On the other end, the GNP exfoliation against a BOPP surface resulted in massive formation of scrolled structures. This different behavior is ascribed to the presence of friction which is more effective in the latter case. In fact, the roughness of BOPP is 4.20 Å [12, 13], comparable

to the graphite interlayer spacing (3.354 Å), thus leading to enhanced mechanical grip between the two sliding surfaces. Results and discussion The role of shear-stress Tanespimycin supplier forces in the treatment of graphite by ball-milling technology has been previously suggested as an explanation for the occasional formation of nanoscrolls [14]. However, a very limited amount of low-quality CNS results at the end of the graphite grinding process. On the

other hand, to the best of our knowledge, we are the first to achieve a massive production of well-formed CNSs by applying a combination of shear stress and friction forces to a GNP sample in a very simple technique that does not require the use of any special apparatus. In particular, an alcoholic (ethanol, 99.9%, Aldrich, St. Louis, MO, USA) dispersion of GNP was prepared, according to our previously developed experimental procedure [15, 16]. This dispersion was slowly rubbed on the surface of a BOPP film (with a thickness of 40 μm, Manucor S.p.A., Sessa Aurunca, Dorsomorphin clinical trial Italy) using a LDPE piece. The suspension was allowed to dry during the rubbing process. After

drying, the concentrated liquid suspension was removed from the BOPP film by pouring ethanol on it. The resulting black suspension contained a large amount of nanoscrolls. Nanoscrolls can be separated from the unrolled and/or partially rolled graphene-based material by sedimentation in ethanol since their Stokes coefficient value is significantly higher than that for graphene sheets. The nanofibrous structure of the BOPP film surface can be conveniently imaged by atomic force microscopy (AFM; see Figure  1a) [17]. As visible, the BOPP surface Resveratrol is made of nanosized polypropylene fibers that provide the resistant friction force inducing the separation of the graphite nanocrystal edges, thus causing a rolling-up process under the concomitant action of the applied shear stress. Figure 1 AFM image of the BOPP film nanoporous surface (a) and SEM micrograph of the GNP precursor (b). The typical morphology of a GNP sample used as a precursor in the CNS fabrication process is shown in Figure  1b. As visible, the starting carbon material contained only flat graphite nanoplatelets with sharp edges. The GNP unities have two main dimensions of a few microns and are characterized by an average thickness of 20 nm. After the simultaneous application of shear and friction forces, the material morphology resulted to be significantly modified.