Resonance Raman spectroscopy of carbon nanotubes: pressure effects on G-mode

We use 488 and 568nm laser Raman spectroscopy under high pressure to selectively follow evolution of Raman G-mode signals of single-walled carbon nanotubes (SWCNTs) of selected diameters and chiralities ((6, 5) and (6, 4)). The G-mode pressure coefficients of tubes from our previous work are consistent with the thick-wall tube model. Here we report the observation of well-resolved G-minus peaks in the Raman spectrum of SWCNTs in a diamond-anvil cell. The pressure coefficients of these identified tubes in water, however, are unexpected, having the high value of over 9cm(-1)GPa(-1) for the G-plus and the G-minus, and surprisingly the shift rates of the same tubes in hexane have clearly lower values. We also report an abrupt increase of G-minus peak width at about 4GPa superposed on a continuous peak broadening with pressure.