Organic nanosheets with charged surface: two dimensional self-assembly of a non-symmetric bis-acylurea with pyridyl end group

We present a novel non-symmetric bis-acylurea that self-assembles into two dimensional nanosheet superstructures. The bis-acylurea (PyrC8Bn) has a pyridyl and a benzyl end group divided by a spacer group [–NHCONHCO–(CH2)8–CONHCONH–, C8] with two hydrogen bonding sites. Upon cooling a hot solution in ethanol, the molecule self-assembles into multilayered nanosheet structures due to the intermolecular biaxial hydrogen bonding. The surface charge of the nanosheets could be switched between positive and neutral by adjusting the pH. The charged character of the nanosheets was utilized in immobilizing negatively charged gold nanoparticles. An attempt to regulate the self-assembly allowed us to find a unique hierarchical structure of PyrC8Bn, where ultrathin (<10 nm) 2D lamellae growing within microspheres were observed. This superstructure with large surface area could serve as a template for inorganic catalytic materials.