Directed Assembly of Gold Nanorods by Terminal-Base Pairing of Surface-Grafted DNA.

Directed assemblies of anisotropic metal nanoparticles exhibit attractive physical and chemical properties. However, an effective methodology to prepare differently directed assemblies from the same anisotropic nanoparticles is not yet available. Gold nanorods (AuNRs) region-selectively modified with different DNA strands can form side-by-side (SBS) and end-to-end (ETE) assemblies in a non-crosslinking manner. When the complementary DNA is hybridized to the surface-bound DNA, stacking interaction between the blunt ends takes place in the designated regions. Such AuNRs assemble into highly ordered structures, assisted by capillary forces emerging on the substrate surface. Moreover, insertion of a mercury(II)-mediated thymine-thymine base pair into the periphery of the DNA layer allows selective formation of the SBS or ETE assemblies from the strictly identical AuNRs with or without mercury(II).