Self-organization of gold nanoparticles capped with liquid crystalline azobenzene ligands: the effect of terminal groups on particle arrangements

The ligands immobilized on the surface of gold nanoparticles (AuNPs) can be classified into two main types: end-on and side-on ligands. In order to investigate the effect of the terminal group of the end-on ligand on the nanoparticle arrangement, three types of AuNPs were employed by using azobenzene ligands with three different terminal groups (ethyl, acetyl, and nitrile). The obtained AuNPs with ethyl group (Au-L1e/d) are in a weakly ordered state, those with acetyl group (Au-L2e) show a hexagonal columnar liquid crystalline phase upon heating, and those with nitrile groups (Au-L3e) are highly aggregated and do not melt even when heated up to 220°C. According to DFT calculations, the dipole moments of each ligand are in the order of ethyl