Non-conducting Poly Research Articles

Electrochemical multi-sensors obtained by applying an electric discharge treatment to 3D-printed poly(lactic acid)

Electrochemical sensors for real-time detection of several bioanalytes have been prepared by additive manufacturing, shaping non-conductive poly(lactic acid) (PLA) filaments, and applying a physical treatment to create excited species. The latter process, which consists of the application of power discharge of 100 W during 2 min in a chamber at a low pressure of O2, converts electrochemically inert PLA into an electrochemically responsive material. The electric discharge caused the oxidation of the PLA surface as evidenced by the increment in the quantity of oxygenated species detected by FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). Indeed, changes in the surface chemical composition became more pronounced with increasing O2 pressure. After demonstrating the performance of the chemically modified material as individual dopamine and glucose sensors, multiplexed detection has been achieved by measuring simultaneously the two voltammetric signals. This has been performed by collecting the signals in two different regions, a naked chemically modified PLA for dopamine detection and a chemically modified PLA region functionalized with Glucose Oxidase. These outcomes led to define a new paradigm for manufacturing electrodes for electrochemical sensors based on 3D printing without using conducting materials at any stage of the process.

All-in-One Single-Print Additively Manufactured Electroanalytical Sensing Platforms.

This manuscript provides the first report of a fully additively manufactured (AM) electrochemical cell printed all-in-one, where all the electrodes and cell are printed as one, requiring no post-assembly or external electrodes. The three-electrode cell is printed using a standard non-conductive poly(lactic acid) (PLA)-based filament for the body and commercially available conductive carbon black/PLA (CB/PLA, ProtoPasta) for the three electrodes (working, counter, and reference; WE, CE, and RE, respectively). The electrochemical performance of the cell is evaluated first against the well-known near-ideal outer-sphere redox probe hexaamineruthenium(III) chloride (RuHex), showing that the cell performs well using an AM electrode as the pseudo-RE. Electrochemical activation of the WE via chronoamperometry and NaOH provides enhanced electrochemical performances toward outer-sphere probes and for electroanalytical performance. It is shown that this activation can be completed using either an external commercial Ag|AgCl RE or through simply using the internal AM CB/PLA pseudo-RE and CE. This all-in-one electrochemical cell (AIOEC) was applied toward the well-known detection of ascorbic acid (AA) and acetaminophen (ACOP), achieving linear trends with limits of detection (LODs) of 13.6 ± 1.9 and 4.5 ± 0.9 μM, respectively. The determination of AA and ACOP in real samples from over-the-counter effervescent tablets was explored, and when analyzed individually, recoveries of 102.9 and 100.6% were achieved against UV-vis standards, respectively. Simultaneous detection of both targets was also achieved through detection in the same sample exhibiting 149.75 and 81.35% recoveries for AA and ACOP, respectively. These values differing from the originals are likely due to electrode fouling due to the AA oxidation being a surface-controlled process. The cell design produced herein is easily tunable toward different sample volumes or container shapes for various applications among aqueous electroanalytical sensing; however, it is a simple example of the capabilities of this manufacturing method. This work illustrates the next step in research synergising AM and electrochemistry, producing operational electrochemical sensing platforms in a single print, with no assembly and no requirements for exterior or commercial electrodes. Due to the flexibility, low-waste, and rapid prototyping of AM, there is scope for this work to be able to span and impact a plethora of research areas.

Improving photoluminescence, optical and electrical characteristics of PMMA films with gamma irradiation

Polymeric materials are macromolecules, essentially a combination of numerous repeated subunits. Polymers are innovative and advanced materials that currently have a strong impact on our daily lives. In recent years, polymer use has been prominent due to the materials’ distinctive properties; thus, they entered different fields of science, technology and industrial-biomedical applications.The improvement of photoluminescence, optical and electrical characteristics of non-conducting Poly(methyl methacrylate) (PMMA) films was studied. Upon gamma irradiation of various doses, the photophysical and electrical properties of PMMA films were investigated using photoluminescence spectroscopy, ultraviolet–visible (UV–vis) spectroscopy and the LCR Meter Bridge Circuit technique. The fluorescent response improved the photoluminescence (PL) spectral emission peaks according to gamma values. Strong fluorescence peaks appeared with the highest gamma dose. The UV–Vis results revealed a significant red-shift in the absorption edge as gamma doses increased. This shift exhibits a continuous decrease in the energy band gap values (from 3.50 to 2.60 eV for direct transition and from 3.05 to 1.55 eV for indirect transition). This was due to the formation of carbon clusters, which led to an increase in the electrical conductivity and improved the dielectric parameters of the irradiated PMMA films. Among a variety of measurements presented and discussed in the present study, the electrical measurements showed improved electrical characteristics of gamma-irradiated PMMA films.

Intercalating ultrathin polymer interim layer for charge transfer cascade towards solar-powered selective organic transformation

Transition metal chalcogenide quantum dots (TMCs QDs) constitute a crucial sector of semiconductors on account of large absorption coefficient for light harvesting, peculiar quantum confinement effect, and abundant active sites stemming from ultra-small size. However, elaborate and tunable modulation of anisotropic photoinduced charge carriers over TMCs QDs represents an enduring challenge in terms of sluggish charge transfer kinetic and ultra-short charge lifetime compared with nanoparticulate counterparts, thereby rendering maneuvering charge transfer of TMCs QDs a tough issue. We herein conceptually unlock the unanticipated charge transport capability of solid-state non-conductive poly(diallyl dimethylammonium chloride) (PDDA) for constructing cascade charge transfer pathway over self-assembled wide bandgap semiconductors (WBS)/PDDA/TMCs QDs multilayered heterostructures, by which unidirectional and accelerated electron transfer from TMCs QDs to WBS support mediums was spontaneously activated, markedly boosting the charge separation/migration efficiency. The integrated roles of such ultrathin insulating PDDA intermediate layer as simultaneous surface charge modifying agent and interfacial charge transfer mediator have been evidenced to be universal. The unexpected electron-withdrawing capability of ultrathin PDDA layer endows WBS (SnO2, TiO2)@PDDA@TMCs (CdSe, CdS) QDs heterostructures with significantly enhanced net efficiency of photoactivities toward selective anaerobic reduction of nitroaromatics to amino derivatives under visible light irradiation. Our work would feature a promising scope for rational design of multifarious novel insulating polymers-based photosystems for solar energy conversion.

Synthesis and characterization of poly(p-phenylenediamine): TiO2 nanocomposites and investigation of conducting properties for optoelectronic application

Abstract Poly(p-phenylenediamine) is a potential precursor for designing of new materials for optoelectronic application. Synthesis and characterization of poly(p-phenylenediamine) – TiO2 nanocomposites has been demonstrated. Structural change observed due to the formation of nanocomposites was correlated with concomitant change in conducting behavior of the parent polymer. Polymer nanocomposite was synthesized through an in-situ oxidative polymerization technique with simultaneous dispersion of TiO2 nanoparticles. TiO2 nanoparticles were synthesized via sol-gel process. Structural characterization was accomplished by using conventional spectroscopic and imaging techniques. I-V measurement of the nanocomposites revealed that the nearly nonconducting poly(p-phenylenediamine) after structural modification exhibits conductivity of 10−6 S/cm leading to formation of wide band gap semiconducting materials.

Biodegradable microspheres made of conductive polyorganophosphazene showing antioxidant capacity for improved bone regeneration

Reactive oxygen species (ROS) are likely to accumulate around severe bone defects, which jeopardizes activities of surrounding cells and hampers new bone formation. An effective strategy to address this issue is to develop scaffolding biomaterials with both antioxidant and osteoinductive capacities. An aniline tetramer (AT) and glycine ethyl ester co-substituted polyorganophosphazene (PATGP) was synthesized, and expected to meet the demands, since the AT moieties were antioxidant and the phosphorus-rich phosphazene moieties were osteocompatible. Moreover, the AT endowed the PATGP with conductivity to match the electrophysiology of bone tissues. By applying in vitro cell culture and in vivo evaluations, microsphere-type scaffolds made of PATGP were systematically characterized on their capacities including ROS-scavenging effect, cytotoxicity and osteoinductivity, using non-conductive poly[(ethylalanato)(ethylglycinato)]phosphazene (PAGP) and poly(lactide-co-glycolide) (PLGA) microspheres as control groups. Among them, PATGP microspheres demonstrated the strongest promotion effects on up-regulating cellular activities and on speeding up neobone formation in rat calvarial defects. Compared to polyester-type biomaterials, in summary, polyorganophosphazenes demonstrated strong flexibility in functionalization by introducing supplementary features such as antioxidant activity and electroactivity, which made them to be quite efficient in enhancing osteogenesis.

Improved stability of thin insulating poly(o-aminophenol) films in aqueous solutions through an efficient strategy for electrosynthesis under neutral pH conditions: Electrochemical and XPS investigation

The stability of non-conducting poly(o-aminophenol) films (PoAP), electrosynthesized on Pt substrates by cyclic voltammetry and chronoamperometry, was investigated through electrochemical tests, evaluating changes in permeability to potassium ferricyanide upon prolonged immersion in water solutions. PoAP growth potentiodynamically evidenced poorer stability despite the similar chemical composition, thickness and morphology as detected by XPS and AFM. The prolonged dipping in water caused a post synthesis oxidation of part of iminic functionalities to carbonyls and the removal of polymeric chains weakly bound. Such a removal was estimated by QCM to be about the 43% of the mass deposited by cyclic voltammetry and about the 12% of the mass deposited by chronoamperometry. Potentiostatic deposition was then selected and implemented to achieve an enhanced stability suitable for film practical application. The novel deposition procedure herein proposed is composed of three successive stages: film potentiostatic deposition for 40 min, immersion in water for 1 h, further potentiostatic deposition for 20 min. The major packing efficiency, testified by the higher degree of platinum covering, was responsible for the notable long-term stability. Film compactness was attributed to the intensification of inter-chain hydrogen bonds, mainly between aminic groups, mediated by water molecules trapped inside the polymer at a high extent. The notable stability, verified in pure water as well as in concentrated saline solutions, and the presence of carbonyl terminal groups on the outermost surface, evidenced by Angular Resolved XPS, encourage a future employment of PoAP as a sensor for biomolecules capture and as anticorrosive coating.

Nanoscale Selective Passivation of Electrodes Contacting a 2D Semiconductor

Abstract2D semiconducting materials have become the central component of various nanoelectronic devices and sensors. For sensors operating in liquid, it is crucial to efficiently block the electron transfer that occurs between the electrodes contacting the 2D material and the interfering redox species. This reduces current leakages and preserves a good signal‐to‐noise ratio. Here, a simple electrochemical method is presented for passivating the electrodes contacting a monolayer of MoS2, a representative of transition metal dichalcogenide semiconductors. The method is based on blocking the electrode surface by a thin and compact layer of electronically nonconductive poly(phenylene oxide), PPO, formed by electrochemical polymerization of phenol. Since the phenol polymerization occurs in the potential window where MoS2 is electrochemically inactive, the PPO deposition is area‐selective, limited to the electrode surface. The deposited PPO film is characterized by electrochemical, X‐ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy techniques. The applicability of this method is demonstrated by coating the electrodes of a MoS2‐based field‐effect transistor coupled with a nanopore. The highly selective deposition, the simple approach, and the compatibility with MoS2 makes this method a good strategy for efficient insulation of micro‐ and nanoelectrodes contacting 2D semiconductor‐based devices.

Interfaced conducting polymers

The materials composed of pairs of conducting polymers, polyaniline, polypyrrole and non-conducting poly(p-phenylenediamine), were prepared by the coating of one polymer with the other. The course of polymerizations and morphology of the resulting composites have been recorded and the products were characterized by FTIR and Raman spectroscopies, DC and broad-band AC conductivity and permittivity measurements. The interfacial interaction between conducting polymers does not introduce any new effects concerning the conductivity. On the other hand, using composites where the conducting polymer is embedded in non-conducting polymer matrix allows for the control of structure at nanoscale and for the design of materials with new conductivity properties. This is illustrated by coating the conducting polymers with the poly(p-phenylenediamine) which has the conductivity by eight orders of magnitude lower, which yields composites with an intermediate conductivity, by three orders of magnitude lower than that of the conducting polymers.

Reducing and multiple-element doping of graphene oxide using active screen plasma treatments

A transparent graphene oxide layer on a non-conductive poly(ethylene terephthalate) film was treated by a new active screen plasma technology at temperatures ranging from 100 °C to 200 °C in pure hydrogen and in a gas mixture of hydrogen and nitrogen. To study the thermal reducing effects of the active screen plasma, parallel thermal annealing treatments were also carried out at the same temperatures. UV–visible absorption spectra, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and electrical properties confirmed that the graphene oxide can be effectively reduced by the active screen plasma treatments. Detailed XPS quantitative analyses have revealed that the carboxylic groups are not stable, and their amount can be decreased effectively by the active screen plasma treatments. Only about one third of the carbonyl type CO can be reduced at the same time. In addition to the reduction, simultaneous multi-element doping of GO with nitrogen from the gas supply and with Fe, Cr and Mo from the stainless steel active screen was also detected by XPS.

Structure and electrochemical properties of polystyrene/CNT nanocomposites

The realization of the outstanding properties of CNTs (carbon nanotubes) is constrained by their inherent tendency to agglomerate. Emulsion polymerization was used for synthesizing poly(styrene)/CNT nanocomposites with functionalized CNTs. Chain transfer agents (CTAs) were incorporated to control polymer molar mass and end-use properties. Data from electrical impedance spectroscopy (EIS) at variable frequencies were analyzed to characterize and elucidate the electrical characteristics of poly(styrene) (PS)/CNT nanocomposites. The incorporation of CNT in the polymer matrix even at modest concentrations enhanced the electrical properties of the non-conductive poly(styrene) significantly as revealed by EIS spectra. The use of CTA enabled modulation of polymer molar mass and variation in the electrical properties for PS/CNT relative to composites with no CTA. The electrical behavior of PS/CNT dispersion has been shown to depend both on the CNT concentration and molecular weight of the substrate. The equivalent electrical circuit (EEC) analyses with the corresponding system parameters enabled determination of relative CNT arrangements for different types of PS/CNT composites. TEM images confirmed the CNT positions within the composites and helped support interpretation of EIS/EEC data.

Unexpected Redox Enhancement and Electrochemical Pseudo-capacitance Performance of Polyaniline/poly(vinyl alcohol) (PAn/PVA) Composite Films

We report significant improvement, though unexpected contrary to intuition, of the redox behaviour and electrochemical pseudo-capacitance of polyaniline (PAn) conducting polymer composited with non-conducting poly(vinyl alcohol) (PVA). Redox and film composition characterizations were carried out using a combination of in situ electrochemical and nanogravimentric techniques. Film structural changes due to the presence of PVA in the matrix of PAn have been studied with FT-IR and XRD as well as thermal analysis techniques such as TGA and DSC. The increase in PAn/PVA film redox responses compared to pure PAn film was observed to be a factor of ca. 2 while electrochemical capacitance enhancement was obtained to be ca. 40% increase (ca. 130 F g−1 for PAn/PVA composite film compared to ca. 94 F g−1 for PAn). These drastic improvements of composite film's redox behaviour were attributed to the increase in film chain-chain interactions due to the presence of multiple hydrogen bonding created by the introduction of PVA chain segments in the bulk of PAn film and thus enhancing the rate of film redox conversions. Redox enhancement was also associated to the increase in composite film's ion doping capacity.

Redox competition and generation-collection modes based scanning electrochemical microscopy for the evaluation of immobilised glucose oxidase-catalysed reactions

Redox competition (RC-SECM) and generation-collection (GC-SECM) modes of scanning electrochemical microscopy were applied for the evaluation of a glucose oxidase (GOx)-modified non-conducting poly(methyl methacrylate) surface.

Poly(ε-Caprolactone)–Carbon Nanotube Composite Scaffolds for Enhanced Cardiac Differentiation of Human Mesenchymal Stem Cells

To evaluate the efficacy of electrically conductive, biocompatible composite scaffolds in modulating the cardiomyogenic differentiation of human mesenchymal stem cells (hMSCs). Electrospun scaffolds of poly(ε-caprolactone) with or without carbon nanotubes were developed to promote the in vitro cardiac differentiation of hMSCs. Results indicate that hMSC differentiation can be enhanced by either culturing in electrically conductive, carbon nanotube-containing composite scaffolds without electrical stimulation in the presence of 5-azacytidine, or extrinsic electrical stimulation in nonconductive poly(ε-caprolactone) scaffolds without carbon nanotube and azacytidine. This study suggests a first step towards improving hMSC cardiomyogenic differentiation for local delivery into the infarcted myocardium.

Polyaniline/poly(vinyl alcohol) (PAN/PVA) composite films: the synergy of film structural stiffening, redox amplification, and mobile species compositional dynamics

In this work, we report an unexpected but significant improvement of the redox behavior of conducting polyaniline (PAN) films by trapping intrinsically nonconducting poly(vinyl alcohol) (PVA) in the matrix of the polymer acting as stiffening and/or cross-linking agents. Film structural stiffening of PAN/PVA inclusion was studied in relation to film compositional dynamics. PAN and PAN/PVA composite films were potentiodynamically deposited using high-frequency electrochemical quartz crystal microbalance under electrochemical potentiodynamic control. From the simultaneously obtained measurements of nanogravimetric and cyclic voltammetric data, it has been found that the presence of PVA in the deposition solution increased the rate of PAN film growth as a function of PVA concentration. Characterization of the resultant composite films in monomer-free acidic electrolyte solutions showed significantly enhanced redox behavior of PAN/PVA composite films (with different PVA contents) compared to pure PAN by a factor of ∼2–4. For the study of structure–composition relationships of composite polymer films, fluxes of instantaneous mobile species dynamics (ion/solvent) as a function of film redox conversion and potential cycling were correlated with film structural stiffening and the observed unusual redox enhancement of PAN/PVA composite films. Using various experimental timescales, we were able to resolve bound (associated with ion transfer) and free solvent compositional dynamics (associated with thermodynamic activity balance).

Determination of epigallocatechin‐3‐gallate with a high‐efficiency electrochemical sensor based on a molecularly imprinted poly(o‐phenylenediamine) film

AbstractAn electrochemical molecularly imprinted polymer (MIP) sensor for detecting the existence of epigallocatechin‐3‐gallate (EGCG) in tea and its products was successfully developed on the basis of a glassy carbon electrode modified with an electropolymerized nonconducting poly(o‐phenylenediamine) film. The properties of the electrode were characterized by cyclic voltammetry, differential pulse voltammetry, and infrared spectroscopy. The template molecules could be rapidly and thoroughly removed by methanol/acetic acid. The linear response range for EGCG was 5.0 × 10−7–1.0 × 10−4 mol/L, and the limit of detection was as low as 1.6 × 10−7 mol/L. The prepared MIP sensor could discriminate between EGCG and its analogs. In addition, satisfactory results were obtained in the detection of real tea samples. The results of our investigation indicate that the MIP sensor was useful for the determination of EGCG with excellent selectivity, high sensitivity, repeatability, and reproducibility. This MIP sensor provides the potential for monitoring the variation of EGCG content during the industrial processes and for predicting the quality of tea and its products. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Non-Conducting Poly(O-Aminophenol) Films in the Field of the Bioelectrochemistry

The practical use of non-conducting poly(o-aminophenol) (POAP) films in the field of the bioelectrochemistry is discussed in this paper. Particular emphasis is given to the effects of applied potential, solution pH and interferents on the response current of biosensors based on POAP.

A simple and controllable nanostructure comprising non-conductive poly(vinylidene fluoride) and graphene nanosheets for supercapacitor

An effective method was used to produce stable and homogeneous colloidal suspensions of highly reduced graphene oxide (RGO) in N,N-dimethylformamide (DMF) without the assistance of dispersing agents. According to the results of general characterization, relatively pure graphene sheets with the morphology of single layer or few-layer structure were obtained. Then nanocomposite powders of RGO and poly (vinylidene fluoride) (PVDF) were prepared by vacuum filtration of the mixed dispersions of both components. The nanocomposites exhibit a high-frequency capacitative response with small equivalent series resistance (ESR) at 0.4 Ω, a nearly rectangular cyclic voltammogram and possess a rapid current response as electrodes for supercapacitor in 5mol/L KOH electrolyte. Furthermore, after 600 galvanostatic charge/discharge cycles, the supercapacitor still performs a very high stability and efficiency of capacitance.

Design of Interpenetrated Networks of Mesostructured Hybrid Silica and Nonconductive Poly(vinylidene fluoride)–Cohexafluoropropylene (PVdF–HFP) Polymer for Proton Exchange Membrane Fuel Cell Applications

Organic-inorganic hybrid membranes of poly(vinylidene fluoride)-cohexafluoropropylene (PVdF-HFP) and mesostructured silica containing sulfonic acid groups were synthesized by using the sol-gel process. These hybrid membranes were prepared by in situ co-condensation of tetraethoxysilane and an organically modified silane (ormosil) by a self-assembly route using organic surfactants as templates for tuning the architecture of the hybrid organosilica component. In this paper, we describe the elaboration and characterization of hybrid membranes all the way from the precursor solution to the evaluation of the fuel cell performances. These hybrid materials were extensively characterized by using NMR and IR spectroscopy, electron microscopy, or impedance spectroscopy so as to determinate their physicochemical and electrochemical properties. Even though the ion-exchange capacity (IEC) was quite weak, the first fuel cell tests performed with these hybrid membranes show promising results relative to optimized Nafion 112 thanks to great water management of the silica inside the hydrophobic polymer.

Determination of the local gold contact morphology on a photoactive polymer film using nanobeam GISAXS

Grazing incidence small-angle X-ray scattering is performed with a nanometer sized X-ray beam (nGISAXS) to probe the local gold contact morphology on a photoactive polymer film. By evaporation a 50 nm thick gold contact is installed on a diblock copolymer film, which consists of a non-conducting poly(styrene) (PS) and a semi-conducting poly(paraphenylene) (PPP) block. The region around the edge of the gold contact of 200 μm is probed with nGISAXS by scanning the sample position in steps of 1 μm with respect to the X-ray beam. The diblock copolymer film has a densely packed micellar structure with a characteristic distance between adjacent micelles of 19 nm which is unaffected by the gold deposition. The gold contact exhibits a tail region which extends its lateral dimension. For the full extended surface area of the gold contact with its tails an interdiffusion of gold into the diblock copolymer film is observed. For comparison imaging ellipsometry, atomic force microscopy and optical microscopy measurements are performed.