Abstract: There are provided non-destructive methods for incorporating an atom such as N into a material such as graphene. The methods can comprise subjecting a gas comprising the atom to conditions to obtain a flowing plasma afterglow then exposing the material to the flowing plasma afterglow. There are also provided materials such as N-doped graphene produced by such methods.

Abstract: A nanofluid includes a base fluid and multiwall carbon nanotubes (MWCNTs) dispersed in the base fluid. The MWCNTs have an outer surface provided with polar functional groups. The outer surface has decorated portions covered with nanoparticles and undecorated portions where the polar functional groups are exposed. A method prepares a nanofluid. In a first step, MWCNTs are grown on substrates by catalyst-free thermal chemical vapor deposition. In the following step, the MWCNTs' outer surface is functionalized to form polar functional groups covalently bonded thereto. Then, nanoparticles are deposited on the MWCNTs' outer surface such that the outer surface has decorated portions covered with the nanoparticles, while leaving undecorated portions where the polar functional groups are exposed. The resulting nanoparticle-decorated functionalized MWCNTs are then detached from the substrates and dispersed in a base fluid.