A DNA-BASED METHOD FOR RATIONALLY ASSEMBLING NANOPARTICLES INTO MACROSCOPIC MATERIALS

COLLOIDAL, particles of metals and semiconductors have potentially use ful optical, optoelectronic and material properties(1-4) that derive f rom their small (nanoscopic) size. These properties might lead to appl ications including chemical sensors, spectroscopic enhancers, quantum dot and nanostructure fabrication, and microimaging methods(2-4). A gr eat deal of control can now be exercised over the chemical composition , size and polydispersity(1,2) of colloidal particles, and many method s have been developed for assembling them into useful aggregates and m aterials, Here we describe a method for assembling colloidal gold nano particles rationally and reversibly into macroscopic aggregates. The m ethod involves attaching to the surfaces of two batches of 13-nm gold particles non-complementary DNA oligonucleotides capped with thiol gro ups, which bind to gold, When we add to the solution an oligonucleotid e duplex with 'sticky ends' that are complementary to the two grafted sequences, the nanoparticles self-assemble into aggregates, This assem bly process can be reversed by thermal denaturation. This strategy sho uld now make it possible to tailor the optical, electronic and structu ral properties of the colloidal aggregates by using the specificity of DNA interactions to direct the interactions between particles of diff erent size and composition.