Assembling gold nanoparticles in solution using phosphorothioate DNA as structural interconnects

The ordered arrangement of nanoparticles in one, two and three-dimensional structures is a problem of current interest. While assembly of nanoparticles from solution into monolayer and superlattice structures on solid surfaces has met with a fair degree of success, the controlled assembly of nanoparticles in solution remains a more difficult and relatively unexplored area. In this communication, we describe the assembly of gold nanoparticles in solution using phosphorothioate DNA as a structural interconnect. Sulphur-substituted DNA cross-links the gold nanoparticles in solution through thiolate linkages with the nanoparticle surface, and organizes them in different geometries. The small length of the phosphorothioate DNA molecules used in the study (ca. 4 nm) renders them rigid and effective as connectors between nanoparticles. The organization of gold nanoparticles by sulphur-substituted DNA has been followed with UV-vis spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy measurements.