Facile method to prepare magnetic multi-walled carbon nanotubes by in situ co-precipitation route

An effective method for preparing magnetic multi-walled carbon nanotubes (M-MWCNTs) was proposed by employing an in situ co-precipitation of ammonium ferrous sulfate hexahydrate and ammonium ferric sulfate dodecahydrate in a suspension of commercial MWCNTs. Microscopic and spectroscopic analyses could confirm the presence of magnetite, maghemite and hematite on the surface of M-MWCNTs. Negative charges on the surfaces of acid-treated MWCNTs would lead to the attachment of iron derivatives which possessed positive charge due to electrostatic attraction. As a result, the prepared M-MWCNTs were clearly responsive to a permanent magnetic while the pristine MWCNTs were not.