Effects of Temperature on the Hydrophobic to Hydrophilic Ligand Ratio on the Surface of Amphiphilic Gold Nanoparticles

Amphiphilic gold nanoparticles were synthesized by the functionalization of gold nanoparticles with hydrophilic and hydrophobic ligands on their surfaces, which can be applied to many disciplines such as biology, photonics, electronics, and so on. The ratio of hydrophilic and hydrophobic ligands plays an important role in such applications since the ratio is closely related to physiochemical properties of the nanoparticles. In this paper, the effect of temperature during the ligand exchange reaction on the ratio of ligands on the gold nanoparticle surface was investigated. Hydrophilic ligands have higher affinity to the nanoparticle surface with an increase of the temperature. Furthermore, the amphiphilic nanoparticles at a higher temperature were more soluble in an aqueous solution even with a lower hydrophilicity of the nanoparticle surface.