Experimental and theoretical studies on the role of silver in gold nanorods growth

Gold nanorods (AuNRs) have attracted high attention because of their multifunctions and potential applications in optical, electronic, catalytic and biomedical areas. This study demonstrates a key role of silver (Ag) atoms/clusters, experimentally and theoretically, in the formation and growth of AuNRs. It was found that the addition of silver salt (silver nitrate) can preferably deposit on certain Au crystalline {100} and/or {110} facets to affect the stacking of Au atoms when form and grow to AuNRs in the reported reaction system, resulting in slower atomic stacking on these two {100} and {110} facets but regular growth on the {111} facets. If no use of silver salt(s), gold nanospheres rather than nanorods were obtained in such a reaction system. It was found, by theoretical simulations (molecular dynamic method, MD), that Ag atoms can be oxidized to Ag⁺ ions by AuCl₄ ⁻ ions and exist in a short lifetime, which finally diffuses out from the Au crystal structure. The findings would be useful for better understanding the role of Ag in the formation and growth of AuNRs with crystal facet control, which will be beneficial for catalytic and gas sensing applications that often require highly exposed crystalline facets.