Self-assembly of CuSO4 nanoparticles and bending multi-wall carbon nanotubes on few-layer graphene surfaces

When a colloidal suspension is allowed to wet a suitable substrate, various patterns emerge that can be varied from isolated island-like structures to fractal patterns. In this work we investigate the patterns arising from the interplay of colloidal copper sulfate suspensions containing carbon nanotubes with few-layer graphene substrates. The compositions of the thin film samples were investigated using X-ray photoelectron spectroscopy, surface topography and the nanostructure of the thin films were probed with atomic force microscope and transmission electron microscope respectively. The colloidal suspensions were characterized using contact angle and viscosity measurements. The colloidal suspensions when dip coated on few-layer graphene substrates exhibited fractal like morphology with the aggregation of copper sulfate crystallites to hexagonal platelets. This aggregation is explained invoking the depletion attraction theory. The various patterns observed experimentally were reproduced using a Monte Carlo simulation.