ЭЛЕКТРОКАТАЛИТИЧЕСКОЕ ВЫДЕЛЕНИЕ ВОДОРОДА НА СТЕКЛОУГЛЕРОДНОМ ЭЛЕКТРОДЕ, МОДИФИЦИРОВАННОМ НИКЕЛЬ-СОДЕРЖАЩИМ КОМПОЗИТОМ С НАНОТРУБКАМИ

Cardiovascular disease is currently the top global cause of death, however, research into new therapies is in decline. Tissue engineering is a solution to this crisis and in combination with the use of carbon nanotubes (CNTs), which have drawn recent attention as a biomaterial, could facilitate the development of more dynamic and complex in vitro models. CNTs’ electrical conductivity and dimensional similarity to cardiac extracellular proteins provide a unique opportunity to deliver scaffolds with stimuli that mimic the native cardiac microenvironment in vitro more effectively. This systematic review aims to evaluate the use and efficacy of CNTs for cardiac tissue scaffolds and was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Three databases were searched: PubMed, Scopus, and Web of Science. Papers resulting from these searches were then subjected to analysis against pre-determined inclusion and quality appraisal criteria. From 249 results, 27 manuscripts met the criteria and were included in this review. Neonatal rat cardiomyocytes were most commonly used in the experiments, with multi-walled CNTs being most common in tissue scaffolds. Immunofluorescence was the experimental technique most frequently used, which was employed for the staining of cardiac-specific proteins relating to contractile and electrophysiological function.

Νέα προσέγγιση στην παρακολούθηση της αναπτυσσόμενης βλάβης υπό μηχανική φόρτιση σε ινώδη σύνθετα υλικά με μήτρα ενισχυμένη με νανοσωληνίσκους άνθρακα

The rapid development of modern technology requires new materials with predetermined properties. There is a need for materials with ultra-high strength, hardness, other characteristics and a common combination of these properties. The work was aimed at solving the problem of creating polymer composite materials that combine high physical and mechanical characteristics and thermal and electrical conductivity. Information was given on fillers, the use of which gives polymers thermal and electrical properties. Shown are the most commonly used in the composition of polymer composites fillers, advantages and disadvantages of each of the fillers. It was established that the use of carbon nanotubes allows obtaining polymer composites with the required performance characteristics. One of the problems when using nanoparticles as modifiers of reactive oligomers is their uniform distribution in the volume of the polymer matrix. Heterogeneity and uneven distribution of the dispersed phase can lead to dangerous defects in the material, so the technology of combining the nanofillers and the polymer matrix plays an important role. The possibility of obtaining polyvinyl butyral structured with carbon nanotubes in the process of its synthesis in the presence of carbon nanotubes was shown and the technological conditions of In situ synthesis are developed. Experimental samples of polyvinyl butyral structured with carbon nanotubes with high thermal and electrically conductive characteristics were obtained. Under optimal conditions of synthesis, in the obtained PVB samples structured with carbon nanotubes, the electrical conductivity of the composite increases by five orders of magnitude due to the high electrical conductivity of CNTs. For the obtained PVB, structured with carbon nanotubes, the fracture stress was significantly (by 62 %) increased, and the fracture deformation is reduced by approximately 38 %. The decrease in the deformation of the fracture during compression indicates an increase in the fragility of the polymer with the inclusion of CNTs. The prospects for the synthesis of polyvinyl butyral in the presence of carbon nanotubes to obtain a composite with a high level of achieved electrical and thermal conductivity were shown.

Carbon nanotubes (CNTs) possess exceptional mechanical, thermal, and electrical properties, facilitating their use as reinforcements or additives in various materials to improve the properties of the materials. Furthermore, chemically modified CNTs can introduce novel functionalities. In the medical field, biomaterials are expected to be developed using CNTs for clinical use. Biomaterials often are placed adjacent to bone. The use of CNTs is anticipated in these biomaterials applied to bone mainly to improve their overall mechanical properties, for applications such as high-strength arthroplasty prostheses or fixation plates and screws that will not fail. In addition, CNTs are expected to be used as local drug delivery systems (DDS) and/or scaffolds to promote and guide bone tissue regeneration. However, studies examining the use of CNTs as biomaterials still are in the preliminary stages. In particular, the influence of CNTs on osteoblastic cells or bone tissue is extremely important for the use of CNTs in biomaterials placed in contact with bone, and some studies have explored this. This review paper clarifies the current state of knowledge in the context of the relationship between CNTs and bone to determine whether CNTs might perform in biomaterials in contact with bone, or as a DDS and/or scaffolding for bone regeneration.

Carbon nanotubes (CNT) are highly versatile materials, with an enormous potential for biomedical applications. Their properties are dependent upon production process and may be modified by subsequent chemical treatment. Carbon nanotubes can be used to improve polymers’ composites mechanical properties. Its tailoring allows for the creation of anisotropic nanocomposites (Kanagaraj et al, 2007; Koerner et al, 2004; Pulskamp et al, 2007; Sen et al, 2004). Due to their semi conductive behaviour, its usage may provide electrical stimulation (Grunlan et al, 2004; Huang et al, 2003). The use of CNT as translocators in drug-delivery systems or in image diagnosis has also been suggested (Bianco et al, 2005; Cherukuri et al, 2004). High tumour accumulation of single-walled CNT (SWCNT) has been described, anticipating the possibility of further therapeutic uses (Liu et al, 2007). There are several studies on gas, temperature, pressure, glucose, chemical force and resonator mass sensors based on CNT (Barone et al, 2005; Barone et al, 2005b; Collins et al, 2000; Hrapovic et al, 2004; Kong et al, 2000; Lee et al, 2007; Lin et al, 2005; Perez et al, 2005; Wood et al, 1999; Yan et al, 2007; Yang et al, 2006; Yun et al, 2007). In face of recent studies, special attention has been drawn into promising orthopaedic use of CNT for improving tribological behaviour and material mechanical properties. However, and considering the conductive properties of CNT the range of orthopaedic application may broaden up, since it is known that electrical fields as small as 0,1 mV/cm may enhance osteoblastic proliferation locally (Brighton et al, 1992). CNT based electrodes could be considered for integrating implantable orthopaedic devices. CNT have been reported to have direct and distinct effects on osteoblasts and osteoclasts metabolic functions (Narita et al, 2009; Sirivisoot et al, 2007; Tutak et al, 2009). CNT have been discovered in 1991 (IIjima, 1991), but seem to have been around for quite a long time, since they were detected in gas combustion streams like the ones in normal households stoves (Murr et al, 2004). The fact that CNT are small enough to be inhaled has

On the conversion of point-to-linear hierarchical micro/nano-structures on the glassy carbon surface by nanosecond pulsed laser irradiation

The hydrogen evolution reaction (HER) produces (di)hydrogen (H2) as a clean energy carrier. Herein, a cobalt(pyridinethiolate N‐oxide)2 complex was synthesized and fully characterized, and tested for HER activity. While this complex did not show any reliable HER activity, we found that in acidic DMF, HER active nanoparticles were reductively deposited onto a glassy carbon electrode. The ellipsoidal Co nanoparticles were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), SEM energy‐dispersive X‐ray spectroscopy (EDS), X‐ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP‐MS). The amount of deposited material, and the size and number of nanoparticles was shown to increase linearly with the number of deposition scans. Cyclic voltammetry scans showed that the onset potential for HER decreases and the catalytic current increases with the diameter of the nanoparticles. A drop‐cast Nafion thin film improved the durability of the nanoparticle‐covered electrodes, allowing for HER for at least 8 hrs. These electrodes have a Faradaic efficiency of 100 ± 3 %, and produce 14.1 mmol H2 per gram Co per second, at pH 1. Cobalt bis(mpo) is thus an ideal precursor complex for the controlled electrodeposition of metallic Co nanoparticles with a defined size and shape.

A critical review of the recent progress on carbon nanotubes-based nanogenerators

We have examined the interaction of H2O vapor with three structurally different carbon surfaces. The edge and basal surface of crystalline graphite as well as a ‘‘paracrystalline’’ glassy carbon were characterized with LEED, UPS, and AES. Structural characterization by LEED showed the typical ‘‘ring’’ pattern for the basal surface; the edge surface showed evidence of structural order distinct from the basal plane and the glassy carbon showed only diffuse scattering. UPS from the glassy carbon and edge graphite surfaces showed increases in emission within 2 eV of EF relative to the basal plane. This is associated with the presence of less saturated surface valence structure. Exposure to H2O vapor at 30 °C produced saturation oxygen coverage after 10−2 Torr s on the glassy carbon and after 10−1 Torr s on the edge surface. Adsorption on the basal surface saturated at lower coverages and the residual adsorption activity is attributed to surface irregularities. UPS of the glassy carbon and edge graphite surfaces provided evidence for the dissociative adsorption of water. The adsorbed oxygen species produced are strongly held and desorbed as CO between 650–800 °C. Our results show that the edge surface of graphite and less ordered carbon surfaces are active for H2O dissociation.

The performance of microchip electrophoresis/electrochemistry system with carbon nanotube (CNT) film electrodes was studied. Electrocatalytic activities of different carbon materials (single-wall CNT (SWCNT), multiwall CNT (MWCNT), carbon powder) cast on different electrode substrates (glassy carbon (GC), gold, and platinum) were compared in a microfluidic setup and their performance as microchip electrochemical detectors was assessed. An MWCNT film on a GC electrode shows electrocatalytic effect toward oxidation of dopamine (E(1/2) shift of 0.09 V) and catechol (E(1/2) shift of 0.19 V) when compared to a bare GC electrode, while other CNT/carbon powder films on the GC electrode display negligible effects. Modification of a gold electrode by graphite powder results in a strong electrocatalytic effect toward oxidation of dopamine and catechol (E(1/2) shift of 0.14 and 0.11 V, respectively). A significant shift of the half-wave potentials to lower values also provide the MWCNT film (E(1/2) shift of 0.08 and 0.08 V for dopamine and catechol, respectively) and the SWCNT film (E(1/2) shift of 0.10 V for catechol) when compared to a bare gold electrode. A microfluidic device with a CNT film-modified detection electrode displays greatly improved separation resolution (R(s)) by a factor of two compared to a bare electrode, reflecting the electrocatalytic activity of CNT.

Carbon nanotubes, with their unique structure, are expected to have a variety of applications as industrial materials. However, carbon nanotubes synthesized using the laser ablation method or arc discharge evaporation method always include other carbonaceous materials. Purification is a very important step in the use of carbon nanotubes as industrial materials. For the efficient recovery of nanotubes it is very important to clarify the gasification behaviour of the nanotube-containing material during the purification step. In this study, the gasification behaviour of a nanotube-containing material with various gasification agents was investigated in detail using a fixed-point observation technique and scanning electron microscopy. The gasification manner of the carbon nanotube-containing material was clarified using oxygen, carbon dioxide and hydrogen plasma as the gasifying agents. The gasification behaviour of the sample depended on the kind of reactant gas. In hydrogen plasma, carbon nanotubes were partly purified. Under the experimental conditions examined, oxygen gasification at 1023 K was the most effective method for purification of carbon nanotubes, and nanotubes were recovered selectively.

Carbon nanotube (CNT) wires are light-weight and robust alternatives to conventional metal conductors. The weight savings, increased flexure tolerance, and corrosion resistance of CNT conductors make them a viable solution for a variety of space, defense, and power transmission applications. An individual CNT has orders of magnitude greater electrical conductivity than conventional metal conductors, but this has not been realized in bulk CNT networks. Recently, the use of chemical dopants has resulted in bulk CNT wire conductivities approaching 10 MS/m. As the electrical conductivity of CNT wires continues to approach that of conventional metals, deployment of these CNT conductors will require an understanding of how these CNT conductors and chemical dopants behave during practical operation.In the present work, commercially scaled CNT wires are physically densified through radial drawing dies and chemically doped with KAuBr4 resulting in an improvement in electrical conductivity to greater than 1 MS/m, a 6x improvement compared to the as-received CNT wire. The current density at failure of CNT wires increases with KAuBr4 doping and densification by 67% to 35 MA/m2. The electrical performance retention is determined by applying increasing current densities with intermittent rest steps and low current I-V sweeps. The low current I-V sweeps allow for changes in electrical conductivity due to permanent material degradation caused by previous high current density exposure to be determined. The instantaneous electrical conductivity averaged over the last 5 seconds of each current “on” step is used to determine the temperature dependent effects on electrical conductivity caused by Joule heat during high current application. The KAuBr4 doped and densified samples experience no permanent change in initial electrical conductivity at current densities up to ~32 MA/m2, 4x greater than the as-received CNT wires.The enhanced electrical conductivity retention of KAuBr4 doped and densified CNT wires at high current density was further probed though an analysis of the thermal stability of these doped CNT conductors. Thermogravimetric analysis indicated that minimal degradation of the KAuBr4 dopant occurs prior to thermal oxidation of the CNT materials at 400 °C. A variety of KAuBr4 doping and 400 °C thermal oxidation procedures were performed on CNT wires to understand how thermal degradation of the dopant relates to changes in the electrical conductivity and high current density stability. Energy dispersive X-ray (EDX) spectroscopy further related the changes in electrical conductivity to the elemental spatial analysis of gold and bromine in the KAuBr4-doped CNT samples before and after 400 °C thermal oxidation. This work concludes that the thermal stability of KAuBr4 results in improved electrical conductivity and stability at high current densities. Trace bromine and gold nanoparticles are maintained at temperatures below the onset of CNT degradation, thus providing residual doping until ultimate CNT wire failure.Recently chemical dopants such as I2 and IBr have also emerged as premiere dopants to improve the electrical conductivity of bulk CNT networks. These dopants will be used to further explore the effect doping procedures and the presence of excess dopant have on the electrical conductivity and high current stability of doped CNT wires. Developing a relationship between dopant thermal stability and electrical conductivity retention will allow for the development of a mechanism explaining dopant degradation at high current densities.

9-Fluorenyl radical: Electrochemical generation and cathodic immobilization at solid interfaces

Carbon Nanotubes (CNTs) grown on substrates are potential electron sources in field emission applications. Several studies have reported the use of CNTs in field emission devices, including field emission displays, X-ray tube, electron microscopes, cathode-ray lamps, etc. Also, in recent years, conventional cold field emission cathodes have been realized in micro-fabricated arrays for medical X-ray imaging. CNT-based field emission cathode devices have potential applications in a variety of industrial and medical applications, including cancer treatment. Field emission performance of a single isolated CNT is found to be remarkable, but the situation becomes complex when an array of CNTs is used. At the same time, use of arrays of CNTs is practical and economical. Indeed, such arrays on cathode substrates can be grown easily and their collective dynamics can be utilized in a statistical sense such that the average emission intensity is high enough and the collective dynamics lead to longer emission life. The authors in their previous publications had proposed a novel approach to obtain stabilized field emission current from a stacked CNT array of pointed height distribution. A mesoscopic modeling technique was employed, which took into account electro-mechanical forces in the CNTs, as well as transport of conduction electron coupled with electron–phonon induced heat generation from the CNT tips. The reported analysis of pointed arrangements of the array showed that the current density distribution was greatly localized in the middle of the array, the scatter due to electrodynamic force field was minimized, and the temperature transients were much smaller compared to those in an array with random height distribution. In the present paper we develop a method to compute the emission efficiency of the CNT array in terms of the amount of electrons hitting the anode surface using trajectory calculations. Effects of secondary electron emission and parasitic capacitive nonlinearity on the current-voltage signals are accounted. Field emission efficiency of a stacked CNT array with various pointed height distributions are compared to that of arrays with random and uniform height distributions. Effect of this parasitic nonlinearity on the emission switch-on voltage is estimated by model based simulation and Monte Carlo method.

Influence of etching of polycrystalline Au-, Pt- and glassy carbon surfaces with OH[rad] radicals on electrodeposition of metals