A Greener Synthesis of Core (Fe, Cu)-Shell (Au, Pt, Pd, and Ag) Nanocrystals Using Aqueous Vitamin C

A greener method to fabricate novel core (Fe and Cu)-shell (noble metals) metal nanocrystals using aqueous ascorbic acid (vitamin C) is described. Transition metal salts such as Cu and Fe were reduced using ascorbic acid, a benign naturally available antioxidant, and then addition of noble metal salts resulted in the formation of the core–shell structure depending on the core and shell material used for the preparation. Pt yielded a tennis ball kind of structure with a Cu core, whereas Pd and Au formed regular spherical nanoparticles. Au, Pt, and Pd formed cube-shaped structures with Fe as the core. Inversely, transition metals with noble metals, such as Pd, as the core also formed interesting structures; these structures were brushlike with indium as the shell and needle-like when Cu was employed as the shell. The method is general uses no surfactant or capping agent and can be extended to noble metals as cores and transition metals as shells. The core–shell nanocrystals were characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), and UV–vis spectroscopy. These nanocrystals have unique properties that are not originally present in either the core or shell materials and may have potential functions in catalysis, biosensors, energy storage systems, nanodevices, and ever-expanding other technological applications.