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Abstract:

A change in the relative abundance of single-walled carbon nanotubes, due to the presence of both nitrogen and boron during synthesis, has been identified through Raman and absorption spectroscopy. Raman spectroscopy shows that for two specific branches boron mediates the growth of smaller-diameter zigzag or near-zigzag nanotubes. We combine our experimental results with an improved Kataura model to identify two of the preferentially grown species as (16,0) and (14,1). © 2005 The American Physical Society.

Abstract:

Strain-induced band gap shifts that depend strongly on the chiral angle have been observed by optical spectroscopy in polyvinylpyrrolidone(PVP)- or Surfactin micelle-wrapped single-walled carbon nanotubes (SWCNTs). Uniaxial and torsional strains are generated by changing the environment surrounding the SWCNTs, using the surrounding D2O ice temperature or the hydration state of a wrapping polymer. These methods can be used as diagnostic tools to determine the quantum number, q, and examine chiral vector indices for specific nanotube species. © 2005 American Institute of Physics.

Abstract:

Single-walled carbon nanotubes (SWCNTs) have been dispersed with three types of amphiphilic materials in aqueous solutions: (i) an anionic aliphatic surfactant, sodium dodecyl sulfate (SDS), (ii) a cyclic lipopeptide biosurfactant, surfactin, and (iii) a water-soluble polymer, polyvinylpyrrolidone (PVP). Solution photoluminescence (PL) studies suggest that SDS wrapping is very sensitive to the temperature whereas the other two give relatively robust wrapping around the SWCNTs. Low temperature PL spectra from both surfactin and PVP dispersed SWCNTs show that peak shifts are strongly dependent on their chiralities, which can be explained by the bandgap modulations with the environmental strain. The uniaxial and torsional strains deduced from their bandgap shifts were similar, indicating the strains are mainly due to the different rates of thermal expansion in SWCNTs and ice. © 2005 IOP Publishing Ltd.

Abstract:

Single-walled carbon nanotubes (SWCNTs) have been dispersed with three types of amphiphilic materials in aqueous solutions: (i) an anionic aliphatic surfactant, sodium dodecyl sulfate (SDS), (ii) a cyclic lipopeptide biosurfactant, surfactin, and (iii) a water-soluble polymer, polyvinylpyrrolidone (PVP). Solution photoluminescence (PL) studies suggest that SDS wrapping is very sensitive to the temperature whereas the other two give relatively robust wrapping around the SWCNTs. Low temperature PL spectra from both surfactin and PVP dispersed SWCNTs show that peak shifts are strongly dependent on their chiralities, which can be explained by the bandgap modulations with the environmental strain. The uniaxial and torsional strains deduced from their bandgap shifts were similar, indicating the strains are mainly due to the different rates of thermal expansion in SWCNTs and ice.