Controlling the Degree of Functionalization: In-Depth Quantification and Side-Product Analysis of Diazonium Chemistry on SWCNTs

Abstract

We present an in-depth qualitative and quantitative analysis of a reaction between 4-iodobenzenediazonium tetrafluoroborate and single-walled carbon nanotubes (SWCNTs) via thermogravimetric analysis coupled with mass spectrometry (TG-MS) or a gas chromatography and mass spectrometry (TG-GC-MS) as well as Raman spectroscopy. We propose a method for precise determination of the degree of functionalization and quantification of physisorbed aromates, detaching around their boiling point, alongside covalently bonded ones (cleavage over 200 °C). While the presence of some side products like phenol- or biphenyl species could be excluded, residual surfactant and minor amounts of benzene could be identified. A concentration-dependent experiment shows that the degree of functionalization increases with the logarithm of the concentration of applied diazonium salt, which can be exploited to precisely adjust the amount of aryl addends on the nanotube sidewall, up to 1 moiety per 100 carbon atoms.