Effects of Branched Ligands on the Structure and Stability of Monolayers on Gold Nanoparticles

The ability to control the structure of monolayers on radial and faceted surfaces is an important goal for the successful application of nanoparticles in devices and materials. To investigate the effect of steric bulk in the monolayer periphery on monolayer protected gold cluster (MPC) properties, we have synthesized a series of gold nanoparticles having amide functionality within the monolayer chains and altering the peripheral end groups of the monolayer. Investigation of these MPCs using IR spectroscopy and cyanide-mediated decomposition of the gold core reveals a strong correlation between the strength of the intra monolayer hydrogen bonding and the maximal decomposition rate. Additionally, comparison with corresponding ester-functionalized derivatives indicates that the hydrogen bonding amide unit in the monolayer emphasizes the effects of the peripheral groups on monolayer surface packing and MPC properties.