Polyaniline-nanodiamond fibers resulting from the self-assembly of nano-fibrils: A nanomechanical study

Based on atomic force microscopy (AFM), torsional harmonics atomic force microscopy (TH-AFM, also referred to with the commercial name HarmoniX™) allows one to perform a quantitative characterization of the mechanical properties of soft samples on the nanometer scale. In this work, such a technique has been employed to study the mechanical properties of self-assembled micrometric fibers of polyaniline (PANI) doped with nanodiamond (ND) particles and to investigate the role of ND in the assembly. In particular, besides PANI–ND fibers, other features, i.e., nano-fibrils and blobs, have also been observed on the sample, the mechanical properties of which have been determined and compared after correcting for the effect of the substrate and of the cylindrical geometry of nano-fibrils. Their similar mechanical properties suggest that PANI–ND micro-fibers are constituted by self-assembly of nano-fibrils. Finally, the combination of nanomechanical characterization with energy dispersive X-ray (EDX) and Raman analyses allowed us to determine that softer blobs are residuals of amorphous PANI not polymerized in nano-fibrils.