Optical anisotropy of dispersed carbon nanotubes induced by an electric field

Bubke, Karsten; Gnewuch, H.; Hempstead, M.; Hammer, Jens; Green, Malcolm L. H.

doi:10.1063/1.119976

Cited by 141 publications

(82 citation statements)

References 12 publications

(1 reference statement)

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“…It is found that the absorption threshold is significantly higher (by about 0.12 eV in the (6, 0) tubule and 0.60 eV in the (7, 0) tubule) for the electronic field E B along the tubule axis than for that vertical to the axis. The optical anisotropy of dispersed CNTs induced by an electric field has been observed in the experiment, 63 and may be used to determine the orientational ordering of the CNTs.…”

Section: E(t) ) (1/ πT H) E -(T/t H)mentioning

confidence: 99%

Localized-Density-Matrix Method and Its Application to Carbon Nanotubes

et al. 1999

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The localized-density-matrix method Chen, G. H. Chem. Phys. Lett. 1998, 292, 379) is employed to simulate the optical responses of very large carbon nanotubes and polyacetylene oligomers containing 10 000 carbon atoms. The Pariser-Parr-Pople Hamiltonian is used to describe the π electrons in these systems, and the time-dependent Hartree-Fock approximation is employed to calculate the linear optical responses. In the calculation, the fast multipole method or the cell multipole method is employed to evaluate the effects of Coulomb interaction. It is illustrated that the computational time scales linearly with the system size for carbon nanotubes while high accuracy is achieved.

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Section: E(t) ) (1/ πT H) E -(T/t H)mentioning

confidence: 99%

Localized-Density-Matrix Method and Its Application to Carbon Nanotubes

et al. 1999

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“…Numerically, the most favorable approach is to use Eq. (14): after choosing a suitable coordinate system, we apply an electric field in the x direction and calculate the cluster polarization by solving Eq. (11).…”

Section: B Static Polarizability and Orientational Energy Of Dipole mentioning

confidence: 99%

“…This self-assembly process can be spontaneous in the case of favorable thermodynamic conditions and suitable effective particle-particle interactions, [3][4][5][6][7][8][9][10] but can also be steered and further manipulated by external fields. Rodlike particles in a liquid dispersion, for instance, can spontaneously align at sufficiently high concentrations solely due to their excluded volume interactions, 11 but their self-organisation has also been driven by external magnetic or electric fields, [12][13][14][15][16] by substrates that preferentially orient the rods, 17,18 or by fluid flow. 19 Also, more complicated shapes have been synthesized and studied, for instance, dumbbells, 2,[20][21][22] cubes, 23 and bowls.…”

Section: Introductionmentioning

confidence: 99%

Polarizability and alignment of dielectric nanoparticles in an external electric field: Bowls, dumbbells, and cuboids

Kwaadgras

Verdult

Dijkstra

et al. 2011

The Journal of Chemical Physics

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We employ the coupled dipole method to calculate the polarizability tensor of various anisotropic dielectric clusters of polarizable atoms, such as cuboid-, bowl-, and dumbbell-shaped nanoparticles. Starting from a Hamiltonian of a many-atom system, we investigate how this tensor depends on the size and shape of the cluster. We use the polarizability tensor to calculate the energy difference associated with turning a nanocluster from its least to its most favorable orientation in a homogeneous static electric field, and we determine the cluster dimension for which this energy difference exceeds the thermal energy such that particle alignment by the field is possible. Finally, we study in detail the (local) polarizability of a cubic-shaped cluster and present results indicating that, when retardation is ignored, a bulk polarizability cannot be reached by scaling up the system.

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“…Many procedures have been proposed to achieve the desired highly ordered structures, e.g., by using systems with substrates or templates, 1 applying external electric, or magnetic fields [2][3][4][5][6] to particles with anisotropic response to these fields, or by using a fluid flow 7 to align the particles. One of the most widely used techniques, however, is the design and manipulation of particle-particle interactions, which can result in spontaneous self-assembly.…”

Section: Introductionmentioning

confidence: 99%

Can nonadditive dispersion forces explain chain formation of nanoparticles?

Kwaadgras

Verdult

Dijkstra

et al. 2013

The Journal of Chemical Physics

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We study to what extent dielectric nanoparticles prefer to self-assemble into linear chains or into more compact structures. To calculate the Van der Waals (VdW) attraction between the clusters we use the Coupled Dipole Method (CDM), which treats each atom in the nanoparticle as an inducible oscillating point dipole. The VdW attraction then results from the full many-body interactions between the dipoles. For non-capped nanoparticles, we calculate in which configuration the VdW attraction is maximal. We find that in virtually all cases we studied, many-body effects only result in local potential minima at the linear configuration, as opposed to global ones, and that these metastable minima are in most cases rather shallow compared to the thermal energy. In this work, we also compare the CDM results with those from Hamaker-de Boer and Axilrod-Teller theory to investigate the influence of the many-body effects and the accuracy of these two approximate methods.

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Optical anisotropy of dispersed carbon nanotubes induced by an electric field

Cited by 141 publications

References 12 publications

Localized-Density-Matrix Method and Its Application to Carbon Nanotubes

Localized-Density-Matrix Method and Its Application to Carbon Nanotubes

Polarizability and alignment of dielectric nanoparticles in an external electric field: Bowls, dumbbells, and cuboids

Can nonadditive dispersion forces explain chain formation of nanoparticles?

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