Multipurpose Nature of Rapid Covalent Functionalization on Carbon Nanotubes

Abstract

In the vast field of functionalization routes to carbon nanoforms, the fulfillment of such critical requirements as quick and nonharsh methods, good dispersibility, introduction of reactive groups, short reaction time, and low cost can be quite challenging. Traditional thermally induced diazonium chemistry on single-walled carbon nanotubes (SWCNTs) is revisited by using commercial anilines and providing useful insight into the versatility of this approach. Functionalized SWCNTs with multiple controllable features, such as degree (and ratio) of coverage, orthogonalization, doping, and high water dispersibility, are obtained by introducing benzenesulfonic acid and benzylamine moieties. The scenario opens up an avenue to address relevant applications in which most functionalization methods could not be applied in a straightforward way.

A tool box to ascertain the nature of doping and photoresponse in single-walled carbon nanotubes

“…The raw material was purified in-house using a non-oxidative method. 34 All other reagents and solvents were purchased from commercial sources and used without further treatment (details in the ESI †).…”

“…The conversion factor (10 4 ) provides data in units of mmol g À1 . 34 In addition, we used another formula to estimate the functionalization degree in terms of the number of functional groups per X carbon atoms in SWCNTs (1/X):…”

“…where X stands for the number of carbon atoms in the SWCNT per covalent functional group, WL (%) is the weight loss in the range of 100-650 1C, R (%) is the residual mass at 450 1C in the TGA plot and M W is the molar mass of the desorbed moieties. 34 This calculation considers SWCNT samples to be entirely constituted by carbon, which is indeed an approximation. The results obtained are summarized in Table 1.…”

“…However, nanotubes with mainly metallic character present large modifications in the RBM intensity (E M 11 yellow region) upon functionalization, in good agreement with the previous literature. 9,34 The tangential modes are the most intense in SWCNTs and form the G-band, which is related to in-plane C-C bond stretching, at around 1590 cm À1 . 25 The line shape of the G-band provides additional information about the metallic and semiconducting SWCNTs in resonance.…”

“…We controlled the experimental variables to end up in a high level of sidewall decoration with one or several functional groups, which can be further derivatized, and minimizing the oligomerization of reactive species. 34 This approach was adapted to obtain functionalized SWCNTs with two different grafted moieties, achieving the dual effect of high functionalization level and the tuning of their electronic structure. In situ Raman spectroelectrochemistry is used to investigate the radial breathing mode (RBM) and to assess the electronic structure of covalently functionalized SWCNT bundles.…”