Discrete Functional Gold Nanoparticles: Hydrogen Bond-Assisted Synthesis, Magnetic Purification, Supramolecular Dimer and Trimer Formation

Amine monofunctional gold nanoparticles (1-AuNPs) were synthesized by employing a solid-supported technique and pH-switchable pseudorotaxane formation. Purification was repeatedly facilitated using crown ether peripherally coated superparamagnetic iron oxide microspheres to yield the monofunctional gold nanoparticles in excellent yield. The product and its related intermediate superstructures were characterized by IR and X-ray photoelectron spectroscopies. Novel supramolecular dimers and trimers were prepared by titrating the 1-AuNPs with bisDB24C8 and trisDB24C8 at different ratios. UV/visible absorption spectroscopic analyses of the supramolecular dinner and trimer solutions, which were formed by mixing their separate components in different ratios, indicated the gradual appearance of two distinct plasmonic resonance bands at 620 and similar to 700 nm. Furthermore, TEM Images of the dinners revealed a significant amount of dinner pairs on the surface, while the TEM images of the trimers demonstrated the presence of both dinners and trimers. The trimers appeared as triangular or near-linear shapes.