Self-assembly of gold nanorods into vertically aligned, rectangular microplates with a supercrystalline structure

Vertically aligned, supercrystalline microplates with a well-defined rectangular shape were fabricated in a large area through self-assembly of gold nanorods by a novel bulk solution evaporation method. This evaporative self-assembly strategy involving continuous movement of the contact line can prevent the coffee-ring effect, thus allowing uniform deposition of discrete GNR superstructures over a large area and favoring the formation of GNR supercrystals with geometrically symmetric shapes. A mechanism based on the continuing nucleation and growth of smectic GNR superstructures accompanying the movement of the contact line was put forward for the formation of the unique GNR supercrystal arrays. Based on this mechanism, a micropatterned substrate was designed to control the nucleation location and growth direction, leading to the spontaneous self-assembly of nearly parallel arrays of vertically aligned, supercrystalline microplates of GNRs. The obtained rectangular-plate-shaped GNR supercrystals exhibited interesting anisotropic optical reflection properties, which were revealed by polarized light microscopy.