We investigate the nitrogen substitutional impurity in semiconducting zigzag and metallic armchair single-wall carbon nanotubes using ab initio density functional theory. At low concentrations (less than 1 at. %), the defect state in a semiconducting tube becomes spatially localized and develops a flat energy level in the band gap. Such a localized state makes the impurity site chemically and e...

We use inelastic light scattering (Raman) to probe individual and isolated single wall carbon nanotubes, suspended in air over trenches to explore the influence of the environment on the electronic transition energies. We find narrow and predominantly symmetric resonance profiles which are significantly downshifted as compared to isolated tubes in aqueous surfactant suspensions. A lower limit o...

We present photoluminescence studies of individual semiconducting single-wall carbon nanotubes at room and cryogenic temperatures. From the analysis of spatial and spectral features of nanotube photoluminescence, we identify characteristic signatures of unintentional exciton localization. Moreover, we quantify the energy scale of exciton localization potentials as ranging from a few to a few te...

We present preliminary results of Raman scattering measurements of multiwall carbon nanotubes (MWCNT). The nanotubes have been carefully dissolved, separated and then characterized by AFM. The micro-Raman spectra of the objects are taken with 514,5nm wavelength excitations and in the temperature range 4K 400K. Basically the spectra are quite similar to the well known single wall carbon nanotube...

Pool boiling heat transfer is measured with two individual working fluids on copper surfaces enhanced with sintered copper powder and carbon nanotubes. The working fluids are a segregated hydrofluoroether, HFE-7300, and deionized water. The surfaces considered in the experiments include smooth copper, copper with sintered copper particles, smooth copper with copper-coated carbon nanotubes (CNT)...

The electronic structure of single-wall nanotubes in intact, undissolved ‘‘buckypaper’’ has been studied using scanning tunneling microscopy ~STM! and scanning tunneling spectroscopy ~STS! at 23 K. STM topography shows, that single-wall carbon nanotubes ~SWNT’s! form microbundles that in turn aggregate in ropes. STS allows us to distinguish between room temperature metallic and wide-gap SWNT’s....

We report a comprehensive theoretical study of structural and electronic properties of substitutional oxygen and zinc contaminations in a model of single wall GaN nanotubes by means of ab initio supercell calculations. Our investigation yields many interesting results. The following ones deserve to be developed. Oxygen forms a shallow donor in the single wall GaN nanotubes as in bulk GaN polyty...

We have carried out momentum-dependent measurements of the density response function of bulk samples of purified single wall nanotubes using electron energy-loss spectroscopy. Carbon nanotubes support both excitations between delocalized and localized electronic states. The p-plasmon exhibits significant q-dependence, with a dispersion relation similar to that of the graphite plane, demonstrati...

The discovery of lower dimensional forms of Carbon with unique mechanical and electronic properties has generated new possibilities in many areas of technology especially in nanotechnology. Recent emergence of some nanoscale device applications show how this potential is turning into a reality. Over the years, we have employed various levels of theory to study the structure and properties of ca...