Formation of gold colloids using thioether derivatives as stabilizing ligands

Thioethers were used as adsorbates for preparing gold nanoparticles. Different thioether derivatives having from 1 to 4 thioether functionalities were synthesized. Colloids were prepared in a two-phase system, and characterized by H-1 NMR and transmission electron microscopy (TEM). The stability of colloids protected by thioethers increases with the number of ligands per molecule. Monothioethers need longer chain lengths or costabilization by (oct)(4)NBr in order to give stable, redispersible gold colloids. Gold colloids stabilized by the bis(thioether) 5 could not be redispersed after precipitation. Colloids stabilized by the tris(thioether) 6 were only formed at elevated temperature (60 degreesC) indicating the need of chain reorientation for attaining stable colloids. Tris(thioether) 7 gave stable colloids at room temperature, which could be redispersed even after precipitation. Tetrakis(thioether) 8 gave the smallest particle size and narrowest size distribution.