Site-specific patterning of highly ordered nanocrystal superlattices through biomolecular surface confinement.

With the increasing demand in recent years for high-performance devices for both energy and health applications, there has been extensive research to direct the assembly of nanoparticles into meso- or macroscale single two- and three-dimensional crystals of arbitrary configuration or orientation. Inorganic nanoparticle arrays can have intriguing physical properties that differ from either individual nanoparticles or bulk materials. For most device applications, it is necessary to fabricate two-dimensional nanoparticle superlattices at programmed sites on a surface. However, it has remained a significant challenge to generate patterned arrays with long-range positional order because most highly ordered close-packed nanocrystal arrays are typically obtained by kinetically driven evaporation processes. In this report, we demonstrate a method to generate patterned nanocrystal superlattices by confining nanoparticles to geometrically defined 2-D DNA sites on a surface and using associative biomolecular interparticle interactions to produce thermodynamically stable arrays of hexagonally packed nanocrystals with significant long-range order observed over 1-2 μm. We also demonstrate the role of chemical and geometrical confinement on particle packing and obtaining long-range order. Finally, we also demonstrate that the formation of DNA-mediated nanocrystal superlattices requires both interparticle DNA hybridization and solvent-less thermal annealing.