Chirality assignment of single-walled carbon nanotubes with strain

Optical spectroscopy in single-walled carbon nanotubes (SWCNT) was used for investigating strain-induced band gap shifts that depended strongly on the chiral angle. Using the surrounding D₂O ice temperature or the hydration state of a wrapping polymer, and by changing the environment surrounding the SWCNT, uniaxial and torsional strains were generated. The chiral vector indices and the quantum number for specific nanotubes were determined using all these methods. The linear thermal contraction was estimated to be 0.1% from 80 to 260 K for the SWCNT that possessed negative linear thermal expansion coefficients fot temperatures below 900 K.