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The influence of the irradiation of single-wall carbon nanotubes and also of graphite by high-energy gamma rays is investigated by Raman spectroscopy. The intensity as well as the position of the G line do not change upon irradiation for graphites, where as the intensity of the D line increases significantly, confirming the defect-based mechanism for Raman scattering from this particular phonon mode.

Discrete nickel catalyst nanoparticles have been used to grow isolated single-walled carbon nanotubes by chemical vapor deposition. Atomic force microscopy, transmission electron microscopy, and micro-Raman spectroscopy have been used to characterize the as-grown, isolated nanotubes.

A study was conducted to determine the electrical activation energy in boron-doped diamond films by the flatband capacitance technique. A Schottky barrier structure was prepared on the semiconductor films using the microwave enhanced chemical vapor deposition technique. Results suggested that the flatband capacitance measurement can be utilized in electrical activation energy investigations related to wide-gap semiconductors.

In spite of the attractive electrical properties of metal oxide nanowires, it is difficult to tune their surface states, notably the ionic adsorbents and oxygen vacancies, both of which can cause instability, degradation, and the irreproducibility or unrepeatable changes of the electrical characteristics. In order to control the surface states of the nanowires, electron beams were locally irradiated onto the channels of metal oxide nanowire field effect transistors. This high energy electron beam irradiation changed the electrical properties of the individual metal oxide nanowires, due to the removal of the negative adsorbents (O2-, O-). The detachment of the ionic adsorbents changes the charge states of the nanowires, resulting in the enhancement of the electrical conductance in n-type nanowires (ZnO, SnO2) and the degradation of the conductance in p-type nanowires (CuO). By investigating the changes in the electrical properties of nanowire devices in air or vacuum, with or without exposure to electron beams, the roles of the physisorbed water molecules or chemisorbed oxygen molecules can be independently understood. Unlike the electron beam irradiation, the vacuum enhanced the conductance of both n-type (ZnO, SnO2) and p-type (CuO) nanowires, due to the release of charges caused by the detachment of the polarized water molecules that were screening them from the surface of the nanowires, irrespective of the major carrier type. The electron beam irradiation technique has the potential to locally modulate the charge carriers in electronic nanowire devices, and the changes could be maintained with proper passivation for the long-term preservation of the device characteristics. [ABSTRACT FROM AUTHOR]

Graphite and single-wall carbon nanotubes irradiated by γ rays of energy of 1.3 MeV were investigated by Raman spectroscopy. Irradiation generates defects in the lattice as confirmed by the increase of the intensity of the defect-induced D line in both materials. On the other hand, the intensity of the radial breathing mode of nanotubes is lowered. The intensity of the G line does not change for graphite but increases for carbon nanotubes. For the latter, this behavior cannot be explained by the defect-mediated double-resonance mechanism. Softening of the q=0 selection rule is suggested as a way to explain the results. [ABSTRACT FROM AUTHOR]

High levels of electrochemical doping of bundled single-walled carbon nanotubes (SWNT) are used to study the transition taking place from the electrochemical double-layer charging to intercalation and functionalization of the system. A significant penetration of chlorine species into the interstitial channels of SWNT bundles happens above the electric potential of 1000mV.

The preparation of the multiwalled carbon nanotube (MWCNT)/poly(L-lactide) composite and their corresponding spectroscopic (Raman), the microscopic characterization, electron transport, thermal properties and biocompatibility are reported. The study of PLLA/MWCNT composite has shown that the MWCNTs in the composite have the effect of inducing crystallization and plasticizing the polymer matrix and its presence in the composite inhibits the growth of the fibroblast cells.

The effect of SOCl2 exposure on the electrical and mechanical properties of entangled networks of single-wall carbon nanotubes (SWNTs) is investigated. A remarkable improvement of the electrical conductivity and mechanical properties due to chemical modification of SWNTs by SOCl2 is observed.

Current research about resistive sensors is rarely focusing on improving the strain range and linearity of resistance-strain dependence. In this paper, a bi-sheath buckled structure is designed containing buckled carbon nanotube sheets and buckled rubber on rubber fiber. Strain decrease results in increasing buckle contact by the rubber interlayer and a large decrease in resistance. The resulting strain sensor can be reversibly stretched to 600%, undergoing a linear resistance increase as large as 102% for 0-200% strain and 160% for 200-600% strain. This strain sensor shows high linearity, fast response time, high resolution, excellent stability, and almost no hysteresis. [ABSTRACT FROM AUTHOR]

Synchrotron radiation circular dichroism (SRCD) is a rapidly growing technique for structure analysis of proteins and other chiral biomaterials. UV-CD12 is a high-flux SRCD beamline installed at the ANKA synchrotron, to which it had been transferred after the closure of the SRS Daresbury. The beamline covers an extended vacuum-UV to near-UV spectral range and has been open for users since October 2011. The current end-station allows for temperature-controlled steady-state SRCD spectroscopy, including routine automated thermal scans of microlitre volumes of water-soluble proteins down to 170 nm. It offers an excellent signal-to-noise ratio over the whole accessible spectral range. The technique of oriented circular dichroism (OCD) was recently implemented for determining the membrane alignment of α-helical peptides and proteins in macroscopically oriented lipid bilayers as mimics of cellular membranes. It offers improved spectral quality <200 nm compared with an OCD setup adapted to a bench-top instrument, and accelerated data collection by a factor of ∼3. In addition, it permits investigations of low hydrated protein films down to 130 nm using a rotatable sample cell that avoids linear dichroism artifacts. [ABSTRACT FROM AUTHOR]

This work addresses the impact of co-percolating carbon nanotubes within a silver nanowire network with regard to the optoelectrical performance as a transparent electrode. We carried out a comprehensive measurement series and focused on ultra-transparent electrodes with optical transmission above 95%. We found an immense improvement of the optoelectrical performance for networks near the percolation threshold of the silver nanowires after carbon nanotubes have been added. We were able to decrease the sheet resistance of the silver nanowire networks by a factor of up to 70 after adding carbon nanotubes. We produced transparent electrodes with industrially acceptable sheet resistance at optical transmission of higher than 97%. This work outlines the potential of co-percolating rod-like conductors as a network for ultra-transparent electrodes. Our experimental work confirms theoretical approaches in percolation theory since we systematically evaluated films with high optical transmission. The most transparent films are beyond the descriptiveness with the percolation scaling law. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

This is a short report on a special workshop on matters 'around' science, held during the Kirchberg Winterschool 2013 on Electronic Properties of Novel Materials. The topics discussed are patents, experiences of small start-up companies, funding and patenting strategies of large research institutes (like CRANN in Ireland and Fraunhofer Society in Germany) and success stories of cooperation between American university institutes and industrial partners (from invention over demonstrator, prototype, and pilot plant to production lines). (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

This report demonstrates application of expanded graphite (ExG) for thermoelectric energy conversion, where it serves as a filler for both p- and n-type organic materials. Thin ExG composite films showing improved thermoelectric properties were prepared. In particular, composites with intrinsically conducting polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) yielding high electrical conductivity (up to 104 S m−1) and enhanced thermopower (Seebeck coefficient) provided promising p-type material. Chemical doping experiments performed on ExG dispersed in polyvinyl alcohol (PVA) revealed that the exfoliated graphitic sheets can be efficiently n-doped with polyethyleneimine (PEI). As a result, n-type ExG/PVA/PEI composite thin films showing improved n-type characteristics with thermopower values as high as −25.3 µV K−1 were prepared. With a 25 wt% ratio of PEI to ExG, the electrical conductivity was measured to be ∼103 S m−1, which is remarkably high for n-type polymer composites. Strips of composite films containing 50 wt% of ExG in PEDOT:PSS were used as p-type components, and composite films containing 20 wt% of ExG in PVA doped with PEI were used as n-type components in thermoelectric modules to demonstrate thermoelectric voltage with one, two, and three p-n couples connected in series. The testing modules produced an output voltage of ∼4 mV at a temperature gradient of 50 K. The module generated 1.7 nW power, when a load resistance matched the internal module resistance of 1 kΩ. Our results show that chemical functionalization of ExG in thin composite films resulted in more effective thermoelectric properties. [ABSTRACT FROM AUTHOR]

We investigated the interaction of chemical materials with flexible graphite foils which were fabricated from the expanded graphite (EG) flakes by mechanical rolling and compressing. A variety of performed experiments demonstrated that the electrical conductivity and thermoelectric power (TEP) of the graphite foils can be modified by chemical treatments. In particular, the 'as prepared' p-type graphite foil was successfully transferred into an n-type doped material upon a treatment with amine containing compounds. Generally, the acceptor-like chemicals increasing the concentration of the electric charge carriers enhanced the conductivity of the graphite foils, thereby, showing a decrease in the TEP reflected by the Seebeck coefficient, whereas the donor molecules significantly affected the conductivity and changed the sign and value of the TEP. Thermal and electrical insulating polymers, such as PVDF, PMMA, PVA, PS or PC, filling the inter-lamellar spacing reduced the conductivity of the foil due to increase of the layer-to-layer resistance. They also blocked heat flow in the foil, and consequently increased the Seebeck coefficient. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We report on single walled carbon nanotubes (SWCNTs) used as a filler material for polycarbonate (PC) composites in this paper. Thin flexible composite films were prepared by solvent casting with a viscous dispersion of SWCNTs in a polymer matrix. The interaction of SWCNTs with PC was studied by Raman spectroscopy. Our investigations focus on the electrical conductivity and thermopower of the carbon nanotube network formed within the matrix. In this paper, we demonstrate that the incorporation of carbon nanotubes in the polymer composite profoundly modifies the electrical properties of the polymer composite in proportion with the SWCNT concentration. Although, the electrical conductivity of the composite increases by 16 orders of magnitude upon adding 1 wt% of SWCNTs, the Seebeck coefficient, which characterizes the thermoelectric properties, appears to be dominated by the type of polymer matrix and decreased slightly throughout the tested filler loading. A reasonable Seebeck coefficient of 65 µV K−1 was determined for these SWCNT composite films and, thus, suggests that thermoelectric power generation would be a good application for them. We also demonstrated that both the electrical conductivity and the Seebeck coefficient of SWCNTs embedded in a polymer can be efficiently modified by means of chemical treatments. In this way, flexible composite films exhibiting positive and negative Seebeck coefficients were fabricated. Assembling these films into a sandwich structure with alternating p/n junctions should produce a higher potential difference when a temperature gradient is applied across a multilayer thermoelectric device. [ABSTRACT FROM AUTHOR]