Fascinating distinct reactivity of 3- or 2-aminopyridines with carbon nanotubes

A rapid and simple, room temperature preparation of new kinds of water-, alcohol- or tetrahydrofuran-dispersible pyridyl-functionalized carbon nanotubes (CNTs) is reported. The reactivity of 3-amino-, 2-amino-, or 2-amino-3-methylpyridine was studied in a diazonium-based functionalization with two types of single walled carbon nanotubes (SWCNTs) prepared by an electric arc or a high-pressure CO conversion method. According to Raman and Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis-mass spectrometry (TGA-MS), the covalent functionalization of the SWCNTs by 3-aminopyridine was successful. Both SWCNT types functionalized with 3-aminopyridine yielded products that showed remarkable solubility. Energy filtrated transmission electron microscopy (EFTEM) analysis of the supernatants of the SWCNT dispersions confirmed the formation of the functionalized soluble carbon nanotubes. The diazotization with 2-amino or 2-amino-3-methylpyridine did not result in the covalent bonding to SWCNTs but it was a fast, gentle and efficient purification method for pristine SWCNTs containing amorphous carbon arising from their preparation process. Distinct reactivity of 3- and 2-aminopyridines with carbon nanotubes is discussed.

► Direct covalent functionalization of SWCNTs with pyridyl diazonium salts.
► 3-Pyridyl functionalized SWCNTs are highly dispersible in water, ethanol or THF.
► Purification of SWCNTs with 2-pyridyl diazonium salts to removal of amorphous carbon.
► Dispersible SWCNTs are possible candidates in printed electronics.