Ordered Gold Nanostructure Assemblies Formed By Droplet Evaporation

摘要

Ordered assemblies of anisotropic nanostructures have attracted increasing interest because of the rich assembling behavior caused by their reduced shape symmetry and the unique collective properties that can be engineered by controlling interparticle spacing and by material processing. The formation of columnar superstructures has been reported for gibbsite and copper sulfide platelets. Beautiful iridescent liquid-crystalline phases (nematic or smectic) have been reported for suspensions of rodlike particles, including DNA, viruses, BaCrO4, β-FeOOH,TiO2, and CdSe. Semiconductor nanorods with interesting optical properties are useful for device applications (light-emitting diodes, memory devices, and solar cells), and efforts have been made to produce large-area ordered semiconductor nanorod superstructures. One approach that has been developed is the deposition of preformed nanorod liquid crystals from suspensions onto substrates. Ordered solid assemblies of CdS and CdSe nanorods have been obtained in this way. Onsager's theory stated that suspensions of hard rods that have zero interaction potential until they touch, at which point they infinitely repel each other, exhibit the nematic phase at critical densities far from the closest packing. In real colloidal systems, attractive van der Waals and dipole-dipole and repulsive electrostatic interactions also influence the liquid-crystalline phase behavior.