Formation of submicrometer-scale gold nanoparticle aggregates and their self-organization into “supracrystals”

Nearly spherical, submicrometer-scale gold nanoparticle aggregates about 250 nm in diameter are formed directly from an HAuCl4-p-phenylenediamine aqueous solution at room temperature. The as-formed aggregates were characterized by various techniques, including scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, and their formation mechanism is discussed. It is very interesting that “supracrystals” can be produced with the use of such gold aggregated nanoparticles.