Modification of tin oxide nanoparticles by fluorocarbon solids via a mechanochemical route

Interfacial reactions at the surface of SnO2 nanoparticles adjacent to the fluorocarbon solids (FCS) under mechanical stressing were compared in an attempt to their modification by introducing fluorine and carbon. Emphasis was laid on the comparison of the reactivity of 3 different species of FCS, i.e., polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), and perfluorooctanoic acid (PFOA). PVdF exhibited the highest reactivity, followed by PTFE and PFOA, as confirmed by Raman, FT-IR, XPS, and F-19 MAS NMR spectra. The preferential reactivity could be explained in terms of the electrophilicity of FCS toward the nucleophilic oxygen in SnO2, since the decomposition of FCS is catalyzed by the coexisting SnO2. PFOA behaved in a different manner, due to its carboxylic groups. At the same time, carbon nanospecies were introduced as a decomposed product of FCS. This results in the formation of SnO2:F/C nanocomposite. Fluorine introduced to SnO2 survived even after heating up to 600 degrees C either in air or in Ar. This indicates the thermal stability of the present partially fluorinated SnO2 nanoparticles.