Nanobubble-assisted formation of carbon nanostructures on basal plane highly ordered pyrolytic graphite exposed to aqueous media.

Ambient gas nanobubbles of size approximately 10(1)-10(2) nm occupying the hydrophobic surface of basal plane highly ordered pyrolytic graphite (HOPG) immersed in aqueous media at room temperature cause exfoliation of the top graphene layers, as revealed by both in situ and ex situ atomic force microscope (AFM) imaging. The formation of nanoparticles composed mostly from graphene-based nanoscrolls, nanohorn-like and onion-like nanostructures was resolved by high resolution transmission electron microscopy (TEM) and examined by diffraction and x-ray photoelectron spectroscopy (XPS) analyses. The diameter of nanostructures varied from about 5 nm for single-layered scrolls to tens of nanometres for multishells. Raman spectroscopy confirmed the structural rearrangement of the HOPG basal plane after the above-mentioned treatment. The implications for nanobubble interfacial forces are discussed.