The surface of individual, relatively dispersed Fe304 nanospheres is coated with a thiol-terminated silane, then the thiol on the Fe304 particles＇ surfaces treats with nano-Ag colloidal solution to form Ag-modified Fe304 nanoparticles. Eventually, a solid shell of Ag is capped onto the Ag-modified Fe304 nanoparticles by reducing aliquots of AgNO3 solution using NaBH4 as a re- ducing agent. The as-prepared Fe304-core@Ag-shell nanoeggs, which are uniform in size, highly monodisperse, stable against aggregation and have high magnetization, were depended on thin shell of the attached nano-Ag, the size of Ee304 nanoparticles, the volume of thiol-terminated silane as well as the ultrasonication. The Fe304-core@Ag-shell nanoeggs are proposed to detect fingermarks on different surface, with which the fingermarks can be viewed directly, due to the clear ridge detail.
