Plasma Treatment of Metal Oxide Nanoparticles: Development of Core–Shell Structures for a Better and Similar Dispersibility

Low-pressure plasma polymerization of cyclopropylamine was employed for the surface functionalization of commercial ZnO, Al2O3, and ZrO2 nanoparticles in a homemade hollow cathode plasma reactor. The analysis of the modified nanoparticles by X-ray photoelectron spectroscopy (XPS) revealed the incorporation of reactive functional groups such as primary and secondary amines, which was confirmed by Fourier transform infrared spectroscopy (FTIR). The raw and the plasma functionalized nanoparticles were evaluated in terms of dispersibility. Application of Hansen solubility parameters (HSP) theory showed that the efficient plasma polymerization that led to the deposition of an approximately 5 nm thick plasma polymer film, as determined by transmission electron microscopy (TEM), causes a similar shift toward the Hansen solubility space for the functionalized nanoparticles and changes their physicochemical affinity within selected solvents, regardless of the kind of nanoparticles used. Hence, a combined exploitation of nanoparticles having different cores is feasible in applications such as nanocomposites and bioapplications having certain reactivity after grafting an amine-based plasma polymer film that allows achieving a similar dispersibility.