The influence of the liquid environment on the formation of different carbon nanostructures by arcing processes, in particular liquid nitrogen (LN2) and de-ionised water (DI-H2O), has been investigated. Large structural differences between the nanomaterials produced in the two cases are shown: the use of DI-H2O induces a large number of pentagon–heptagon defects in the nanotubes, compared to the use of LN2. A large amount of graphene layers has been observed by scanning electron microscopy and transmission electron microscopy in the case of arc discharge in DI-H2O. Micro-Raman analysis confirms the electron microscopy results.