Convenient approaches for the synthesis of gold nanowires by successive utilization of two kinds of reducing agents in the solution of hexadecyl-trimethylammonium bromide

In spite that several empirical approaches for the synthesis of gold nanowires have been reported, there still remains ambiguity and controversy for their mechanisms. In this study, we report very easy and highly-reproducible synthetic method of gold (Au) nanowires with the size and the length of 40–50 nm and several micrometers, respectively. The method includes an extremely higher concentration of hexadecyl-trimethylammonium bromide (CTAB) at room temperature. We successively used two kinds of reducing agents, firstly sodium borohydride for the reduction of Au(III) ion into mostly Au(I) ion, and secondly triethylamine (TEA) leading Au(I) ion to Au(0) and its growth to Au nanowires. The former should be added very slowly, while the latter at once. Effects of oxygen were crucial for the growth to nanowires, and copper ion was quite effective for reductive scavenging of unwanted oxygen. It is strongly suggested that Cu(I) ion first generates the complex with TEA and then reduces Au(I) ion to Au(O). Thus, the Au nanowires grow in higher concentrations of Cu(I) ion. The concentration of CTAB was also found to be very important for the generation of Au nanowires.