Search results for "NANOTUBES"
showing 10 items of 383 documents
Launching propagating surface plasmon polaritons by a single carbon nanotube dipolar emitter.
2011
International audience; We report on the excitation of propagating surface plasmon polaritons in thin metal films by a single emitter. Upon excitation in the visible regime, individual semiconducting single-walled carbon nanotubes are shown to act as directional near-infrared point dipole sources launching propagating surface plasmons mainly along the direction of the nanotube axis. Plasmon excitation and propagation is monitored in Fourier and real space by leakage radiation microscopy and is modeled by rigorous theoretical calculations. Coupling to plasmons almost completely reshapes the emission of nanotubes both spatially and with respect to polarization as compared to photoluminescence…
Surfactant-Dependent Exciton Mobility in Single-Walled Carbon Nanotubes Studied by Single-Molecule Reactions
2010
Measurements of stepwise photoluminescence quenching in individual, (n,m)-selected single-walled carbon nanotubes (SWCNTs) undergoing chemical reaction have been analyzed to deduce mobilities of optically generated excitons. For (7,5) nanotubes, the mean exciton range varies between approximately 140 and 240 nm for different surfactant coatings and correlates weakly with nanotube PL intensity. The results are consistent with a model of localized SWCNT excitons having substantial diffusional mobility along the nanotube axis.
Hierarchical Assembly of TiO2 Nanoparticles on WS2 Nanotubes Achieved Through Multifunctional Polymeric Ligands
2007
Thefunctionalization of nanotubes is required in order to bene-fit from their outstanding properties, as any application inmaterials and devices is hindered by processing and manipu-lation difficulties. Only the attachment of appropriate chem-ical functionalities on the nanotube surface allows tailoringof the properties for the respective applications. As an ex-ample, the enhancement of the nanotube solubility is onemajor task since most pristine nanotubes are insoluble inboth water and organic solvents. Thus, the improvement ofthe solubility by chemical functionalization is an importantconcept for synthetic chemists and materials scientists. Tai-loring of the surface chemical bonds might a…
In situ nucleation of carbon nanotubes by the injection of carbon atoms into metal particles.
2007
The synthesis of carbon nanotubes (CNTs) of desired chiralities and diameters is one of the most important challenges in nanotube science and achieving such selectivity may require a detailed understanding of their growth mechanism. We report the formation of CNTs in an entirely condensed phase process that allows us, for the first time, to monitor the nucleation of a nanotube on the spherical surface of a metal particle. When multiwalled CNTs containing metal particle cores are irradiated with an electron beam, carbon from graphitic shells surrounding the metal particles is ingested into the body of the particle and subsequently emerges as single-walled nanotubes (SWNTs) or multiwalled nan…
Multiwalled carbon nanotube reinforced polymer composites
2008
Due to their high stiffness and strength, as well as their electrical conductivity, carbon nanotubes are under intense investigation as fillers in polymer matrix composites. The nature of the carbon nanotube/polymer bonding and the curvature of the carbon nanotubes within the polymer have arisen as particular factors in the efficacy of the carbon nanotubes to actually provide any enhanced stiffness or strength to the composite. Here the effects of carbon nanotube curvature and interface interaction with the matrix on the composite stiffness are investigated using micromechanical analysis. In particular, the effects of poor bonding and thus poor shear lag load transfer to the carbon nanotube…
OH-functionalized open-ended armchair single-wall carbon nanotubes (SWCNT) studied by density functional theory
2011
The structures of ideal armchair (5,5) single-wall carbon nanotubes (SWCNTs) of different lengths (3.7, 8.8, and 16.0 A for C40H20, C80H20, and C140H20) and with 1–10 hydroxyl groups at the end of the nanotube were fully optimized at the B3LYP/3-21G level, and in some cases at the B3LYP/6-31G* level, and the energy associated with the attachment of the OH substituent was determined. The OH-group attachment energy was compared with the OH functionalization of phenanthrene and picene models and with previous results for zigzag (9.0) SWCNT systems. In comparison to zigzag SWCNTs, the armchair form is more (by about 5 to 10 kcal mol−1) reactive toward hydroxylation. Figure The structures of ide…
Stability of carbon nanotubes under electron irradiation: Role of tube diameter and chirality
2005
As recent experiments demonstrate, the inner shells of multiwalled carbon nanotubes are more sensitive to electron irradiation than the outer shells. To understand the origin of such counterintuitive behavior, we employ a density-functional-theory based tight-binding method and calculate the displacement threshold energies for carbon atoms in single-walled nanotubes with different diameters and chiralities. We show that the displacement energy and the defect production rate strongly depend on the diameter of the nanotube and its chirality, with the displacement energy being lower, but saturating towards the value for graphite when the tube diameter increases. This implies that the threshold…
Quantum Transport and Current Distribution at Radio Frequency in Multiwall Carbon Nanotubes
2012
Multiwall carbon nanotubes represent a low-dimensional material that could serve as building blocks for future carbon-based nanoelectronics. The understanding of the electromagnetic performances at radio frequency of these materials for use in nanointerconnects is strictly related to the analysis of their transport properties as function of the working conditions. In this paper, we present an explicit expression of the conducting channels as function of diameter, temperature, doping, and supply voltage for both metallic and semiconducting carbon nanotubes. The proposed formula is based on the Dirac cone approximation of the conducting band energy of graphene nearby the Fermi points, combine…
Local photo-oxidation of individual single walled carbon nanotubes probed by femtosecond four wave mixing imaging
2014
Photo-oxidation of individual, air-suspended single walled carbon nanotubes (SWCNTs) is studied by femtosecond laser spectroscopy and imaging. Individual SWCNTs are imaged by four wave mixing (FWM) microscopy under an inert gas (Ar or N2) atmosphere. When imaging is performed in an ambient air atmosphere, the decay of the FWM signal takes place. Electron microscopy shows that SWCNTs are not destroyed and the process is attributed to photoinduced oxidation reactions which proceed via a non-linear excitation mechanism, when irradiation is performed with ∼30 fs pulses in the visible spectral region (500-600 nm). Photo-oxidation can be localized in specific regions of SWCNTs within optical reso…
Carbon nanotubes as high-pressure cylinders and nanoextruders.
2006
Closed-shell carbon nanostructures, such as carbon onions, have been shown to act as self-contracting high-pressure cells under electron irradiation. We report that controlled irradiation of multiwalled carbon nanotubes can cause large pressure buildup within the nanotube cores that can plastically deform, extrude, and break solid materials that are encapsulated inside the core. We further showed by atomistic simulations that the internal pressure inside nanotubes can reach values higher than 40 gigapascals. Nanotubes can thus be used as robust nanoscale jigs for extruding and deforming hard nanomaterials and for modifying their properties, as well as templates for the study of individual n…