Compared with rGO, the nitrogen-doped rGO became very hard to be dispersed into NMP by probe sonication; For example, after 20 min sonication, the rGO can be well dispersed into NMP, while it takes >4hr sonication to disperse most of the N-rGO in NMP.

PS. I use ammonia solution as precursor and hydrothermal route to prepare the N-rGO.