Hydrophobic properties of colloidal films coated with multi-wall carbon nanotubes/reduced graphene oxide multilayers

We introduce a novel and versatile approach for preparing superhydrophobic structures composed only of carbon nano-objects with tunable hydrophobicity can be realized via the LbL deposition of positively charged multiwall nanotubes (MWNTs) and negatively charged reduced grapheme oxide sheets (rGO) onto colloidal particles. Protonated MWNT (MWNT-NH₃+) and anionic reduced graphene oxide (rGO-COO-) were used as building blocks for the layer-by-layer assembly of MWNT/rGO multilayer films onto silica (Si) colloids. After fluorination, it has been shown that the surface hydrophobicity, as measured by the water contact angle, can be readily controlled from 119 to 151° by controlling the nanoscale roughness of the colloidal particles, which, in turn, is controlled by the number of bilayers. SEM and ζ-potential analysis suggested the successful preparation of multilayer films on colloidal particles.