Rippled mixed monolayer protected nanoparticles with charged ligands

We present here the first molecular-level resolution STM images of water-soluble nanoparticles with a sulfonate group. We show that when mixed self-assembled monolayers (SAMs) of mercaptoundecasulfonic acid (MUS) and octanethiol (OT) in a 1:1 ratio are assembled on gold nanoparticles, they spontaneously phase-separate into highly ordered ribbon-like phases ("ripples"). These MUS:OT 1:1 nanoparticles have unprecedented solubility in aqueous environments and are thus ideal for use in biological applications. Their water solubility and net negative charge prevented traditional sample preparation methods from being viable and we present new methods for characterization. This new family of water- soluble nano-structured nano-materials may demonstrate new properties due to this novel and unique morphology in their ligand shell.