Structure-dependent reactivity of semiconducting single-walled carbon nanotubes with benzenediazonium salts.
The addition of diazonium salts to single-walled carbon nanotubes (SWCNTs) in aqueous surfactant suspensions quenches the intrinsic near-infrared fluorescence of semiconducting SWCNTs through sidewall chemical reactions. Spectrally resolved fluorescence spectroscopy of mixed SWCNT samples has been used to measure structure-dependent relative reactivities in the initial stages of these reactions. For several 4-substituted benzenediazonium salts, Ar-R (Ar = N 2 (+)-C 6H 4 and R = Cl, NO 2, OMe), reactivities at pH 10 were found to be greatest for SWCNTs having the largest band gaps. The magnitude of this band gap dependence varies according to the R-group of the salt, with R = OMe showing the strongest variation. For R = OH, acidification of the sample to pH 5.5 results in reversal of the structural trend, as smaller band gap SWCNTs show slightly greater reactivities. The derivatization reactions observed here proceed concurrently, although at different rates, for semiconducting and metallic SWCNT species. These results therefore provide insight into the difficulties of separating metallic and semiconducting SWCNTs through selective reaction schemes and underscore the need for fluorescence spectroscopy to be used in assessing semiconducting SWCNT reactions.
Doyle
Condell D
CD
Departments of Chemistry and Mechanical Engineering and Materials Science, the R.E. Smalley Institute for Nanoscale Science and Technology, MS-222, Rice University, 6100 Main Street, Houston, Texas 77005, USA.
Rocha
John-David R
JD
Weisman
R Bruce
RB
Tour
James M
JM
D003979:Diazonium Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D037742:Nanotubes, Carbon / Q000737:chemistry*; D012666:Semiconductors; D013050:Spectrometry, Fluorescence / Q000379:methods; D013059:Spectrum Analysis, Raman; D013329:Structure-Activity Relationship; D013501:Surface-Active Agents / Q000737:chemistry; D013535:Suspensions
D003979:Diazonium Compounds; D037742:Nanotubes, Carbon; D013501:Surface-Active Agents; D013535:Suspensions; C035176:benzenediazonium