Layer-by-layer polypyrrole coated graphite oxide and graphene nanosheets as catalyst support materials for fuel cells

For the production of advanced types of catalyst support materials, the distinguished properties of graphene nanosheets were combined with the structural properties of conducting polypyrrole by the incorporation of graphene nanosheets into a polymer matrix by the proposed simple and low-cost fabrication technique. A precise tuning of electrical conductivity and thermal stability was achieved by controlling the polymer thickness of randomly dispersed graphene nanosheets. Initially, graphene nanosheets were fabricated in large quantities via a mild chemical synthetic route involving graphite oxidation, ultrasonic treatment, and chemical reduction. Then, polypyrrole/graphene nanosheet composites with improved conductivity, thermal stability, and high surface area were synthesized by in situ polymerization with the different pyrrole feed ratios. Although graphite oxide sheets have electrically insulating property, partially oxidized graphite oxide was also utilized as conductive fillers in polymer matrix. However, polypyrrole/graphene nanosheet composites have better electrical conductivity than polypyrrole/graphite oxide composites

Layer-by-layer polypyrrole coated graphite oxide and graphene nanosheets as catalyst support materials for fuel cells

For the production of advanced type of catalyst support materials, the distinguished properties of graphene nanosheets were combined with the structural properties of conducting polypyrrole by the incorporation of graphene nanosheets into a polymer matrix by the proposed simple and low-cost fabrication technique. A precise tuning of electrical conductivity and thermal stability was also achieved by controlling the thickness of randomly dispersed graphene nanosheets by a layer-by-layer polymer coating. Initially, graphene nanosheets were fabricated in large quantities via a mild chemical synthetic route involving graphite oxidation, ultrasonic treatment and chemical reduction. Then, polypyrrole/graphene nanosheet composites with improved conductivity, thermal stability and high surface area were synthesized by in situ polymerization with the different pyrrole feed ratios. Although graphite oxide sheets have electrically insulating property, partially oxidized graphite oxide was also utilized as conductive fillers in polymer matrix. However, polypyrrole/graphene nanosheet composites have better electrical conductivity than polypyrrole/graphite oxide composites

The metallic state in disordered quasi-one-dimensional conductors

The unusual metallic state in conjugated polymers and single-walled carbon nanotubes is studied by dielectric spectroscopy (8--600 GHz). We have found an intriguing correlation between scattering time and plasma frequency. This relation excludes percolation models of the metallic state. Instead, the carrier dynamics can be understood in terms of the low density of delocalized states around the Fermi level, which arises from the competion between disorder-induced localization and interchain-interactions-induced delocalization.Comment: 4 pages including 4 figure

Dual sensing-actuation artificial muscle based on polypyrrole-carbon nanotube composite

Dual sensing artificial muscles based on conducting polymer are faradaic motors driven by electrochemical reactions, which announce the development of proprioceptive devices. The applicability of different composites has been investigated with the aim to improve the performance. Addition of carbon nanotubes may reduce irreversible reactions. We present the testing of a dual sensing artificial muscle based on a conducting polymer and carbon nanotubes composite. Large bending motions (up to 127 degrees) in aqueous solution and simultaneously sensing abilities of the operation conditions are recorded. The sensing and actuation equations are derived for incorporation into a control system.The research was supported by European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 641822

Zinc-rich paint coatings containing either ionic surfactant-modified or functionalized multi-walled carbon nanotube-supported polypyrrole utilized to protect cold-rolled steel against corrosion

The intense anodic action of sacrificial zinc pigments ensured viable galvanic function of the highly porous liquid zinc-rich paints (ZRPs) result in deteriorated long-term corrosion resistance often accompanied by cathodic delamination phenomena. In our approach, such a efficacy problem related to the corrosion preventive function of ZRPs is addressed by the application of intimately structured anodic inhibitor particles composed of nano-size alumina and either polyelectrolyte-modified or chemically functionalized multi-walled carbon nanotubes (MWCNT) supported polypyrrole (PPy) in one specific zinc-rich hybrid paint formulation providing balanced active–passive protective functionality. High dispersity of the nanotube-free PPy-deposited inhibitor particles (PDIPs) with uneven polymer distribution on the alumina carrier was confirmed by transmission electron microscopy (TEM) observations. Furthermore, the MWCNT-embedded PDIPs indicated almost complete surface coverage of the alumina-nanotube carriers by PPy with decreased microstructure dispersity which is attributed to the effect of double-flocculants type co-deposition of the oppositely charged polymers causing coalescence of the modified particles. Depending on the amount of the nanotubes and their proportion to the quantities of the deposited PPy and polyelectrolyte as well as the concentration of the surfactant, varied micron-scale association of the PDIPs in the suspensions of dissolved alkyd matrix was disclosed by rheology characterization carried out at particular solid contents similar to hybrid paint formulation. The evenly distributed but less densely packed nano-structure of PPy was evidenced on the polyelectrolyte-modified nanotubes by Fourier-transform infrared (FTIR) spectroscopy whereas more compact polymer film formation was confirmed on the surface of functionalized nanotubes. According to the greater electrical conductivity, enhanced electroactivity and reversibility of the nanotube-embedded PDIPs were indicated over the nanotube-free particles by cyclic voltammetry, depending on the type and the amount of the nanotubes and their modification. Protection function of the hybrid paint coatings (formulated with spherical zinc pigment at 70 wt.%) was investigated by immersion and salt-spray chamber tests over 254 and 142 day periods, respectively. Firm barrier nature of the nanotube-embedded PDIP contained hybrids was proved by electrochemical impedance spectroscopy (EIS) and radio-frequency glow-discharge optical-emission-spectroscopy (RF-GD-OES). Furthermore, due to the increased conductivity of the nanotube-embedded PDIPs cemented in epoxy primers optimally at 0.4 and 0.6 wt.%, altered corrosion preventive behaviour of the hybrid coatings was indicated by the positively polarized open-circuit potentials (OCPs) and the X-ray photoelectron spectroscopy (XPS) detected lower relative quantities of the interfacially accumulated zinc corrosion products, moderate oxidative degradation of the epoxy vehicle. Decreasing oxidative conversion of iron at the surface was indicated by XPS found to correlate with the increasing intensity of zinc corrosion and decreasing oxidative degradation of the epoxy binder, according to the higher nanotube contents of hybrid coatings. In addition, inhibited zinc corrosion caused low rate of oxidative degradation of epoxy, allowing increased durability of coating adhesion and cohesion thereby ensuring reliable protection by zinc-rich compositions. As a conclusion, modified or functionalized MWCNTs acting as unexchangeable doping agents promote enhanced reversibility and increased conductivity of PPy, forming nano-size inhibitor particles with advanced features. Thus, such inhibitor nano-particles in zinc-rich hybrid compositions afford improved barrier and high efficiency galvanic–cathodic corrosion preventive function, exceeding long-term protection capability of the conventional ZRPs

Organic electrode coatings for next-generation neural interfaces

Traditional neuronal interfaces utilize metallic electrodes which in recent years have reached a plateau in terms of the ability to provide safe stimulation at high resolution or rather with high densities of microelectrodes with improved spatial selectivity. To achieve higher resolution it has become clear that reducing the size of electrodes is required to enable higher electrode counts from the implant device. The limitations of interfacing electrodes including low charge injection limits, mechanical mismatch and foreign body response can be addressed through the use of organic electrode coatings which typically provide a softer, more roughened surface to enable both improved charge transfer and lower mechanical mismatch with neural tissue. Coating electrodes with conductive polymers or carbon nanotubes offers a substantial increase in charge transfer area compared to conventional platinum electrodes. These organic conductors provide safe electrical stimulation of tissue while avoiding undesirable chemical reactions and cell damage. However, the mechanical properties of conductive polymers are not ideal, as they are quite brittle. Hydrogel polymers present a versatile coating option for electrodes as they can be chemically modified to provide a soft and conductive scaffold. However, the in vivo chronic inflammatory response of these conductive hydrogels remains unknown. A more recent approach proposes tissue engineering the electrode interface through the use of encapsulated neurons within hydrogel coatings. This approach may provide a method for activating tissue at the cellular scale, however, several technological challenges must be addressed to demonstrate feasibility of this innovative idea. The review focuses on the various organic coatings which have been investigated to improve neural interface electrodes

Glass Transition Temperature Depression at the Percolation Threshold in Carbon Nanotube-Epoxy Resin and Polypyrrole-Epoxy Resin Composites

The glass transition temperatures of conducting composites, obtained by blending carbon nanotubes (CNTs) or polypyrrole (PPy) particles with epoxy resin, were investigated by using both differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). For both composites, dc and ac conductivity measurements revealed an electrical percolation threshold at which the glass transition temperature and mechanical modulus of the composites pass through a minimum