Polypyrrole Nanowire Arrays Research Articles

Biofunctionalisation of Polypyrrole Nanowires Array with Sulfite Oxidase Coupled with the Integration of Platinum Nanoparticles for Ultrasensitive Amperometric Detection of Sulfite

Sulfite determination in foods and alcoholic beverages is a common requirement by food and drug administration organisations in most countries. In this study, the enzyme, sulfite oxidase (SOx), is used to biofunctionalise a platinum-nanoparticle-modified polypyrrole nanowire array (PPyNWA) for the ultrasensitive amperometric detection of sulfite. A dual-step anodisation method was used to prepare the anodic aluminum oxide membrane used as a template for the initial fabrication of the PPyNWA. PtNPs were subsequently deposited on the PPyNWA by potential cycling in a platinum solution. The resulting PPyNWA-PtNP electrode was then biofuntionalised by adsorption of SOx onto the surface. The confirmation of the adsorption of SOx and the presence of PtNPs in the PPyNWA-PtNPs-SOx biosensor was verified by scanning electron microscopy and electron dispersive X-ray spectroscopy. Cyclic voltammetry and amperometric measurements were used to investigate the properties of the nanobiosensor and to optimise its use for sulfite detection. Ultrasensitive detection of sulfite with the PPyNWA-PtNPs-SOx nanobiosensor was accomplished by use of 0.3 M pyrrole, 10 U mL−1 of SOx, adsorption time of 8 h, a polymerisation period of 900 s, and an applied current density of 0.7 mA cm−2. The response time of the nanobiosensor was 2 s, and its excellent analytical performance was substantiated with a sensitivity of 57.33 μA cm−2 mM−1, a limit of detection of 12.35 nM, and a linear response range from 0.12 to 1200 μM. Application of the nanobiosensor to sulfite determination in beer and wine samples was achieved with a recovery efficiency of 97–103%.

Fabrication of polypyrrole nanowire arrays-modified electrode for point-of-use water disinfection via low-voltage electroporation

Still ∼10% of world's population has no sustainable access to centralized water supply system, causing millions of deaths annually by waterborne diseases. Here, we develop polypyrrole nanowire arrays (PPyNWs)-modified electrodes by polymerization of pyrrole on graphite felt for point-of-use water disinfection via low-voltage electroporation. A flow-through mode is specially applied to alleviate diffusion barrier of pyrrole in the porous graphite felt for uniform PPyNWs growth. The flow-through disinfection device using the optimized PPyNWs electrode achieves above 4-log removal for model virus (MS2) and gram-positive/negative bacteria (E. faecalis and E. coli) at applied voltage of 1.0 V and fluxes below 1000 and 2500 L/m2/h. Electroporation is recognized as the dominant disinfection mechanism by using square-wave alternating voltage of ±1.0 V to eliminate the electrochemical reactions. In-situ sampling experiments reveal that anode acts as the main disinfection function due to its electric field attraction with negatively charged E. coli cells. The live/dead baclight staining experiments indicate an adsorption-desorption process of E. coli cells on anode, and the adsorption-desorption balance determines the disinfection abilities of PPyNWs anode. Under 1.0 V and 2000 L/m2/h, the disinfection device enables above 4-log E. coli removal in tap water within 7-day operation with energy consumption below 20 mJ/L, suggesting its sound application potential for point-of-use water disinfection.

Electrochemical sensor based on Prussian blue/multi-walled carbon nanotubes functionalized polypyrrole nanowire arrays for hydrogen peroxide and microRNA detection.

Adual-sensing platform is proposedbased on multi-walled carbon nanotubes/Prussian blue-functionalized polypyrrole nanowire array (PPY/MWCNTs/PB). Highly aligned PPY nanowire arrays were electrochemically prepared on the surface of glassy carbon electrodes, which were doped with MWCNTs/PB nanocomposites. The nanomaterial combines the characteristics of the PPY nanowires (high conductivity and large specific surface area) and MWCNTs/PB (excellent catalytic performance and intrinsic redox activity). Owing to the nanowire microstructure and outstandingelectrical properties, the PPY/MWCNTs/PB nanowire arrays show excellent electrocatalysis of the reduction of hydrogen peroxide and facilitate the construction of ahigh-performance biosensing platform for microRNA(miRNA). Alinear relationship betweenanalytical signal and concentration ofhydrogen peroxide and miRNA was obtained in the range5 to 503µM (1.4-5.1mM) and 0.1pM to 1nM, and detection limits of1.7μM and 33.4fM, respectively. This new supersensitive sensing platform has broad application prospects of biomolecule and other analyte determinationin drug, biomedical, plant protection, and environmental analysis. Prussian blue/multi-walled carbon nanotubes functionalized polypyrrole nanowire arrays (PPY/MWCNTs/PB) were prepared by a facile one-step electrochemical method. PPY/MWCNTs/PB nanowire arrays show excellent electrocatalysis of the reduction of H2O2 and facilitate the construction of a high-performance biosensing platform for microRNA.

Nanostructured polypyrrole cathode based dual rotating disk photo fuel cell for textile wastewater purification and electricity generation

Polypyrrole (PPy) nanosilk, nanowire array and nanorod array films are synthesized on carbon cloth substrate through electrochemical polymerization by only controlling the concentration of p-toluenesulfonate acid (TsOH) in electrolyte. The nanostructured films exhibit much better electricity generation performances in photoelectrochemical cell in comparison with flat film being as cathode due to their high surface areas and low combined series resistances. The optimized synthesized films are further applied in an efficient dual rotating disk photo fuel cell to treat real textile wastewater with the initial chemical oxygen demand (COD) and conductivity of 108 ± 5 mgO2 L−1 and 11600 μS cm−1, respectively, for simultaneous electricity generation. With nanosilk film as cathode, 0.44 V open circuit voltage and 2.00 mA short circuit current are obtained, the maximum output power reaches 0.22 mW. Similar results are also obtained with nanowire and nanorod arrays. Stable currents can be measured during 4 h treatment when the output voltage is 0 (short circuit condition), 0.15 and 0.25 V with any film. The COD is removed to 28 mgO2 L−1 under short circuit condition with nanosilk or nanowire cathode. However, they are 36 and 47 mgO2 L−1, respectively, when nanorod and flat cathodes are used. Moreover, the effects of pH and rotating speed are also investigated in this research.

Antimicrobial Peptide Functionalized Conductive Nanowire Array Electrode as a Promising Candidate for Bacterial Environment Application

AbstractConductive polymer electrodes are widely used for electrical signal detection owing to their unique mechanical, redox, and impedance characteristics. However, the performance of electrodes is compromised due to the interference of adhered bacteria and most of the scientists have not taken the microbial environment into consideration during electrode design. Here, a facile approach to construct antimicrobial peptide (AMP) functionalized polypyrrole nanowire array conductive electrodes (PNW‐AMP) is reported. Instead of compromising the electrochemical properties as the other antibacterial agents do, the PNW‐AMP electrodes exhibit excellent redox and low interfacial impedance properties. More importantly, the PNW‐AMP can eliminate bacterial adhesion and maintain electrochemical stability simultaneously in the microbial microenvironment for a long time. The antibacterial rate of the PNW‐AMP electrode reaches 95.8% after exposing the electrode to air for one month, while the charge transfer resistance ( Rct) value only increases by 9% at a bacterium (Escherichia. Coli ) concentration of 1 × 104 colony forming unit (CFU) mL−1. This research makes it possible to construct highly stable conductive polymer electrodes for bacterial environment electrical signal detection.

Electrosynthesis of polypyrrole nano/micro structures using an electrogenerated oriented polypyrrole nanowire array as framework

The purpose of this paper is to show that it is possible to increase the diameter and length of the nanostructures of a framework formed of oriented polypyrrole nanowires that has been prepared by a templateless electrochemical method based on the use of a pyrrole solution containing a high concentration of weak-acid anion and a low concentration of non-acidic anion. The dimensions of the initial nanowires are increased by performing an additional electrosynthesis in a ‘classical’ monomer solution. Depending on the polarization time of this last synthesis (a few tens of seconds), wires with various diameters, from one hundred up to several hundred nanometers, are obtained. In addition to the variation of the nanowire size, these findings confirm, as outlined in the reaction mechanism we have proposed, that the base of the nanowires is surrounded by a thin non-conductive polymer i.e. by an overoxidized polypyrrole film. Actually this paper shows a proof-of-concept. Indeed one can imagine that the second polymeric electrodeposit could be performed using an organic monomer solution, using functionalized pyrrole monomer to fabricate a biosensor having large specific area, and/or using anions which could be drugs.

Gradient doped polymer nanowire for moistelectric nanogenerator

A “moistelectric” nanogenerator based on gradient doped polypyrrole nanowire has been fabricated by concentration-controlled electro-deposition (CCED) technique. The specially designed composition and structure of the gradient doped polypyrrole nanowire endow it with huge surface area and one-dimensional transport nanochannels, which can largely facilitate the diffusion of water molecules to generate the dissociated charged ions as free carriers. For a polypyrrole nanowire with a diameter of 200 nm, it exhibits a high-output voltage in excess of 72 mV, a remarkable output current of 0.45 nA, and a maximum output power density of 103.13 mW cm−2 by area and 9.0 × 104 W kg−1 by mass under the ΔRH of 75%. On this basis, a vertically aligned gradient doped polypyrrole nanowire arrays show high current output of 0.14 μA without voltage drop. This work presents the first example that the power is gathered from moisture via polymer nanogenerators for energy-conversion application.

Ordered Polypyrrole Nanowire Arrays Grown on a Carbon Cloth Substrate for a High-Performance Pseudocapacitor Electrode.

Highly aligned nanoarchitecture arrays directly grown on conducting substrates open up a new direction to accelerate Faradaic reactions for charge storage as well as address "dead volume" limitations for high-performance pseudocapacitor electrodes. Here we reported the electrochemical fabrication of well-ordered polypyrrole (PPy) nanowire arrays (NWAs) on surfaces of carbon fibers in an untreated carbon cloth to construct hierarchical structures constituted by the three-dimensional conductive carbon fiber skeleton and the atop well-ordered electroactive polymer nanowires. The morphologies, wetting behaviors, and charge-storage performances of the polymer were investigated by scanning electron microscopy, transmission electron microscopy, contact-angle measurement, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The well-ordered PPy NWA electrode exhibited a high specific capacitance of 699 F/g at 1 A/g with excellent rate capability, and 92.4% and 81.5% of its capacitance could be retained at 10 and 20 A/g, respectively. An extremely high energy density of 164.07 Wh/kg could be achieved by the PPy NWAs at a power density of 0.65 kW/kg. It also displayed a quite high energy density of 133.79 Wh/kg at a high power density of 13 kW/kg. The assembled symmetric supercapacitor of PPy NWAs//PPy NWAs also exhibited excellent rate capability, and only 19% of its energy density decreased when the power density increased 20 times from 0.65 to 13 kW/kg.

Electroactive polypyrrole nanowire arrays: synergistic effect of cancer treatment by on-demand drug release and photothermal therapy.

An electroresponsive drug release system based on polypyrrole (Ppy) nanowires was developed to induce the local delivery of anticancer drug, doxorubicin (DOX), according to the applied electric field. DOX-conjugated Ppy nanowire (NW) (DOX/Ppy NW) array was initially prepared by electrochemical deposition of a mixture of pyrrole monomers and biotin as dopants in the anodic alumina oxide membrane as a sacrificial template. Morphological observation by scanning electron microscopy revealed free-standing and 3D nanotopographical features with large surface area and high density. In addition, we investigated the antitumor efficacy of DOX released from DOX/Ppy NW array in response to the external electric field using two kinds of cancer cell lines, human oral squamous carcinoma cells (KB cells) and human breast cancer cells (MCF7 cells). Meanwhile, strong photothermal effect as a result of a near-infrared absorbing ability of Ppy synergistically maximizes the chemotherapeutic efficacy. Our results suggested that the proposed multifunctional Ppy platform possessing several beneficial features is very promising for many therapeutic applications including cancer.

Hybrid bio-organic interfaces with matchable nanoscale topography for durable high extracellular electron transfer activity.

Here, we developed a novel hybrid bio-organic interface with matchable nano-scale topography between a polypyrrole nanowire array (PPy-NA) and the bacterium Shewanella, which enabled a remarkably increased extracellular electron transfer (EET) current from genus Shewanella over a rather long period. PPy-NA thus exhibited outstanding performance in mediating bacterial EET, which was superior to normal electrodes such as carbon plates, Au and tin-doped In₂O₃. It was proposed that the combined effect of the inherent electrochemical nature of PPy and the porous structured bacterial network that was generated on the PPy-NA enabled long-term stability, while the high efficiency was attributed to the enhanced electron transfer rate between PPy-NA and microbes caused by the enhanced local topological interactions.

Conducting Polymer Nanowire Arrays for High Performance Supercapacitors

This Review provides a brief summary of the most recent research developments in the fabrication and application of one-dimensional ordered conducting polymers nanostructure (especially nanowire arrays) and their composites as electrodes for supercapacitors. By controlling the nucleation and growth process of polymerization, aligned conducting polymer nanowire arrays and their composites with nano-carbon materials can be prepared by employing in situ chemical polymerization or electrochemical polymerization without a template. This kind of nanostructure (such as polypyrrole and polyaniline nanowire arrays) possesses high capacitance, superior rate capability ascribed to large electrochemical surface, and an optimal ion diffusion path in the ordered nanowire structure, which is proved to be an ideal electrode material for high performance supercapacitors. Furthermore, flexible, micro-scale, threadlike, and multifunctional supercapacitors are introduced based on conducting polyaniline nanowire arrays and their composites. These prototypes of supercapacitors utilize the high flexibility, good processability, and large capacitance of conducting polymers, which efficiently extend the usage of supercapacitors in various situations, and even for a complicated integration system of different electronic devices.

Influence of Anodizing Parameters on Pore Diameter of Anodic Aluminium Oxide (AAO) Films Using Taguchi Design

Nanoporous anodic aluminium oxide (AAO) films were fabricated by using a two-step anodizing process of aluminium foils in oxalic acid electrolyte. The effect of synthesis conditions including applied voltage, electrolyte concentration and temperature on the pore diameter of AAO films was investigated. To reduce the number of experiments, the Taguchi L9 orthogonal array was adopted and the results were analyzed using minitab15 software. It was found that the pore size increased in direct proportion with the applied voltage. The proportion of the pore size with increasing electrolyte concentration was at first direct and then inverse and the maximum pore diameter was obtained in the case of 0.3 M. The pore size relation with increasing electrolyte temperature was at first inverse and then direct and the minimum pore diameter was seen at 10 ◦C. The diameter of the nanopores were predicted with the software in the range of 35–71 nm in different conditions of selected experimental parameters. Also, as a practical application of obtained AAO films, template-synthesis fabrication of polypyrrole nanowire arrays by electrochemical polymerization of pyrrole within the pores of the obtained AAO was successfully demonstrated.

Vertically oriented polypyrrolenanowire arrays on Pd-plated Nafion® membrane and its application in direct methanolfuel cells

Highly ordered polypyrrole nanowire arrays are constructed via electrochemically polymerizing pyrrole directly on Pd-modified Nafion® membrane. A significant enhancement in the performance and durability of direct methanol fuel cells (DMFCs) is observed when such an ordered structure is used as an ordered electrode.

PH sensors based on polypyrrole nanowire arrays

The hydroquinone monosulfonate-doped polypyrrole (PPy-HQS) nanowires were successfully fabricated by potentiostatic electropolymerization of pyrrole (Py) inside the pores of home-made through-hole anodic aluminum oxide (AAO) membranes. The AAO templates with a nominal pore diameter of 80nm were prepared by a two-step anodization process. The potentiostatic electropolymerization of HQS-doped polymer nanowires was carried out in 0.1M NaClO4, or 0.1M LiClO4 or 0.1M citric acid containing 0.05M pyrrole and 0.05M potassium hydroquinone monosulfonate. The synthesized PPy-HQS nanowire arrays were tested as potential potentiometric pH sensors. It was found that pH sensors based on PPy-HQS nanowires exhibited better electrochemical performance toward pH sensing than those based on PPy-HQS thin films. The best potentiometric response to pH changes and a very good stability in time showed the sensor based on the PPy-HQS nanowires polymerized in a 0.1M LiClO4 solution.

Chemical synthesis of high density and long polypyrrole nanowire arrays using alumina membrane and their hydrogen sensing properties

Polypyrrole nanowire arrays were synthesized through chemical polymerization inside the nanochannels of alumina membrane. By optimizing the polymerization time and applying appropriate oxidant:monomer molar ratio with proper concentrations, the pores filling and also the continuity of the obtained polypyrrole inside the nanochannels improved and therefore after dissolution of the host membrane, high density and long nanowire arrays appeared. The obtained nanostructures were characterized by SEM, FTIR and BET techniques. The synthesized nanostructures had high surface areas of 75.66–172.90m2/g. Since nanowires are attractive for gas sensing applications owing to their high surface areas, their hydrogen gas sensing was investigated at room temperature. The results show that the electrical resistance of the polypyrrole nanostructure arrays reduced upon exposure to hydrogen gas.

Patterned Growth of Vertically Aligned Polypyrrole Nanowire Arrays

A facile strategy for preparing vertically aligned polypyrrole (PPy) nanoarrays with precisely controlled density and quantity is presented. The method involves two steps: (1) the fabrication of the patterned substrate via electron beam lithography and (2) the controlled growth of PPy nanowires via electrochemical polymerization on the patterned substrate. The electrical property of a single PPy nanowire is investigated via in situ conducting probe atomic force microscopy.

Polypyrrole Nanowire Array with High Aspect Ratio Fabricated by Block-Copolymer-Templated Electropolymerization

ABSTRACTConducting polypyrrole (PPy) nanowire array was electrochemically fabricated by using microphase-separated block copolymer (PEOm-b-PMA(Az)n) thin film as an electrode template. Electropolymerization proceeds selectively through the perpendiculary oriented PEO nanocylindrical microdomains on an ITO electrode coated by the above polymer film. The length of the PPy nanowires was controllable in range of 10-120 nm by the thickness of the coated template film and the amount of passed charge. A 10 nm of diameter, 27 nm of periodicity, and 12 of aspect ratio of the crystalline PPy nanowires were successfully achieved. Selective removal of the template is also achieved simply by rinsing with solubility-controlled mixed solvent.

Conducting polymernanowire arrays with enhanced electrochemical performance

A template-free approach to fabricate a large area of length-controllable and well-oriented polypyrrole nanowire arrays is developed by using a facial electrochemical polymerization strategy. The diameters of the nanowires range from 80 to 100 nm, and their length can be controlled within the range 1–4 μm. Further, the corresponding enhanced electrochemical performance of polypyrrole nanowire arrays is demonstrated. The nanowire arrays exhibited a remarkable capacitance of 566 F g−1 and retained 70% of its initial capacitance with little fading after hundreds of charge–discharge cycles, which are much better than disordered nanowire networks and conventional film.

A novel ammonia sensor based on high density, small diameter polypyrrole nanowire arrays

A novel sensor based on the PPy nanowire arrays with high density, small diameter (about 50 nm) presented a significantly high surface-to-volume ratio. Conducting polypyrrole (PPy) nanowire arrays were synthesized by electropolymerization in the anodic aluminum oxide (AAO) template which was fabricated by two-step anodizing process. Then, two sides of the PPys/AAO were pasted by Si substrates and the AAO template was etched by HF acid. At last, the gold wires were attached on Si substrates, and the sensor came into being. The sensor was sensitive to ammonia at room temperature and showed relatively high response in low concentration and comparatively short response and recovery time.

Template-free one-step electrochemical formation of polypyrrole nanowire array

Oriented polypyrrole nanowire (nanorod) array readily forms using one-step pyrrole electropolymerization without using a template. These nanostructures having diameter in the range of 40–120 nm are obtained by electrogenerating polypyrrole in the presence of jointly non-acidic and weak-acidic anions. The latter are essential, their presence leads to the formation of an overoxidized polypyrrole thin layer that surrounds the polypyrrole nanostructure base. This simple and convenient method allows direct polymer nanowire array fabrication on various conductive substrates, the length of nanostructures being controlled by the polymerization time . Finally, a reaction mechanism involving oxidation of pyrrole and water and polypyrrole overoxidation is discussed.