ABSTRACT
Finely divided iron has long been known to be pyrophoric, which is a major reason that Fe nanoparticles (Nps) have not been more fully studied to date.1 This extreme reactivity has traditionally made Fe Nps dif£cult to study and inconvenient for practical applications. However, iron has a great deal to offer at the nanoscale, including very potent magnetic, catalytic, and medical applications, so methods for reducing its reactivity with simultaneous retention of magnetic and catalytic properties have been developed. Although pure metal iron Nps are unstable in air, by a coating of noble metal on Nps surface, these formed air-stable Nps are protected from the oxidation and retain most of the favorable magnetic properties, which possess the potential applications mentioned here, as well as in high density memory devices by forming self-assembling nanoarrays.2a
Gold coating is very promising for magnetic and other particles to be functionalized for targeted drug delivery.2b This metal (Au), as well as iron oxides Fe2O3 and Fe3O4, is biocompatible with human organisms,3,4 could easily be tracked in it, and can be functionalized with organic and bioorganic molecules, such as proteins or enzymes, and bind bacteria; at the same time, Nps of iron and its oxides possess magnetic properties facilitating their delivery to an organ, tissue, or cancer tumor by using an external magnetic £eld. Therefore, the unique combination of the nanoscale magnetic core and the functional shell makes Fe-doped Au Nps ideal for biological and biomedical applications due to their conjugation chemistry, optical properties, and surface chemistry.
