Synthesis of Au nanoparticle superlattices using amide bond reaction

Abstract

Superlattice or supercrystal, in which nanoparticles are regularly arranged, has a unique and novel physical property that can not be realized by single nanoparticles through the collective effect of particles. Until now, various methods such as solvent evaporation method and DNA mediated method have been actively studied to produce nanoparticle superlattice, but since the structural stability is limited in various environmental conditions (temperature, acidity and solvent) so that there is a difficulty in applying it to an application field. Therefore, it is essential to develop a nanoparticle self-assembly method capable of securing stability under various environmental conditions. In this thesis, we have conducted a study to fabricate the gold nanoparticle superlattices by using amide bond, a covalent bond. First, two types of ligands with acyl chloride and amine functional groups were functionalized to form amide bonds in 5.4 nm gold nanoparticles of monodisperse size. The covalent bond reaction was carried out by adding acid ($H^+ ion$) as a reaction catalyst to gold nanoparticles whose surfaces were functionalized with different ligands. It was confirmed by electron microscopy and incineration X-ray scattering that gold nanoparticle superlattices with the most crystal structure of FCC was formed at specific gold nanoparticle concentration and acid concentration. This is the world's first nanoparticle superlattices using amide bonds. Since the covalent bond, which is the bond between the molecules, is applied to the inter-particle bonding, it is expected to have an advantage of being superior in stability compared to the conventional method, the structure was stable in various polar solvents (DMF, EtOH, Toluene) and at high temperature (170 ° C). Therefore, based on the results obtained in this study, it is expected to open new possibilities in applying to various environmental conditions.