Metals Doped with Functional Nanoparticles

The merging of the properties of metals with the vast variety of properties of organic molecules and polymers, offers the possibility to create new composite materials with properties that are the sum of the two components’ properties, such as forming acidic or basic metal. Moreover, these composites, denoted dopant@metal, also show new properties that result from synergism and combination of the two components’ properties, such as inducing chirality to silver, gold and palladium by entrapping chiral molecules, corrosion resistance of iron composite and synergistic biocidal effects of biomolecule@Ag.

In this study, an important extension is made in this field by development of procedures for the entrapment, for the first time, of oxide and metals nanoparticles (NPs). The general synthetic procedures which have been developed for these purposes are based on the reduction of the metal cation in solution in the presence of the dispersed NPs to be entrapped. The following NPs were successfully entrapped and characterized, resulting in several new functional materials: The potentially catalytic oxidizing CeO₂-NPs@Ag, CeO₂@Pd and NiO@Pd; the catalytic Au-NPs@Ag for which catalytic properties were already observed; and the magnetic SrFe₁₂O₁₉ (SFO)-NPs which were successfully entrapped within copper, silver and gold, inducing magnetism in these metals, and enhancing both the remanence and the saturation magnetization. Initial characterizations showed that the amount of the entrapped NPs can be varied in the range of 0.5-15 wt %. The morphology of the new composites, revealed by SEM imaging, shows hierarchical structure of metal aggregates with the NPs dispersed on the surface of the metallic cage between the metal crystallites. This was also confirmed by imaging of the inner structure of the metal aggregates with a FIB instrument coupled to SEM and EDX. Surface area and density measurements, along with the SEM imaging, show that even low dopant loadings have significant influence on the composite properties.