Mechanistic study on galvanic replacement reaction and synthesis of Ag-Au alloy nanoboxes with good surface- enhanced Raman scattering activity to detect melamine

Abstract Tree-type multiple-head surfactant, bis (amidoethyl-carbamoylethyl) octadecylamine (C18N3), which functions as both reducing and capping agent in the reaction system, has been used to fabricate Ag nanocubes with size over hundreds nanometer. These as-prepared Ag nanocubes could be used as template to fabricate Ag-Au nanoboxes through galvanic replacement reaction by adding HAuCl 4 aqueous solution. And the inner diameter of the Ag-Au nanoboxes could be adjusted by changing the concentration of HAuCl 4 in the reacted solution. Other influences on the structure of the products of galvanic replacement reaction, such as temperature, were also studied. We find that the structure of the final products are totally different when adding ammonia into the reacted solution of galvanic replacement reaction, they became hexapod and spherical Ag-Au alloy nanostructures. It was suggested that the additive of ammonia water alter the mechanism of the Ag/Au galvanic replacement reaction, which is a new way to increase the types of prepared materials with various structures. We believe that our method opens a new way and will be useful for preparing other kinds of metallic nanostructures. And the SERS (Surface Enhanced Raman Scattering) measurements proved that the prepared Ag-Au alloy nanoboxes possess excellent potential applications in the field of food safety.