Conducting Polymer Nanowires Research Articles

Nanoporous Conducting Polymer Nanowire Network-Encapsulated MnO2-Based Flexible Supercapacitor with Enhanced Rate Capability and Cycling Stability

Transition-metal-oxide-based electrochemical electrodes usually suffer from poor electron and ion transport, leading to deteriorated rate performance and cycling stability. Herein, we address these issues by developing a facile "conducting encapsulation" strategy toward a nanoporous PEDOT nanowire/MnO2 nanoparticle/PEDOT nanowire composite electrode. Through encapsulation of the PEDOT nanowire network, the overall electrochemical performance of the resultant composite electrode is substantially enhanced. Specifically, the rate capability and capacitance retention are improved by ∼48.2 and ∼33%, respectively, which are 89.8% at 0.8-40 mA/cm2 and 93% after 3000 charge/discharge cycles at 2.0 mA/cm2, respectively. Moreover, the specific capacitance is increased by ∼6 times of that of the MnO2@PEDOT NW electrode at ∼200 mA/cm2. We find that a nanoporous conducting nanowire network that encapsulates a MnO2 nanoparticle layer can provide efficient electron and ion transport paths and stabilize the structure of MnO2 from collapse during charge/discharge cycling and mechanical deformation. This strategy can be applied to other pseudocapacitive material-based electrochemical electrodes, such as transition-metal oxides and conducting polymers.

Preparation and Electrochemical Properties of Polyaniline Nanostructures Using Vertically Aligned Mesochannels as Confinement

AbstractOne‐dimensional conducting polymer nanowire arrays have shown promising potential in applications of electrochemical supercapacitors, sensors, and more. Herein, vertically aligned mesoporous silica films (VMSF) with hexagonally packed mesochannels were generated on indium‐tin oxide (ITO) electrodes by an electrochemically‐assisted self‐assembly (EASA) method. The prepared VMSF/ITO electrode was then exploited as a hard template for electrochemical growth of well‐aligned polyaniline (PANI) nanofilaments within silica mesochannels, eventually forming a PANI/VMSF/ITO composite electrode. The electrochemical conditions of the PANI growth through the mesochannnels were investigated in detail, and the electrochemical capacitance was also tested. It is shown that the resulting nanofilaments separated through silica walls exhibit significantly improved electrochemical performance, including better electrochemical reversibility and high specific capacitance (3.00 mF/cm2 at 20 μA/cm2), which is increased by about 152 % in comparison to PANI directly on an ITO (PANI/ITO) substrate. Such an improved electrochemical performance is mainly contributed to by enhanced charge transfer efficiency and improved electrochemical reaction kinetics resulting from the well‐aligned PANI nanostructure.

Charge Storage and Solar Rechargeable Battery Devices Based on Electrodes Electrochemically Modified with Conducting Polymer Nanowires.

In this work, the use of nanostructured conducting polymer deposits on energy-storing devices is described. The cathode and the anode are electrochemically modified with nanowires of polypyrrole and poly(3,4-ethylenedioxythiophene), respectively, prepared after the use of a mesoporous silica template. The effect of aqueous or ionic liquid medium is assayed during battery characterization studies. The nanostructured device greatly surpasses the performance of the bulk configuration in terms of specific capacity, energy, and power. Moreover, compared with devices found in the literature with similar designs, the nanostructured device prepared here shows better battery characteristics, including cyclability. Finally, considering the semi-conducting properties of the components, the device was adapted to the design of a solar-rechargeable device by the inclusion of a titanium oxide layer and cis-bis(isothiocyanate)-bis(2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium (II) dye. The device proved that the nanostructured design is also appropriate for the implementation of solar-rechargeable battery, although its performance still requires further optimization.

Flexible Networks of Patterned Conducting Polymer Nanowires for Fully Polymeric Bioelectronics

Patterning of conducting polymers (CPs) into fully functioning devices remains a challenge for the creation of polymeric bioelectronics. Presently, the most successful method for patterning CPs is preprocess blending with structural components and using either subtractive or additive processes to produce the desired design. This work focuses on the development and characterization of a filter‐based processing method for direct pattern transfer of the CP poly(3,4‐ethylenedioxythiophene) (PEDOT) to elastomeric substrates. Laser sintering of a pattern into the surface of a filter membrane and the subsequent filtering of PEDOT nanowires onto the surface of the filter enable feature sizes of approximately 400 μm to be resolved without the need for any postprocessing. The resulting films of patterned PEDOT nanowires are found to possess high conductivity as well as improved wet electrochemical properties in comparison to platinum. Using the process developed in this work, thin and flexible arrays of PEDOT nanowire films are produced and used as an EMG device to test muscle contractions.

A conductive polymer nanowire including functional quantum dots generated via pulsed laser irradiation for high-sensitivity sensor applications

The fabrication of functional conductive polymer nanowires (CPNWs), including ultrahigh-sensitive flexible nanosensors has attracted considerable attention in field of the Internet of Things. However, the controllable and space-selective growth of CPNWs remains challenging, and a novel synthetic technique is required. Herein, we demonstrate the synthesis of space-selective CPNWs that include quantum dots (QDs) with changeable optical properties via single-pulse laser irradiation in air at atmospheric pressure. Time-resolved shadowgraphy was applied to monitor the synthetic process of the CPNWs and optimise the process conditions. The electrical conductivity of the CPNWs with QDs (QD-CPNWs) was analysed in the presence and absence of light irradiation and was found to change drastically (over six times) under light irradiation. QD-CPNW synthesis under laser irradiation shows great potential for fabricating highly photosensitive functional nanomaterials and is expected to be applied in the production of ultrahigh-sensitive photosensors in the future.

Optical Tuning of Wigner Lattice in Conducting Polymer Nanowires

The well‐known characteristics such as switching transition of resistivity of charge density wave (CDW) can be observed in soft materials such as carbon nanotubes and conducting polymer nanowires due to Wigner lattice (WL) formation when long‐range Coulomb repulsion dominates over kinetic energy of charge carriers in confined geometry. Herein, it is shown that CDW energy‐gap and associated 1D WL parameters in polypyrrole nanowires depend on charge‐carrier (bipolarons) density, which can be tuned continuously with photoexcitation. Observed linear dependence of CDW energy‐gap with charge‐carrier density provides evidence of the WL formation in these conducting polymer nanowires. The observation is consistent with earlier findings of linear dependence of energy‐gap with lattice parameter, which can be tuned by pressure or substitution of ions in conventional CDW materials.

Nano-FET-enabled biosensors: Materials perspective and recent advances in North America

Field-effect transistor (FET) is a very promising platform for biosensor applications due to its magnificent properties, including label-free detection, high sensitivity, fast response, real-time measurement capability, low running power, and the feasibility to miniaturize to a portable device. 1D (e.g. carbon nanotubes, Si nanowires, conductive polymer nanowires, 1D metal oxides, and others) and 2D (e.g. graphene materials, transition metal dichalcogenides, black phosphorus, and 2D metal oxides) materials, with their unique structural and electronic properties that are unavailable in bulk materials, have helped improve the sensitivity of FET biosensors and enabled detection down to single molecule. In this review, we give insights into the rapidly evolving field of 1D and 2D materials-based FET biosensors, with an emphasis on structure and electronic properties, synthesis, and biofunctionalization approaches of these nanomaterials. In addition, the progress in the 1D/2D-FET biosensors in North America, in the last decade, is summarized in tables. Moreover, challenges and future perspectives of 1D/2D-FET biosensors are covered.

Observation of Energy-Dependent Carrier Scattering in Conducting Polymer Nanowire Blends for Enhanced Thermoelectric Performance.

Without sacrificing the intrinsic softness and flexibility of conducting polymers, their blends have been demonstrated to be promising to improve thermoelectric properties of conducting polymers. However, the underlying mechanism for the thermoelectric enhancement is hitherto far from clear and is worthy of being explored deeply. In this work, we report novel conducting polymer nanowire blends by physically mixing poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires and polypyrrole (PPy) nanowires. By carefully tuning the energetic structure of PPy nanowires (nanofillers), the Seebeck coefficients and power factors of nanowire blends are surprisingly increased by ∼20 and ∼32% (compared to PEDOT nanowires), respectively. By means of first-principles calculations and experimental characterizations, we qualitatively confirm that the improved thermoelectric property is a consequence of a built-in energy barrier at nanowire interfaces rather than the commonly used doping/de-doping effect. Subsequently, we further employ the Kang-Snyder transport model and quantitatively demonstrate that the energy barrier involves energy-dependent carrier scattering (thus, a change of total relaxation time) at nanowire heterojunctions, which contributes to the enhanced Seebeck coefficients and power factors. Our work sheds light on the mechanism that can be adopted to design soft but high-performance thermoelectric materials with conducting polymer blends.

Metal-Conductive Polymer Core-Shell Nanowires: Electroless Reduction of Pd and Cu On Polypyrrole/DNA Templates Bearing 2-2'-Bipyridyl Groups

A method for the preparation of conductive polymer nanowires bearing metal ion chelating 2,2’-bipyridyl groups is described. N-(3-pyrrol-1-yl-propyl)-2,2'-bipyridinium hexafluorophosphate (NP2PBH) was templated on λ-DNA in aqueous solution using FeCl3 as oxidant to initiate polymerization. The polyNP2PBH/DNA nanowires were then decorated with metals (Cu or Pd) by electroless deposition [Cu(NO3)2/ascorbate or PdCl42-/NaBH4]. UV-vis absorption spectra of the hybrid materials show the absorption peak due to the plasmon resonance of Cu at about 550 nm and a broad continuous band consistent with metallic Pd in the range 300−700 nm. The morphology, size and electrical properties of the hybrid nanostructures have been characterized using scanning probe techniques (atomic force microscopy (AFM), scanning conductance microscopy (SCM) and conductive atomic force microscopy (cAFM)). The polyNP2PBH/DNA nanowires show a continuous, smooth and uniform appearance (mean diameter 5.0 nm). Cu deposits on polyNP2PBH/DNA nanowires by a nucleation and growth process that leads eventually to smooth, conductive Cu nanowires. In contrast, Pd deposits in a non-uniform manner on polyNP2PBH/DNA and has inconsistent electrical conductivity. The electrical conductivity of single Cu/polyNP2PBH/DNA nanowires was estimated to be 1.6 ± 0.27 S cm-1 which we suggest is limited by electron transfer between Cu grains.

Nanowires: Printed Highly Ordered Conductive Polymer Nanowires Doped with Biotinylated Polyelectrolytes for Biosensing Applications Adv. Mater. Interfaces 18/2019)

In article 1900671, Qiannan Xue, Xuexin Duan, and co-workers demonstrate a nanoscale impedimetric immunosensor based on biotin doped conductive polymer nanowire arrays which are fabricated through simple solution printing approach. This sensor can be a general platform for various bio-analytical applications with ultrahigh sensitivity.

MEG actualized by high-valent metal carrier transport

Moist-electric (ME) is a promising energy that generates electricity from the air by absorbing the gaseous or vaporous water molecules that are ubiquitous in the atmosphere. Even so, all the moisture-generated carriers in the ME generator (MEG) are monovalent ions, which severely limits the diversification of ME materials as well as the further improvement and application of ME. We creatively designed the concentration gradient of high-valent metal cation carriers containing Mg (II) and Al (III) ions in one-dimensional conductive polymer nanowires and applied them to MEG. High-valent metal cation carriers have significant advantages of high ME performance based on two- and three-electron transfer property compared to monovalent ion carriers. Under the stimulation of moisture, Mg MEG achieved a high energy density of 20.8 mWcm−3 in a test circuit with a load resistance, while Al MEG produced a new record of energy density approaching 40 mWcm−3 in MEG research. By integrating Mg MEGs, the manufacture of self-powered intelligent monitoring devices that use human respiratory is developed, which is expected to be applied in wearable energy devices. This work provides insight for the design of the innovative MEG and opens up a pioneering avenue for future energy conversion and storage system.

Printed Highly Ordered Conductive Polymer Nanowires Doped with Biotinylated Polyelectrolytes for Biosensing Applications

AbstractThe demand for fast and ultratrace biomarkers detection is increasing in bioanalytical chemistry. In this work, highly ordered nanowires array and sensor integration are achieved with nanoscale printing approach. Negatively charged poly(3,4‐ethylenedioxythiophene)–poly(styrenesulfonate) doped with positively charged PEGylated biotin‐derivatized polyelectrolytes results a direct biofunctionalization on the nanowire surface without multiple postmodification steps. It provides homogeneous dispersed biofunctional sites and nonfouling surface on the nanowires. The ordered nanowires array enables the immunosensor to detect biotargets quickly and ultrasensitively. The nanowires impedimetric immunosensor is demonstrated for specific biomarkers detection and achieved a minimum responsive concentration as low as 10 pg mL−1 for protein biomarker and 10 CFU mL−1 for pathogen.

Efficient two-terminal artificial synapse based on a network of functionalized conducting polymer nanowires

A two-terminal artificial synaptic device based on functionalized polythiophene nanowires network is fabricated and successfully used to emulate important biological synaptic functions, including PPF, SRDP and STDP.

Graphene Oxide-Doped Conducting Polymer Nanowires Fabricated by Soft Lithography for Gas Sensing Applications

This paper reported a high-performance e-nose type chemiresistive gas sensor composed of graphene oxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) nanowires. Large scale and well-defined sub-100-nm nanowires were prepared using nanoscale soft lithography in a highly efficient and facile way, facilitating subsequent device integration. The responses of the nanowire sensors to volatile organic compounds (VOCs) can be tuned by different polymer components, which are utilized to constitute unique identification codes for ethanol, n-hexane, acetone, and p-xylene and realize the discrimination of different VOCs. Besides, the score plot and classification matrix obtained, respectively, from the principal component analysis and linear discriminant analysis provide sufficient information to differentiate different VOCs.

(Invited) Electrochemically Synthesized High Density Chemical Sensor Arrays

Electronic detection of molecules is rapidly emerging as an alternative to the tranditional optical and electrochemical methods because of the small size, low-power consumption, improved sensing performance and most of all possibility of developing high density arrays for simulatenous analyses of multiple species in small sample volumes. Recently, one-dimensional nanostructures (e.g., carbon nanotubes (CNTs), inorganic, and organic nanowires) as conduction channels of field effect transistors (FETs) have been developed for detection of a variety of gaseous molecules with excellent low detection limit, sensitivity, and selectivity. These features are a consequence of dramatic decrease in characteristic length and increase in the ratio of surface to volume atoms, allowing for rapid diffusion into the bulk and for a more significant fraction of the atoms to participate in surface processes such as chemical and biochemical binding interactions. One-dimensional geometries also enhance response times by virtue of their two-dimensional mass transfer profile. Furthermore, nanowires are heralded for device miniaturization and sensor arrays, enabling duplicate elements to reduce false positives/negatives and pattern recognition systems termed electronic noses where each sensor in the array has a unique response to every analyte creating a fingerprint type response that increases sensitivity and selectivity. Finally, sensors are also attractive for their proven commercial viability, as this approach uses a single material behaving as both the sensitive layer and transducer to directly covert chemical information into an electronic signal without the need for labels, allowing for real-time, continuous monitoring. In this presentation, synthesis, functionalization, and assembly of various nanoengineered materials including CNTs and conducting polymer nanowires will be discussed to create “true” high density gaseous sensor arrays with superior sensing performance in cost-effective manner. Finally, Android based smartphone integratable sensor will be demonstrated.

A chemiresistive sensor array from conductive polymer nanowires fabricated by nanoscale soft lithography.

One-dimensional organic nanostructures are essential building blocks for high performance gas sensors. Constructing an e-nose type sensor array is the current golden standard in developing portable systems for the detection of gas mixtures. However, facile fabrication of nanoscale sensor arrays is still challenging due to the high cost of the conventional nanofabrication techniques. In this work, we fabricate a chemiresistive gas sensor array composed of well-ordered sub-100 nm wide conducting polymer nanowires using cost-effective nanoscale soft lithography. Poly(3,4-ethylene-dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) nanowires functionalized with different self-assembled monolayers (SAMs) are capable of identifying volatile organic compounds (VOCs) at a low concentration range. The side chains and functional groups of the SAMs introduce different sensitivities and selectivities to the targeted analytes. The distinct response pattern of each chemical is subjected to pattern recognition protocols, which leads to a clear separation towards ten VOCs, including ketones, alcohols, alkanes, aromatics and amines. These results of the chemiresistive gas sensor array demonstrate that nanoscale soft lithography is a reliable approach for fabricating nanoscale devices and has the potential of mass producibility.

Conductive polymer nanowire gas sensor fabricated by nanoscale soft lithography

Resistive devices composed of one-dimensional nanostructures are promising candidates for the next generation of gas sensors. However, the large-scale fabrication of nanowires is still challenging, which restricts the commercialization of such devices. Here, we report a highly efficient and facile approach to fabricating poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) nanowire chemiresistive gas sensors by nanoscale soft lithography. Well-defined sub-100 nm nanowires are fabricated on silicon substrate, which facilitates device integration. The nanowire chemiresistive gas sensor is demonstrated for NH3 and NO2 detection at room temperature and shows a limit of detection at ppb level, which is compatible with nanoscale PEDOT:PSS gas sensors fabricated with the conventional lithography technique. In comparison with PEDOT:PSS thin-film gas sensors, the nanowire gas sensor exhibits higher sensitivity and a much faster response to gas molecules.

Conductive biomaterials in cardiac tissue engineering

Conductive biomaterials (including conductive polymer, carbon-base materials, nanogold, and conductive silicon nanowires etc.) with prominent electrical conductivity, good cellular response, and promotion of cell-cell signaling transduction are possibly more suitable for cardiac tissue engineering. To date, their excellent properties catch more attention of the researchers to investigate their roles in life science research. Due to the limited therapeutic approaches of myocardial infarction (MI), engineered cardiac patches have received more attention in the treatment of MI. While, conductive biomaterial taken as a scaffold for cardiac tissue engineering is a promising strategy to repair infarct myocardium and improve the cardiac function. In this review, we summarized the fabrication of various conductive biomaterials for cardiac tissue engineering, and discuss the interaction between the conductive biomaterials and the cells [cardiomyocytes (CMs) and stem cells]. The advance of conductive biomaterials in tissue engineering, regenerative medicine and bio-sensing are also demonstrated.

Conducting polymer nanowires for control of local protein concentration in solution

Interfacing devices with cells and tissues requires new nanoscale tools that are both flexible and electrically active. We demonstrate the use of PEDOT:PSS conducting polymer nanowires for the local control of protein concentration in water and biological media. We use fluorescence microscopy to compare the localization of serum albumin in response to electric fields generated by narrow (760 nm) and wide (1.5 µm) nanowires. We show that proteins in deionized water can be manipulated over a surprisingly large micron length scale and that this distance is a function of nanowire diameter. In addition, white noise can be introduced during the electrochemical synthesis of the nanowire to induce branches into the nanowire allowing a single device to control multiple nanowires. An analysis of growth speed and current density suggests that branching is due to the Mullins–Sekerka instability, ultimately controlled by the roughness of the nanowire surface. These small, flexible, conductive, and biologically compatible PEDOT:PSS nanowires provide a new tool for the electrical control of biological systems.

Interfacial Assembly of Photosystem II with Conducting Polymer Films toward Enhanced Photo‐Bioelectrochemical Cells

A biohybrid photoanode is constructed by integrating photosystem II with doped conducting polymer nanowires that are synthesized by template‐directed electrochemical deposition. Interestingly, at the same applied bias potential ranging from 0 to 0.5 V versus saturated calomel electrode (SCE), this hybrid photoanode shows a higher photocurrent than that of pure photosystem II coated on a bare indium tin oxide (ITO) surface. Particularly, the photocurrent for the integrated photoanode above is enhanced about 39.0‐fold with increased stability (0.25 V vs SCE). Such assembled system combining natural photoactive protein with artificial low‐cost conducting polymer shows great potential for advanced solar energy conversion.