Photoluminescence study of aqueous-surfactant-wrapped single-walled carbon nanotubes under hydrostatic pressure

We present an experimental study of sodium-dodecylbenzene-sulfate-wrapped single-walled carbon nanotube (SWCNT) suspensions in D2O under hydrostatic pressure. Photoluminescence excitation mapping allows identification of the first and second Van Hove optical transitions (E-11 and E-22) in a pressure range of P=0-9.1 kbar using a liquid clamp pressure cell. Shifts were observed in both E-11 and E-22 that allow the identification of two independent pressure effects. The first results from a uniaxial strain component with positive and negative energy shifts for structural factors [q=mod(n-m,3)] q=2 and 1 in agreement with theoretical band structure predictions. The second results from environmental effects that produce for all SWCNT's a downshift in energy caused by significant changes in the Coulomb interactions for a higher-dielectric medium.