Controllable synthesis of gold nanoparticle dimers via site-selective growth.

Random aggregation of nanoparticles follows step-growth kinetics, and thus the synthesis of large nanoparticle dimers is still a challenge. Here, we report a site-selective growth route to producing gold nanoparticle dimers in a high yield of up to 71%. The polymer contraction exposed two tips of gold nanorods, which provided active sites for further growth, setting the ability for a high yield of large dimers. Methods to fine tune the reaction rate allowed us to control the spacing between nanoparticles, giving a good SERS performance. Our method was shown to make up for the shortcomings of the existing synthetic method, and to achieve the synthesis of large dimers in solution.