Direct synthesis of size-tailored bimetallic Ag/Au nano-spheres and nano-chains with controllable compositions by laser ablation of silver plate in HAuCl 4 solution

The direct conversion of bulk silver metal to size-tailored bimetallic silver–gold (Ag/Au) nano-spheres and nano-chains with controllable compositions has been achieved by laser ablation of an Ag target in HAuCl 4 solution. Taking advantage of the replacement reaction between Ag and Au ions, the average sizes of the bimetallic Ag/Au nano-particles substantially decreased from tens of nanometers to sub-2 nm with the increase in HAuCl 4 concentration (0.12–4.59 mM). Meanwhile, the relative ratio of Ag and Au elements in individual Ag/Au nano-particles has been systematically changed from about 9 : 1 to 1 : 9. The UV-visible absorption spectra of the Ag/Au nano-particles significantly red shifted from about 400 nm to 785 nm. The designed simplistic, single-step, versatile strategy does not require seed preparations, intermediate workup processes or any potential toxic surfactants. This will offer a convenient and valuable new way to fabricate bimetallic nano-particles with desired structures and functions.