Behind the role of bromide ions in the synthesis of ultrathin silver nanowires

The bromide-mediated polyol method has been widely used to synthesize ultrathin silver nanowires , however, the reason why the addition of bromide ions can reduce the diameter of silver nanowires is unclear. To elucidate this mechanism, we have conducted a series of experiments in which the amount of halide ions is kept constant while the ratio of Cl − to Br − ions is varied, to investigate how the halide ions influence the morphology of AgNWs. Based on these experiments and previous studies, we propose herein that the bromide ions fulfill three roles: (i) facilitating the formation of AgBr cubes as nucleation events, (ii) limiting the lateral growth of AgNWs and (iii) enabling the formation of more stable AgBr complexes. Our current study should be useful for enabling size-controlled synthesis of silver nanowires via the bromide-mediated polyol method.