From single molecules to nanoscopically structured materials: Self-assembly of metal chalcogenide/metal oxide nanostructures based on the degree of Pearson hardness

A chemically specific and facile method for the immobilization of metal oxide nanoparticles onto the surface of IF-MoS₂ nested fullerenes is reported. The modification strategy is based on the chalcophilic affinity of transition metals such as Fe²⁺/Fe³⁺, Fe³⁺, or Zn²⁺ as described by the Pearson HSAB concept. The binding capabilities of the 3d metals are dictated by their Pearson hardness. Pearson hard cations such as Fe³⁺ (Fe₂O₃) do not bind to the chalcogenide surfaces; borderline metals such as Fe²⁺ (Fe ₃O₄) or Zn²⁺ (ZnO) bind reversibly. Pearson-soft metals like Au bind irreversibly. The immobilization of metal oxide nanoparticle colloids was monitored by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) combined with energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD).