D printing to create novel patterns. The MP film with a fracture strength of 18.59 MPa displays excellent electrochemical performance in both aqueous Na₂SO₄ electrolyte (474 mF cm^-2) and solid-state PVA-H₃PO₄ electrolyte (360 mF cm^-2). Flexibility and robustness can be evidenced by high capacitance retention rates of 94 and 89% after being repeatedly bent to 180° for 5000 cycles in aqueous and solid-state electrolytes, respectively.

Interstitial boron-doped mesoporous semiconductor oxides for ultratransparent energy storage

Realizing transparent and energy-dense supercapacitor is highly challenging, as there is a trade-off between energy storing capability and transparency in the active material film. We report here that interstitial boron-doped mesoporous semiconductor oxide shows exceptional electrochemical capacitance which rivals other pseudocapacitive materials, while maintaining its transparent characteristic. This improvement is credited to the robust redox reactions at interstitial boron-associated defects that transform inert semiconductor oxides into an electrochemically active material without affecting its transparency. By precisely tuning the level of doping, the pseudocapacitive reactivity of these materials is optimized, resulting in a volumetric capacitance up to 1172 F cm-3. Attributing to such efficient charge storage utilization on the active film, the fabricated transparent supercapacitor delivers a maximum areal energy density of 1.36 × 10-3 mWh cm-2 that is close to those of conventional pseudocapacitive materials, with nearly 100% capacitance retention after 15000 cycles and ultrahigh transparency (up to 85% transmittance at 550 nm). In addition, this device shows excellent durability and flexibility with multiple optional outputs, demonstrating the potential as a transparent energy supply in planar electronics.

Triaxial Carbon Nanotube/Conducting Polymer Wet-Spun Fibers Supercapacitors for Wearable Electronics

The ubiquity of wearables, coupled with the increasing demand for power, presents a unique opportunity for nanostructured fiber-based mobile energy storage systems. When designing wearable electronic textiles, there is a need for mechanically flexible, low-cost and light-weight components. To meet this demand, we have developed an all-in-one fiber supercapacitor with a total thickness of less than 100 μm using a novel facile coaxial wet-spinning approach followed by a fiber wrapping step. The formed triaxial fiber nanostructure consisted of an inner poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) core coated with an ionically conducting chitosan sheath, subsequently wrapped with a carbon nanotube (CNT) fiber. The resulting supercapacitor is highly flexible, delivers a maximum energy density 5.83 Wh kg-1 and an extremely high power of 1399 W kg-1 along with remarkable cyclic stability and specific capacitance. This asymmetric all-in-one fiber supercapacitor may pave the way to a future generation of wearable energy storage devices.

High-performance flexible asymmetric supercapacitor based on rGO anode and WO3/WS2 core/shell nanowire cathode

Flexible smart electronics require their energy storage device to be flexible in nature. Developing high-performance flexible energy storage devices require direct integration of electrode active materials on current collectors to satisfy the high electronic/ionic conductivity and long-term durability requirements. Herein, we develop a flexible all-solid-state asymmetric supercapacitor comprised of reduced graphene oxide (rGO) and core/shell tungsten trioxide/tungsten disulfide (WO₃/WS₂) nanowire based electrodes. The electrodes synthesized via electrochemical deposition and chemical vapor deposition avoided the necessity to use non-conductive binders and offered excellent cyclic stability. The structural integrity provided by the rGO and WO₃/WS₂ electrodes facilitated excellent electrochemical stability with capacitance retention of 90% and 100% after 10 000 charge-discharge cycles, respectively. An all-solid-state device provides a voltage window of 1.5 V and more than 70% capacitance retention after 10 000 charge-discharge cycles. Providing 97% capacitance retention upon mechanical bending reveals its potential to be used as an energy storage devices in flexible electronics.

A Review of Conductive Hydrogel Used in Flexible Strain Sensor

Hydrogels, as classic soft materials, are important materials for tissue engineering and biosensing with unique properties, such as good biocompatibility, high stretchability, strong adhesion, excellent self-healing, and self-recovery. Conductive hydrogels possess the additional property of conductivity, which endows them with advanced applications in actuating devices, biomedicine, and sensing. In this review, we provide an overview of the recent development of conductive hydrogels in the field of strain sensors, with particular focus on the types of conductive fillers, including ionic conductors, conducting nanomaterials, and conductive polymers. The synthetic methods of such conductive hydrogel materials and their physical and chemical properties are highlighted. At last, challenges and future perspectives of conductive hydrogels applied in flexible strain sensors are discussed.

Anti-Bacterial and Anti-Fouling Capabilities of Poly(3,4-Ethylenedioxythiophene) Derivative Nanohybrid Coatings on SUS316L Stainless Steel by Electrochemical Polymerization

We have successfully fabricated poly(3,4-ethylenedioxythiophene) (PEDOT) derivative nanohybrid coatings on flexible SUS316L stainless steel by electrochemical polymerization, which can offer anti-fouling and anti-bacterial capabilities. PEDOT derivative nanohybrids were prepared from polystyrene sulfonates (PSS) and graphene oxide (GO) incorporated into a conducting polymer of PEDOT. Additionally, the negative charge of the PEDOT/GO substrate was further modified by poly-diallyldimethylammonium chloride (PDDA) to form a positively charged surface. These PEDOT derivative nanohybrid coatings could provide a straightforward means of controlling the surface energy, roughness, and charges with the addition of various derivatives in the electrochemical polymerization and electrostatically absorbed process. The characteristics of the PEDOT derivative nanohybrid coatings were evaluated by Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), water contact angle, and surface potential (zeta potential). The results show that PEDOT/PSS and PEDOT/GO nanohybrid coatings exhibit excellent anti-fouling capability. Only 0.1% of bacteria can be adhered on the surface due to the lower surface roughness and negative charge surface by PEDOT/PSS and PEDOT/GO modification. Furthermore, the anti-bacterial capability (7 mm of inhibition zone) was observed after adding PDDA on the PEDOT/GO substrates, suggesting that the positive charge of the PEDOT/GO/PDDA substrate can effectively kill bacteria (Staphylococcus aureus). Given their anti-fouling and anti-bacterial capabilities, PEDOT derivative nanohybrid coatings have the potential to be applied to biomedical devices such as cardiovascular stents and surgical apparatus.

A Wearable Supercapacitor Based on Conductive PEDOT:PSS-Coated Cloth and a Sweat Electrolyte

A sweat-based flexible supercapacitor (SC) for self-powered smart textiles and wearable systems is presented. The developed SC uses sweat as the electrolyte and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the active electrode. With PEDOT:PSS coated onto cellulose/polyester cloth, the SC shows specific capacitance of 8.94 F g^-1 (10 mF cm^-2 ) at 1 mV s^-1 . With artificial sweat, the energy and power densities of the SC are 1.36 Wh kg^-1 and 329.70 W kg^-1 , respectively for 1.31 V and its specific capacitance is 5.65 F g^-1 . With real human sweat the observed energy and power densities are 0.25 Wh kg^-1 , and 30.62 W kg^-1 , respectively. The SC performance is evaluated with different volumes of sweat (20, 50, and 100 µL), bending radii (10, 15, 20 mm), charging/discharging stability (4000 cycles), and washability. With successful on-body testing, the first demonstration of the suitability of a sweat-based SC for self-powered cloth-based sensors to monitor sweat salinity is presented. With attractive performance and the use of body fluids, the presented approach is a safe and sustainable route to meet the power requirements in wearable systems.

High performance flexible supercapacitors based on secondary doped PEDOT-PSS-graphene nanocomposite films for large area solid state devices

In this work, we propose the development of high performance and flexible supercapacitors using reduced graphene oxide (rGO) incorporated poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT-PSS) nanocomposites by secondary doping. The structural and morphological features of the composite film were analyzed in detail using SEM, AFM, FTIR, XPS and TGA. Secondary doping of ethylene glycol (EG) assisted by rGO incorporation significantly enhances the room temperature conductivity of PEDOT-PSS films from 3 S cm-1 to nearly 1225 S cm-1 for a 10 wt% composite. The secondary doped PEDOT-PSS:EG/rGO composite film demonstrated improved electrochemical performances with specific capacitance of 174 (F g-1) and energy density of 810 (W h kg-1) which is nearly 4 times greater than pristine PEDOT-PSS due to synergetic interactions between rGO and PEDOT-PSS. The prepared composite films show long term stability with capacitance retention of over 90% after 5000 cycles of charging-discharging. The nanocomposite films used in the present investigation demonstrates percolative behavior with a percolation threshold at 10 wt% of rGO in PEDOT-PSS. The assembled supercapacitor device could be bent and rolled-up without a decrease in electrochemical performance indicating the potential to be used in practical applications. To demonstrate the practical applicability, a rolled-up supercapacitor device was constructed that demonstrates operation of a red LED for 40 seconds when fully charged. This study will provide new dimensions towards designing cost effective, flexible and all solid-state supercapacitors with improved electrochemical performance using electrodes based on secondary doped PEDOT-PSS/rGO organic thin films.

Work function modification of PEDOT:PSS by mixing with barium acetylacetonate

Poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS) is often used as a hole injection and extractor for various organic electronic devices. This study investigated whether it is possible to n-dope PEDOT:PSS with barium acetylacetonate (Ba(acac)₂) to change its work function so that to be more suitable for electron injection and extraction. Molecular dynamics simulations suggested that barium cations can interact with the aromatic rings of PEDOT and the negatively charged sulfonate in PSS. At high doping concentration, we found that PEDOT became dedoped and precipitated resulting in a clear solution after filtration. The absence of the absorption peak of PEDOT at 263 nm indicates the removal of PEDOT after filtration. The shift in O 1s to a lower binding energy as seen in X-ray photoelectron spectroscopy suggested that the polystyrene sulfonic acids are being ionized to form barium polystyrene sulfonate (Ba–PSS). By spin-coating the solution on top of indium tin oxide, the work function can be adjusted to as low as 3.6 eV. The ability of such a mixture to inject and extract electrons is demonstrated using 2,7-bis(diphenylphosphoryl)-9,9′-spirobifluorene as an electron transporting layer. We attributed the lowering of the work function as the result of the formation of an interfacial dipole as large as 1.37 eV at the ITO/Ba–PSS interface.

Modification of poly(3,4-ethylenedioxythiophene)polystyrene sulfonate as electron injection layer.

All-solid-state flexible supercapacitor based on nanotube-reinforced polypyrrole hollowed structures

Nanotube-reinforced polypyrrole nanowires with hollowed cavities allow the fabrication of a flexible supercapacitor with a large specific capacitance.

Effect of Ti3C2Tx–PEDOT:PSS modified-separators on the electrochemical performance of Li–S batteries

Lithium–sulfur (Li–S) batteries have attracted much attention due to their high theoretical energy density, environmental friendliness, and low cost. However, the practical application of Li–S batteries is impeded by a severe shuttle effect. Using polar and conductive materials to prepare a modified separator as the second collector is an effective strategy to solve the shuttle effect. Herein, a Ti₃C₂T_x–PEDOT:PSS hybrid for modifying PP separators is successfully fabricated. In this hybrid, PEDOT:PSS can effectively prevent Ti₃C₂T_x nanosheets from restacking and enhance the electrical conductivity of Li–S batteries, thereby promoting fast Li⁺/electron transport and improving the sulfur utilization. Meanwhile, the introduction of Ti₃C₂T_x–PEDOT:PSS makes Ti₃C₂T_x nanosheets effectively anchor polysulfide, thus inhibiting the shuttle effect. As a result, Li–S cells with Ti₃C₂T_x–PEDOT:PSS modified-separators exhibit superior performances, including a high discharge capacity of 1241.4 mA h g⁻¹ at 0.2C, a long cycling stability, and a low decay rate of 0.030% per cycle at 0.5C for 1000 cycles.

Lithium–sulfur (Li–S) batteries have attracted much attention due to their high theoretical energy density, environmental friendliness, and low cost.

Hybrid Graphene/Conducting Polymer Strip Sensors for Sensitive and Selective Electrochemical Detection of Serotonin

There is an urgent need for electrochemical sensor materials that exhibit electrochemically compliant properties while also retaining high durability under physiological conditions. Herein, we demonstrate a novel strip-style electrochemical sensor using reduced graphene oxide (rGO) and poly(ethylene dioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) nanocomposite films. The fabricated rGO-PEDOT/PSS sensor with and without nafion has shown an effective electrochemical response for both selectivity and sensitivity of the serotonin (5-hydroxytryptamine, 5-HT) neurotransmitter. The developed high-performance hybrid graphene/conducting polymer strip sensors are likely to find applications as chip electrochemical sensor devices for patients diagnosed with Alzheimer's disease.

Electrochemical Polymerization of PEDOT-Graphene Oxide-Heparin Composite Coating for Anti-fouling and Anti-clotting of Cardiovascular Stents

In this study, a novel hemocompatible coating on stainless steel substrates was prepared by electrochemically copolymerizing 3,4-ethylenedioxythiophene (EDOT) with graphene oxide (GO), polystyrene sulfonate (PSS), or heparin (HEP) on SUS316L stainless steel, producing an anti-fouling (anti-protein adsorption and anti-platelet adhesion) surface to avoid the restenosis of blood vessels. The negative charges of GO, PSS, and HEP repel negatively charged proteins and platelets to achieve anti-fouling and anti-clotting. The results show that the anti-fouling capability of the poly(3,4-ethylenedioxythiophene) (PEDOT)/PSS coating is similar to that of the PEDOT/HEP coating. The anti-fouling capability of PEDOT/GO is higher than those of PEDOT/HEP and PEDOT/PSS. The reason for this is that GO exhibits negatively charged functional groups (COO⁻). The highest anti-fouling capability was found with the PEDOT/GO/HEP coating, indicating that electrochemical copolymerization of PEDOT with GO and HEP enhances the anti-fouling capability. Furthermore, the biocompatibility of the PEDOT coatings was tested with 3T3 cells for 1–5 days. The results show that all PEDOT composite coatings exhibited biocompatibility. The blood clotting time (APTT) of PEDOT/GO/HEP was prolonged to 225 s, much longer than the 40 s of pristine SUS316L stainless steel (the control), thus greatly improving the anti-blood-clotting capability of cardiovascular stents.

Three-step-in-one synthesis of supercapacitor MWCNT superparamagnetic magnetite composite material under flow

Composites of multi-walled carbon nanotubes (MWCNTs) and superparamagnetic magnetite nanoparticles, Fe₃O₄@MWCNT, were synthesized in DMF in a vortex fluidic device (VFD). This involved in situ generation of the iron oxide nanoparticles by laser ablation of bulk iron metal at 1064 nm using a pulsed laser, over the dynamic thin film in the microfluidic platform. The overall processing is a three-step in one operation: (i) slicing MWCNTs, (ii) generating the superparamagnetic nanoparticles and (iii) decorating them on the surface of the MWCNTs. The Fe₃O₄@MWCNT composites were characterized by transmission electron microscopy, scanning transmission electron microscope, TG analysis, X-ray diffraction and X-ray photoelectron spectroscopy. They were used as an active electrode for supercapacitor measurements, establishing high gravimetric and areal capacitances of 834 F g^-1 and 1317.7 mF cm^-2 at a scan rate of 10 mV s^-1, respectively, which are higher values than those reported using similar materials. In addition, the designer material has a significantly higher specific energy of 115.84 W h kg^-1 at a specific power of 2085 W kg^-1, thereby showing promise for the material in next-generation energy storage devices.

Modifying Reduced Graphene Oxide by Conducting Polymer Through a Hydrothermal Polymerization Method and its Application as Energy Storage Electrodes

We report chemical in situ deposition of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) on reduced graphene oxide (rGO) nanosheets through a simple hydrothermal polymerization method. The functional groups on graphene oxide (GO) were directly employed as an oxidant to trigger the polymerization of 3,4-ethylenedioxythiophene (EDOT), and the GO nanosheets were reduced into rGO accordingly in an aqueous environment. Well anchoring of ultrathin PEDOT on rGO through this oxidant-free method was confirmed by UV-Vis spectrum, FT-IR spectrum, SEM, and TEM analysis. The obvious enhancement of conductivity was observed after the covering of PEDOT on rGO, and this composite showed high conductivity about 88.5 S/cm. The electrochemical performance results revealed that rGO/PEDOT composite electrode exhibits high specific capacitance about 202.7 F/g. The good synergetic effect between PEDOT and rGO also makes sure highly stable reversibility of composite electrode during charging/discharging process, and more than 90% initial capacitance retains after 9000 times cycles. In addition, the electrode based on rGO/PEDOT deposited on the cotton fabric shows excellent flexible ability with the evidence that 98% of the initial capacitance of electrode maintained after three thousands of free bending, which shows promising energy storage performance for flexible devices. .

Two-Dimensional Growth of Large-Area Conjugated Polymers on Ice Surfaces: High Conductivity and Photoelectrochemical Applications

Polymerizing monomers on an atomically flat solid surface and air/water, solid/liquid, or liquid/liquid interface is now a rapidly emerging frontier. Dimension-controlled synthesis of π-conjugated polymers is of particular interest, which can be achieved by precise control of monomer distribution during the polymerization. The surface of ice allows rapid polymerization of monomers in the plane direction along the air-water interface to yield large-area two-dimensional sheet-like poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (2D sheet-like PEDOT:PSS) films with a thickness of ca. 30 nm. The persuasive role of ice chemistry is reflected in the high degree of crystallinity and superior conductivity of resultant PEDOT:PSS films. Excellent photoelectrochemical features were further disclosed when the ice-templated PEDOT:PSS films were coupled to quantum dots. Utilization of these polymer films in photovoltaic devices also resulted in excellent current density and power conversion efficiency. This work presents an innovative material technology that goes beyond traditional and ubiquitous inorganic 2D materials such as graphene and MoS₂ for integrated electronic applications.

Novel chemical route for CeO2/MWCNTs composite towards highly bendable solid-state supercapacitor device

Electrode materials having high capacitance with outstanding stability are the critical issues for the development of flexible supercapacitors (SCs), which have recently received increasing attention. To meet these demands, coating of CeO₂ nanoparticles have been performed onto MWCNTs by using facile chemical bath deposition (CBD) method. The formed CeO₂/MWCNTs nanocomposite exhibits excellent electrochemical specific capacitance of 1215.7 F/g with 92.3% remarkable cyclic stability at 10000 cycles. Light-weight flexible symmetric solid-state supercapacitor (FSSC) device have been engineered by sandwiching PVA-LiClO₄ gel between two CeO₂/MWCNTs electrodes which exhibit an excellent supercapacitive performance owing to the integration of pseudocapacitive CeO₂ nanoparticles onto electrochemical double layer capacitance (EDLC) behaved MWCNTs complex web-like structure. Remarkable specific capacitance of 486.5 F/g with much higher energy density of 85.7 Wh/kg shows the inherent potential of the fabricated device. Moreover, the low internal resistance adds exceptional stability along with unperturbed behavior even under high mechanical stress which can explore its applicability towards high-performance flexible supercapacitor for advanced portable electronic devices.

Three-Dimensional Carbon Nitride Nanowire Scaffold for Flexible Supercapacitors

Herein, a 3D composite electrode supported by g-C3N4 nanowire framework as scaffold and poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT: PSS) as conducting polymer is reported for flexible solid-state electrochemical capacitors. Compared to pure PEDOT: PSS, the composite electrodes have a greatly increased specific surface and showed good electrochemical performance. A specific capacitance of 202 F g-1 is achieved, and 83.5% of initial capacitance maintained after 5000 cycles. The device based on the 3D g-C3N4/PEDOT: PSS electrode also exhibits good performance in capacitance, flexibility, and cycling stability.

Solid-State rGO-PEDOT:PSS Transducing Material for Cost-Effective Enzymatic Sensing

Performance of a sensing device is dependent on its construction material, especially for components that are directly involved in transporting and translating signals across the device. Understanding the morphology and characteristics of the material components is therefore crucial in the development of any sensing device. This work examines the morphological and electrochemical characteristics of reduced graphene oxide interspersed with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (rGO-PEDOT:PSS) used as a transducer material deposited on a commercially available screen-printed carbon electrode (SPCE). Electron microscopy shows that PEDOT:PSS is interspersed between rGO layers. Raman and XRD analyses suggest that the graphene crystallinity in GO-PEDOT:PSS and rGO-PEDOT:PSS remains intact. Instead, PEDOT:PSS undergoes a change in structure to allow PEDOT to blend into the graphene structure and partake in the π-π interaction with the surface of the rGO layers. Incorporation of PEDOT:PSS also appears to improve the electrochemical behavior of the composite, leading to a higher peak current of 1.184 mA, as measured by cyclic voltammetry, compared to 0.522 mA when rGO is used alone. The rGO-PEDOT:PSS transducing material blended with glucose oxidase was tested for glucose detection. The sensitivity of glucose detection was shown to be 57.3 µA/(mM·cm²) with a detection limit of 86.8 µM.