Dendrimer-controlled one-pot synthesis of gold nanoparticles with a bimodal size distribution and their self-assembly in the solid state

Gold nanoparticles have been precipitated in the presence of a stiff polyphenylene dendrimer template with 16 thiomethyl groups on the outside. Powder X-ray diffraction analysis shows an average particle size of similar to3.7 nm; surprisingly, transmission electron microscopy (TEM) reveals a bimodal particle size distribution. Most of the small particles are single crystals and the large ones have multiple crystalline domains, as observed by high resolution TEM. The particles aggregate in the solid state due to the cross-linking ability of the dendrimer. They are reversibly soluble in chloroform and toluene for extended periods of time, and can be solution cast onto flat substrates. A strong plasmon band at 560 nm and a shoulder at similar to370 nm are observed in the UV/Vis spectrum of the material.