Processing routes and characterization methods commonly used in carbon nanotubes research require agood dispersion of nanotubes in liquid media. In particular, single walled carbon nanotubes (SWNT) mustbe dispersed, preferably as individuals in order to tap their full potential in optical applications [1]. Onesensitive probe of dispersion is photoluminescence (PL), since it is quenched as long as semiconductingSWNT are bundled with metallic ones. However, the detailed interpretation of the mechanismsresponsible for PL and the relation between PL intensity and dispersion state are still a matter ofcontroversy [2].
In this work, we present new insights on the near infrared photoluminescence of aqueous suspensions ofSWNT stabilized by bile salts surfactants. In one hand, the dispersion of the nanotubes is probed byabsorption spectroscopy, where the absorption coefficient shows high sensitivity to nanotube exfoliation.On the other hand, we revisit the interpretation of the NIR-PL spectra, and we discuss the differentphysical mechanisms responsible of the PL, i.e. Direct Excitonic Transitions (DET), Exciton-PhononCoupling (EPC), and Exciton Energy Transfer (EET) between nanotubes [3-7]. Finally, we discuss thekinetics of PL as a function of sonication time and debundling/exfoliation of SWNT (Figure 1).
References
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[2] V.C Moore, et al. Nano letters, 3 (2003). pp 1379-1382.
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[4] J. Maultzsch, et al. PRB, 72(24) (2005). pp. 241402.
[5] F. Wang, et al. Science, 308(5723) 2005. pp. 838-841.
[6] S. Chou, et al. PRL, 94(12) (2005), pp. 127402.
[7] P. Tan, et al. PRL, 99(13) (2007) pp. 137402.