Nanoscale physics

Thiol compound interaction with single-walled carbon nanotubes covered by DNA: Raman spectroscopy study
Kurnosov N.V.1, Leontiev V.S.1, Karachevtsev V.A.1
1 B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine. Nauky Ave., 47, Kharkiv-61103, Ukraine.
E-mail: n.kurnosov@ilt.kharkov.ua

	Thiol compounds cysteine and dithiothreitol (DTT) enhance photoluminescence of single-walled carbon nanotubes (SWNTs) [1] due to passivation of quenching defects, which appear in aqueous environment at oxygen-induced SWNT hole doping. In the present report DTT influence on SWNTs in aqueous suspensions with DNA was studied using Raman spectroscopy. Excitation with λex.=488 nm fulfilled resonance Raman conditions for semiconducting and metallic SWNTs. Raman spectra were registered in the ranges of 200–400 cm-1 and 1200–1800 cm-1 corresponding to SWNT radial breathing mode (RBM) and tangential modes (G). Approximation of RBM spectra revealed that the band of metallic (8,2) SWNT should be fitted with two lorentzian components presumably originating from doped and undoped metallic SWNTs [2]. Undoped component was increased at DTT addition into suspension. RBM bands of semiconducting SWNTs displayed chirality-dependent response to DTT correlating with our earlier photoluminescence results. DTT-induced changes also occurred in the G mode range. If resonance conditions are fulfilled for metallic SWNTs, the approximation of G mode generally includes Breit-Wigner-Fano (BWF) band. At DTT addition BWF band was downshifted, its width and asymmetry was increased. The possible reason of observed spectral changes is charge transfer to SWNTs at redox reaction of thiol-containing compound so that the extrinsic hole doping of SWNTs is removed. This work has been partially supported by National Academy of Sciences of Ukraine (Grant N 15/18-H within the program ‘‘Fundamental Problems of the creation of new Nanomaterials and Nanotechnology” and Grant N 0117U002287). 

1.	. Kurnosov N.V, Leontiev V.S., Karachevtsev V.A. Enhancement of photoluminescence from semiconducting nanotubes in aqueous suspensions due to cysteine and dithiothreitol doping: influence of the sonication treatment // Nanoscale Res. Lett.-2016.-11.-P. 490-1-8.
2.	Farhat H., Sasaki K., Kalbac M., Hofmann M., Saito R., Dresselhaus M.S., Kong J. Softening of the radial breathing mode in metallic carbon nanotubes // Phys. Rev. Lett.-2009.-102.-P. 126804-1-4.