Reconstructing the radial breathing mode resonance Raman spectra for HiPco single-wall carbon nanotubes

The radial breathing mode (RBM) region of the resonance Raman spectra of HiPco single-wall carbon nanotubes (SWNTs) was investigated as a function of aggregation and presence of environmental contaminants. This was modeled using an energetic deviation term (ΔE), imparted to the optical transitions [Eᵢᵢ(n,m)] by the change in SWNT physicochemical environment. Three sets of Eᵢᵢ(n,m) values were used to reconstruct these RBM profiles, based on (i) photoluminescence (PL) measurements, (ii) a simple tight-binding (TB) model, and (iii) a set of modified (TB-based) Eᵢᵢ(n,m) values to account for the underestimation of the influence of chiral angle for SWNTs with diameters below 10.3em0exnm. The simulation revealed that the PL-determined Eᵢᵢ(n,m) set provided a good fit in terms of peak position as opposed to TB-calculated values. Moderate improvement was attained using the third set of Eᵢᵢ(n,m) values, indicative of the importance of both curvature and chirality effects. Providing an accurate set of Eᵢᵢ(n,m) values becomes available, the RBM profile reconstruction methodology discussed herein could greatly enhance our ability to model a range of physicochemical changes to the immediate environment of SWNTs.