A simple and rapid method of making 2D and 3D arrays of gold nanoparticles

Monodispersive gold nanoparticles can be synthesized by a dropwise addition of a reducing agent microemulsion to a gold ion microemulsion followed by immediate stabilization with 1-decanethiol. No size-selective precipitations or digestive ripening procedures are necessary. There is no need for metal functionalization of the surfactant AOT. Gold nanoparticles with an average size of 3.8 nm and a relative size dispersion of 5.4% were observed using n-heptane as a solvent. It seems possible to adjust the nanoparticle size by small changes in the carbon chain length of the solvent. Self-assembled 2D and 3D arrays of gold nanoparticles with adjustable sizes have been obtained on carbon-coated copper grids and on a silicon wafer. The arrays have good crystallinity as evidenced by the external morphology and transmission electron diffraction results. The size of the gold nanoparticle 3D arrays depends on the immersion time and can be greater than 15 microm. This approach could be used to synthesize other noble metal nanoparticle arrays that may lead to new materials for electronic and photonic applications.