bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local measurement of charge density in carbon nanotubes by Raman spectroscopy
Authors: Freitag Marcus , Tsang James , Avouris Phaedon 
Published: August 2008

AbstractThe energies of the Raman G‐band transitions in both metallic and semiconducting CNTs are renormalized by the electron‐phonon interaction, leading to energy shifts in Raman spectra of gated CNT devices. In addition in metallic CNTs, the linewidth decreases sharply upon electrostatic doping because the Γ‐point phonon can no longer decay into electron‐hole pairs when the Fermi level is removed by more than 1/2 the phonon energy from the K‐point. Raman spectroscopy can therefore be used to locally measure charge density and capacitance of individual CNTs in a nanotube field‐effect transistor. Experiments under bias reveal breaks in nanotubes and depleted nanotube segments close to the contacts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ge‐doping dependence of gamma‐ray induced germanium lone pair centers in Ge‐doped silica
Authors: Alessi Antonino , Agnello Simonpietro , Gelardi Franco Mario , Boscaino Roberto 
Published: August 2008

AbstractWe report an experimental study on the γ irradiation effects in Ge‐doped sol‐gel silica samples doped with Ge from 102 up to 104 part per million molar. The samples were exposed to the radiation generated by a 60Co source up to an accumulated dose value of 10 MGy. Our data evidence that the γ irradiation significantly increases the number of Germanium Lone Pair Centers (GLPC). Such defects are induced with a concentration that depends on the Ge content of the employed material in those samples where no optical activity related to GLPC was detected before irradiation. Furthermore an increase of the GLPC concentration was detected also in a sample that already contains this defect after the production. These findings show that, in addition to the GLPC bleaching effect already reported in the literature, γ rays can generate such defects and a range of doses exists in which the generation processes overcome the bleaching processes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic properties of bilayer graphene probed by Resonance Raman Scattering
Authors: Malard L. M. , Nilsson J. , Mafra D. L. , Elias D. C. , Brant J. C. , Plentz F. , Alves E. S. , Neto A. H. Castro , Pimenta M. A. 
Published: August 2008

AbstractIn this work we have measured the G′ Raman band of bilayer graphene using several laser lines. We show that from the analysis of the experimental data in the framework of the double resonance Raman model we can derive the Slonczewski‐Weiss‐McClure band parameters of bilayer graphene. We analyze the behavior of the theoretical model as a function of these band parameters by comparing with the experimental results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of humidity on the hysteresis of single walled carbon nanotube field‐effect transistors
Authors: Rinkiö Marcus , Zavodchikova Marina Y. , Törmä Päivi , Johansson Andreas 
Published: August 2008

AbstractSingle walled carbon nanotube field‐effect transistors (SWCNT FETs) are attributed as possible building blocks for future molecular electronics. But often these transistors seem to randomly display hysteresis in their transfer characteristics. One reason for this is suggested to be water molecules adsorbed to the surface of the gate dielectric. In this study we investigate the hysteresis of SWCNT FETs at different relative humidities. We find that SWCNT FETs having atomic layer deposited (ALD) HfO2 – TiO2 – HfO2 as a gate dielectric retain their ambient condition hysteresis better in dry N2 environment than the more commonly used SiO2 gate oxide. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Suspended and non‐suspended carbon nanotube transistors for NO2 sensing – A qualitative comparison
Authors: Helbling Thomas , Hierold Christofer , Durrer Lukas , Roman Cosmin , Pohle Roland , Fleischer Maximilian 
Published: August 2008

AbstractA qualitative comparison of the NO2 sensitivity of carbon nanotube field effect transistors (CNFETs) has been performed on CNFETs with 1) suspended channels, and 2) channels that are in contact with the SiO2 substrate. No significant response difference to NO2 is apparent in the two CNFET configurations. Therefore, the SiO2 substrate acting as a dominant indirect sensing mechanism can be ruled out.Additionally, two measurement modes in CNFETs are presented and discussed. The measurement modes are: 1) chemiresistor response, and 2) the shift of the CNFET gate characteristic toward positive gate voltages. A method is proposed to acquire the shift in the gate threshold for future CNFET sensor applications, and examples of such transduction curves of two sensors are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theory of the elastic constants of graphite and graphene
Authors: Michel K. H. , Verberck B. 
Published: August 2008

AbstractBorn's long wave method is used to study the elastic properties of graphite and graphene. Starting from an empirical force constant model derived from full inplane phonon dispersions of graphite [Mohr et al., Phys. Rev. B 76, 035439 (2007)] we calculate the tension coefficients of graphene. Extending the model by interplanar interactions, we calculate the elastic constants of graphite. The agreement of our theoretical values with inelastic x‐ray scattering results on elastic constants of graphite [Bosak et al., Phys. Rev. B 75, 153408 (2007)] is very satisfactory. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparative study on thermal and plasma enhanced CVD grown carbon nanotubes from gas phase prepared elemental and binary catalyst particles
Authors: Schäffel Franziska , Schünemann Christoph , Rümmeli Mark H. , Täschner Christine , Pohl Darius , Kramberger Christian , Gemming Thomas , Leonhardt Albrecht , Pichler Thomas , Rellinghaus Bernd , Büchner Bernd , Schultz Ludwig 
Published: August 2008

AbstractThe preparation of nanoparticles in the gas phase through inert gas condensation is a very versatile method to fabricate catalyst particles that act as catalytic templates for carbon nanotube synthesis since the method allows for easy control of the catalysts' elemental composition and their morphology. In this contribution we report on the synthesis of carbon nanotubes via two distinct chemical vapour deposition routes, thermal and plasma enhanced chemical vapour deposition, using such gas phase prepared elemental Fe catalyst particles as well as binary FePt nanoparticles. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luther‐Emery liquid in the NMR relaxation rate of carbon nanotubes
Authors: Dóra Balázs , Gulacsi Miklós , Simon Ferenc , Wzietek Pawel , Kuzmany Hans 
Published: August 2008

AbstractWe analyze a recent NMR experiments by Singer et al. [Singer et al. Phys. Rev. Lett. 95, 236403 (2005).], which showed a deviation fromFermi‐liquid behavior in carbon nanotubes with an energy gap evident at low temperatures. A comprehensive theory for the magnetic field and temperature dependent NMR 13C spin‐lattice relaxation is given in the framework of the Luther‐Emery and Luttinger liquids.The low temperature properties are governed by a gapped relaxation due to a spin gap (∼ 30 K), described by the Luther‐Emery liquid picture, which crosses over smoothly to the Luttinger liquid behaviour with increasing temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Novel carbon nanotube network deposition technique for electronic device fabrication
Authors: Zavodchikova Marina Y. , Nasibulin Albert G. , Kulmala Tero , Grigoras Kestutis , Anisimov Anton S. , Franssila Sami , Ermolov Vladimir , Kauppinen Esko I. 
Published: August 2008

AbstractWe present a novel dry and room‐temperature method for the deposition of random carbon nanotube networks (CNTNs) onto various substrates. This method is based on natural charging of carbon nanotube (CNT) bundles in the gas‐phase and their efficient deposition directly downstream of the synthesis reactor by means of an electric field. The density of the deposited CNTNs was controllably adjusted by varying the deposition time and the electric field strength. Application of this deposition technique for the fabrication of single‐walled CNTNbased field‐effect transistors (FETs), where a random CNTN serves as a transport channel, is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ Vis/NIR spectroelectrochemistry of single‐walled carbon nanotubes enriched with (6,5) tubes
Authors: Frank Otakar , Kavan Ladislav , Green Alexander A. , Hersam Mark C. , Dunsch Lothar 
Published: August 2008

AbstractAn in‐situ optical Vis/NIR spectroelectrochemistry study was performed on single‐walled carbon nanotubes (CoMoCat) enriched with (6,5) tubes via density‐gradient ultracentrifugation. Thin semitransparent solid films were prepared from the solution of sorted nanotubes by vacuum filtration and purification with water. Despite the appearance of some bundling of the nanotubes during this procedure, peaks corresponding to optical transitions of tubes with distinct chiralities may be observed in the spectra. The effects of electrochemical redox doping on the electronic state of the nanotubes were investigated in an electrode potential window between –2 and +1.7 V vs. Ag‐pseudoreference electrode. The bleaching of ΔE11S and ΔE22S optical transitions is traced for particular tubes, which allows a partial quantification of changes in the electronic density of states (DOS) caused by their filling with electrons or holes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature dependence and pressure dependence of the vibrational properties of corannulene
Authors: Alvarez Laurent , Parc Rozenn Le , Jourdain Vincent , Dennler Samuel , Bantignies Jean Louis , Sauvajol Jean Louis , Rose Jonathan A. , Scott Lawrence T. 
Published: August 2008

AbstractHerein, we report the experimental investigation of the vibrational properties of corannulene using Raman spectroscopy. The temperature dependences of the Raman spectra between 300 and 20 K reveal a very high sensitivity of the low frequency domain between 40 and 200 cm–1 compared to the intramolecular domain. The behavior of the Raman modes of the corannulene under pressure, between 0.53 GPa and 8 GPa, is also studied. Under pressure, in the intermolecular vibrational domain (<150 cm–1), two transitions occur suggesting metastable intermediate stages under pressure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of artichoke (Cynara scolymusL.) extract on ROS generation in HUVEC cells
Authors: Juzyszyn Z. , Czerny B. , Pawlik A. , Droździk M. 
Published: August 2008

AbstractThe effect of an artichoke extract on induced reactive oxygen species (ROS) generation in cultured human umbilical endothelial cells (HUVECs) and its reductive properties were evaluated. Preincubation of HUVEC cells with the artichoke extract at concentrations of 25–100 µg/mL for 24 h abolished ROS generation induced by LPS and oxyLDL as evaluated by the fluorescence intensity of 2′,7′‐dichlorofluorescein (DCF). Potent, concentration‐dependent reductive properties of the artichoke extract were demonstrated by the reduction kinetics of cytochrome c in reference to ascorbate were also revealed. The results of the present study the warrant application of artichoke extracts as endothelium protecting agents. Copyright © 2008 John Wiley & Sons, Ltd.
Effect of seabuckthorn (Hippophae rhamnoides) leaf aqueous and ethanol extracts on avoidance learning during stressful endurance performance of rats: a dose dependent study
Authors: Saggu S. , Kumar R. 
Published: August 2008

AbstractAqueous and 70% ethanol extracts of seabuckthorn (Hippophae rhamnoides L., Elaeagnaceae) dry leaves were examined in rats for their dose dependent effect on active avoidance learning, if any. Avoidance learning was studied during endurance performance in multiple stressful environments consisting of light, noise and electric shock (10 mV) by using Runimex, a circular runway animal model. Neither of the evaluated extracts showed activity in rats to enhance cognitive functions with reference to avoidance learning during exposure to stressful conditions of multiple stressors. But both extracts were found to possess physical performance enhancing activity during the studied stressful conditions. Copyright © 2008 John Wiley & Sons, Ltd.
Azadirachta indica modulates carcinogen biotransformation and reduced glutathione at peri‐initiation phase of benzo(a)pyrene induced murine forestomach tumorigenesis
Authors: Gangar Subhash Chander , Koul Ashwani 
Published: August 2008

AbstractThe present study evaluated the effects of aqueous Azadirachta indica leaf extract (AAILE) on the activities of certain phase I (cytochrome P450, cytochrome b5 and aryl hydrocarbon hydroxylase) as well as phase II (glutathione‐S‐transferase and UDP‐glucuronosyl transferase) biotransformation enzymes; and reduced glutathione (GSH) (in forestomach and hepatic tissues) during/after intra‐gastric instillations of B(a)P in murine forestomach tumorigenesis bioassay protocol. The activities of phase I biotransformation enzymes were found to increase, whereas a decrease in GSH content as well as glutathione‐S‐transferase was observed in mice receiving only B(a)P during as well as 2 weeks after B(a)P instillations. The activity of UDP‐glucuronosyltransferase decreased during B(a)P instillations, whereas after the latter, the activity increased when compared with the control mice. However, in mice that received AAILE along with B(a)P instillations, a decrease in phase I enzymes was accompanied by an increase in phase II enzymes as well as GSH contents. Only AAILE treatment reduced the activities of phase I biotransformation enzymes and enhanced the GSH contents as well as the activities of phase II enzymes. Observations of the present study seem to be quite significant and (when taken together with our earlier findings) provides evidence for A. indica mediated modulation of the peri‐initiation phase of the process of forestomach tumorigenesis. Copyright © 2008 John Wiley & Sons, Ltd.
Size dependent structural and electronic properties of MgO nanotube clusters
Authors: Chen Liang , Xu Can , Zhang Xiaofang , Cheng Chuan , Zhou Tao 
Published: August 2008

AbstractMgO nanotube clusters which cross sections are composed of two‐, three‐, four‐, and five‐membered rings are constructed and studied by the density functional theory at B3LYP/6‐31G(d) level. The variations of bond length present anisotropic effect. Three‐membered ring nanotube cluster is the most stable tube among these MgO isomers. Mixed covalent and ionic bonding always exists in MgO nanotube clusters. With increasing length of MgO nanotube clusters, the averaged atomic charge increases, and converge to 1.227; the s‐p separation of O bands decreases; whereas energy gap nearby frontier orbitals present dramatic difference corresponding to various structure family. It is possible that MgO nanotube clusters show electronic properties of semiconductor. An interpretation for MgO nanotube clusters fabricated by simply thermal methods is proposed. The structural and electronic properties of MgO nanotube clusters are discussed systematically in details. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
CCSD(T) and MRCI studies on the ground and excited states of BrOClO and ClOBrO
Authors: Li Yumin 
Published: August 2008

AbstractIn this work, three forms (cis, trans and nonplanar) of ClOBrO and BrOClO were optimized at CCSD(T)/cc‐pVTZ level of theory. At the most stable forms (nonplanar form) of ClOBrO and BrOClO, the vertical excitation energies for the lowest six singlet states and two triplet states were calculated at the multireference internally contracted configuration interaction (MRCI) level of theory using cc‐pVDZ, Aug‐cc‐pVDZ, cc‐pVTZ, and Aug‐cc‐pVTZ basis sets. The scalar relativistic effect on the excited states of BrOClO and ClOBrO were estimated. In addition, the potential energy curves of the lowest six singlet states and two triplet states of BrOClO and ClOBrO, as well as BrOOCl were calculated at both MCSCF (complete active space self‐consistent field) and MRCI levels of theory using Aug‐cc‐pVDZ basis set on the active space (18e,12o) along the distances of BrOClO, ClOBrO, and BrOOCl. The results were compared among BrOOCl, ClOBrO, and BrOClO. The first singlet excited state of BrOOCl is 1.12 eV higher than that of BrOClO and 1.36 eV higher than that of ClOBrO at MRCI/cc‐pVTZ level of theory. The first triplet excited state of BrOOCl is 0.77 eV higher than that of BrOClO and 0.86 eV higher than that of ClOBrO at MRCI/cc‐pVTZ level of theory. Most of the excited states of BrOClO studied in this work are unbound states; but most of the ClOBrO and BrOOCl excited states studied in this work are weakly bound states at MRCI level of theory. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Theoretical calculations of transition probabilities and oscillator strengths for Ti III and Ti IV
Authors: Zhang Tian‐Yi , Zheng Neng‐Wu , Ma Dong‐Xia 
Published: August 2008

AbstractDue to the complicated electronic configuration of atoms and ions of the transition metal elements, the studies for properties such as transition probabilities and oscillator strengths for these atoms and ions are not systematic. Because of the existence in a variety of stellar objects and wide use in the field of astrophysics, titanium has long been of interest for many researchers. In this article within the Weakest Bound Electron Potential Model (WBEPM) theory, comprehensive set of calculations for transition probabilities and oscillator strengths for Ti III and Ti IV are performed. Many of our results had no previous experimental or theoretical values, so these predictive results could be of some value to the workers in this field. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Quantum‐chemical study of the singlet oxygen emission
Authors: Minaev Boris F. , Minaeva Valentina A. , Evtuhov Yurij V. 
Published: August 2008

AbstractIntensity distribution in rotational lines of the 0–0 band of the a1Δg → X3Σ transition in the oxygen molecule at λ = 1270 nm is studied by quadratic response (QR) method in a framework of multiconfiguration self‐consisted field (MCSCF) theory. The distance dependence of the transition magnetic moment and the (0–0)/(0–1) bands intensity ratio are calculated. A short review of previous theory of the red and infrared atmospheric oxygen bands and of their enhancement by collisions is presented to analyze and compare the new results. Enhancement of these bands in O2 collisions with Li2 and N2 molecules is calculated by QR method. Diamagnetic species simulate solvent molecules of different optical polarizability. Specific influence of collisions on vibronic bands is stressed. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Extended Hartree–Fock theory of chemical reactions. VIII. Hydroxylation reactions by P450
Authors: Isobe Hiroshi , Nishihara Satomichi , Shoji Mitsuo , Yamanaka Shusuke , Shimada Jiro , Hagiwara Masayuki , Yamaguchi Kizashi 
Published: August 2008

AbstractWe have investigated the reaction pathways for the primary hydroxylation reaction of trimethylmethane by a high‐valent Fe(IV)O porphyrin π‐cation radical species known as compound I at the B3LYP/CEP‐31G level. The isoelectronic analogy of the Fe(IV)O core of compound I to a molecular oxygen (O2) has been successfully used to clarify the important roles of the singlet excited state of the Fe(IV)O core in the alkane hydroxylation, which has hitherto been neglected. The reaction is initiated by the rate‐determining hydrogen‐atom abstraction from the substrate to give a discrete radical intermediate complex, in accordance with the conventional radical rebound mechanism. Similar to the chemistry of O2, however, one of the singlet excited states, i.e., the diradical component of the 1Δ state of the Fe(IV)O core intercepts the triplet ground state (the 3Σ state) in the region of the transition state for the hydrogen abstraction. Our findings strongly indicate that the exchange polarization or intersystem crossing for the nonradiative transition to the locally singlet state is highly important to enhance the reactivity of compound I. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Driving with tentacles: Integral structures for sensing and motion
Authors: von Hundelshausen Felix , Himmelsbach Michael , Hecker Falk , Mueller Andre , Wuensche Hans‐Joachim 
Published: August 2008

AbstractIn this paper we describe a LIDAR‐based navigation approach applied at both the C‐Elrob (European Land Robot Trial) 2007 and the 2007 DARPA Urban Challenge. At the C‐Elrob 2007 the approach was used without any prior knowledge about the terrain and without global positioning system (GPS). At the Urban Challenge the approach was combined with a GPS‐based path follower. At the core of the method is a set of “tentacles” that represent precalculated trajectories defined in the ego‐centered coordinate space of the vehicle. Similar to an insect's antennae or feelers, they fan out with different curvatures discretizing the basic driving options of the vehicle. We detail how the approach can be used for exploration of unknown environments and how it can be extended to combined GPS path following and obstacle avoidance allowing safe road following in case of GPS offsets. © 2008 Wiley Periodicals, Inc.
Microtubule‐Based Gold Nanowires and Nanowire Arrays
Authors: Zhou Jing C. , Gao Yao , Martinez‐Molares Alfredo A. , Jing Xiaoye , Yan Dong , Lau Joseph , Hamasaki Toshikazu , Ozkan Cengiz S. , Ozkan Mihrimah , Hu Evelyn , Dunn Bruce 
Published: August 2008

AbstractBiological structures are attractive as templates to form nanoscale architectures for electronics because of their dimensions and the ability to interact with inorganic materials. In this study, we report the fabrication and electrical properties of microtubule (MT)‐templated Au nanowires, and methods for assembling Au nanowire arrays based on these templates. The adsorption of MTs on silicon substrates is an effective means for preserving the conformation of the MT and provides a convenient platform for electrical measurements. To improve the metallization of MTs, a photochemical route for gold reduction is adapted, which leads to continuous coverage. The conductivity values measured on micrometer‐long nanowires are similar to those reported for other biotemplated gold nanowires. A protocol for fabricating arrays of MT‐templated gold nanowires is demonstrated.
Characterization of Self‐Assembled Metallodendrimers in Solution, in the Gas Phase, and at Air/Solid Interfaces
Authors: Baytekin H. Tarik , Sahre Mario , Rang Alexander , Engeser Marianne , Schulz Andrea , Schalley Christoph A. 
Published: August 2008

AbstractIt is found that 4,4′‐bipyridines functionalized in their 3,3′‐positions with Fréchet dendrons of 0th to 3rd generation self‐assemble with (dppp)M(II) triflates (dppp: bis‐(diphenylphosphino)propane; M = Pd, Pt) into metallo–supramolecular squares. They bear a nanometer‐sized cavity inside an unpolar dendritic shell. A total of eight amide groups decorate the rims of the cavity connecting the dendrons to the square. Evidence for their formation up to the third generation comes from ESI‐FTICR mass spectrometry and NMR experiments. Based on these results, the presence of significant amounts of other polygons or open‐chain oligomers can be excluded. Exchange processes have been studied by variable‐temperature NMR spectroscopy and by following the ligand exchanges between different squares by mass spectrometry. The ligand exchange is much slower for the Pt(II) squares as compared to their Pd(II) analogs. Visualization of films of these dendrimers using atomic force microscopy (AFM) provides information on their molecular dimensions. After deposition of a square monolayer on the surface, a slow reorganization within this layer is observed which leads to the formation of “tower‐like” aggregates and multi‐layer formation. The interplay of interactions between the dendrimers and the surface and interactions between different dendrimers are invoked to rationalize the observations.