470 research outputs found
Incidence of the Tomonaga-Luttinger liquid state on the NMR spin lattice relaxation in Carbon Nanotubes
We report 13C nuclear magnetic resonance measurements on single wall carbon
nanotube (SWCNT) bundles. The temperature dependence of the nuclear
spin-lattice relaxation rate, 1/T1, exhibits a power-law variation, as expected
for a Tomonage-Luttinger liquid (TLL). The observed exponent is smaller than
that expected for the two band TLL model. A departure from the power law is
observed only at low T, where thermal and electronic Zeeman energy merge.
Extrapolation to zero magnetic field indicates gapless spin excitations. The
wide T range on which power-law behavior is observed suggests that SWCNT is so
far the best realization of a one-dimensional quantum metal.Comment: 5 pages, 4 figure
Stabilization of carbon nanotubes by filling with inner tubes: An optical spectroscopy study on double-walled carbon nanotubes under hydrostatic pressure
The stabilization of carbon nanotubes via the filling with inner tubes is
demonstrated by probing the optical transitions in double-walled carbon
nanotube bundles under hydrostatic pressure with optical spectroscopy.
Double-walled carbon nanotube films were prepared from fullerene peapods and
characterized by HRTEM and optical spectroscopy. In comparison to single-walled
carbon nanotubes, the pressure-induced redshifts of the optical transitions in
the outer tubes are significantly smaller below 10 GPa, demonstrating the
enhanced mechanical stability due to the inner tube already at low pressures.
Anomalies at the critical pressure P12 GPa signal the onset of the
pressure-induced deformation of the tubular cross-sections. The value of P
is in very good agreement with theoretical predictions of the pressure-induced
structural transitions in double-walled carbon nanotube bundles with similar
average diameters.Comment: 6 pages, 4 figures; to appear in Phys. Rev.
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The polycyclic aromatic hydrocarbon concentrations in soils in the Region of Valasske Mezirici, the Czech Republic
The polycyclic aromatic hydrocarbon (PAH) contamination of urban, agricultural and forest soil samples was investigated from samples obtained in the surroundings of Valasske Mezirici. Valasske Mezirici is a town located in the north-east mountainous part of the Czech Republic, where a coal tar refinery is situated. 16 PAHs listed in the US EPA were investigated. Organic oxidizable carbon was also observed in the forest soils. The PAH concentrations ranged from 0.86-10.84 (with one anomalous value of 35.14) and 7.66-79.39 mg/kg dm in the urban/agricultural and forest soils, respectively. While the PAH levels in the urban/agricultural soils are within the range typically found in industrialized areas, the forest soils showed elevated PAH concentrations compared to other forest soils in Western and Northern Europe. The PAH concentrations and their molecular distribution ratios were studied as functions of the sample location and the meteorological history. The soils from localities at higher altitudes above sea level have the highest PAH concentrations, and the PAH concentrations decrease with increasing distance from the town
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On the efficiency of bile salt for stable suspension and isolation of single-walled carbon nanotubes-spectroscopic and microscopic investigations
In this contribution we present a systematic study on the dispersion of SWCNTs in a water-based solution of biocompatible detergent: sodium deoxycholate (DOC). By avoiding harsh chemical conditions, which are known to damage nanotubes structure, a stable SWCNTs suspension was created. Long term stirring of the solution led to preparation of a stable transparent solution, containing welldispersed isolated SWCNTs. The as-prepared dispersion remained stable and clear for two months. Optical absorption spectroscopy was employed to measure SWCNTs suspension stability. Nanotube aggregation was evaluated through the tangential mode (G mode) present in the Raman spectrum. High-resolution transmission electronmicroscopy was employed to observe the mechanism of debundling process. © 2010 Springer-Verlag
The polycyclic aromatic hydrocarbon concentrations in soils in the Region of Valasske Mezirici, the Czech Republic
The polycyclic aromatic hydrocarbon (PAH) contamination of urban, agricultural and forest soil samples was investigated from samples obtained in the surroundings of Valasske Mezirici. Valasske Mezirici is a town located in the north-east mountainous part of the Czech Republic, where a coal tar refinery is situated. 16 PAHs listed in the US EPA were investigated. Organic oxidizable carbon was also observed in the forest soils. The PAH concentrations ranged from 0.86-10.84 (with one anomalous value of 35.14) and 7.66-79.39 mg/kg dm in the urban/agricultural and forest soils, respectively. While the PAH levels in the urban/agricultural soils are within the range typically found in industrialized areas, the forest soils showed elevated PAH concentrations compared to other forest soils in Western and Northern Europe. The PAH concentrations and their molecular distribution ratios were studied as functions of the sample location and the meteorological history. The soils from localities at higher altitudes above sea level have the highest PAH concentrations, and the PAH concentrations decrease with increasing distance from the town
On the efficiency of bile salt for stable suspension and isolation of single-walled carbon nanotubes-spectroscopic and microscopic investigations
In this contribution we present a systematic study on the dispersion of SWCNTs in a water-based solution of biocompatible detergent: sodium deoxycholate (DOC). By avoiding harsh chemical conditions, which are known to damage nanotubes structure, a stable SWCNTs suspension was created. Long term stirring of the solution led to preparation of a stable transparent solution, containing welldispersed isolated SWCNTs. The as-prepared dispersion remained stable and clear for two months. Optical absorption spectroscopy was employed to measure SWCNTs suspension stability. Nanotube aggregation was evaluated through the tangential mode (G mode) present in the Raman spectrum. High-resolution transmission electronmicroscopy was employed to observe the mechanism of debundling process. © 2010 Springer-Verlag
The catalytic potential of high-k dielectrics for graphene formation
The growth of single and multilayer graphene nano-flakes on MgO and ZrO2 at
low temperatures is shown through transmission electron microscopy. The
graphene nano-flakes are ubiquitously anchored at step edges on MgO (100)
surfaces. Density functional theory investigations on MgO (100) indicate C2H2
decomposition and carbon adsorption at step-edges. Hence, both the experimental
and theoretical data highlight the importance of step sites for graphene growth
on MgO
Graphene: Piecing it together
Graphene has a multitude of striking properties that make it an exceedingly
attractive material for various applications, many of which will emerge over
the next decade. However, one of the most promising applications lie in
exploiting its peculiar electronic properties which are governed by its
electrons obeying a linear dispersion relation. This leads to the observation
of half integer quantum hall effect and the absence of localization. The latter
is attractive for graphene-based field effect transistors. However, if graphene
is to be the material for future electronics, then significant hurdles need to
be surmounted, namely, it needs to be mass produced in an economically viable
manner and be of high crystalline quality with no or virtually no defects or
grains boundaries. Moreover, it will need to be processable with atomic
precision. Hence, the future of graphene as a material for electronic based
devices will depend heavily on our ability to piece graphene together as a
single crystal and define its edges with atomic precision. In this progress
report, the properties of graphene that make it so attractive as a material for
electronics is introduced to the reader. The focus then centers on current
synthesis strategies for graphene and their weaknesses in terms of electronics
applications are highlighted.Comment: Advanced Materials (2011
In situ observations of freestanding single-atom-thick gold nanoribbons suspended in graphene
Bulk gold's attributes of relative chemical inertness, rarity, relatively low melting point and its beautiful sheen make it a prized material for humans. Recordings suggest it was the first metal employed by humans dating as far back to the late Paleolithic period approximate to 40 000 BC. However, at the nanoscale gold is expected to present new and exciting properties, not least in catalysis. Moreover, recent studies suggest a new family of single-atom-thick two-dimensional (2D) metals exist. This work shows single-atom-thick freestanding gold membranes and nanoribbons can form as suspended structures in graphene pores. Electron irradiation is shown to lead to changes to the graphene pores which lead to dynamic changes of the gold membranes which transition to a nanoribbon. The freestanding single-atom-thick 2D gold structures are relatively stable to electron irradiation for extended periods. The work should advance the development of 2D gold monolayers significantly.Web of Scienceart. no. 200043
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